A phospholipase D-dependent process forms lipid droplets containing caveolin, adipocyte differentiation-related protein, and vimentin in a cell-free system. (25/121)

We developed a microsome-based, cell-free system that assembles newly formed triglyceride (TG) into spherical lipid droplets. These droplets were recovered in the d +info)

The phosphorylation of caveolin-2 on serines 23 and 36 modulates caveolin-1-dependent caveolae formation. (26/121)

Caveolin-1 and -2 are the two major coat proteins found in plasma membrane caveolae of most of cell types. Here, by using adenoviral transduction of either caveolin-1 or caveolin-2 or both isoforms into cells lacking both caveolins, we demonstrate that caveolin-2 positively regulates caveolin-1-dependent caveolae formation. More importantly, we show that caveolin-2 is phosphorylated in vivo at two serine residues and that the phosphorylation of caveolin-2 is necessary for its actions as a positive regulator of caveolin-1 during organelle biogenesis in prostate cancer cells. Mutation of the primary phosphorylation sites on caveolin-2, serine 23 and 36, reduces the number of plasmalemma-attached caveolae and increases the accumulation of noncoated vesicles, but does not affect trafficking of caveolin-2, interaction with caveolin-1 or its biophysical properties. Thus, the phosphorylation of caveolin-2 is a novel mechanism to regulate the dynamics of caveolae assembly.  (+info)

Caveolin-1 knockout mice show an impaired angiogenic response to exogenous stimuli. (27/121)

Recent studies have shown that caveolin-1 (Cav-1) plays an important role as a regulator of angiogenesis in vitro. Here, we use Cav-1 knockout (KO) mice as a model system to examine the in vivo relevance of these findings. A primary mediator of angiogenesis is basic fibroblast growth factor (bFGF). Thus, we studied bFGF-induced angiogenesis in Cav-1 KO mice using a reconstituted basement membrane system, ie, Matrigel plugs, supplemented with bFGF. In Cav-1 KO mice, implanted Matrigel plugs showed a dramatic reduction in both vessel infiltration and density, as compared with identical plugs implanted in wild-type control mice. We also examined the necessity of Cav-1 to support the angiogenic response of an exogenous tumor by subcutaneously injecting Cav-1 KO mice with the melanoma cell line, B16-F10. We show that tumor weight, volume, and vessel density are all reduced in Cav-1 KO mice, consistent with diminished angiogenesis. Ultrastructural analysis of newly formed capillaries within the exogenous tumors reveals a lack of endothelial caveolae and incomplete capillary formation in Cav-1 KO mice. These results provide novel evidence that Cav-1 and caveolae play an important positive role in the process of pathological angiogenesis in vivo.  (+info)

Cellular apoptosis is associated with increased caveolin-1 expression in macrophages. (28/121)

Macrophage apoptosis is an important factor in determining the efficiency of the immune response, atherosclerotic lesion stability, and clearance of aged cells by phagocytosis. The involvement of caveolin-1 in the regulation of apoptosis has been previously suggested in fibroblasts and epithelial cells. Here we show that treatment of thioglycollate-elicited mouse peritoneal macrophages with various unrelated apoptotic agents, including simvastatin, camptothecin, or glucose deprivation, is associated with a specific and large increase in caveolin-1 expression. In contrast, caveolin-2 levels remain unaffected. Induction of apoptosis was measured by changes in cell morphology, annexin V-labeling, and DNA fragmentation. We demonstrate that caveolin-1 in macrophages is present in lipid rafts and colocalizes with phosphatidylserine (PS) at the cell surface of apoptotic macrophages. Our data suggest that caveolin-1 increase is an early event, closely accompanied by PS externalization and independent of caspase activation and nuclear DNA fragmentation. The increase in caveolin-1 levels does not require new protein synthesis, as cycloheximide does not prevent the apoptosis-mediated increase in caveolin-1 levels. We propose that increased levels of caveolin-1 characterize the apoptotic phenotype of macrophages. Caveolin-1 may be involved in the efficient externalization of PS at the surface of the apoptotic cells.  (+info)

Caveolin-1 and caveolin-2,together with three bone morphogenetic protein-related genes, may encode novel tumor suppressors down-regulated in sporadic follicular thyroid carcinogenesis. (29/121)

Thyroid cancer is common, occurring in 1% of the general population. The relative frequencies of two of the most common subtypes of thyroid carcinoma, follicular (FTC) and papillary (PTC), vary depending on the regional prevalence of iodine deficiency. Although PTC has been more extensively studied, the etiology of sporadic FTC is poorly understood. To further elucidate this, we conducted microarray expression comparison of FTC tumors and normal thyroid tissue. Three commonly down-regulated genes, caveolin-1, caveolin-2, and GDF10/BMP3b, were chosen for further study on the basis of their localization to two chromosomal regions, 7q31.1 and 10q11.1, that commonly show loss of heterozygosity in FTC. Two additional genes, glypican-3 and a novel chordin-like gene, were also analyzed in view of their involvement in bone morphogenetic protein signaling and possible interaction with GDF10. Each of these five genes was down-regulated in >or=15 of 19 FTC tumors (79%) by semiquantitative reverse transcription-PCR. Caveolin-1 showed preferential down-regulation of its beta-isoform at both the mRNA and protein level, suggesting a distinct function for this isoform. Caveolin-1 is of particular functional interest because it has been shown to interact with PTEN, the tumor suppressor gene mutated in Cowden syndrome, an inherited multiple hamartoma syndrome that includes predisposition to FTC. Immunohistochemical analysis of 141 thyroid tumors of various histological types showed significantly fewer caveolin-1-positive tumors in FTCs, including insular type tumors, and Hurthle cell carcinomas in comparison with normal thyroid. PTC and anaplastic thyroid carcinomas did not show significant down-regulation, and thus, caveolin-1 may become a useful molecular marker to differentiate the various histologies of thyroid malignancies.  (+info)

Mechanical unloading increases caveolin expression in the failing human heart. (30/121)

OBJECTIVE: Implantation of a left ventricular assist device (LVAD) in the failing human heart initiates structural and functional changes termed reverse remodeling. Mechanical unloading improves cardiac adrenergic responsiveness and lipid metabolism, processes regulated by caveolar function. We tested the hypothesis that mechanical unloading alters the expression of caveolins and these changes are linked to altered expression of markers of reverse remodeling. METHODS: Paired human myocardial samples were obtained from patients who received an LVAD as a bridge to cardiac transplantation. Transcript levels were measured using real-time Q-RT-PCR in RNA prepared from 34 pairs of formalin-fixed myocardial tissue blocks. Caveolin-1 and -3 protein levels were determined from frozen tissue (n=5) by Western blots. Caveolin-3 localization was demonstrated by immunohistochemistry. RESULTS: Caveolin-1 protein levels were upregulated in all LVAD-patients after mechanical unloading (P=0.002). Caveolin-1 mRNA was increased in 76% of the patients (n=34, P<0.001). Larger induction of caveolin-1 was associated with greater suppression of ANF. Caveolin-3 transcript levels increased in 82% of the cohort, along with a 2.5-fold induction of caveolin-2. Sarcolemmal caveolin-3 staining was increased after LVAD-support, although no change in total caveolin-3 protein was detected. The mRNA levels of the caveolin-associated CD36 also increased with unloading. Patients with ischemic cardiomyopathy showed greater induction of CD36 (P<0.05) than non-ischemic cases, as well as highly correlated changes in the expression of caveolin isoforms. CONCLUSION: Mechanical unloading induces the expression of caveolins and CD36. The induction of caveolin-1 and the reciprocal suppression of ANF suggest that the changes in the expression of both genes are linked to decreased hemodynamic load. Enhanced caveolin expression during mechanical unloading of failing human hearts may be a part of the reverse remodeling of lipid metabolism, nitric oxide production and adrenergic signaling.  (+info)

Expression of caveolin-1 and caveolin-2 in urothelial carcinoma of the urinary bladder correlates with tumor grade and squamous differentiation. (31/121)

We immunohistochemically evaluated 94 cases of urothelial carcinoma (UC) of the urinary bladder for the expression of caveolin (Cav)-1 and Cav-2. Neither benign urothelium present in 22 cases nor flat carcinoma in situ present in 10 cases stained for Cav-1 or Cav-2. Thirty-five (37%) of 94 cases and 45 (51%) of 89 cases of UC stained positively for Cav-1 and Cav-2, respectively. The percentages of positive cases for Cav-1 in grades 1, 2, and 3 tumors were 0% (0/6), 0% (0/25), and 56% (35/63), respectively (P < .001), and for Cav-2, 0% (0/6), 13% (3/23), and 70% (42/60), respectively (P < .001). Multivariate analysis showed no significant correlation between tumor stage and Cav-1 or Cav-2 expression after correction for tumor grade. Eighty-two percent (14/17) of cases with squamous differentiation were positive for Cav-1 compared with 43% (20/46) of grade 3 tumors without squamous differentiation (P < .001). These results indicate a positive correlation of the expression of Cav-1 and Cav-2 with tumor grade and squamous features of UC and suggest that Cav-1 and Cav-2 be studied further for a possible role in tumor progression and squamous differentiation.  (+info)

HDL-mediated cholesterol uptake and targeting to lipid droplets in adipocytes. (32/121)

Adipocytes express high levels of the HDL scavenger receptor class B type I in a differentiation-dependent manner. We thus have analyzed the routes of HDL cholesterol trafficking at different phases of adipocyte differentiation in the 3T3-L1 cell line. One novel and salient feature of this paper is the observation of a widespread distribution in the cell cytoplasm of Golgi markers, caveolin-2, and a fluorescent cholesterol analog NBD-cholesterol (NBD-chol), observed in the early phases of adipocyte formation, clearly distinct from that observed in mature fat cells (i.e., with fully formed lipid vesicles). Thus, in cells without visible lipid droplets, Golgi markers (Golgi 58K, Golgin 97, trans-Golgi network 38, Rab 6, and BODIPY-ceramide), caveolin-2, and NBD-chol all colocalize in a widespread distribution in the cell. In contrast, when lipid droplets are fully formed at latter stages, these markers clearly are distributed to distinct cell compartments: a compact juxtanuclear structure for the Golgi markers and caveolin-2, while NDB-chol concentrates in lipid droplets. In addition, disorganization of the Golgi using three different agents (Brefeldin, monensin, and N-ethyl-maleimide) drastically reduces NBD-chol uptake at different phases of adipocyte formation, strongly suggesting that the Golgi apparatus plays a critical role in HDL-mediated NBD uptake and routing to lipid droplets.  (+info)