Mechanism of Stretch-Induced Activation of the Mechanotransducer Zyxin in Vascular Cells

Abstract

Vascular cells respond to supraphysiological amounts of stretch with a characteristic phenotypic change that results in dysfunctional remodeling of the affected arteries. Although the pathophysiological consequences of stretch-induced signaling are well characterized, the mechanism of mechanotransduction is unclear. We focused on the mechanotransducer zyxin, which translocates to the nucleus to drive gene expression in response to stretch. In cultured human endothelial cells and perfused femoral arteries isolated from wild-type and several knockout mouse strains, we characterized a multistep signaling pathway whereby stretch led to a transient receptor potential channel 3-mediated release of the endothelial vasoconstrictor peptide endothelin-1 (ET-1). ET-1, through autocrine activation of its B-type receptor, elicited the release of pro-atrial natriuretic peptide (ANP), which caused the autocrine activation of the ANP receptor guanylyl cyclase A (GC-A). Activation of GC-A, in turn, led to protein kinase G-mediated phosphorylation of zyxin at serine 142, thereby triggering the translocation of zyxin to the nucleus, where it was required for stretch-induced gene expression. Thus, we have identified a stretch-induced signaling pathway in vascular cells that leads to the activation of zyxin, a cytoskeletal protein specifically involved in transducing mechanical stimuli.

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“…Zyxin is a protein attached to the cytoskeleton helping to organize function, dynamics and maintenance of actin fibers [54]. In endothelial cells, zyxin is activated in response to stretch, followed by translocation from the cytoskeleton to the nucleus [55]. Prohibitin (PHB) acts as a mediator of mitochondria shuttling in response to oxidative stress [56].…”

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“…Upon reaching confluence, cells were incubated for 14 hrs in low serum media (1% FCS) and then treated as indicated in the Results with TGFβ (0.1-12 ng/ml), BMP-2 (50-100 ng/ml), PDGF (50 ng/ml), VEGF (20 ng/ml), bFGF (10 ng/ml), IL-6 10 ng/ml), PMA (60 ng/ml), SB43152 (1 μM), and/or α-amanitin (20 μg/ml), for different time periods as noted. Using previously reported methods [31,32], vascular smooth muscle cells (SMC) were isolated from the aortae of CD248 WT/WT or CD248 KO/KO pups, cultured in SMC growth media (Promocell, Heidelberg, Germany) with 15% FCS and 1% Penicillin/Streptomycin (Invitrogen) and used at passages 2-5. Wehi-231 and A20 (mouse B-lymphoma) cell lines (gift of Dr. Linda Matsuuchi, University of British Columbia) were cultured in RPMI media with 10% fetal calf serum (FCS), 1% Penicillin/Streptomycin and 0.1% mercaptoethanol.…”

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