Biochemical and functional characterization of the interaction between liprin-?1 and GIT1: implications for the regulation of cell motility.

ABSTRACT: We have previously identified the scaffold protein liprin-?1 as an important regulator of integrin-mediated cell motility and tumor cell invasion. Liprin-?1 may interact with different proteins, and the functional significance of these interactions in the regulation of cell motility is poorly known. Here we have addressed the involvement of the liprin-?1 partner GIT1 in liprin-?1-mediated effects on cell spreading and migration. GIT1 depletion inhibited spreading by affecting the lamellipodia, and prevented liprin-?1-enhanced spreading. Conversely inhibition of the formation of the liprin-?1-GIT complex by expression of liprin-?CC3 could still enhance spreading, although to a lesser extent compared to full length liprin-?1. No cumulative effects were observed after depletion of both liprin-?1 and GIT1, suggesting that the two proteins belong to the same signaling network in the regulation of cell spreading. Our data suggest that liprin-?1 may compete with paxillin for binding to GIT1, while binding of ?PIX to GIT1 was unaffected by the presence of liprin-?1. Interestingly, GIT and liprin-?1 reciprocally regulated their subcellular localization, since liprin-?1 overexpression, but not the GIT binding-defective liprin-?CC3 mutant, affected the localization of endogenous GIT at peripheral and mature central focal adhesions, while the expression of a truncated, active form of GIT1 enhanced the localization of endogenous liprin-?1 at the edge of spreading cells. Moreover, GIT1 was required for liprin-?1-enhanced haptotatic migration, although the direct interaction between liprin-?1 and GIT1 was not needed. Our findings show that the functional interaction between liprin-?1 and GIT1 cooperate in the regulation of integrin-dependent cell spreading and motility on extracellular matrix. These findings and the possible competition of liprin-?1 with paxillin for binding to GIT1 suggest that alternative binding of GIT1 to either liprin-?1 or paxillin plays distinct roles in different phases of the protrusive activity in the cell.

SUBMITTER: Asperti C 

PROVIDER: S-EPMC3113849 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature