title: The endocytic protein GRAF1 is directed to cell-matrix adhesion sites and regulates cell spreading.
abstract: The rho GTPase-activating protein GTPase regulator associated with focal adhesion kinase-1 (GRAF1) remodels membranes into tubulovesicular clathrin-independent carriers (CLICs) mediating lipid-anchored receptor endocytosis. However, the cell biological functions of this highly prevalent endocytic pathway are unclear. In this article, we present biochemical and cell biological evidence that GRAF1 interacted with a network of endocytic and adhesion proteins and was found enriched at podosome-like adhesions and src-induced podosomes. We further demonstrate that these sites comprise microdomains of highly ordered lipid enriched in GRAF1 endocytic cargo. GRAF1 activity was upregulated in spreading cells and uptake via CLICs was concentrated at the leading edge of migrating cells. Depletion of GRAF1, which inhibits CLIC generation, resulted in profound defects in cell spreading and migration. We propose that GRAF1 remodels membrane microdomains at adhesion sites into endocytic carriers, facilitating membrane turnover during cell morphological changes.
authors.affiliation: MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Doherty
authors.forename: Monika K
authors.initials: MK
authors.lastname: Åhlund
authors.forename: Mark T
authors.initials: MT
authors.lastname: Howes
authors.forename: Björn
authors.initials: B
authors.lastname: Morén
authors.forename: Robert G
authors.initials: RG
authors.lastname: Parton
authors.forename: Harvey T
authors.initials: HT
authors.lastname: McMahon
authors.forename: Richard
authors.initials: R
authors.lastname: Lundmark
mesh_terms: D002448:Cell Adhesion; D002462:Cell Membrane; D002465:Cell Movement; D021982:Cell-Matrix Junctions / Q000378:metabolism*; D002966:Clathrin / Q000378:metabolism; D004705:Endocytosis; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D022001:Focal Adhesions / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008055:Lipids; D021962:Membrane Microdomains / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D034622:RNA Interference
chemical_list: C115971:ARHGAP26 protein, human; D002966:Clathrin; D020690:GTPase-Activating Proteins; D008055:Lipids; D051417:Focal Adhesion Kinase 1