Prefoldin subunit MM1 promotes cell migration via facilitating filopodia formation

c-Myc modulator 1 (MM1), also known as PFDN5, is the fifth subunit of prefoldin. It was previously reported that MM1-based prefoldin promotes folding of actin during assembly of cytoskeleton, which plays key roles in cell migration. However, no evidence supports that MM1 affects cell migration. In the present study, we found that MM1 promotes cell migration in multiple cell lines. Further study revealed that MM1 promotes polymerization of β-actin into filamentous form and increases both density and length of filopodia. Effects of MM1 on filopodia formation and cell migration depend on its prefoldin activity. Though c-Myc is repressed by MM1, simultaneous knock-down of c-Myc fails to rescue migration inhibition induced by MM1 ablation. Taken together, we here, for the first time, report that prefoldin subunit MM1 is involved in cell migration; this involvement of MM1 in cell migration is due to its prefoldin activity to boost polymerization of β-actin during filopodia formation. Our findings may be helpful to elucidate the mechanism of cell migration and cancer metastasis.