HOME ABOUT FEEDBACK RECENT CONTENT PUBLISH IN NoL ARCHIVE WITH US
HELP MENU
Read NoL Noteworthy articles right at your iGoogle page, click here! Follow this link to setup Neurobiology of Lipids Noteworthy titles screening right at My Yahoo home page!
Neurobiol Lipids 1, 7 (14 March 2003)
find out how to cite this article


Original Research: 32nd Society for Neuroscience Annual Meeting Proceedings article#:
ABNORMAL CHOLESTEROL PROCESSING IN ALZHEIMER'S DISEASE PATIENT'S FIBROBLASTS

Franck Dufour,CA Wei-Qin Zhao, Lakshmi Ravindranath, Daniel L. Alkon

Blanchette Rockefeller Neurosciences Institute, Rockville, MD, USA
email: fdufour@brni-jhu.org

This article was edited by Bruce Teter

Accepted for publication 5 November, 2002; Published online: 14 March, 2003  | Article readership
Copyright © 2003 F Dufour et al., Licensee Neurobiology of Lipids

Article view and respond options:
GOOGLE SCHOLAR CITATION DOAJ CITATION FULL TEXT ACROBAT .PDF SFN PRESENTATION SUBMIT E-LETTER CITED IN...
AUTHORSPUBMED


ARTICLE NAVIGATION MENU


ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
FIGURE 1 AND FIGURE 2


ABSTRACT 
[Original SFN Abstract]

Cholesterol has recently received attention as a potentially important factor in Alzheimer’s disease etiology. Caveolin, which binds cholesterol, plays a prominent role in cellular cholesterol transport. Here, we found a higher level of cholesterol and caveolin in the caveolae-enriched fractions prepared from Alzheimer's disease patients' (AD) fibroblasts compared with age and sex matched controls (AC). Furthermore, the cross-linking activation of the prion protein, which is known to link to signal transduction of caveolin, is altered in AD fibroblasts. Our results suggest a dysregulation of cholesterol processing in AD fibroblasts which may contribute to the pathogenesis of AD.

INTRODUCTION 

Caveolae are vesicular invaginations of the plasma membrane involved in transcytosis, protocytosis, intracellular cholesterol transport and signal transduction [1, 2]. The main structural proteins of caveolae are the caveolins. Multiple isoforms have been isolated: caveolin-1a, caveolin-1b, -2, -3 [3, 4, 5, 6]. Although they show general similarities in structure and function, they differ in tissue distribution. Caveolin-1 and -2 are coexpressed and form a hetero-oligomeric complex [7] in many cell types [1], whereas caveolin-3 seems to be expressed predominantly in muscles [6, 8] and astrocytes [9, 10].

Beside its crucial stuctural role, caveolin undergoes determinant caveolae functions. Caveoale are membrane compartments for integration of signal-transduction pathways, and caveolin forms a scaffold to bind and concentrate several signaling molecules [5] through its scaffolding domain [11]. The functional processing of caveolin (and caveolae) is dependent on the cellular level of cholesterol [12, 13, 14, 15, 16]. The cholesterol itself regulates the expression of caveolin [17, 18] and binds it [19].

Previously, biochemical, epidemiological and genetic characterictics have linked cholesterol levels to Alzheimer’s disease [20, 21, 22ED+, 23ED+, 24]. In this study, we compared the expression of caveolin in fibroblasts isolated from Alzheimer’s patients (AD) and a control population (AC). We have shown that caveolin expression and cholesterol concentration are increased in AD caveolae cellular fractions; these alterations seem to affect signal transduction processes. We propose a new hypothesis that includes a critical role for caveolin in regulating cholesterol in Alzheimer’s disease.

MATERIALS AND METHODS 

Cell culture

The present studies were carried out with human skin fibroblasts purchased from Coriell Cell Repositories (Camden, NJ, http://locus.umdnj.edu), seeded and grown to confluence in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum in T-25 (or T-75 for caveolae isolation) culture flasks (Falcon).

Cell fractioning

Preparation of Triton-soluble cell lysate

Triton-soluble cell lysates were prepared from 6 AC cell lines (AG11020, AG09697, AG09603, AG09878, AG04461, AG13300; 72.5 ± 8.8 years, mean ± SD) and 6 AD cell lines (AG05810, AG09908, AG06869, AG06844, AG06264, AG06265; 67 ± 10.1, mean ± SD). All the steps were carried out at 40C. Each flask was washed twice with PBS, then cells  were scraped into 0.8 ml of lysis buffer (10 mM Tris-HCl, 150 mM NaCl, 1 mM EDTA, 1 mM EGTA, 0.5% NP40, 1% Triton X-100, 1% protease inhibitor cocktail, pH 7.4). The 6 flask contents were pooled and the cells were pelleted for 5 min, 1400 g (Sorvall RT7 centrifuge). The cells were resuspended in 0.5 ml of lysis buffer, then, passed through a 261/2 needle 20 times, and sonicated 7 x 15 s on ice with 1 min rest in between times (total power, 50 J/W) with an Ultrasonic Homogenizer (4710 series, Cole-Parmer Instrument Co, IL). The sonicate was centrifuged for 10 min at 8,000 g (Eppendorf 5417R centrifuge). The supernatant was collected and designated as the Triton-soluble cell lysate.

Preparation of membrane fractions

The following buffers were used: buffer 1 (10 mM Tris-HCl, 150 mM NaCl, 1 mM EDTA, 1 mM EGTA, 1% protease inhibitor cocktail), buffer 2 (10 mM Tris HCl, 150 mM NaCl, 1 mM EDTA, 1mM EGTA, 0.5% NP40, 1% Triton X-100, 1% protease inhibitor cocktail, pH 7.4). To prepare AC and AD membrane fractions we used 6 AC cell lines: AG04461, AG11020, AG09697, AG11011, AG09603, AG09158 (68.8 ± 9.2 years old, mean ± SD); and 6 AD cell lines: AG06263, AG04400, AG06844, AG06265, AG06869, AG06205 (62.5 ± 3.6 years old, mean ± SD). A membrane fraction was prepared for each cell line. All steps were carried out at 40C. Each flask was washed twice with PBS, then scraped into 0.8 ml of buffer 1. The suspension was sonicated 3 x 10 s on ice with 1 min rest in between times (total power, 50 J/W) with an Ultrasonic Homogenizer (4710 series, Cole-Parmer Instrument Co, IL). An aliquot of the sonicate was saved and designed as the whole cell fraction. The remaining sonicate was centrifuged for 1 h at 100,000 g (Beckman TL-100 ultracentrifuge). The pellet was resuspended in 100 ml of buffer 2; then, the same centrifugation was repeated. The supernatant was collected and designated as the membrane fraction (plasma and intracellular membranes).

Membrane fractions were also prepared from another set of the same cell lines previously incubated for 1 h with polyclonal anti-PrP Ab-1 (Oncogene Research Products, Cambridge, MA), and diluted in DMEM (1/10,000).

Caveolae isolation

The following buffers were used to prepare caveolae-enriched fractions: buffer A (0.25 M sucrose, 20 mM Tricine, 1 mM EDTA,  pH 7.8), buffer B (0.25 M sucrose, 120 mM Tricine, 6 mM EDTA,  pH 7.8), buffer C (50% OptiPrep in buffer B).

AC and AD caveolae-enriched fractions were purified at 40C as previously described [25] with slight modifications. A plasma membrane fraction was prepared from 10 T-75 flasks of confluent AC or AD fibroblasts (AD cell lines: AG06265, AG06264, AG06844, AG09908, AG06869, 64.6 ± 9.2 years, mean ± SD; age-matched AC cell lines: AG11020, AG07310, AG09697, AG04461, AG13300, AG09878 69 ± 9.0 years, mean ± SD), and each cell line was grown in a separate flask. Each flask was washed twice with 5 ml of buffer A and then the cells were scraped into 3 ml of buffer A. The 10 AC (or AD) flask volumes were combined to pellet the cells by centrifugation for 5 min, 1400 g (Sorvall RT7 centrifuge). Cells were resuspended in 1 ml of buffer A, homogenized in a 2 ml tissue grinder (20 stokes), then passed through a 261/2 needle 20 times. The suspension was transferred to a 1.5 ml Eppendorf tube and centrifuge for 10 min, 1000 g (Eppendorf 5417R centrifuge). The postnuclear supernatant fraction (PNS) was saved on ice, the pellet was resuspended in 1 ml of buffer A, then centrifuged again for 10 min at 1000 g. Both of the PNSs were combined and layered on the top of 23 ml of 30% Percoll in buffer A, and centrifuged for 30 min at 84,000 g (Beckman L8-55 ultracentrifuge, 70 Ti rotor, Beckman 355631 polycarbonate centrifuge tube). The plasma membrane fraction (PMF), a visible band at about 5 cm from the bottom of the tube, was collected and its volume was adjusted to 4 ml, before being sonicated with an Ultrasonic Homogenizer (4710 series, Cole-Parmer Instrument Co, IL). The PMF was sonicated 7 x 15 s on ice with 1 min rest in between times (total power, 50 J/W). The sonicate was mixed and homogenized with 3.68 ml of buffer C and 0.32 ml of buffer A in a Beckman 355631 polycarbonate centrifuge tube. A 20% to 10% linear OptiPrep gradient (12 ml, prepared by diluting buffer C with buffer A) was poured on the top of the sample, then centrifuged for 90 min at 52,000 g (Beckman L8-55 ultracentrifuge, SW28 swinging out bucket rotor). The top 10 ml of the gradient was collected and mixed with 8 ml of buffer C, then transferred to a Beckman 355631 polycarbonate centrifuge tube. The sample was overlaid with 4 ml of 5% OptiPrep (prepared by diluting buffer C with buffer A), and centrifuged for 90 min at 52,000 g (Beckman L8-55 ultracentrifuge, SW28 swinging out bucket rotor). The caveolae-enriched fraction was a visible opaque band present in the 5% OptiPrep overlay about 1 cm under the surface.

Gel electrophoresis and immunoblots

The level of caveolin was quantified in each cell fraction by immunoblotting. All experiments were triplicated. Initially, the same amount of proteins from each sample was boiled for 10 min with an equal volume of 2X SDS sample buffer. The samples were loaded on a SDS polyacrylamide gel to separate the proteins, before transferring them to a nitrocellulose membrane. The samples were immunoblotted with anti-caveolin (BD Biosciences - Transduction Laboratories, Lexington, KY) at 40C overnight. After several washes, the membranes were incubated with peroxidase-conjugated anti-rabbit IgG (Jackson ImmunoResearch Laboratories, Inc., West Grove, PA) at room temperature for 1 h. Then, the signal was detected by ECL TM Western blotting detection reagents (Amersham Pharmacia Biotech Inc., NJ), and exposed to a Kodak Biomax MR Film (Eastman Kodak Company, Rochester, NY). Immunoblots were quantified by measuring the optical density with an appropriate software (UN-SCAN-IT, Silk Scientific Corporation).

Immunoprecipitation of phospho-caveolin

The level of caveolin phosphorylation was compared in AC and AD whole cell fractions, prepared from 5 AC (AG04461, AG11020, AG09697, AG11011, AG09603, 70.8 ± 8.7 years, mean ± SD) and 6 AD (AG06263, AG04400, AG06844, AG06265, AG06869, 61.6 ± 3.1 years, mean ± SD) cell lines, according to the protocol decribed above. Whole cell fractions were incubated with end-to-end rocking (40C, overnight) with anti-phosphotyrosine antibodies (PY-20, Transduction Laboratories, Lexington, KY) in a buffer containing 50 mM Tris (pH 7.5), 150 mM NaCl, 1% protease inhibitor mixture (Sigma, St. Louis, MO), and 1% phosphatase inhibitor mixture (Sigma, St. Louis, MO). Protein A and G (1/3 ratio respectively) agarose beads were added to the mixture, and rocked at 40C for 2 hours. After the wash, the precipitated proteins were separated by SDS-PAGE, and caveolin was detected in each sample with immunoblotting assays. Sample proteins were quantified to normalize the immunoblot optical density values.

Immunocytochemistry

AC (AG09697, AG09603, AG11020) and AD (AG06844, AG06869, AG06265) fibroblasts were grown on glass coverslips to reach confluence. Cells were washed twice in pre-chilled PBS, and fixed for 30 min at room temperature with 4% formaldehyde (wt/vol) in PBS. After fixation, cells were washed 3 times with PBS at room temperature for 10 min, then permeabilized with 0.1% Triton X-100, 10% normal horse serum, made in PBS, at room temperature for 30 min. Cells were washed in PBS, incubated for 2 h at room temperature with anti-caveolin (BD Biosciences - Transduction Laboratories, Lexington, KY) diluted 1/500 in PBS, and washed again before the incubation with fluorescein anti-rabbit IgG diluted in PBS 1/400 (1.25 mg/ml) for 1 h at room temperature in the dark. Finally, cells were washed and coverslips were mounted with a drop of Vectashield mounting medium, and observed using a Nikon Eclipse E800 microscope (FITC filter).  Immunofluorescence measurements was also carried out on the same cell lines previously incubated for 1 h with polyclonal anti-PrP Ab-1, prepared in DMEM (1/10,000).

Protein and cholesterol assays

Protein concentrations were determined by the Micro BCATM Protein Assay Reagent Kit (Pierce, Rockford, IL). Cholesterol concentrations were quantified by the Amplex® Red Cholesterol Assay Kit (Molecular Probes, Eugene, OR). All assays were duplicated.

RESULTS 

Triton-soluble cell lysate and whole cell fractions

The amount of caveolin detected in Triton-soluble cell lysate was 72% lower in AD than AC (6 pooled cell lines, experiment triplicated, p<0.01) (Figure 1a). Two bands were detected around 22 Kd, corresponding to previously described a (slowest band) and b (fastest band) isoforms of caveolin [26]. In the same preparation, the amount of cholesterol was 22% lower in AD than AC (6 pooled cell lines, experiment triplicated, p<0.05) (Figure 1b). Moreover, in a preliminary study of the cholesterol detected in AC cell lysate, we measured that 77% was esterified, and 23% was free cholesterol. In AD, we found 34% esterified and 66% free cholesterol.

The amount of caveolin was the same in AC and AD whole cell fractions, and no difference was found in caveolin phosphorylation (data not shown).
 
Figure 1

Expression of caveolin (a) and cholesterol concentration (b) in Alzheimer’s and control fibroblast Triton-soluble lysate


Figure 1 shows the xpression of caveolin (a) and cholesterol concentration (b) in Alzheimer’s and control fibroblasts' Triton-soluble lysate
Note: you may need to resize your browser window for better scheme view

Six Alzheimer’s or 6 control cell lines were pooled to prepare the lysates as described in Materials and Methods. a) 2 mg of total proteins were separated on SDS polyacrylamide gel, then transferred to a nitrocellulose membrane. The samples were immunoblotted with anti-caveolin, then with peroxidase-conjugated anti-rabbit IgG. The signal was detected by chemiluminescence and exposition to a film. Immunoblots were quantified by measuring the mean optical density on the film; the experiment was triplicated (* p<0.01). b) cholesterol concentrations were measured in 15 mg of total proteins by using a fluorometric method; the experiment was duplicated (* p<0.05).

Membrane fractions

Only the a-caveolin isoform was detected in the plasma membrane fractions. The level of caveolin was 74% lower in AD than in the AC plasma membrane fractions (Figure 2).
 
Figure 2

Expression of caveolin in Alzheimer’s and control fibroblast plasma membrane fractions

Figure 2 shows the expression of caveolin in Alzheimer’s and control fibroblast plasma membrane
Note: you may need to resize your browser window for better scheme view

Six Alzheimer’s or 6 control cell lines were pooled to prepare the plasma membrane fractions as described in Materials and Methods. 0.2 mg of total proteins were separated on SDS polyacrylamide gel, then transferred to a nitrocellulose membrane. The samples were immunoblotted with anti-caveolin, then with peroxidase- conjugated anti-rabbit IgG. The signal was detected by chemiluminescence and exposition to a film. Immunoblots were quantified by measuring the mean optical density on the film; the experiment was triplicated (* p<0.001).

Caveolae fraction

In accordance with the findings of Smart and colleagues [25], we found that caveolin was enriched in fraction 3 of the final Optiprep gradient. This fraction was called the caveolae fraction. Only the a-caveolin isoform was detected in this fraction. In this preparation, the caveolin concentration was 3 times higher in AD than AC (Figure 3a). The cholesterol concentration was also higher (+41%) in the AD caveolae fraction than in AC (Figure 3b).
 
Figure 3

Expression of caveolin (a) and cholesterol concentration (b) in Alzheimer’s and control fibroblast caveolae fractions

Figure 3 shows the expression of caveolin (a) and cholesterol concentration (b) in Alzheimer’s and control fibroblast caveolae fractions
Note: you may need to resize your browser window for better scheme view

Five Alzheimer’s or 6 control cell lines were pooled to prepare the caveolae fractions as described in Materials and Methods. a) 0.2 mg of total proteins were separated on SDS polyacrylamide gel electrophoresis, then transferred to a nitrocellulose membrane. The samples were immunoblotted with anti-caveolin, then with peroxidase-conjugated anti-rabbit IgG. The signal was detected by chemiluminescence and exposition to a film. Immunoblots were quantified by measuring the mean optical density on the film; the experiment was triplicated (* p<0.01). b) cholesterol concentrations were measured in 4 mg of total proteins by using a fluorometric method; the experiment was duplicated (* p<0.05).

Cross-linking with anti-PrP

Incubation of AC fibroblasts with a polyclonal anti-PrP increased the amount of caveolin found in the membrane fraction (n=6, p<0.05), (Figures 4a, 4b). The same incubation did not induce any increase of caveolin expression in AD fibroblast membranes (Figures 4a, 4b).
 
 
Figure 4

Effect of anti-prion cross-linking on caveolin expression in Alzheimer’s and control fibroblast membrane

Figure 4 shows the effect of anti-prion cross-linking on caveolin expression in Alzheimer’s and control fibroblast membrane
Note: you may need to resize your browser window for better scheme view

Six Alzheimer’s or 6 control cell lines were incubated with anti-prion antibodies for 1 h, then a membrane fraction was prepared from each cell line as described in Materials and Methods. 1 mg of total proteins were separated on SDS polyacrylamide gel, then transferred to a nitrocellulose membrane. The samples were immunoblotted with anti-caveolin, then with peroxidase-conjugated anti-rabbit IgG. The signal was detected by chemiluminescence and exposition to a film. Immunoblots were quantified by measuring the mean optical density on the film (* p<0.05). Figure 4a shows the expression of caveolin in Alzheimer’s and control fibroblast membrane in basal conditions and after incubation with anti-prion (+). Figure 4b shows the distribution of anti-prion cross-linking effect on caveolin level in Alzheimer’s and control fibroblast membrane fractions. Results are expressed in percentage of basal level.

Immunocytochemistry

A qualitative localization of caveolin in fibroblasts was performed with immunofluorescence. In basal conditions, caveolin was mostly scattered through the cells in AC (Figure 5A), whereas it was more specifically located on the plasma membrane in AD fibroblasts (Figure 5C). Caveolin moved to membranes after anti-PrP incubation of AC fibroblasts (Figure 5B). This incubation did not change the pattern of caveolin distribution in AD fibroblasts (Figure 5D).
 
Figure 5

Immunocytochemical localization of caveolin in control (A, B) and Alzheimer’s (C, D) fibroblasts in basal conditions (A, C) and after anti-prion cross-linking (B, D)

Figure 5 shows immunocytochemical localization of caveolin in control (A, B) and Alzheimer’s (C, D) fibroblasts in basal conditions (A, C) and after anti-prion cross-linking (B, D)
Note: you may need to resize your browser window for better scheme view

Immunofluorescence localization of caveolin was performed on 3 Alzheimer’s and 3 control fibroblast cell lines previously incubated for 1 h with anti-prion, or in basal conditions. Panels presented in Figure 5 are representative of the observed patterns (20X magnification).

DISCUSSION 

Alzheimer’s patient fibroblasts

The use of skin fibroblasts is based on the hypothesis that an affliction of the human brain markers and pathological processes of Alzheimer’s disease might also be expressed in peripheral tissues. A number of abnormalities in metabolic and biochemical processes described in AD brains have been found in cultured skin fibroblasts derived from AD patients [27]. Previous data have demonstrated a decrease in PKC activity [28, 29, 30, 31], alterations of calcium metabolism [32, 33, 34], dysfunctions of potassium channels [35] and MAP kinase signaling cascade [36] in AD fibroblasts. Thus, past findings suggest that fibroblasts might be useful to identify and test hypotheses on brain pathological mechanisms leading to Alzheimer’s disease. Peripheral tissues do offer the potential of avoiding variables introduced by differences in the post-mortem state of brain tissues.

Specific pattern of caveolin distribution in AD fibroblasts

We measured the basal expression of caveolin-1 in AC and AD fibroblast cellular fractions. Two bands (around 22 Kd) were detected on western blots by incubating the membranes with rabbit polyclonal anti-caveolin-1 antibodies (C 13630 from Transduction Lab.), except in the plasma membrane and caveolae fractions. These bands correspond to the 2 isoforms of caveolin-1, a slower (a) and faster (b) migrating species [3, 26]. Moreover, Fujimoto et al. (2000, Ref. 3) have reported that C 13630 antibodies react  better with the a than the b isoform. This could explain the weakest signal, or the absence of the caveolin b-isoform detected here. Because both a- and b-caveolin have different roles in caveolae formation, it may be important to measure the isoform specific expression of caveolin in AC and AD cells. However, it has to be pointed out that in normal human skin fibroblasts, the a-isoform seems to be more efficient in and sufficient for forming functional caveolae [3].

Because of their lipid-enriched content, caveolae are insoluble in Triton X-100 at 40C [1, 37, 38]. We used this specific property to compare the expression of caveolin in whole cell preparations with and without caveolae (i.e., Triton-soluble cell lysate). No differences were found between AC and AD whole cell fractions (data not shown). However, in Triton-soluble cell lysate, we found a higher caveolin expression in AC than AD fibroblasts. Moreover, in the plasma membrane fraction, caveolin expression was also higher in AC fibroblasts. This finding tends to argue that in AD, caveolin is mostly segregated to caveolae. Based on these data, we inferred that caveolin might be highly concentrated in caveolae of AD fibroblasts.

To test this possibility, a detergent-free method was used for purifying caveolae [25]. In these conditions, AD caveoale fractions were effectively richer in caveolin than AC. These results suggest an AD-specific distribution among cell compartments of caveolin in fibroblasts. The detection of caveolin in AC and AD fibroblasts by immunocytochemistry is in accordance with these biochemical results. Instead of being widely dispersed through out the internal and plasma membranes as was true for AC fibroblasts, caveolin was preferentially located in aggregates that appeared as dots in AD plasma membranes. Such aggregates may correspond to clustered caveolin in caveolae. Further studies with immunoelectron microscopy will be needed to clarify this issue. Nevertheless, considering that the expression of caveolin-1 led to de novo formation of caveolae [39], a higher concentration of caveolin in a caveolae-enriched fraction could reflect a higher number of caveolae in AD fibroblasts.

The cellular localization of caveolin could depend on its phosphorylation status as previously shown [40, 41]. In the present study, however, we did not find any specific pattern of caveolin phosphorylation in AD. Thus, to understand the specific expression of caveolin in AD fibroblasts, we measured the concentration of cholesterol in Triton-soluble cell lysates and in caveolae fractions. Cholesterol plays an important role in caveolae structure and function [12, 13, 14, 16]. It binds caveolin [19] and regulates its expression [17, 18]. In caveolae fractions, the amount of cholesterol was significantly higher in AD than in AC, consistent with the observed pattern of caveolin distribution. In a preliminary experiment, the level of cholesterol in Triton-soluble cell lysate was lower in AD. Interestingly, we found that instead of 23% in AC fibroblasts, 66% of the total cholesterol was present as free cholesterol (FC) in AD. This observation could be critical for the final caveolin distribution, since the expression of caveolae, caveolin expression, and caveolin mRNA levels, are very sensitive to the FC content of the cell [17, 42], and the newly formed FC is recovered mainly in caveolae [12, 43]. Thus, in AD fibroblasts, an abnormal level of FC, whatever its origin, could be responsible for the high level of caveolin sequestration in caveolae.

Signal transduction in AD fibroblasts

The subcellular distribution of several signaling molecules is restricted and regulated by their association with scaffolding proteins [44] of which caveolin is one [1, 11] (see Ref. 5 for review). Thus, we wondered if the overexpression of caveolin in caveolae fractions could affect cellular signal transduction in AD fibroblasts. Glycosyl-phosphatidylinositol (GPI) –anchored proteins are sequestrated with caveolin in caveolae by antibody cross-linking [45, 46, 47, 48]. Prion protein, which is a GPI-anchored protein,  has been localized in fibroblast caveolae after cross-linking [49]. We therefore tested  the effect of prion cross-linking on caveolin expression in membrane fractions from AC and AD fibroblasts. In five AC fibroblast cell lines (6 tested), the incubation with a rabbit polyclonal anti-prion induced an increase of caveolin expression in membranes; no changes were observed in AD cell lines (6 tested). In AC fibroblasts, the same cross-linking stimulation changed the distribution of caveolin. In brief, prion cross-linking induced a caveolin shift from cytosol to membrane in most of the AC fibroblasts. This membrane localization of caveolin was quite similar to the caveolin localization in unstimulated AD fibroblasts. Such a concentration of caveolin in caveolae fractions might alter signal transduction in AD cells.

Previous studies have, in fact,  shown abnormalities of signal transduction in AD fibroblasts [28, 32, 35, 50, 51, 52]. For instance, AD fibroblasts exhibit an enhanced response (calcium signaling) to bradykinin [33], probably due to an enhanced IP3 production in response to this neuropeptide [53], which is correlated with an up-regulation of bradykinin receptors [53]. Bradykinin receptors are G protein-coupled receptors, sequestered in caveolae after agonist-stimulation [54, 55]. Furthermore, the cellular bradykinin-stimulated calcium waves preferentially originate from caveolin-rich locations [56]. Considering these published data and the results presented in this study, the high expression of caveolin in AD caveolae fraction could participate in the enhancement of bradykinin-stimulated calcium response by facilitating the recruitment of bradykinin receptors.

Cholesterol metabolism and Alzheimer’s disease

It is now well accepted that cholesterol may play a crucial role in pathological processes of Alzheimer’s disease [23ED+, also see Related Articles]. Epidemiological studies showed that treatment with statins, cholesterol-lowering drugs initially prescribed for hypercholesterolemia, decreased the risk of developing Alzheimer’s disease [57ED+, 58ED+]. In lab animals, a cholesterol-enriched diet induced amyloid burden in the brain [59ED+]. APP, the amyloid precursor protein, can be processed either by a-secretase, and produce a non-amyloid Ab sequence, or, by b- and g-secretase, generating the Ab amyloid peptide. The competition between these two alternative pathways is therefore crucial to the etiology of Alzheimer’s disease. It has been suggested that at the cellular level, high cholesterol concentration could switch the secretase activities from the non-amyloidogenic to the amyloidogenic pathway. Cholesterol decreases the activity of the non-amyloidogenic a-secretase [60], whereas it increases the activity of the amyloidogenic b-secretase [22ED+]. Although an alteration of APP glycosylation [61], or a direct binding on a-secretase [22ED+] by the cholesterol were proposed, no clear mechanism can yet explain the modulation of APP metabolism by cholesterol.

Here, we suggest an alternative hypothesis to understand the role of cholesterol in Alzheimer’s disease (Scheme 1), in which caveolin would play a pivotal role. Caveolin upregulation activates b-secretase-mediated cleavage of APP in AD astrocytes [10]. We suggest that the accumulation of (free?) cholesterol would induce an overexpression of caveolin in caveolae compartments. It was demonstrated that caveolin binds PKC [62], which is located in caveolae [63, 64, 65], and inhibits its activity [62, 66]. PKC activity has been reported to be weaker in AD cells [31]. An important role of a-secretase pathway activation has been attributed to PKC [67, 68]. In our hypothesis, the overexpression of caveolin would dramatically inhibit PKC. Such a process would result in an “underactivation” of a-secretase, and a consequent, progressive switch to the amyloidogenic pathways in Alzheimer’s disease. PKC has been involved in memory processes [69], and the initial inhibition of PKC proposed in our  model could contribute to memory alteration which is shown in the early stages of Alzheimer’s disease; this model would also explain the progressive formation of amyloid plaques. Further investigations are planned to test this hypothesis.
 
Scheme 1

Hypothesis including a critical role for caveolin in regulating APP metabolism in Alzheimer’s disease


Scheme 1 illustrates the authors' hypothesis on a critical role for caveolin in regulating APP metabolism in Alzheimer's disease
Note: you may need to resize your browser window for better scheme view

The overexpression of caveolin would dramatically inhibit PKC, a well-known mechanism. Such a process would result in an "underactivation" of alpha-secretase pathway, and a consequent switch to the amyloidogenic pathways in a progressive process, as in Alzheimer’s disease. PKC has been involved in memory processes, and the initial inhibition of PKC proposed in our model could contribute to memory alteration which is shown in the early stage of Alzheimer's disease; this model would also explain the progressive formation of amyloid plaques.

CONCLUSION 

In conclusion, we found a caveolin enrichment in AD fibroblasts caveolae fraction. We suggest that this specificity could come from an alteration of cholesterol metabolism, and caveolin itself could play a pivotal role in the pathological process of Alzheimer’s disease.

WEB ENHANCED REFERENCES 

Please note:
All links below provide free access to citations. ED+ citations/notes were compiled by Alexei Koudinov

1. Anderson RG. The caveolae membrane system. Annu Rev Biochem. 67, 199-225 (1998) [ PubMed ][ Back2Text ].

2. Couet J, Belanger MM, Roussel E, Drolet MC. Cell biology of caveolae and caveolin. Adv Drug Deliv Rev. 49, 223-35 (2001) [ PubMed ][ Back2Text ].

3. Fujimoto T, Kogo H, Nomura R, Une T. Isoforms of caveolin-1 and caveolar structure. J Cell Sci. 113, 3509-17 (2000) [ PubMed ][ Back2Text ].

4. Scherer PE, Okamoto T, Chun M, Nishimoto I, Lodish HF, Lisanti MP. Identification, sequence, and expression of caveolin-2 defines a caveolin gene family. Proc Natl Acad Sci USA.93, 131-5 (1996) [ PubMed ][ Back2Text ].

5. Okamoto T, Schlegel A, Scherer PE, Lisanti MP. Caveolins, a family of scaffolding proteins for organizing "preassembled signaling complexes" at the plasma membrane. J Biol Chem. 273, 5419-22 (1998) [ PubMed ][ Back2Text ].

6. Tang Z, Scherer PE, Okamoto T, et al. Molecular cloning of caveolin-3, a novel member of the caveolin gene family expressed predominantly in muscle. J Biol Chem. 271, 2255-61 (1996) [ PubMed ][ Back2Text ].

7. Scherer PE, Lewis RY, Volonte D, et al. Cell-type and tissue-specific expression of caveolin-2. Caveolins 1 and 2 co-localize and form a stable hetero-oligomeric complex in vivo. J Biol Chem. 272, 29337-46 (1997) [ PubMed ][ Back2Text ].

8. Song KS, Scherer PE, Tang Z, et al. Expression of caveolin-3 in skeletal, cardiac, and smooth muscle cells. Caveolin-3 is a component of the sarcolemma and co-fractionates with dystrophin and dystrophin-associated glycoproteins. J Biol Chem. 271, 15160-5 (1996) [ PubMed ][ Back2Text ].

9. Ikezu T, Ueda H, Trapp BD, et al. Affinity-purification and characterization of caveolins from the brain: differential expression of caveolin-1, -2, and -3 in brain endothelial and astroglial cell types. Brain Res. 804, 177-92 (1998) [ PubMed ][ Back2Text ].

10. Nishiyama K, Trapp BD, Ikezu T, et al. Caveolin-3 upregulation activates beta-secretase-mediated cleavage of the amyloid precursor protein in Alzheimer's disease. J Neurosci. 19, 6538-48 (1999) [ PubMed ][ Back2Text ].

11. Couet J, Li S, Okamoto T, Ikezu T, Lisanti MP. Identification of peptide and protein ligands for the caveolin-scaffolding domain. Implications for the interaction of caveolin with caveolae-associated proteins. J Biol Chem. 272, 6525-33 (1997) [ PubMed ][ Back2Text ].

12. Smart EJ, Ying Y, Donzell WC, Anderson RG. A role for caveolin in transport of cholesterol from endoplasmic reticulum to plasma membrane. J Biol Chem. 271, 29427-35 (1996) [ PubMed ][ Back2Text ].

13. Anderson RG, Kamen BA, Rothberg KG, Lacey SW. Potocytosis: sequestration and transport of small molecules by caveolae. Science. 255, 410-1 (1992) [ PubMed ][ Back2Text ].

14. Anderson RG. Caveolae: where incoming and outgoing messengers meet. Proc Natl Acad Sci USA.90, 10909-13 (1993) [ PubMed ][ Back2Text ].

15. Chang WJ, Rothberg KG, Kamen BA, Anderson RG. Lowering the cholesterol content of MA104 cells inhibits receptor-mediated transport of folate. J Cell Biol. 118, 63-9 (1992) [ PubMed ][ Back2Text ].

16. Fielding CJ, Fielding PE. Caveolae and intracellular  trafficking of cholesterol. Adv Drug Deliv Rev. 49, 251-64 (2001) [ PubMed ][ Back2Text ].

17. Fielding CJ, Bist A, Fielding PE. Caveolin mRNA levels are up-regulated by free cholesterol and down-regulated by oxysterols in fibroblast monolayers. Proc Natl Acad Sci USA.94, 3753-8  (1997) [ PubMed ][ Back2Text ].

18. Bist A, Fielding PE, Fielding CJ. Two sterol regulatory element-like sequences mediate up-regulation of caveolin gene transcription in response to low density lipoprotein free cholesterol. Proc Natl Acad Sci USA. 94, 10693-8 (1997) [ PubMed ][ Back2Text ].

19. Murata M, Peranen J, Schreiner R, Wieland F, Kurzchalia TV, Simons K. VIP21/caveolin is a cholesterol-binding protein. Proc Natl Acad Sci USA. 92, 10339-43 (1995) [ PubMed ][ Back2Text ].

20. Kivipelto M, Helkala EL, Laakso MP,  et al. Apolipoprotein E epsilon4 allele, elevated midlife total cholesterol level, and high midlife systolic blood pressure are independent risk factors for late-life Alzheimer disease. Ann Intern Med. 137, 149-55 (2002) [ PubMed ][ Back2Text ].

21. Kivipelto M, Laakso MP, Tuomilehto J, Nissinen A, Soininen H. Hypertension and hypercholesterolaemia as risk factors for Alzheimer's disease: potential for pharmacological intervention. CNS Drugs. 16, 435-44 (2002) [ PubMed ][ Back2Text ].

22. Yao ZX, Papadopoulos V. Function of beta-amyloid in cholesterol transport: a lead to neurotoxicity. FASEB J. 16, 1677-9 (2002)  [ PubMed ]. The following ED+ citations alert readers about earlier contributions on the subject of the Ref. 22:  Walters CE, Austen BM. Intracellular cholesterol and b-amyloid as factors in Alzheimer’s disease. Neurobiol Aging. 19, 49S (1998); Koudinova NV, Koudinov AR, Yavin E. Alzheimer’s Ab1-40 peptide modulates lipid synthesis in neuronal cultures and intact rat fetal brain under normoxic and oxidative stress conditions. Neurochem Res.25, 653-60 (2000) [ PubMed ]; Chochina SV, Avdulov NA, Igbavboa U, Cleary JP, O'Hare EO, Wood WG. Amyloid beta-peptide(1-40) increases neuronal membrane fluidity. Role of cholesterol and brain region. J Lipid Res. 42, 1292-7 (2001) [ PubMed ]; Muller WE, Kirsch C, Eckert GP. Membrane-disordering effects of beta-amyloid peptides. Biochem Soc Trans. 29, 617-23 (2001) [ PubMed ]; Koudinov AR, Koudinova NV. Essential role for cholesterol in synaptic plasticity and neuronal degeneration. FASEB J. 15, 1858-60 (2001). Originally published online June 27, 2001, 10.1096/ fj.00-0815fje [ PubMed ][ FullText ][ Correspondence ][ Back2Text ].

23. Hartmann T. Cholesterol, Abeta and Alzheimer's disease. Trends Neurosci. 24, S45-8  (2001) [ PubMed ][ Back2Text ]; ED+ citation: Hartmann T, organizer. Live discussion "Cholesterol and Alzheimer's disease". AlzForum web site. (19 Nov 2002) [ Transcipt ][ Background text ].

24. Sparks DL, Martin TA, Gross DR, Hunsaker JC, III. Link between heart disease, cholesterol, and Alzheimer's disease: a review. Microsc Res Tech. 50, 287-90 (2000) [ PubMed ][ Back2Text ].

25. Smart EJ, Ying YS, Mineo C, Anderson RG. A detergent-free method for purifying caveolae membrane from tissue culture cells. Proc Natl Acad Sci USA. 92, 10104-8 (1995) [ PubMed ][ Back2Text ].

26. Scherer PE, Tang Z, Chun M, Sargiacomo M, Lodish HF, Lisanti MP. Caveolin isoforms differ in their N-terminal protein sequence and subcellular distribution. Identification and epitope mapping of an isoform-specific monoclonal antibody probe. J Biol Chem. 270, 16395-401 (1995) [ PubMed ][ Back2Text ].

27. Govoni S, Gasparini L, Racchi M, Trabucchi M. Peripheral cells as an investigational tool for Alzheimer's disease. Life Sci. 59, 461-8 (1996) [ PubMed ][ Back2Text ].

28. Etcheberrigaray R, Ibarreta D. Ionic channels and second messenger alterations in Alzheimer's disease. Relevance of studies in nonneuronal cells. Rev Neurol.33, 740-9 (2001) [ PubMed ][ Back2Text ].

29. Van Huynh T, Cole G, Katzman R, Huang KP, Saitoh T. Reduced protein kinase C immunoreactivity and altered protein phosphorylation in Alzheimer's disease fibroblasts. Arch Neurol. 46, 1195-9 (1989) [ PubMed ][ Back2Text ].

30. Govoni S, Racchi M, Bergamaschi S, et al. Defective protein kinase C alpha leads to impaired secretion of soluble beta-amyloid precursor protein from Alzheimer's disease fibroblasts. Ann N Y Acad Sci. 777, 332-7 (1996) [ PubMed ][ Back2Text ].

31. Bruel A, Cherqui G, Columelli S, et al. Reduced protein kinase C activity in sporadic Alzheimer's disease fibroblasts. Neurosci Lett. 133, 89-92 (1991) [ PubMed ][ Back2Text ].

32. Hirashima N, Etcheberrigaray R, Bergamaschi S, et al. Calcium responses in human fibroblasts: a diagnostic molecular profile for Alzheimer's disease. Neurobiol Aging. 17, 549-55 (1996) [ PubMed ][ Back2Text ].

33. Ito E, Oka K, Etcheberrigaray R, et al. Internal Ca2+ mobilization is altered in fibroblasts from patients with Alzheimer disease. Proc Natl Acad Sci USA. 91, 534-8 (1994) [ PubMed ][ Back2Text ].

34. Palotas A, Kalman J, Laskay G, Juhasz A, Janka Z, Penke B. Comparative studies on [Ca2+]i-level of fibroblasts from Alzheimer patients and control individuals. Neurochem Res. 26, 817-20 (2001) [ PubMed ][ Back2Text ].

35. Etcheberrigaray R, Ito E, Oka K, Tofel-Grehl B, Gibson GE, Alkon DL. Potassium channel dysfunction in fibroblasts identifies patients with Alzheimer disease. Proc Natl Acad Sci USA. 90, 8209-13 (1993) [ PubMed ][ Back2Text ].

36. Zhao WQ, Ravindranath L, Mohamed AS, et al. MAP kinase signaling cascade dysfunction specific to Alzheimer's disease in fibroblasts. Neurobiol Dis. 11, 166-83 (2002) [ PubMed ][ Back2Text ].

37. Brown DA, London E. Functions of lipid rafts in biological membranes. Annu Rev Cell Dev Biol.14, 111-36 (1998) [ PubMed ][ Back2Text ].

38. Moldovan NI, Heltianu C, Simionescu N, Simionescu M. Ultrastructural evidence of differential solubility in Triton X-100 of endothelial vesicles and plasma membrane. Exp Cell Res. 219, 309-13 (1995) [ PubMed ][ Back2Text ].

39. Fra AM, Williamson E, Simons K, Parton RG. De novo formation of caveolae in lymphocytes by expression of VIP21-caveolin. Proc Natl Acad Sci USA.92, 8655-9 (1995) [ PubMed ][ Back2Text ].

40. Nomura R, Fujimoto T. Tyrosine-phosphorylated caveolin-1: immunolocalization and molecular characterization. Mol Biol Cell. 10, 975-86 (1999) [ PubMed ][ Back2Text ].

41. Aoki T, Nomura R, Fujimoto T. Tyrosine phosphorylation of caveolin-1 in the endothelium. Exp Cell Res. 253, 629-36 (1999) [ PubMed ][ Back2Text ].

42. Fielding CJ, Fielding PE. Cholesterol and caveolae: structural and functional relationships. Biochim Biophys Acta. 1529, 210-22 (2000) [ PubMed ][ Back2Text ].

43. Fielding PE, Fielding CJ. Plasma membrane caveolae mediate the efflux of cellular free cholesterol. Biochemistry.34, 14288-92 (1995) [ PubMed ][ Back2Text ].

44. Faux MC, Scott JD. Molecular glue: kinase anchoring and scaffold proteins. Cell. 85, 9-12 (1996) [ PubMed ][ Back2Text ].

45. Mayor S, Rothberg KG, Maxfield FR. Sequestration of GPI-anchored proteins in caveolae triggered by cross-linking. Science.264, 1948-51 (1994) [ PubMed ][ Back2Text ].

46. Sargiacomo M, Sudol M, Tang Z, Lisanti MP. Signal transducing molecules and glycosyl-phosphatidylinositol-linked proteins form a caveolin-rich insoluble complex in MDCK cells. J Cell Biol. 122, 789-807 (1993) [ PubMed ][ Back2Text ].

47. Harder T, Scheiffele P, Verkade P, Simons K. Lipid domain structure of the plasma membrane revealed by patching of membrane components. J Cell Biol. 141, 929-42 (1998) [ PubMed ][ Back2Text ].

48. Verkade P, Harder T, Lafont F, Simons K. Induction of caveolae in the apical plasma membrane of Madin-Darby canine kidney cells. J Cell Biol. 148, 727-39 (2000) [ PubMed ][ Back2Text ].

49. Ying YS, Anderson RG, Rothberg KG. Each caveola contains multiple glycosyl-phosphatidylinositol-anchored membrane proteins. Cold Spring Harb Symp Quant Biol. 57, 593-604 (1992) [ PubMed ][ Back2Text ].

50. Gibson G, Martins R, Blass J, Gandy S. Altered oxidation and signal transduction systems in fibroblasts from Alzheimer patients. Life Sci. 59, 477-89 (1996) [ PubMed ][ Back2Text ].

51. Etcheberrigaray R, Ito E, Kim CS, Alkon DL. Soluble beta-amyloid induction of Alzheimer's phenotype for human fibroblast K+ channels. Science. 264, 276-9 (1994) [ PubMed ][ Back2Text ].

52. Etcheberrigaray R, Payne JL, Alkon DL. Soluble beta-amyloid induces Alzheimer's disease features in human fibroblasts and in neuronal tissues. Life Sci. 59, 491-8 (1996) [ PubMed ][ Back2Text ].

53. Huang HM, Lin TA, Sun GY, Gibson GE. Increased inositol 1,4,5-trisphosphate accumulation correlates with an up-regulation of bradykinin receptors in Alzheimer's disease. J Neurochem. 64, 761-6 (1995) [ PubMed ][ Back2Text ].

54. Haasemann M, Cartaud J, Muller-Esterl W, Dunia I. Agonist-induced redistribution of bradykinin B2 receptor in caveolae. J Cell Sci. 111, 917-28 (1998) [ PubMed ][ Back2Text ].

55. de Weerd WF, Leeb-Lundberg LM. Bradykinin sequesters B2 bradykinin receptors and the receptor-coupled Galpha subunits Galphaq and Galphai in caveolae in DDT1 MF-2 smooth muscle cells. J Biol Chem. 272, 17858-66 (1997) [ PubMed ][ Back2Text ].

56. Isshiki M, Ando J, Korenaga R, et al. Endothelial Ca2+ waves preferentially originate at specific loci in caveolin-rich cell edges. Proc Natl Acad Sci USA. 95, 5009-14 (1998) [ PubMed ][ Back2Text ].

57. Wolozin B, Kellman W, Ruosseau P, Celesia GG, Siegel G. Decreased prevalence of Alzheimer disease associated with 3-hydroxy-3-methyglutaryl coenzyme A reductase inhibitors. Arch Neurol. 57, 1439-43 (2000) [ PubMed ][ Back2Text ]; ED+ note: Beware  of five correspondence items links at PubMed record . Also see Related articles collection below.

58. Jick H, Zornberg GL, Jick SS, Seshadri S, Drachman DA. Statins and the risk of dementia. Lancet. 356, 1627-31 (2000) [ PubMed ][ FullText ]; ED+ notes: Erratum in: Lancet. 357, 562 (2001) [ FullText ]; Seven correspondence items by: Birkenhager WH, Wang Ji-G, Staessen JA ; Cheung BMY , Kumana CR ; Blauw GJ, Shepherd J, Murphy MB for the PROSPER study group ; Kast RE ; Lowe G, Rumley A, Packard C, Shepherd J ; Ebrahim S, Shlomo YB, Smith GD, Whincup P, Emberson J. Dementia and statins. Lancet. 357, 880 (2001) [ FullText ][ Back2Text ] (Please note: Free access to FullText links at Lancet website requires free registration at The Lancet); Koudinov AR, Koudinova NV. Dementia, cholesterol and the soft science of dietary fat. BMJ (25 July 2001) [ FullText ].

59. Sparks DL, Scheff SW, Hunsaker JC, III, Liu H, Landers T, Gross DR. Induction of Alzheimer-like beta-amyloid immunoreactivity in the brains of rabbits with dietary cholesterol. Exp Neurol. 126, 88-94 (1994) [ PubMed ]; ED+ citations: Refolo LM, Pappolla MA, Malester B, et al. Hypercholesterolemia accelerates the Alzheimer’s amyloid pathology in a transgenic mouse model. Neurobiol Dis. 7, 321-31 (2000) [ PubMed ]; Koudinov AR, Koudinova NV. Modulation of cholesterol metabolism initiates Alzheimer’s amyloid deposition and neuronal dysfunction. Soc Neurosci Abstr. 26, 497 (2000) [ Abstract ][ FullText ]; Kuo Y, Wu C, Lin C, Kuo C, Chen S, Chen H. Brain region-dependent increases in b-amyloid and apolipoprotein E levels in hypercholesterolemic rabbits. Soc Neurosci Abstr. Session No.883.9 (2002) [ Abstract ][ Back2Text ].

60. Bodovitz S, Klein WL. Cholesterol modulates alpha-secretase cleavage of amyloid precursor protein. J Biol Chem. 271, 4436-40 (1996) [ PubMed ][ Back2Text ].

61. Galbete JL, Martin TR, Peressini E, Modena P, Bianchi R, Forloni G. Cholesterol decreases secretion of the secreted form of amyloid precursor protein by interfering with glycosylation in the protein secretory pathway. Biochem J. 348, 307-13 (2000) [ PubMed ][ Back2Text ].

62. Oka N, Yamamoto M, Schwencke C, et al. Caveolin interaction with protein kinase C. Isoenzyme-dependent regulation of kinase activity by the caveolin scaffolding domain peptide. J Biol Chem. 272, 33416-21 (1997) [ PubMed ][ Back2Text ].

63. Smart EJ, Ying YS, Anderson RG. Hormonal regulation of caveolae internalization. J Cell Biol.131, 929-38 (1995) [ PubMed ][ Back2Text ].

64. Liu J, Oh P, Horner T, Rogers RA, Schnitzer JE. Organized endothelial cell surface signal transduction in caveolae distinct from glycosylphosphatidylinositol-anchored protein microdomains. J Biol Chem. 272, 7211-22 (1997) [ PubMed ][ Back2Text ].

65. Mineo C, Ying YS, Chapline C, Jaken S, Anderson RG. Targeting of protein kinase Calpha to caveolae. J Cell Biol. 141, 601-10 (1998) [ PubMed ][ Back2Text ].

66. Taggart MJ, Leavis P, Feron O, Morgan KG. Inhibition of PKCalpha and rhoA translocation in differentiated smooth muscle by a caveolin scaffolding domain peptide. Exp Cell Res. 258, 72-81 (2000) [ PubMed ][ Back2Text ].

67. Ibarreta D, Duchen M, Ma D, Qiao L, Kozikowski AP, Etcheberrigaray R. Benzolactam (BL) enhances sAPP secretion in fibroblasts and in PC12 cells. Neuroreport. 10, 1035-40 (1999) [ PubMed ][ Back2Text ].

68. McLaughlin M, Breen KC. Protein kinase C activation potentiates the rapid secretion of the amyloid precursor protein from rat cortical synaptosomes. J Neurochem. 72, 273-81 (1999) [ PubMed ][ Back2Text ].

69. Nogues X. Protein kinase C, learning and memory: a circular determinism between physiology and behaviour. Prog Neuropsychopharmacol Biol Psychiatry. 21, 507-29  (1997) [ PubMed ][ Back2Text ].
 
RELATED ARTICLES 
Please note: all links below provide no registration free access to articles

At Neurobiology of Lipids:

Simmonds MA. The emerging neurobiology of cholesterol. Neurobiol Lipids 1, 1 (2002) Available at: http://neurobiologyoflipids.org/content/1/1/

Wood GW, et al. Cholesterol and Alzheimer's disease. Neurobiol Lipids 1, 4 (2002) Available at: http://neurobiologyoflipids.org/content/1/4/

Koudinova NV, et al. Amyloid beta, neural lipids, cholesterol and Alzheimer’s disease. Neurobiol Lipids. 1, 6 (2003) Available at: http://neurobiologyoflipids.org/content/1/6/

Noteworthy articles on neurobiology of lipids. Neurobiol Lipids. [Noteworthy page].

At PubMed:

PubMed search for 'caveolae and Alzheimer's disease' [Search result].

CLICK HERE OR PRESS <CTRL><D> TO BOOKMARK THIS ARTICLE  
This article should be cited in the following way

Dufour F et al. Abnormal cholesterol processing in Alzheimer’s disease patient’s fibroblasts. Neurobiol. Lipids  Vol.1, 7 (2003), Published online March 14, 2003, Available at: http://neurobiologyoflipids.org/content/1/7/
( Provide web address when citing this paper )
Please note: Because Neurobiology of Lipids is published online only, the articles should be cited with an article number rather than with traditional (printed) page numbers. Acrobat (.PDF) reprints of NoL article, however,  serve the algorithmic needs of tenure committees to count published print pages.


 
CACorresponding author: Franck Dufour, Ph.D., Blanchette Rockefeller Neurosciences Institute, 9601 Medical Center Drive, Rockville, MD 20850, USA ;  tel: (301) 294-7177, fax: (301) 294-7007 ; e-mail: fdufour@brni-jhu.org ; URL: http://www.brni.org

#Footnote: Prior to the 32nd Society for Neuroscience Meeting (Orlando, Nov. 2-7, 2002) Neurobiology of Lipids published the editorial (2002, Vol.1, 5) that compiled the abstracts on the subject of the journal scope. Neurobiology of Lipids editors were invited to select the most noteworthy abstracts from the list of more then two hundered presentations. The short list yielded eighteen presentations. The authors of these presentations were invited to publish in NoL proceedings articles matching the content of the SFN 2002 presentations. This article represents the only editors' platinum choice presentation. The acceptance date represents the day of the article appearence at the 32nd SFN Annual Meeting in Orlando, Florida, Nov 2-7, 2002.

To review other neurobiology of lipids SFN Annual Meeting abstracts 2002 and the editors' choice shortlist please click here.


 
This article has been cited by other articles:



Neurobiology of Aging
Gaudreault SB, Dea D, Poirier J.
Cholesterol, synaptic function and Alzheimer's disease.
Neurobiol Aging 25(6), 753-759 (July 2004)
[ PubMed ]
 


HOME ABOUT FEEDBACK RECENT CONTENT SUBJECT COLLECTIONS PUBLISH WITH US
HELP MENU
Copyright © 2002+ by the Neurobiology of Lipids, ISSN 1683-5506   Locations of visitors to this page