Search results for "Caveolins"
showing 10 items of 10 documents
Tumorigenic conversion of endothelial cells.
2003
Tumors of endothelial origin develop rarely. Until now, only two angiosarcoma (AS)-derived endothelial cell lines have been be isolated, ISO-HAS and AS-M. Both AS-derived endothelial cell lines presented the typical endothelial characteristics, such as the expression of CD31 and von Willebrand factor, but differed from normal endothelial cells in a nuclear expression of p53, in a delayed angiogenic reaction, and a reduced expression of caveolin. In addition, differences in the expression of cytokines and cell adhesion molecules responsive to proinflammatory stimuli were observed. While AS-M showed an expression pattern similar to that of human umbilical vein endothelial cells (HUVEC), ISO-H…
Protein targeting to the plasma membrane of adult skeletal muscle fiber: an organized mosaic of functional domains.
2001
The plasma membrane of differentiated skeletal muscle fibers comprises the sarcolemma, the transverse (T) tubule network, and the neuromuscular and muscle-tendon junctions. We analyzed the organization of these domains in relation to defined surface markers, beta-dystroglycan, dystrophin, and caveolin-3. These markers were shown to exhibit highly organized arrays along the length of the fiber. Caveolin-3 and beta-dystroglycan/dystrophin showed distinct, but to some extent overlapping, labeling patterns and both markers left transverse tubule openings clear. This labeling pattern revealed microdomains over the entire plasma membrane with the exception of the neuromuscular and muscle-tendon j…
Caveolin and GLT-1 gene expression is reciprocally regulated in primary astrocytes: Association of GLT-1 with non-caveolar lipid rafts
2004
Caveolae represent membrane microdomains acting as integrators of cellular signaling and functional processes. Caveolins are involved in the biogenesis of caveolae and regulate the activity of caveolae-associated proteins. Although caveolin proteins are found in the CNS, the regulation of caveolins in neural cells is poorly described. In the present study, we investigated different modes and mechanisms of caveolin gene regulation in primary rat astrocytes. We demonstrated that activation of cAMP-dependent signaling pathways led to a marked reduction in protein levels of caveolin-1/-2 in cortical astrocytes. Application of transforming growth factor-alpha (TGF-alpha) also resulted in a decre…
Functional interaction of estrogen receptor α and caveolin isoforms in neuronal SK-N-MC cells
2003
Estrogen receptors (ERs) are expressed in neuronal cells and exhibit a wide variety of activities in the central nervous system. The actions of ERs are regulated in a hormone-dependent manner as well as by a number of co-activators and -repressors. A recently identified co-activator of ERalpha is caveolin-1 which has been shown to mediate the ligand-independent activation of this steroid receptor. In the present study we have demonstrated that neuronal SK-N-MC cells lacking functional ERalpha show high levels of caveolin-1/-2 specific transcripts and proteins. Ectopic expression of ERalpha in SK-N-MC cells leads to the transcriptional suppression of caveolin-1 and -2 genes. This silencing e…
Internalization of Echovirus 1 in Caveolae
2002
ABSTRACT Echovirus 1 (EV1) is a human pathogen which belongs to the Picornaviridae family of RNA viruses. We have analyzed the early events of infection after EV1 binding to its receptor α2β1 integrin and elucidated the route by which EV1 gains access to the host cell. EV1 binding onto the cell surface and subsequent entry resulted in conformational changes of the viral capsid as demonstrated by sucrose gradient sedimentation analysis. After 15 min to 2 h postinfection (p.i.) EV1 capsid proteins were seen in vesicular structures that were negative for markers of the clathrin-dependent endocytic pathway. In contrast, immunofluorescence confocal microscopy showed that EV1, α2β1 integrin, and …
Requirement of caveolae microdomains in extracellular signal-regulated kinase and focal adhesion kinase activation induced by endothelin-1 in primary…
1999
Endothelin-1 (ET-1) mitogenic activity in astrocytes is mediated by the activation of the extracellular signal-regulated kinase (ERK) pathway together with the Rho-dependent activation of the focal adhesion kinase (FAK) pathway. To clarify the mechanisms responsible for the coordinate activation of both pathways in the ET-1 signal propagation, the involvement of caveolae microdomains, suggested to play a role in signal transduction, was evaluated. In this study, it is reported that caveolae of primary astrocytes are enriched in endothelin receptor (ETB-R). Furthermore, signaling molecules such as the adaptor proteins Shc and Grb2, and the small G protein Rho, also reside within these microd…
Oxytocin receptors and cholesterol: interaction and regulation.
2000
Cholesterol affects the ligand binding function of the oxytocin receptor in a highly specific manner. While the structurally-related cholecystokinin receptor shows a strong correlation between the membrane fluidity and its binding function, the oxytocin receptor behaves differently. A stringent and unique requirement of the affinity state of the oxytocin receptor for structural features of the sterol molecule has been found. The molecular requirements differ both from those postulated for sterol-phospholipid interactions and from those known to be necessary for the activity of other proteins. Employing a new detergent-free subcellular fractionation protocol, a two-fold enrichment of the oxy…
Entry of Human Parechovirus 1
2001
ABSTRACT Human parechovirus 1 (HPEV-1) is a prototype member of parechoviruses, a recently established picornavirus genus. Although there is preliminary evidence that HPEV-1 recognizes α V integrins as cellular receptors, our understanding of early events during HPEV-1 infection is still very limited. The aim of this study was to clarify the entry mechanisms of HPEV-1, including the attachment of the virus onto the host cell surface and subsequent internalization. In blocking experiments with monoclonal antibodies against different receptor candidates, antibodies against α V and β 3 integrin subunits, in particular in combination, appeared to be the most efficient ones in preventing the HPE…
Clustering induces a lateral redistribution of α2β1 integrin from membrane rafts to caveolae and subsequent protein kinase C-dependent internalization
2004
Integrin alpha 2 beta 1 mediates the binding of several epithelial and mesenchymal cell types to collagen. The composition of the surrounding plasma membrane, especially caveolin-1- and cholesterol-containing membrane structures called caveolae, may be important to integrin signaling. On cell surface alpha 2 beta 1 integrin was located in the raft like membrane domain, rich in GPI-anchored proteins, rather than in caveolae. However, when antibodies were used to generate clusters of alpha 2 beta 1 integrin, they started to move laterally on cell surface along actin filaments. During the lateral movement small clusters fused together. Finally alpha 2 beta 1 integrin was found inside caveolae …
A Raft-derived, Pak1-regulated Entry Participates in α2β1 Integrin-dependent Sorting to Caveosomes
2008
We have previously shown that a human picornavirus echovirus 1 (EV1) is transported to caveosomes during 2 h together with its receptor alpha2beta1 integrin. Here, we show that the majority of early uptake does not occur through caveolae. alpha2beta1 integrin, clustered by antibodies or by EV1 binding, is initially internalized from lipid rafts into tubulovesicular structures. These vesicles accumulate fluid-phase markers but do not initially colocalize with caveolin-1 or internalized simian virus 40 (SV40). Furthermore, the internalized endosomes do not contain glycosylphosphatidylinositol (GPI)-anchored proteins or flotillin 1, suggesting that clustered alpha2beta1 integrin does not enter…