c-Src and HSP72 interact in ATP-depleted renal epithelial cells

Disruption of cell contact sites during ischemia contributes to the loss of organ function in acute renal failure. Because prior heat stress protects cell contact sites in ATP-depleted renal epithelial cells in vitro, we hypothesized that heat shock protein 72 (HSP72), the major inducible cytoprotectant in mammalian cells, interacts with protein kinases that regulate cell-cell and cell-matrix interactions. ATP depletion increased the content of Tyr(416) Src, the activated form of this kinase. c-Src activation was associated with an increase in the tyrosine phosphorylation state of beta-catenin, paxillin, and vinculin, three c-Src substrate proteins that localize to and regulate cell contact sites. Prior heat stress inhibited c-Src activation and decreased the degree of tyrosine phosphorylation of all three Src substrates during ATP depletion and/or early recovery. HSP72 coimmunoprecipitated with c-Src only in cells subjected to heat stress. ATP depletion markedly increased the interaction between HSP72 and c-Src, supporting the hypothesis that HSP72 regulates Src kinase activity. These results suggest that alterations in the tyrosine phosphorylation state of proteins located at the cell-cell and cell-matrix interface mediate, at least in part, the functional state of these structures during ATP depletion and may be modulated by interactions between HSP72 and c-Src.