Gudi S R, Lee A A, Clark C B, Frangos J A
Department of Bioengineering, University of California, San Diego, La Jolla 92093, USA.
Am J Physiol. 1998 May;274(5):C1424-8. doi: 10.1152/ajpcell.1998.274.5.C1424.
Cardiac fibroblasts are responsible for the production of the extracellular matrix of the heart, with alterations of fibroblast function implicated in myocardial infarction and cardiac hypertrophy. Here the role of heterotrimeric GTP-binding proteins (G proteins) in the mechanotransduction of strain in rat cardiac fibroblasts was investigated. Cells in an equibiaxial stretch device were incubated with the photoreactive GTP analog azidoanalido [alpha-32P]GTP (AAGTP) and were subjected to various regimens of strain. Autoradiographic analysis showed a 42-kDa protein labeled for cells exposed to 12 cycles of 3% strain or 6 cycles of 6% strain over 60 s (strain rate of 1.2%/s), whereas 6 cycles of 3% strain (0.6%/s) elicited no measurable response. To further investigate the role of strain rate, a single 6% cycle over 10 or 60 s (1.2% and 0.2%/s, respectively) was applied, with the more rapid cycle stimulating AAGTP binding, whereas the lower strain rate showed no response. In cells subjected to a single 6% cycle/10 s, immunoprecipitation identified the AAGTP-labeled 42-kDa band as the G protein subunits G alpha q and G alpha i1. These results demonstrate that G protein activation represents one of the early mechanotransduction events in cardiac fibroblasts subjected to mechanical strain, with the rate at which the strain is applied modulating this response.
心脏成纤维细胞负责心脏细胞外基质的生成，成纤维细胞功能的改变与心肌梗死和心脏肥大有关。在此，研究了异源三聚体GTP结合蛋白（G蛋白）在大鼠心脏成纤维细胞应变机械转导中的作用。将处于双轴拉伸装置中的细胞与光反应性GTP类似物叠氮苯胺基[α-32P]GTP（AAGTP）一起孵育，并使其承受各种应变方案。放射自显影分析显示，在60秒内暴露于12个周期的3%应变或6个周期的6%应变（应变率为1.2%/秒）的细胞中，有一个42 kDa的蛋白质被标记，而6个周期的3%应变（0.6%/秒）未引起可测量的反应。为了进一步研究应变率的作用，分别在10秒或60秒内施加单个6%的周期（分别为1.2%和0.2%/秒），较快的周期刺激AAGTP结合，而较低的应变率则无反应。在经受单个6%周期/10秒的细胞中，免疫沉淀确定AAGTP标记的42 kDa条带为G蛋白亚基Gαq和Gαi1。这些结果表明，G蛋白激活是心脏成纤维细胞在受到机械应变时早期机械转导事件之一，施加应变的速率调节这种反应。
