The Study On The Action Of P38-HSP27 Signaling Pathway Mediating The Actin Cytoskeleton Remodeling In Renal Tubular Epithelial Cells During ATP Depletion

The remodeling of actin cytoskeleton in renal tubular epithelial cells is a main reason which cause renal injury during the early ischemic stage . However, the mechanism of this remodeling process remains poorly understood. We established an ATP depletion model in vitro to investigate the remodeling of actin cytoskeleton and its possible mechanism during ATP depletion. Based on some existing investigations we hypothesized that p38-HSP27 signaling pathway might mediate the remodeling of actin cytoskeleton in ATP depleted renal tubular epithelial cells. To address this hypothesis, the following studies were designed and performed. In our study, we established the ATP depletion model in vitro. The remodeling of actin cytoskeleton was detected by FITC-phallodin staining and the F-actin contents were measured by the fluorescence indensity. The expression of p38 and HSP27, phospho-p38 and phospho-HSP27 was evaluated by western blotting analysis. The expression of HSP27 in cytosolic fraction and cytoskeletal fraction was also detected by western blotting. After ATP depletion treatment the actin cytoskeleton changed obviously. The contents of F-actin were directly correlating with the ATP depletion periods. P38 kinase was activated corresponding with the phosphorylation of HSP27 dring ATP depletion. And HSP27 was shifting from cytoskeletal fraction to cytosolic fraction. When p38 inhibitor SB203580 was included in the experiment, the remodeling of actin cytoskeleton caused by ATP depletion was partially reversed, the phosphorylation of HSP27 was markedly inhibited and the translocation of HSP27 was reversed. All these results suggested that p38 kinase might influence the activity of capping protein HSP27 through its phosphorylation effect on HSP27, which might contribute to the remodeling of actin cytoskeleton during ATP depletion.Taken together with our studies, we conclude that:1. The actin cytoskeleton in renal tubular epithelial cells has a polymerizing effect during ATP depletion.2. p38-HSP27 signaling pathway partially mediates the actin cytoskeleton remodeling caused by ATP depletion in NRK52E cells.