Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The localization of proteases to cell surfaces via receptors may facilitate cell migration, invasion, and matrix degradation. Since vascular smooth muscle cell (SMC) migration may be an important event in atherosclerosis and in intimal thickening after vascular injury, we studied the cell surface expression of a receptor for urokinase-type plasminogen activator (u-PAR) in cultured human vascular SMC. Using immunofluorescence microscopy, we demonstrated several staining patterns of SMC u-PAR: at the periphery of the cell membrane, at the leading edge, and at cell-cell contact sites. When migration experiments were performed using a wound assay, one-third of the SMC at the wound edge demonstrated polarization of cell surface u-PAR toward the leading edge of the cell membrane (32 +/- 2%, +/- SEM, n = 7). A similar pattern was seen with an antibody to caveolin, a transmembrane protein found in caveolae, but not with an antibody to 5'-nucleotidase, another cell surface glycophosphatidylinositol-anchored protein, which was homogeneously expressed on the cell surface. Low-density lipoprotein receptor-related protein, which mediates internalization of u-PAR bound ligands, was distributed in a diffuse punctate pattern, not polarized to the leading edge. Double immunofluorescent studies demonstrated codistribution of SMC u-PAR with vinculin and caveolin in migrating SMC at the leading edge in a wound assay. Polarization of cell surface u-PAR was not observed in either nonwounded or subconfluent cultures, despite random migratory behavior. These studies suggest that in response to wounding, human vascular SMC polarize and concentrate cell surface u-PAR to their leading edge, perhaps facilitating directional migration.
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PMID:Migrating vascular smooth muscle cells polarize cell surface urokinase receptors after injury in vitro. 786 16

Extraction of ECV304 endothelial cells in 1% Triton X-100 at 4 degrees C resulted in a detergent-insoluble pellet that contained 90% of the caveolin, 78% of the src family kinases and 99% of the annexin II. When detergent-treated cells were loaded beneath a 10-30% sucrose gradient the caveolin and a large proportion of the cellular cholesterol floated at a density of 1.09 g/cm3, characteristic of caveolae and glycosphingolipid-rich membranes. With extended centrifugation the src family kinases, which were initially associated with this floating material, sedimented to the bottom of the gradient. Annexin II remained on the bottom of the gradient under both centrifugation conditions. After 24-h incubation with oxidised low density lipoprotein (oxLDL) about 7.5% of the total sterol in the cells was replaced by 7-ketocholesterol, the major oxysterol found in oxLDL. The majority of this 7-ketocholesterol was found in the light membrane fraction on sucrose gradients. Under these conditions src kinase activity more than doubled in the Triton-resistant fraction, without changes in the concentration of src kinase protein. Introducing oxysterols directly into the medium bathing ECV304 cells for 1 h also modulated the activity of src family kinases in the detergent-resistant membranes. An elevation in activity was observed for 7-ketocholesterol while 7alpha-hydroxycholesterol, 7alpha-hydroxycholesterol and cholesterol epoxide all produced decreases in the background level of src kinase activity. We conclude that 7-ketocholesterol and possibly other components of oxLDL can equilibrate into glycosphingolipid-rich membranes and increase the activity of src kinases, possibly by interaction with caveolin.
Atherosclerosis 1999 Apr
PMID:Src family kinase activation in glycosphingolipid-rich membrane domains of endothelial cells treated with oxidised low density lipoprotein. 1021 69

Hypercholesterolemia-induced vascular disease and atherosclerosis are characterized by a decrease in the bioavailability of endothelium-derived nitric oxide. Endothelial nitric-oxide synthase (eNOS) associates with caveolae and is directly regulated by the caveola protein, caveolin. In the present study, we examined the effects of oxidized low density lipoprotein (oxLDL) on the subcellular location of eNOS, on eNOS activation, and on caveola cholesterol in endothelial cells. We found that treatment with 10 microgram/ml oxLDL for 60 min caused greater than 90% of eNOS and caveolin to leave caveolae. Treatment with oxLDL also inhibited acetylcholine-induced activation of eNOS but not prostacyclin production. oxLDL did not affect total cellular eNOS abundance. Oxidized LDL also did not affect the palmitoylation, myristoylation or phosphorylation of eNOS. Oxidized LDL, but not native LDL, or HDL depleted caveolae of cholesterol by serving as an acceptor for cholesterol. Cyclodextrin also depleted caveolae of cholesterol and caused eNOS and caveolin to translocate from caveolae. Furthermore, removal of oxLDL allowed eNOS and caveolin to return to caveolae. We conclude that oxLDL-induced depletion of caveola cholesterol causes eNOS to leave caveolae and inhibits acetylcholine-induced activation of the enzyme. This process may be an important mechanism in the early pathogenesis of atherosclerosis.
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PMID:Oxidized low density lipoprotein displaces endothelial nitric-oxide synthase (eNOS) from plasmalemmal caveolae and impairs eNOS activation. 1054 98

Atherosclerosis is preceded by cholesterol-induced diminution in vascular nitric oxide (NO) production and proatherogenic changes in endothelial cell function. Careful dissection of the steps involved in regulating endothelial nitric oxide synthase (eNOS) activity has revealed that cholesterol-induced caveolin expression reduces NO production by stimulating the production of inhibitory caveolin eNOS complexes.
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PMID:Cholesterol-dependent regulation of nitric oxide production: potential role in atherosclerosis. 1056 38

Scavenger receptors bind and internalize modified low-density lipoprotein (LDL) and high-density lipoprotein (HDL). Because the expression of scavenger receptors is not down-regulated by cholesterol, macrophages (Mphi) expressing scavenger receptors can internalize substantial quantities of cholesteryl ester from oxidized LDL and HDL, leading to foam cell formation. Mphi express several different classes of the growing scavenger receptor family on their cell surface and their relative contribution to Mphi cholesterol physiology and atherogenesis is the subject of intense investigation. We focus on the potential role of two scavenger receptors, macrosialin and SR-BI/II in Mphi cholesterol metabolism. Macrosialin is a predominantly Mphi-specific oxidized LDL-binding protein and an atherogenic diet markedly up-regulates its hepatic expression in atherosclerosis-susceptible and atherosclerosis-resistant mouse strains. The HDL receptor, SR-BI and its splicing variant SR-BII, colocalize with caveolin in caveolae in Mphi. Caveolae are initial acceptor sites for cholesteryl esters and these findings indicate a possible role for caveolae and SR-BI in Mphi-selective lipid uptake and in regulating Mphi cholesterol flux in the vascular wall.
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PMID:Macrophage scavenger receptors and foam cell formation. 1057 3

Aortic smooth muscle cells (SMC) from several animal species have been reported to resist depletion of cellular cholesterol by the major apolipoprotein of HDL, apoAI. Resistance of SMC to this protective action of apoAI, if present in humans, could contribute to the overaccumulation of arterial wall cholesterol seen in atherosclerosis. We investigated the ability of human aortic medial SMC to bind and be depleted of cholesterol and phospholipids by apoAI. In contrast to rat aortic SMC, but similar to human fibroblasts, human SMC were readily depleted of cholesterol by apoAI, measured by a marked depletion of intracellular cholesterol available for esterification, and an increase in cholesterol efflux to the medium. Human SMC were also actively depleted of the phospholipids phosphatidylcholine and sphingomyelin by apoAI. In contrast, rat SMC released only a small fraction of these cellular phospholipids to apoAI-containing medium. (125)I-labeled apoAI bound with high affinity and specificity to human SMC, but failed to bind to rat SMC. Similar levels of expression of class B, type I scavenger receptor (SR-BI) and caveolin in human and rat SMC suggested these proteins do not account for the differences in apoAI binding or lipid efflux seen in these cells. An enhancer of apolipoprotein-mediated cholesterol efflux, tyrosyl radical-oxidized HDL, markedly amplified the depletion of cholesterol available for esterification in human SMC compared to HDL, but had no enhanced effect in rat SMC. These results show that human SMC bind and are readily depleted of cellular lipids by apoAI, and suggest that apoAI-mediated cholesterol efflux from arterial SMC may contribute significantly to the circulating pool of HDL cholesterol in vivo. The marked difference in apoAI binding to human and rat arterial SMC provides an excellent model to study the nature of the apoAI-cell binding interaction.
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PMID:Apolipoprotein AI efficiently binds to and mediates cholesterol and phospholipid efflux from human but not rat aortic smooth muscle cells. 1058 56

Cellular cholesterol homeostasis is a balance of influx, catabolism and synthesis, and efflux. Unlike vascular lipoprotein cholesterol transport, intracellular cholesterol trafficking is only beginning to be resolved. Exogenous cholesterol and cholesterol ester enter cells via the low-density lipoprotein (LDL) receptor/lysosomal and less so by nonvesicular, high-density lipoprotein (HDL) receptor/caveolar pathways. However, the mechanism(s) whereby cholesterol enters the lysosomal membrane, translocates, and transfers out of the lysosome to the cell interior are unknown. Likewise, the steps whereby cholesterol enters the cytofacial leaflet of the plasma membrane caveolae, rapidly translocates, leaves the exofacial leaflet, and transfers to extracellular HDL are unclear. Increasing evidence obtained with model and isolated cell membranes, transfected cells, genetic mutants, and gene-ablated mice suggests that proteins such as caveolin, sterol carrier protein-2 (SCP-2), Niemann-Pick C1 protein, steroidogenic acute regulatory protein (StAR), and other intracellular proteins mediate intracellular cholesterol transfer. While these proteins bind cholesterol and/or interact with cholesterol-rich membrane microdomains (e.g., caveolae, rafts, and annuli), their relative contributions to direct molecular versus vesicular cholesterol transfer remain to be resolved. The formation, regulation, and role of membrane microdomains in regulating cholesterol uptake/efflux and trafficking are unclear. Some cholesterol-binding proteins exert opposing effects on cellular cholesterol uptake/efflux, transfer of cholesterol out of the lysosomal membrane, and/or intracellular cholesterol trafficking to select membranous organelles. Resolving these cholesterol pathways and the role of membrane cholesterol microdomains is essential to our understanding not only of processes that affect cholesterol metabolism, but also of the abnormal regulation that may lead to disease (diabetes, obesity, atherosclerosis, neutral lipid storage, Niemann-Pick C, congenital lipoid adrenal hyperplasia, etc.).
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PMID:Recent advances in membrane microdomains: rafts, caveolae, and intracellular cholesterol trafficking. 1168 93

3-Hydroxy-3-methylglutaryl (HMG)-coenzyme A reductase inhibitors or statins exert direct beneficial effects on the endothelium in part through an increase in nitric oxide (NO) production. Here, we examined whether posttranslational modifications of the endothelial NO synthase (eNOS) could account for the proangiogenic effects of statins. We used endothelial cells (ECs) isolated from cardiac microvasculature, aorta, and umbilical veins, as well as dissected microvessels and aortic rings, that were cultured on reconstituted basement membrane matrix (Matrigel). Tube or precapillary formation was evaluated after statin treatment, in parallel with immunoblotting and immunoprecipitation experiments. Atorvastatin stimulated NO-dependent angiogenesis from both isolated and outgrowing (vessel-derived) ECs, independently of changes in eNOS expression. We found that in macro- but not microvascular ECs, atorvastatin stabilized tube formation through a decrease in caveolin abundance and its inhibitory interaction with eNOS. We also identified the chaperone protein hsp90 as a key target for the proangiogenic effects of statins. Using geldanamycin, an inhibitor of hsp90 function, and overexpression of recombinant hsp90, we documented that the statin-induced phosphorylation of eNOS on Ser1177 was directly dependent on the ability of hsp90 to recruit Akt in the eNOS complex. Finally, we showed that statin promoted the tyrosine phosphorylation of hsp90 and the direct interaction of hsp90 with Akt, which further potentiated the NO-dependent angiogenic processes. Our study provides new mechanistic insights into the NO-mediated angiogenic effects of statins and underscores the potential of these drugs and other modulators of hsp90 and caveolin abundance to promote neovascularization in disease states associated or not with atherosclerosis.
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PMID:Hsp90 and caveolin are key targets for the proangiogenic nitric oxide-mediated effects of statins. 1170 13

Caveolae are 50-100 nm plasma membrane invaginations, which function in cell signaling, in transcytosis, and in regulating cellular cholesterol homeostasis. These subcompartments of the plasma membrane are characterized by the presence of caveolin proteins. Recent studies have indicated that caveolae may be involved in the regulation of cellular cholesterol efflux to high-density lipoproteins (HDL), as well as selective cholesteryl ester uptake mediated by scavenger receptor class B type I (SR-BI). In the present studies, we show that caveolin-1 expression in HEK-293T cells has no effect on SR-BI-mediated cellular cholesterol efflux to reconstituted HDL. However, SR-BI-mediated selective cholesteryl ester uptake is significantly inhibited by caveolin-1. Interestingly, we also found that SR-BI, but not CD36, can induce the dramatic stabilization of the caveolin-1 protein, independently of its transcriptional control. On the other hand, caveolin-1 has little effect on SR-BI stability, but clearly increases CD36 stability. Since SR-BI expression has been shown to increase cellular cholesterol levels, we next examined the effect of cholesterol itself on caveolin-1 stabilization and localization. When cells were loaded with cholesterol, we observed the dramatic stabilization of caveolin-1 with significant clustering of caveolin-1 at the cell surface. In addition, a palmitoylation-deficient caveolin-1 mutant was still responsive to cholesterol-induced stabilization, indicating that palmitoylation of caveolin-1 is not required for the cholesterol-induced stabilization of caveolin-1. These results suggest an important role for cholesterol and SR-BI in the regulation of caveolin functioning, especially in cell types such as endothelial cells and macrophages, which can be dramatically affected by changes in their cholesterol content during the development of atherosclerosis.
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PMID:Stabilization of caveolin-1 by cellular cholesterol and scavenger receptor class B type I. 1226 38

Insulin-like growth factors (IGFs) play a central role in the integration of proliferative and survival responses of most mammalian cell types. IGF-binding protein-3 (IGFBP-3) influences IGF action directly as a carrier of IGFs but also modulates these actions indirectly via independent mechanisms involving interactions with plasma, extracellular matrix and cell surface molecules, conditional proteolysis, cellular uptake, and nuclear transport. Here we demonstrate that a short C-terminal metal-binding domain (MBD) of IGFBP-3 mediates binding to metals. MBD epitopes, sequestered in the intact molecule, are unmasked by incubation in the presence of ferrous (but not ferric or zinc) ions. An isolated 14-mer MBD peptide triggered apoptotic effects in stressed HEK293 cells as effectively as IGFBP-3. The MBD, which encompasses a nuclear localization sequence and an adjacent putative caveolin-binding sequence, mobilizes rapid cellular uptake and nuclear localization of unrelated proteins such as green fluorescent protein and streptavidin-horseradish peroxidase conjugate. Metal ions stimulate MBD-mediated cellular/nuclear uptake in vivo. Cross-linking studies showed a direct physical interaction of MBD with integrins alphav and beta1, caveolin-1, and transferrin receptor. MBD-mediated protein mobilization and pro-apoptotic effects are inhibited by nystatin but not chlorpromazine, suggesting an involvement of caveolar-mediated endocytosis. However, MBD effects are inhibited by antibodies to transferrin receptor or integrins. These results are discussed with particular reference to the cell target specificity of IGFBP-3 in disease processes such as cancer and atherosclerosis.
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PMID:Insulin-like growth factor-independent effects mediated by a C-terminal metal-binding domain of insulin-like growth factor binding protein-3. 1457 63


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