Identification of a filamin docking site on PTP-PEST.

PTP-PEST is a cytoplasmic protein-tyrosine phosphatase (PTP) implicated in the regulation of biological processes such as cell motility, cytokinesis, focal adhesion disassembly, and lymphocyte activation. Using a proteomics approach, filamin-A was identified as a novel interacting protein that bound to GST-PTP-PEST. This interaction was confirmed in vitro and in cells by coimmunoprecipitation. The site of filamin interaction on PTP-PEST was mapped to the fourth proline-rich region (Pro4). PTP-PEST has previously been implicated in the regulation of cytokinesis. In further support of this finding, expression of PTP-PEST in HeLa cells resulted in the formation of multinucleated cells. A PTP-PEST mutant lacking Pro4 and unable to bind filamin-A failed to induce the multinucleated phenotype. Further, depletion of filamin-A in HeLa cells was found to reduce the PTP-PEST-dependent multinucleation phenotype. Hence, we conclude that the interaction of PTP-PEST with filamin-A may function in the control of cytokinesis in mammalian cells.