Focal Adhesion Protein Zyxin Is a Mechanosensitive Modulator of Gene Expression in Vascular Smooth Muscle Cells

Abstract

Excessive deformation of vascular smooth muscle cells (SMCs) caused by a prolonged increase in blood pressure (eg, in hypertension) results in an adaptive remodeling of the vessel wall that is characterized by SMC hypertrophy or hyperplasia and contributes to fixation of the increase in blood pressure. The onset of this process is characterized by a unique change in gene expression in the SMC. However, thus far, no transcription factor has been identified that specifically mediates mechanosensitive gene expression in these cells. Therefore, the role of a putative mechanotransducer, the cytoskeletal protein zyxin, was investigated in rat aortic cultured SMCs. Immunofluorescence and Western blot analysis revealed that on exposure to cyclic stretch, but not to osmotic stress or treatment with proinflammatory cytokines, zyxin dissociates from focal adhesions and accumulates in the nucleus. Unlike zyxin, vinculin, another focal adhesion-associated protein, did not translocate. Moreover, antisense oligonucleotide downregulation of zyxin protein abundance suggested that zyxin accumulation in the nucleus is a prerequisite for mechanosensitive gene expression in these cells. Thus, stretch-induced endothelin B receptor expression, for example, was attenuated, whereas that of tenascin-C was augmented after zyxin suppression. The data are consistent with a role for zyxin in transducing mechanical stimuli from the cell membrane to the nucleus in vascular SMCs and in controlling the expression of mechanosensitive genes that have been implicated in hypertension-induced arterial remodeling.