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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The tight junction (TJ) determines epithelial barrier function. Actin depolymerization disrupts TJ structure and barrier function, but the mechanisms of this effect remain poorly understood. The goal of this study was to define these mechanisms. Madin-Darby canine kidney (MDCK) cells expressing enhanced green fluorescent protein-, enhanced yellow fluorescent protein-, or monomeric red fluorescent protein 1-fusion proteins of beta-actin, occludin, claudin-1, ZO-1, clathrin light chain A1, and caveolin-1 were imaged by time-lapse multidimensional fluorescence microscopy with simultaneous measurement of transepithelial electrical resistance (TER). Actin depolymerization was induced with latrunculin A (LatA). Within minutes of LatA addition TER began to fall. This coincided with occludin redistribution and internalization. In contrast, ZO-1 and claudin-1 redistribution occurred well after maximal TER loss. Occludin internalization and TER loss, but not actin depolymerization, were blocked at 14 degrees C, suggesting that membrane traffic is required for both events. Inhibition of membrane traffic with 0.4 M sucrose also blocked occludin internalization and TER loss. Internalized occludin colocalized with caveolin-1 and dynamin II, but not with clathrin, and internalization was blocked by dominant negative dynamin II (K44A), but not by Eps15Delta95-295 expression. Inhibition of caveolae-mediated endocytosis by cholesterol extraction prevented both LatA-induced TER loss and occludin internalization. Thus, LatA-induced actin depolymerization causes TJ structural and functional disruption by mechanisms that include caveolae-mediated endocytosis of TJ components.
Mol Biol Cell 2005 Sep
PMID:Actin depolymerization disrupts tight junctions via caveolae-mediated endocytosis. 1595 94

We have shown that the caveolar Na/K-ATPase transmits ouabain signals via multiple signalplexes. To obtain the information on the composition of such complexes, we separated the Na/K-ATPase from the outer medulla of rat kidney into two different fractions by detergent treatment and density gradient centrifugation. Analysis of the light fraction indicated that both PLC-gamma1 and IP3 receptors (isoforms 2 and 3, IP3R2 and IP3R3) were coenriched with the Na/K-ATPase, caveolin-1 and Src. GST pulldown assays revealed that the central loop of the Na/K-ATPase alpha1 subunit interacts with PLC-gamma1, whereas the N-terminus binds IP3R2 and IP3R3, suggesting that the signaling Na/K-ATPase may tether PLC-gamma1 and IP3 receptors together to form a Ca(2+)-regulatory complex. This notion is supported by the following findings. First, both PLC-gamma1 and IP3R2 coimmunoprecipitated with the Na/K-ATPase and ouabain increased this interaction in a dose- and time-dependent manner in LLC-PK1 cells. Depletion of cholesterol abolished the effects of ouabain on this interaction. Second, ouabain induced phosphorylation of PLC-gamma1 at Tyr(783) and activated PLC-gamma1 in a Src-dependent manner, resulting in increased hydrolysis of PIP2. It also stimulated Src-dependent tyrosine phosphorylation of the IP3R2. Finally, ouabain induced Ca(2+) release from the intracellular stores via the activation of IP3 receptors in LLC-PK1 cells. This effect required the ouabain-induced activation of PLC-gamma1. Inhibition of Src or depletion of cholesterol also abolished the effect of ouabain on intracellular Ca(2+).
Mol Biol Cell 2005 Sep
PMID:Na/K-ATPase tethers phospholipase C and IP3 receptor into a calcium-regulatory complex. 1597 99

A functional aspect of horizontal molecular networks has been investigated experimentally, namely the heteromerization between adenosine A2A and dopamine D2 receptors and the possible role of caveolin-1 in the co-trafficking of these molecular complexes. This study has been carried out by means of computer-assisted image analysis procedure of laser images of membrane immunoreactivity of caveolin-1, A2A, D1, and D2 receptors obtained in two clones of Chinese hamster ovary cells one transfected with A2A and dopamine D1 receptors and the other one with A2A and D2 receptors. Cells were treated for 3 h with 10 microM D1 receptor agonist SKF 38393, 50 microM D2-D3 receptor agonist quinpirole, and 200 nM A2A receptor agonist CGS 21680. In A2A-D1-cotransfected cells, caveolin-1 was found to colocalize with both A2A and D1 receptors and treatment with SKF 38393 induced internalization of caveolin-1 and D1 receptors, with a preferential internalization of D1 receptors colocalized with caveolin-1. In A2A-D2-cotransfected cells, caveolin-1 was found to colocalize with both A2A and D2 receptors and either CGS 21680 or quinpirole treatment induced internalization of caveolin-1 and A2A and D2 receptors, with a preferential internalization of A2A and D2 receptors colocalized with caveolin-1. The results suggest that A2A and D2 receptors and caveolin-1 likely interact forming a macrocomplex that internalizes upon agonist treatment. These observations are discussed in the frame of receptor oligomerization and of the possible functional role of caveolin-1 in the process of co-internalization and, hence, in controlling the permanence of receptors at the plasma membrane level (prerequisite for receptor mosaic organization and plastic adjustments) and in the control of receptor desensitization.
J Mol Neurosci 2005
PMID:Computer-assisted image analysis of caveolin-1 involvement in the internalization process of adenosine A2A-dopamine D2 receptor heterodimers. 1601 91

Lipid architecture of the plasma membrane plays an important role in the capacitation process of the sperm cell. During this process, an increase in membrane fluidity takes place, which coincides with a redistribution of cholesterol to the apical region of the head plasma membrane and subsequently an efflux of cholesterol. Cholesterol is also a major player in the formation of lipid rafts or microdomains in the membrane. Lipid rafts favour specific protein-protein interactions by concentrating certain proteins in these microdomains while excluding others. In this study, we investigated the organization of lipid rafts during in vitro capacitation of boar sperm cells. We report on the presence of the lipid raft-specific proteins caveolin-1 and flotillin-1 in sperm cells. Capacitation induced a change in membrane distribution of these proteins. Lipid analysis on detergent-resistant membranes (DRMs) of sperm cells indicated that capacitation induces a lipid raft concentration rather than a disintegration of lipid rafts, because the total amount of lipid in the DRM fraction remained unaltered. Using a proteomic approach, we identified several major DRM proteins, including proteins involved in capacitation-dependent processes and zona pellucida binding. Our data indicate that sperm raft reorganization may facilitate capacitation-specific signalling events and binding to the zona pellucida.
Mol Hum Reprod 2005 Aug
PMID:Capacitation-dependent concentration of lipid rafts in the apical ridge head area of porcine sperm cells. 1605 81

CD26 is a T-cell costimulatory molecule with dipeptidyl peptidase IV enzyme activity in its extracellular region. We have previously reported that the addition of recombinant soluble CD26 resulted in enhanced proliferation of human T lymphocytes induced by the recall antigen tetanus toxoid (TT) via upregulation of CD86 on monocytes and that caveolin-1 was a binding protein of CD26, and the CD26-caveolin-1 interaction resulted in caveolin-1 phosphorylation (p-cav-1) as well as TT-mediated T-cell proliferation. However, the mechanism involved in this immune enhancement has not yet been elucidated. In the present work, we perform experiments to identify the molecular mechanisms by which p-cav-1 leads directly to the upregulation of CD86. Through proteomic analysis, we identify Tollip (Toll-interacting protein) and IRAK-1 (interleukin-1 receptor-associated serine/threonine kinase 1) as caveolin-1-interacting proteins in monocytes. We also demonstrate that following stimulation by exogenous CD26, Tollip and IRAK-1 dissociate from caveolin-1, and IRAK-1 is then phosphorylated in the cytosol, leading to the upregulation of CD86 via activation of NF-kappaB. Binding of CD26 to caveolin-1 therefore regulates signaling pathways in antigen-presenting cells to induce antigen-specific T-cell proliferation.
Mol Cell Biol 2005 Sep
PMID:CD26 mediates dissociation of Tollip and IRAK-1 from caveolin-1 and induces upregulation of CD86 on antigen-presenting cells. 1610 20

1,1-Bis-(3'-indolyl)-1-(p-substitutedphenyl)methanes containing p-trifluoromethyl (DIM-C-pPhCF3), p-t-butyl (DIM-C-pPhtBu), and phenyl (DIM-C-pPhC6H5) substituents decrease survival of HCT-116 colon cancer cells and activate peroxisome proliferator-activated receptor (PPAR) gamma in this and other cancer cell lines. These PPARgamma-active compounds had minimal effects on expression of cell cycle proteins and did not induce caveolin-1 in HCT-116 cells. However, these compounds induced nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1) and apoptosis in HCT-116 cells, and in time-course studies, the PPARgamma agonists maximally induced early growth response-1 (Egr-1) protein within 2 h, whereas a longer time course was observed for induction of NAG-1 protein. These data, coupled with deletion and mutation analysis of both the Egr-1 and NAG-1 gene promoters, indicate that activation of NAG-1 by these compounds was dependent on prior induction of Egr-1, and induction of these responses was PPARgamma-independent. Results of kinase inhibitor studies also demonstrated that activation of Egr-1/NAG-1 by methylene-substituted diindolylmethanes (C-DIMs) was phosphatidylinositol 3-kinase-dependent, and this represents a novel receptor-independent pathway for C-DIM-induced growth inhibition and apoptosis in colon cancer cells.
Mol Pharmacol 2005 Dec
PMID:1,1-Bis(3'-indolyl)-1-(p-substitutedphenyl)methanes are peroxisome proliferator-activated receptor gamma agonists but decrease HCT-116 colon cancer cell survival through receptor-independent activation of early growth response-1 and nonsteroidal anti-inflammatory drug-activated gene-1. 1615 8

Caveolin-1, the principal integral membrane protein of caveolae, has been implicated in regulating the structural integrity of caveolae, vesicular trafficking, and signal transduction. Although the functions of caveolin-1 are beginning to be explored in caveolin-1-/- mice, these results are confounded by unknown compensatory mechanisms and the development of pulmonary hypertension, cardiomyopathy, and lung fibrosis. To address the role of caveolin-1 in regulating lung vascular permeability, in the present study we used small interfering RNA (siRNA) to knock down caveolin-1 expression in mouse lung endothelia in vivo. Intravenous injection of siRNA against caveolin-1 mRNA incorporated in liposomes selectively reduced the expression of caveolin-1 by approximately 90% within 96 h of injection compared with wild-type mice. We observed the concomitant disappearance of caveolae in lung vessel endothelia and dilated interendothelial junctions (IEJs) as well as increased lung vascular permeability to albumin via IEJs. The reduced caveolin-1 expression also resulted in increased plasma nitric oxide concentration. The nitric oxide synthase inhibitor L-NAME, in part, blocked the increased vascular albumin permeability. These morphological and functional effects of caveolin-1 knockdown were reversible within 168 h after siRNA injection, corresponding to the restoration of caveolin-1 expression. Thus our results demonstrate the essential requirement of caveolin-1 in mediating the formation of caveolae in endothelial cells in vivo and in negatively regulating IEJ permeability.
Am J Physiol Lung Cell Mol Physiol 2006 Feb
PMID:siRNA-induced caveolin-1 knockdown in mice increases lung vascular permeability via the junctional pathway. 1618 67

Caveolin is a major component of caveolae which is a plasma membrane microdomain. The emerging role of caveolin in tumorigenesis was based mainly on in vitro experiments with cancer cell lines. We performed semi-quantitative RT-PCR for caveolin, Akt and EGFR to understand the role of caveolins in colorectal tumor biology. Cancer tissue samples and the neighboring normal colon mucosa were obtained from 95 colorectal cancer patients who underwent operations at Ewha Womans University Mokdong Hospital. With these fresh tissues, semi-quantitative RT-PCR was performed by coamplification of the gene for caveolin-1, EGFR and Akt-1 with beta-actin. The average age was 60.21+/-13.33 years old, and sex ratio was 1.44:1. Caveolin-1 is more expressed in tumors than normal mucosa (P=0.025). The expression of caveolin-1 and Akt-1 had a definitive positive relationship (P=0.002). But, the expression of caveolin-1 and EGFR was not significantly related. We could not find correlations between caveolin-1 expression and clinical factors. In conclusion, caveolin-1 is more expressed in cancer tissues than normal colon and related with Akt-1, not with EGFR expression in colorectal cancer tissues, which suggests that signaling for caveolin-1 affects Akt-1 activation, but this reaction is not initiated by EGFR stimulation in colon cancer.
Exp Mol Pathol 2006 Apr
PMID:Expression of caveolin-1 is correlated with Akt-1 in colorectal cancer tissues. 1620 96

Caveolin, the essential structural component of caveolae, serves as a scaffolding protein onto which signaling molecules are assembled, and functions as a negative regulator for signal transduction. Caveolin-1 and -2 are expressed in most cell types, but are not expressed in normal blood cells and cell lines. We previously demonstrated that caveolin-1 is expressed in a panel of human leukemia cell lines that show an activated T cell phenotype. In that study, we detected two caveolin bands by Western blotting using a polyclonal antibody (pAb) reacting with caveolin-1, -2, and -3. We identified caveolin-1alpha by its large molecular weight, but did not discriminatively detect other caveolin families. Since anti-caveolin-1 monoclonal antibody (mAb) was reported not to detect caveolin-1 in some cases, here we developed a sensitive method for the discriminative detection of caveolin-1, -2, and -3 by modified Western blotting. Caveolins were solubilized using a two-step procedure and detected by immunoprecipitation with a pAb to caveolins followed by Western blotting with mAbs specific to each caveolin. Using this method we detected caveolin-1beta, -2alpha and -2beta, but not caveolin-3 in the leukemia cell lines. Caveolin-1alpha, which was identified by pAb, was not detected by this method. We show here that caveolin-1alpha and -2alpha, but not caveolin-1beta and -2beta, are tyrosine phosphorylated. This modification is likely to cause the lack of reactivity of caveolin-1alpha to the mAb, and suggests a possible close relationship to cell activation.
Int J Mol Med 2005 Nov
PMID:Differential-expression and tyrosine-phosphorylation profiles of caveolin isoforms in human T cell leukemia cell lines. 1621 Dec 60

Caveolin-1 has been implicated in apical transport of glycosylphosphatidylinositol (GPI)-anchored proteins and influenza virus hemagglutinin (HA). Here we have studied the role of caveolin-1 in apical membrane transport by generating caveolin-1-deficient Madin-Darby canine kidney (MDCK) cells using retrovirus-mediated RNA interference. The caveolin-1 knockdown (cav1-KD) MDCK cells were devoid of caveolae. In addition, caveolin-2 was retained in the Golgi apparatus in cav1-KD MDCK cells. However, we found no significant alterations in the apical transport kinetics of GPI-anchored proteins or HA upon depletion of caveolin-1. Similar results were obtained using embryonic fibroblasts from caveolin-1-knockout mice. Thus, we conclude that caveolin-1 does not play a major role in lipid raft-mediated biosynthetic membrane trafficking.
Mol Cell Biol 2005 Nov
PMID:Caveolin-1 is not essential for biosynthetic apical membrane transport. 1626 Jun 22


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