The kinase Pyk2 is involved in renal fibrosis by means of mechanical stretch–induced growth factor expression in renal tubules

Abstract

Unilateral ureteral obstruction is a well-established experimental model of progressive renal fibrosis. We tested whether mechanical stretch and subsequent renal tubular distension might lead to renal fibrosis by first studying renal tubular epithelial cells in culture. We found that mechanical stretch induced reactive oxygen species that in turn activated the cytoplasmic proline-rich tyrosine kinase-2 (Pyk2). This kinase is abundantly expressed in tubular epithelial cells where it is activated by several stimuli. Using mice with deletion of Pyk2 we found that the expression of transforming growth factor-β1 induced by mechanical stretch in renal tubular epithelial cells was significantly reduced. The expression of connective tissue growth factor was also reduced in the Pyk2(-/-) mice. We also found that expression of connective tissue growth factor was independent of transforming growth factor-β1, but dependent on the Rho-associated coiled-coil forming protein kinase pathway. Thus, Pyk2 may be an important initiating factor in renal fibrosis and might be a new therapeutic target for ameliorating renal fibrosis.

Activation of Glycogen Synthase Kinase 3β Ameliorates Diabetes-induced Kidney Injury

“…Ϫ/Ϫ mice have decreased renal fibrosis following ureteral obstruction (39). In contrast to our data, Src activates GSK3␤ by tyrosine phosphorylation in prostate cancer (40), suggesting cell-and contextspecific regulation of GSK3␤ by its upstream kinases.…”

Cyclic stretch-induced TGF-β1 and fibronectin expression is mediated by β1-integrin through c-Src- and STAT3-dependent pathways in renal epithelial cells

“…The culture plates were placed on vacuum-based loading docks of the Flexcell FX-4000T apparatus (Flexcell) in the incubator and subjected to pulsatile mechanical stretch (10 -20% of equibiaxial elongation) at a frequency of 0.1 Hz. Previous reports have shown that these parameters induce a significant difference in TGF-␤1 secretion between nonstretched renal proximal tubule cells and stretched cells (41,42,54,57). Nonstretched cells (control) were exposed to identical experimental conditions but without mechanical stretch.…”

“…In addition, the activation of ERK1/2 is abrogated by the Src family kinase inhibitor 3-(4-chlorophenyl)-1-(1,1-dimethylethyl)-1H-pyrazolo [3,4-d]pyrimidin-4-amine (PP2) and by transfection of proximal tubule cells with a dominant negative mutant of c-Src (DN-Src), indicating that c-Src is critical for stretch-induced ERK1/2 activation in renal proximal tubular cells (1). Moreover, studies carried out in vitro have recently shown that mechanical stretch induces transforming growth factor (TGF)-␤1 expression in renal proximal tubular cells (35,41,54,57). However, the molecular mechanisms by which mechanical stretch contributes to TGF-␤1 production leading to renal fibrosis are not yet completely understood.…”

Delayed skin wound repair in proline-rich protein tyrosine kinase 2 knockout mice

“…3A). Overexpressed calcium-dependent tyrosine kinase-related nonkinase (CRNK) inhibits autophosphorylation of endogenous Pyk2 and functions as a dominant-negative inhibitor of Pyk2 signaling (28). Amplification of Pyk2-and CRNK-encoding adenoviruses was provided by ViraQuest (North Liberty, IA).…”