Abstract
Melanoma cells have been shown to undergo fast amoeboid or Leader Bleb-Based Migration (LBBM), requiring a large and stable bleb for migration. In leader blebs, is a rapid flow of cortical actin that drives the cell forward. Here, we tested the hypothesis that the actin severing factors, ADF and cofilin-1, are essential for contractility and actin flow for LBBM. Using RNAi in melanoma A375 cells, we find that co-depleting ADF and cofilin-1 led to a large increase in the level of cortical actin, suggesting that ADF and cofilin-1, together, regulate cortical actin in these cells. Moreover, RNAi of ADF and cofilin-1 increased the number of cortical, polymerization competent, barbed-ends. Therefore, severing by these proteins appears to promote cortical actin turnover. Furthermore, actin severing factors can promote contractility through the regulation of actin architecture. However, RNAi of cofilin-1 but not ADF led to a significant decrease in cell stiffness. As LBBM is stimulated by cell confinement, we then used confined cells to evaluate the role of ADF and cofilin-1 in regulating actin dynamics. We found cofilin-1 to be enriched at leader bleb necks, whereas RNAi of ADF and cofilin-1 reduced bleb sizes and the frequency of motile cells. Strikingly, cells without ADF and cofilin-1 had blebs with abnormally long necks. Many blebs failed to retract and displayed slower actin turnover and flow in the absence of ADF and cofilin-1. Collectively, our data identifies ADF and cofilin-1 as actin remodeling factors required for the amoeboid migration of melanoma cells.
Competing Interest Statement
The authors have declared no competing interest.
