Abstract
We studied the molecular mechanism of cyclic stretch dependent stress fiber disassembly using a semi-intact cell system. Human umbilical vein endothelial cells were cultured on an elastic substratum, permeabilized by digitonin, termed semi-intact cells here, and mechanically stretched (20%, 1 Hz) in standard buffer or in brain extract solution. Stress fibers disassembled when the cells were cyclically stretched in the presence of brain extract. The disassembly was also observed when tension in stress fibers was decreased with compression (30%) of the substratum, implying that loss of mechanical tension caused stress fiber disassembly in a cytoplasmic factor dependent way. We examined two candidate molecules for the stress fiber disassembly: cofilin and gelsolin, actin severing proteins. Purified cofilin (2μg/ml) disassembled stress fibers in semi-intact cells during cyclic stretch, but gelsolin (2μg/ml) did not even in the presence of 1 mM Ca2+. Cofilin alone disassembled stress fiber without cyclic stretch when actomyosin ATPase was inhibited or ATP was removed from the buffer; these treatments decline the tension in stress fibers. By contrast continuous stretch of the cell inhibited the cofilin dependent stress fiber disassembly with or without ATP. These results indicate that mechanical tension in actin cytoskeleton prevents actin cytoskeleton from ADF/cofilin dependent disassembly. [Jpn J Physiol 54 Suppl:S76 (2004)]
