Caveolin-2, a protein about 20 kD, is a major component of the inner surface of caveolae, small invaginations of the plasma membrane. Similar with caveolin-1 and caveolin-3, it serves as a protein marker of caveolae. Caveolin-1 and -2 are located next to each other at 7q31.1 on human chromosome, the proteins encoded are co-localized and form a stable hetero-oligomeric complex, distributing similarly in tissue and cultured cells. Caveolin-3 is located on different chromosomes but confirmed to interact with caveolin-2. Caveolin-2 is similar to caveolin-1 in many respects but differs from the latter in functional domains, especially in G-protein binding domain and caveolin scaffolding domain. The mRNAs of both caveolin-1 and caveolin-2 are most abundantly expressed in white adipose tissue and are induced during differentiation of 3T3-L1 cells to adipocytes. Caveolin-2-deficient mice demonstrate clear pulmonary defects, with little or no change in caveolin-1 expression and caveolae formation, suggesting that caveolin-2 plays a selective role in lung functions. Caveolin-2 is also involved in lipid metabolism and human cancers.
Biomarkers ; metabolism ; Caveolae ; metabolism ; Caveolin 2 ; genetics ; metabolism ; Chromosomes, Human, Pair 7 ; Humans

The release of microvesicles(MV) is one of the critical mechanisms underlying the angiogenesis-promoting activity of mesenchymal stem cells(MSC). This study was aimed to explore the appropriate condition under which MSC releases MV. Bone marrow samples from 5 healthy adults were collected, and MSC were isolated, culture-expanded and identified. MSC at passage 5 were suspended in medium without or medium with 10% fetal(FCS) calf serum and seeded into culture dishes. The culture was separately maintained in hypoxia (1% oxygen) or normoxia (around 20% oxygen), and 20 dishes of cells (2×10(6)/dish) were used for each group. The supernatants were collected for MV harvesting. The cell number was counted with trypan blue exclusion test and the protein contents in the MV were determined. MV were identified by observation under an electron microscope. The surface markers on MV were analyzed by flow cytometry. MTT test was performed to observe the pro-proliferative activity of MV that were added into the culture of human umbilical cord vein endothelial cells at a concentration of 10 µg/ml. The results showed that the majority of MV released by MSC were with diameters of less than 100 nm, and MV took the featured membrane-like structure with a hypodense center. They expressed CD29, CD44, CD73 and CD105, while they were negative for CD31 and CD45. The increase multiples of the adherent trypan blue-resistant cells cultured in normoxia with serum, in normoxia without serum, in hypoxia with serum and hypoxia in the absence of serum were 4.05 ± 0.73, 1.77 ± 0.48, 5.80 ± 0.65 and 3.69 ± 0.85 respectively, and the estimated protein contents per 10(8) cells were 463.48 ± 138.74 µg, 1604.07 ± 445.28 µg, 2389.64 ± 476.75 µg and 3141.18 ± 353.01 µg. MTT test showed that MV collected from MSC in hypoxia seemed to promote the growth of endothelial cells more efficiently than those from cells in normoxia. It is concluded that hypoxia can enhance the release of microvesicles from MSC, and cultivation of MSC in hypoxia and medium without serum may provide an appropriate condition for MV harvesting.
Bone Marrow Cells ; cytology ; metabolism ; Caveolae ; metabolism ; Cell-Derived Microparticles ; metabolism ; Cells, Cultured ; Humans ; Mesenchymal Stromal Cells ; cytology ; metabolism

Caveolae are specialized lipid rafts that form flask-shaped invaginations of the plasma membrane. Many researches show that caveolae are involved in cell signaling and transport. Caveolin-1 is the major coat protein essential for the formation of caveolae. Recently, several reports indicated that the other caveolae-associated proteins, Cavins, are required for caveola formation and organization. It's worth noting that Cavin-1 could cooperate with Caveolin-1 to accommodate the structural integrity and function of caveolae. Here, we reviewed that the relationship between Cavins and Caveolins and explore the role of them in regulating caveolae.
Animals ; Caveolae ; physiology ; Caveolin 1 ; metabolism ; physiology ; Caveolins ; metabolism ; physiology ; Humans ; Membrane Proteins ; metabolism ; physiology ; RNA-Binding Proteins ; metabolism ; physiology

Membrane microparticles are shed from the plasma membrane of most eukaryotic cells when these cells were undergone activation or apoptosis, and released into the extracellular environment. Their composition depends on the cellular origin and processes triggering their formation. Several lines of evidence suggest that membrane microparticles might be able to facilitate cell-cell cross-talk and play an important roles in the regulation of survival, proliferation, differentiation, adhesion and chemotaxis of hematopoietic cells. Here, the components, mechanism of formation and the regulatory roles of membrane microparticles in hematopoiesis were reviewed.
Caveolae ; metabolism ; physiology ; Cell Membrane ; metabolism ; physiology ; Hematopoiesis ; physiology ; Humans ; Models, Biological ; R-SNARE Proteins ; metabolism ; physiology

We investigated the effect of phenylephrine (PE)- and isoproterenol (ISO)-induced cardiac hypertrophy on subcellular localization and expression of caveolin-3 and STAT3 in H9c2 cardiomyoblast cells. Caveolin-3 localization to plasma membrane was attenuated and localization of caveolin-3 to caveolae in the plasma membrane was 24.3% reduced by the catecholamine-induced hypertrophy. STAT3 and phospho-STAT3 were up-regulated but verapamil and cyclosporin A synergistically decreased the STAT3 and phospho-STAT3 levels in PE- and ISO-induced hypertrophic cells. Both expression and activation of STAT3 were increased in the nucleus by the hypertrophy. Immunofluorescence analysis revealed that the catecholamine-induced hypertrophy promoted nuclear localization of pY705-STAT3. Of interest, phosphorylation of pS727-STAT3 in mitochondria was significantly reduced by catecholamine-induced hypertrophy. In addition, mitochondrial complexes II and III were greatly down-regulated in the hypertrophic cells. Our data suggest that the alterations in nuclear and mitochondrial activation of STAT3 and caveolae localization of caveolin-3 are related to the development of the catecholamine-induced cardiac hypertrophy.
Animals ; Catecholamines/*pharmacology ; Caveolae/*metabolism ; Caveolin 3/*metabolism ; Cell Line ; Hypertrophy/metabolism ; Mitochondria/*metabolism ; Myocardium/cytology/*pathology ; Myocytes, Cardiac/cytology/*drug effects/metabolism ; Rats ; STAT3 Transcription Factor/*metabolism

This article deals with the influence of shear stress on endothelial NO synthesis, and the role of caveolae in shear stress-induced eNOS activation. Human umbilical vascular endothelial cells (HUVEC) were cultured and exposed to different levels of laminal shear stress and Filipin, the perfused cultures were collected, and NO(2-)/NO(3-) was detected using nitrate reduction method. The structure of caveolae was observed through transmission electron microscopy (TEM). The level of NO(2-)-/NO(3-) was found to increase with the elevation of shear stress level (P < 0.01). It was the highest at 1.5 N/m2. After treatment with Filipin, the level of NO produced by HUVEC decreased significantly (P < 0.01), but after recovery and shear without Filipin, the level of NO synthesis bounded back (P < 0.01). It was then concluded that shear stress can induce endothelial NO synthesis and caveolae plays a key role in shear stress-induced eNOS activation.
Caveolae ; physiology ; Cells, Cultured ; Endothelium, Vascular ; cytology ; Filipin ; pharmacology ; Humans ; Nitric Oxide Synthase Type III ; metabolism ; Shear Strength ; Umbilical Veins ; cytology

Lipid rafts provide a platform for regulating cellular functions and participate in the pathogenesis of several diseases. However, the role of caveolin-1 in this process has not been elucidated definitely in neuron. Thus, this study was performed to examine whether caveolin-1 can regulate amyloid precursor protein (APP) processing in neuronal cells and to identify the molecular mechanisms involved in this regulation. Caveolin-1 is up-regulated in all parts of old rat brain, namely hippocampus, cerebral cortex and in elderly human cerebral cortex. Moreover, detergent-insoluble glycolipid (DIG) fractions indicated that caveolin-1 was co-localized with APP in caveolae-like structures. In DIG fractions, bAPP secretion was up-regulated by caveolin-1 over-expression, which was modulated via protein kinase C (PKC) in neuroblastoma cells. From these results we conclude that caveolin-1 is selectively expressed in senescent neurons and that it induces the processing of APP by beta-secretase via PKC downregulation.
Up-Regulation ; Receptors, Cell Surface/*metabolism ; Rats ; Protein Kinase C/metabolism ; Middle Aged ; Microscopy, Electron ; Humans ; Caveolin 1/*metabolism/physiology ; Caveolae/*metabolism/ultrastructure ; Brain/metabolism/pathology/ultrastructure ; Animals ; Amyloid beta-Protein Precursor/*metabolism ; Amyloid beta-Protein/*metabolism ; Alzheimer Disease/*metabolism ; Aging/metabolism ; Aged, 80 and over ; Aged

We investigated glucose uptake and the translocation of Akt and caveolin-3 in response to insulin in H9c2 cardiomyoblasts exposed to an experimental insulin resistance condition of 100 nM insulin in a 25 mM glucose containing media for 24 h. The cells under the insulin resistance condition exhibited a decrease in insulin-stimulated 2-deoxy[3 H]glucose uptake as compared to control cells grown in 5 mM glucose media. In addition to a reduction in insulin-induced Akt translocation to membranes, we observed a significant decrease in insulin-stimulated membrane association of phosphorylated Akt with a consequent increase of the cytosolic pool. Actin remodeling in response to insulin was also greatly retarded in the cells. When translocation of Akt and caveolin-3 to caveolae was examined, the insulin resistance condition attenuated localization of Akt and caveolin-3 to caveolae from cytosol. As a result, insulin-stimulated Akt activation in caveolae was significantly decreased. Taken together, our data indicate that the decrease of glucose uptake into the cells is related to their reduced levels of caveolin-3, Akt and phosphorylated Akt in caveolae. We conclude that the insulin resistance condition induced the retardation of their translocation to caveolae and in turn caused an attenuation in insulin signaling, namely activation of Akt in caveolae for glucose uptake into H9c2 cardiomyoblasts.
Animals ; Biological Transport ; Caveolae/drug effects/*metabolism ; Caveolins/*metabolism ; Cell Membrane/metabolism ; Cells, Cultured ; Cytosol/metabolism ; Enzyme Activation/drug effects ; Glucose/*metabolism ; Heart/embryology ; Insulin/pharmacology ; *Insulin Resistance ; Myocytes, Cardiac/drug effects/*metabolism ; Phosphorylation ; Protein Transport ; Protein-Serine-Threonine Kinases/*metabolism ; Proto-Oncogene Proteins/*metabolism ; Rats ; Research Support, Non-U.S. Gov't

The purpose of this study was to demonstrate the cellular localization of cyclooxygenase-2 (COX-2) and caveolin-3 (Cav-3) in primarily cultured rat chondrocytes. In normal rat chondrocytes, we observed relatively high levels of Cav-3 and a very low level of COX-2 mRNA and protein. Upon treating the chondrocytes with 5 microM of CdCl2 (Cd) for 6 hr, the expressions of COX-2 mRNA and protein were increased with the decreased Cav-3 mRNA and protein expressions. The detergent insoluble caveolae-rich membranous fractions that were isolated from the rat chondrocytes and treated with Cd contained the both proteins of both COX-2 and Cav-3 in a same fraction. The immuno-precipitation experiments showed complex formation between the COX-2 and Cav-3 in the rat chondrocytes. Purified COX-2 with glutathione S-transferase-fused COX-2 also showed complex formation with Cav-3. Confocal and electron microscopy also demonstrated the co-localization of COX-2 and Cav-3 in the plasma membrane. The results from our current study show that COX-2 and Cav-3 are co-localized in the caveolae of the plasma membrane, and they form a protein-protein complex. The co-localization of COX-2 with Cav-3 in the caveolae suggests that the caveolins might play an important role for regulating the function of COX-2.
Animals ; Animals, Newborn ; Blotting, Western ; Cadmium Chloride/pharmacology ; Caveolae/drug effects/metabolism/ultrastructure ; Caveolin 3/*genetics/metabolism ; Cell Membrane/drug effects/metabolism ; Cells, Cultured ; Chondrocytes/cytology/drug effects/*metabolism ; Cyclooxygenase 2/*genetics/metabolism ; Gene Expression ; Immunoprecipitation ; Microscopy, Confocal ; Microscopy, Electron ; RNA, Messenger/genetics/metabolism ; Rats ; Reverse Transcriptase Polymerase Chain Reaction