Shifrin Yulia, Arora Pamela D, Ohta Yasutaka, Calderwood David A, McCulloch Christopher A
CIHR Group in Matrix Dynamics, University of Toronto, Toronto, Ontario, Canada.
Mol Biol Cell. 2009 Mar;20(5):1269-79. doi: 10.1091/mbc.e08-08-0872. Epub 2009 Jan 14.
Cells in mechanically active environments are subjected to high-amplitude exogenous forces that can lead to cell death. Filamin A (FLNa) may protect cells from mechanically induced death by mechanisms that are not yet defined. We found that mechanical forces applied through integrins enhanced Rac-mediated lamellae formation in FLNa-null but not FLNa-expressing cells. Suppression of force-induced lamella formation was mediated by repeat 23 of FLNa, which also binds FilGAP, a recently discovered Rac GTPase-activating protein (GAP). We found that FilGAP is targeted to sites of force transfer by FLNa. This force-induced redistribution of FilGAP was essential for the suppression of Rac activity and lamellae formation in cells treated with tensile forces. Depletion of FilGAP by small interfering RNA, inhibition of FilGAP activity by dominant-negative mutation or deletion of its FLNa-binding domain, all resulted in a dramatic force-induced increase of the percentage of annexin-V-positive cells. FilGAP therefore plays a role in protecting cells against force-induced apoptosis, and this function is mediated by FLNa.
处于机械活性环境中的细胞会受到高幅度的外力作用,这可能导致细胞死亡。细丝蛋白A(FLNa)或许能通过尚未明确的机制保护细胞免受机械诱导的死亡。我们发现,通过整合素施加的机械力会增强Rac介导的片状伪足形成,但在缺乏FLNa的细胞中而非表达FLNa的细胞中。FLNa的第23个重复序列介导了对力诱导的片状伪足形成的抑制作用,该重复序列还与FilGAP结合,FilGAP是最近发现的一种Rac GTP酶激活蛋白(GAP)。我们发现FilGAP被FLNa靶向到力传递位点。这种力诱导的FilGAP重新分布对于抑制受拉伸力处理的细胞中的Rac活性和片状伪足形成至关重要。通过小干扰RNA使FilGAP缺失、通过显性负性突变抑制FilGAP活性或缺失其FLNa结合结构域,均导致力诱导的膜联蛋白V阳性细胞百分比显著增加。因此,FilGAP在保护细胞免受力诱导的凋亡中发挥作用,且该功能由FLNa介导。