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Overexpression, genetic amplification and mutations of p21-activated kinase 4 (PAK4) were found in a variety of human cancers. PAK4 regulated actin cytoskeleton reorganization by phosphorylating LIMK1 and promoted cancer cells migration. Using yeast two-hybrid screen, we identified a novel PAK4 binding protein, DGCR6L, which was associated with cancer cell metastasis. We confirmed PAK4 binding to the DGCR6L specifically by GST pull-down assay, and found an association between endogenous PAK4 and DGCR6L by immunoprecipitation in mammalian cells. Furthermore, L115 of DGCR6L was the critical amino acid to bind 466-572aa in the very C-terminus of PAK4. Importantly, DGCR6L was required for the formation of PAK4-DGCR6L-beta-actin complex. Overexpressed DGCR6L promoted migration of AGS cells mediated by PAK4, whereas knock-down of DGCR6L markedly inhibited the migration of those cells. Moreover, DGCR6L (L115V), which did not bind to PAK4, lost the ability to promote AGS cells migration. DGCR6L colocalized with PAK4 or F-actin and enhanced the phosphorylation level of LIMK1 and cofilin in a dose dependent manner. Taken together, our results demonstrated that DGCR6L, a novel PAK4 interacting protein, regulated PAK4-mediated migration of human gastric cancer cells via LIMK1.
