title: Focal adhesion-localization of START-GAP1/DLC1 is essential for cell motility and morphology.
abstract: There is a class of GTPase activating proteins for the Rho family GTPases (RhoGAPs) that contain the steroidogenic acute regulatory protein (STAR)-related lipid transfer (START) domain. In mammals three genes encode such proteins and they are designated START-GAP1-3 or deleted in liver cancer 1-3 (DLC1-3). In this study, we examined the intracellular localization and roles of START-GAP1/DLC1 in cell motility. Immunofluorescence microscopic analysis of NRK cells and HeLa cells revealed that START-GAP1 was localized in focal adhesions. Amino acid residues 265-459 of START-GAP1 were found to be necessary for focal adhesion targeting and we name the region "the focal adhesion-targeting (FAT) domain." It was previously known that ectopic expression of START-GAP1 induced cell rounding. We demonstrated that the FAT domain of START-GAP1 was partially required for this morphological change. Furthermore, expression of this domain in HeLa cells resulted in dissociation of endogenous START-GAP1 from focal adhesions as a dominant negative modulator, reducing cell migration and spreading. Taken together, START-GAP1 is targeted to focal adhesions via the FAT domain and regulates actin rearrangement through down-regulation of active RhoA and Cdc42. Its absence from focal adhesions could, therefore, cause abnormal cell motility and spreading.
authors.affiliation: University of Hyogo, Harima Science Garden City, Hyogo-ken, Japan.
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Kawai
authors.forename: Yui
authors.initials: Y
authors.lastname: Iwamae
authors.forename: Masaki
authors.initials: M
authors.lastname: Yamaga
authors.forename: Minoru
authors.initials: M
authors.lastname: Kiyota
authors.forename: Hiroko
authors.initials: H
authors.lastname: Ishii
authors.forename: Hajime
authors.initials: H
authors.lastname: Hirata
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Homma
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yagisawa
mesh_terms: D002465:Cell Movement / Q000502:physiology; D048430:Cell Shape / Q000502:physiology; D002478:Cells, Cultured; D022001:Focal Adhesions / Q000378:metabolism* / Q000502:physiology; D020690:GTPase-Activating Proteins; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D014018:Tissue Distribution; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: C112352:DLC1 protein, human; D020690:GTPase-Activating Proteins; D025521:Tumor Suppressor Proteins; D020764:cdc42 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein