title: GC-GAP, a Rho family GTPase-activating protein that interacts with signaling adapters Gab1 and Gab2.
abstract: Gab1 and Gab2 are scaffolding proteins acting downstream of cell surface receptors and interact with a variety of cytoplasmic signaling proteins such as Grb2, Shp-2, phosphatidylinositol 3-kinase, Shc, and Crk. To identify new binding partners for GAB proteins and better understand their functions, we performed a yeast two-hybrid screening with hGab2-(120-587) as bait. This work led to identification of a novel GTPase-activating protein (GAP) for Rho family GTPases. The GAP domain shows high similarity to the recently cloned CdGAP and displays activity toward RhoA, Rac1, and Cdc42 in vitro. The protein was named GC-GAP for its ability to interact with GAB proteins and its activity toward Rac and Cdc42. GC-GAP is predominantly expressed in the brain with low levels detected in other tissues. Antibodies directed against GC-GAP recognized a protein of approximately 200 kDa. Expression of GC-GAP in 293T cells led to a reduction in active Rac1 and Cdc42 levels but not RhoA. Suppression of GC-GAP expression by siRNA inhibited proliferation of C6 astroglioma cells. In addition, GC-GAP contains several classic proline-rich motifs, and it interacts with the first SH3 domain of Crk and full-length Nck in vitro. We propose that Gab1 and Gab2 in cooperation with other adapter molecules might regulate the cellular localization of GC-GAP under specific stimuli, acting to regulate precisely Rac and Cdc42 activities. Given that GC-GAP is specifically expressed in the nervous system and that it is localized to the dendritic processes of cultured neurons, GC-GAP may play a role in dendritic morphogenesis and also possibly in neural/glial cell proliferation.
authors.affiliation: Burnham Institute, La Jolla, California 92037, USA.
authors.forename: Chunmei
authors.initials: C
authors.lastname: Zhao
authors.forename: Hong
authors.initials: H
authors.lastname: Ma
authors.forename: Ella
authors.initials: E
authors.lastname: Bossy-Wetzel
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Lipton
authors.forename: Zhuohua
authors.initials: Z
authors.lastname: Zhang
authors.forename: Gen-Sheng
authors.initials: GS
authors.lastname: Feng
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D003712:Dendrites / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D017403:In Situ Hybridization; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism*; D011233:Precipitin Tests; D011392:Proline / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014162:Transfection; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism; D018909:src Homology Domains
chemical_list: C470196:ARHGAP32 protein, human; D048868:Adaptor Proteins, Signal Transducing; D018076:DNA, Complementary; C098587:GAB1 protein, human; C490895:GAB2 protein, human; C477752:GC-GAP protein, mouse; D020690:GTPase-Activating Proteins; C490897:Gab1 protein, mouse; C490894:Gab2 protein, mouse; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D004247:DNA; D011392:Proline; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein