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A PLCdelta1-binding protein, p122/RhoGAP, is localized in caveolin-enriched membrane domains and regulates caveolin internalization. 2004

Masaki Yamaga, and Masayuki Sekimata, and Makoto Fujii, and Katsuhisa Kawai, and Hideaki Kamata, and Hajime Hirata, and Yoshimi Homma, and Hitoshi Yagisawa
Department of Life Science, Graduate School of Science, Himeji Institute of Technology, Harima Science Garden City, Hyogo 678-1297, Japan.

A GTPase activating protein (GAP), p122, has previously been cloned as a phospholipase C (PLC)delta1-interacting protein. p122 shows a specific GAP activity for Rho and enhances the enzyme activity of PLCdelta1. In this study, we examined the localization and functions of p122/RhoGAP, using enhanced green fluorescent protein (EGFP)-tagged proteins. EGFP-p122 was observed as punctate structures at the plasma membrane of BHK (fibroblastic) cells and MDCK (epithelial) cells. This patchy distribution depended on membrane cholesterol levels and the C-terminal region of p122 containing the GAP domain was responsible for it. Sucrose density gradient centrifugation and immunostaining of caveolin-1 revealed that p122 was localized in caveolin-enriched membrane domains mainly via its GAP domain. We demonstrated that transient expression of EGFP-p122 caused internalization of caveolin-1. Moreover, when the EGFP-tagged GAP domain was introduced in another fibroblastic cell line, NRK cells, punctate fluorescent structures were co-localized with caveolin-1. In this case, caveolin-1-positive structures were found in patches of F-actin, unlike those of untransfected cells that formed linear arrays along with actin stress fibres. These results suggest that p122 is localized in caveolae and plays an important role in caveolin distribution through reorganization of the actin cytoskeleton.

UI MeSH Term Description Entries
D008856 Microscopy, Fluorescence Microscopy of specimens stained with fluorescent dye (usually fluorescein isothiocyanate) or of naturally fluorescent materials, which emit light when exposed to ultraviolet or blue light. Immunofluorescence microscopy utilizes antibodies that are labeled with fluorescent dye. Fluorescence Microscopy,Immunofluorescence Microscopy,Microscopy, Immunofluorescence,Fluorescence Microscopies,Immunofluorescence Microscopies,Microscopies, Fluorescence,Microscopies, Immunofluorescence
D002462 Cell Membrane The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells. Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D002784 Cholesterol The principal sterol of all higher animals, distributed in body tissues, especially the brain and spinal cord, and in animal fats and oils. Epicholesterol
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000199 Actins Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or F-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or G-actin. In conjunction with MYOSINS, actin is responsible for the contraction and relaxation of muscle. F-Actin,G-Actin,Actin,Isoactin,N-Actin,alpha-Actin,alpha-Isoactin,beta-Actin,gamma-Actin,F Actin,G Actin,N Actin,alpha Actin,alpha Isoactin,beta Actin,gamma Actin
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D051242 Caveolin 1 A tyrosine phosphoprotein that plays an essential role in CAVEOLAE formation. It binds CHOLESTEROL and is involved in LIPIDS transport, membrane traffic, and SIGNAL TRANSDUCTION. Caveolin-1,VIP21 Protein,Vesicular Integral Membrane Protein 21 kDa,alpha-Caveolin,beta-Caveolin,alpha Caveolin,beta Caveolin
D017930 Genes, Reporter Genes whose expression is easily detectable and therefore used to study promoter activity at many positions in a target genome. In recombinant DNA technology, these genes may be attached to a promoter region of interest. Reporter Genes,Gene, Reporter,Reporter Gene
D020690 GTPase-Activating Proteins Proteins that activate the GTPase of specific GTP-BINDING PROTEINS. GAP Proteins,GAP Protein,GTPase-Activating Protein,GTPase Activating Protein,GTPase Activating Proteins
D021941 Caveolae Endocytic/exocytic CELL MEMBRANE STRUCTURES rich in glycosphingolipids, cholesterol, and lipid-anchored membrane proteins that function in ENDOCYTOSIS (potocytosis), transcytosis, and SIGNAL TRANSDUCTION. Caveolae assume various shapes from open pits to closed vesicles. Caveolar coats are composed of CAVEOLINS. Caveola,Caveolas

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