Tensin1 Requires Protein Phosphatase-1α in Addition to RhoGAP DLC-1 to Control Cell Polarization, Migration, and Invasion

Tensin is a family of multidomain scaffold proteins that bind the cytoplasmic tail of beta-integrins and localize to adhesions that anchor stress fibers in cells. Tensin expression is suppressed in cancer, especially metastatic cancer. The N-terminal domain of tensin1 associates with protein phosphatase-1 alpha (PP1 alpha) and mediates PP1 alpha localization to adhesions. Here, we show F302A mutation in aKVXF motif of tensin1 abrogates binding to PP1 alpha. The SH2 domain in tensin family member c-ten requires R474 to bind a RhoGAP called DLC-1 (deleted in liver cancer). We mutated the corresponding residue in tensin1, R1488A, and showed this reduces association with DLC-1. Unexpectedly, tensin1 F302A also had reduced association with DLC-1. Expression of tensin1 F302A or R1488A showed similar dominant phenotypes, with reduced cell polarization, lowered MLC20 phosphorylation and reduced levels of RhoA(GTP) compared with cells expressing tensin1 WT. However, migration and invasion of metastatic MDA MB 231 breast cancer cells were differentially affected by tensin1 mutated at F302A or R1488A. Cancer cells stably expressing F302A tensin1 showed increased migration and invasion compared with cells stably expressing either R1488A tensin1 or WT tensin1. This suggests that PP1 alpha bound to tensin1 has additional effects in reducing migration and invasion that are not mediated through DLC-1. Our results show the importance of PP1 alpha binding to tensin1 for the regulation of cell polarization, migration, and invasion.