Yamane Masako, Matsuda Takahisa, Ito Takashi, Fujio Yasushi, Takahashi Kyoko, Azuma Junichi
Department of Clinical Pharmacology and Pharmacogenomics, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita City, Osaka 565-0871, Japan.
Biochem Biophys Res Commun. 2007 Feb 23;353(4):1023-7. doi: 10.1016/j.bbrc.2006.12.144. Epub 2006 Dec 27.
Mechanical stretch is essential for the cardiac growth. The exposure of cardiac myocytes to the mechanical stretch leads to the cell alignment in parallel to the stretch direction, determining the cell polarity, though it remains to be addressed how mechanical stretch regulates cell orientation. In the present study, we investigated the signal transduction pathways responsible for the cell orientation response to mechanical stretch, focusing on Rho family proteins. Neonatal rat cardiomyocytes were cultured on silicon chambers and exposed to artificial uniaxial cyclic stretch. The pull-down assays revealed that Rac1 was rapidly activated by stretch, but not RhoA. To analyze the roles of Rho family proteins in cardiomyocyte orientation, adenoviral vectors expressing dominant-negative (dn) RhoA and Rac1 were generated. The transfection with adenovirus vector expressing dnRac1, but not dnRhoA, inhibited stretch-induced cell alignment. In conclusion, Rac1 activity is necessary for cardiomyocyte alignment in response to directional stretch.
机械牵张对心脏生长至关重要。心肌细胞暴露于机械牵张下会导致细胞沿牵张方向平行排列，从而决定细胞极性，不过机械牵张如何调节细胞取向仍有待研究。在本研究中，我们聚焦于Rho家族蛋白，研究了负责细胞对机械牵张取向反应的信号转导途径。将新生大鼠心肌细胞培养在硅室中，并使其暴露于人工单轴循环牵张下。下拉实验表明，牵张可迅速激活Rac1，但不能激活RhoA。为分析Rho家族蛋白在心肌细胞取向中的作用，构建了表达显性负性（dn）RhoA和Rac1的腺病毒载体。用表达dnRac1而非dnRhoA的腺病毒载体转染可抑制牵张诱导的细胞排列。总之，Rac1活性是心肌细胞对定向牵张产生排列反应所必需的。
