title: Novel function of Chat in controlling cell adhesion via Cas-Crk-C3G-pathway-mediated Rap1 activation.
abstract: Chat (Cas/HEF1-associated signal transducer) is a novel signaling molecule with an N-terminal SH2 domain and C-terminal Cas/HEF1 association domain that is implicated in the regulation of cell adhesion. The Cas/HEF1 association domain also shows sequence similarity with guanine nucleotide exchange factors for Ras family small GTPases. In this study, we found significant activation of Rap1 in Chat-overexpressing cells. Myr-Chat, a membrane-targeted form of Chat, activated Rap1 more efficiently. Interestingly, Chat and Cas synergistically activated Rap1. Certain Cas, Crk or C3G mutants suppressed Rap1 activation by Chat. We also confirmed the ternary complex formation consisting of Chat, Cas and Crk. Thus, it is likely that Chat-induced Rap1 activation was mediated by upregulation of the Cas-Crk-C3G signaling pathway rather than direct guanine nucleotide exchange factor activity of Chat. We further demonstrated that Myr-Chat expression induced cell periphery spreading and cell shape branching and that this activity also depended on the Cas-Crk-C3G pathway and Rap1 activity. Moreover, expression of Myr-Chat enhanced integrin-mediated cell adhesion. Taken together we propose a novel role for the Chat-Cas complex in controlling cell adhesion via the activation of Rap1.
authors.affiliation: Division of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan. as6by@virginia.edu
authors.forename: Akira
authors.initials: A
authors.lastname: Sakakibara
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ohba
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kurokawa
authors.forename: Michiyuki
authors.initials: M
authors.lastname: Matsuda
authors.forename: Seisuke
authors.initials: S
authors.lastname: Hattori
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000502:physiology*; D002448:Cell Adhesion / Q000502:physiology*; D002460:Cell Line; D005455:Fluorescent Antibody Technique; D006801:Humans; D051379:Mice; D011233:Precipitin Tests; D020827:rap1 GTP-Binding Proteins / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C405695:Sh2d3c protein, mouse; D020827:rap1 GTP-Binding Proteins