Filamin A protects cells against force-induced apoptosis by stabilizing talin- and vinculin-containing cell adhesions.

Abstract

In mechanically loaded tissues such as weight-bearing joints, myocardium and periodontal ligament, pathophysiological forces can disrupt cell-matrix contacts, which in turn induce cell death leading to tissue and organ dysfunction. Protection against force-induced cell death may be mediated by filamin A (FLNa), an actinbinding protein that regulates β1 integrin-mediated cell adhesion. We examined collagen distribution, cell densities and cell death in periodontal ligament of filamin A wildtype and fibroblast conditional-knockout mice. Deletion of FLNa in fibroblasts was associated with 2-fold increase of acellular areas in the periodontal ligament and a 7-fold higher proportion of apoptotic cells. In cultured fibroblasts with FLNa knockdown, we examined the impact of supra-physiological forces (1 pN/μm2 cell area; applied through the β1 integrin) on recruitment of talin and vinculin to focal adhesions and on apoptosis. Compared with wildtype, FLNa knockdown cells exhibited 3-fold increases of floating cells after overnight force application and a 2-fold increase of cell detachment. Force induced time-dependent reductions (p<0.05) of the numbers of activated β1 integrin, talin and vinculin-stained adhesions in FLNa knockdown compared with wildtype cells. We conclude that FLNa protects against apoptosis in cells subjected to mechanical forces and this protection is mediated by enhanced formation and maturation of matrix adhesions.