Yunhao Liu
 
 

University of Virginia
Department of Microbiology
1300 Jefferson Park Avenue
Room 2-25 Jordan Hall
Charlottesville, VA 22908
Phone: 434-924-5341 (lab)
FAX: 434-982-0689
email: yl6b
@virginia.edu

 

Research:

I work on a protein called ASAP1 (Arf-GAP containing SH3 domain, Ankyrin repeats and PH domain). It was originally cloned as a Src binding partner and phosphorylation substrate. Although ADP-Ribosylation Factor (Arf) family GTP-binding proteins are best known as regulators of membrane trafficking, recent studies also implicate them in cytoskeletal remodeling. Using yeast two-hybrid approach, we successfully identified ASAP1 as a FAK (Focal Adhesion Kinase) binding protein and its C-terminal SH3 domain as the major FAK-interacting motif. Study done with Glutathione-S-transferase (GST) fusion proteins indicated that ASAP1 primarily targeted the proline-rich motif proximal to the FAT (Focal Adhesion Targeting) domain of FAK. Other FAK-binding proteins which possess the same feature include Cas and Graf (These two proteins were also cloned in Dr. J. Thomas Parsons' laboratory in 1996 and 1997). The recruitments of these molecules and ASAP1 to focal adhesions are believed to be mediated by their interactions with FAK.

I am currently using biochemical and cell biology approaches to further characterize ASAP1. Endogenous ASAP1 and FAK could be co-immunoprecipitated from REF52 fibroblast cell lysate, indicating that ASAP1 interacts with FAK in vivo. In agreement with the biochemical study, ASAP1 colocalized with FAK and another focal adhesion marker paxillin in REF52 cells. Transiently overexpressed wild type ASAP1 in these cells inhibited cell spreading and focal adhesion localization of paxillin while either an inactivating mutation in the GAP domain or deletion of the C-terminal SH3 region blocked the inhibitory effects observed with wild type ASAP1. The association of ASAP1 with FAK is likely to be functionally important in the coordination of integrin signaling and ARFs activities.

Future direction: we are interested in the dynamics of the recruitment of ASAP1 to focal adhesions upon integrin engagement and activation. This study is not restricted to ASAP1-we would like to include c-Src, Cas and paxillin on the investigation list.

Publications:

Liu Y, Loijens JC, Martin KH, Karginov AV, Parsons JT. The Association of ASAP1, an ADP Ribosylation Factor-GTPase Activating Protein, with Focal Adhesion Kinase Contributes to the Process of Focal Adhesion Assembly. Mol Biol Cell. 2002 Jun;13(6):2147-56