ATP RELEASES HSP-72 FROM PROTEIN AGGREGATES AFTER RENAL ISCHEMIA

The pattern of 72-kDa heat-shock protein (HSP-72) induction after rena l ischemia suggests a role in restoring cell structure. HSP-72 activit y in the repair and release from denatured and aggregated proteins req uires ATP. Protein aggregates were purified from normal and ischemic f at renal cortex. The addition of ATP to cortical homogenates reduced N SP-72, Na+-K+-ATPase, and actin in aggregates subsequently isolated, s uggesting that their interaction is ATP dependent. Altering ATP hydrol ysis in the purified aggregates, however, had different effects. ATP r eleased HSP-72 during reflow and preserved Na+-K+-ATPase association w ith aggregates at 2 h but bad no effect in controls or at 6 h reflow a nd caused no change in actin. These results indicate that HSP-72 compl exes with aggregated cellular proteins in an ATP-dependent manner and suggests that enhancing RSP-72 function after ischemic renal injury as sists refolding and stabilization of Na+-R+-ATPase or aggregated eleme nts of the cytoskeleton, allowing reassembly into a more organized sta te.