αvβ3 integrin and cofilin modulate K1735 melanoma cell invasion

Cytoskeletal reorganization is partially mediated through cofilin, an actin assembly regulatory protein. Cofilin activity is modulated by reversible phosphorylation at Ser3. In this study, using K1735 murine melanoma cells, we examined the relationship between β3-integrin expression, phosphorylation of cofilin, and metalloproteinase production. The levels of phosphorylated cofilin were 10-fold higher in cells expressing αvβ3 than in αvβ3-negative cells when plated on vitronectin for 30 min. However, by 60 min, phosphorylation of cofilin was greater in the β3-negative cells. Expression of the wild type (WT) or non-phosphorylatable cofilin (A3 mutant) increased melanoma cell migration on vitronectin and invasion through a reconstituted basement membrane. Expression of a pseudophosphorylated, poorly active cofilin (E3 mutant) reduced cell motility. Expression of active cofilin accelerated the phosphorylation of FAK at Y397 and at Y576, strongly implicating cofilin as a mediator of cell signaling. The expression of MT1-MMP and MMP2 was also increased by expression of wild type or A3 cofilin. A 50% reduction of both enzymes was observed by the expression of the E3 cofilin. Overexpression of non-phosphorylatable cofilin was sufficient to induce the expression of MT1-MMP and MMP2 in the β3-negative M2Tβ3 cells. Interestingly, the invasion of M2Tβ3 cells could be sustained by overexpression of cofilin A3. These results suggest that the integrin αvβ3 and cofilin together regulate K1735 melanoma cell invasion.