HEAT-SHOCK-PROTEIN-25 INDUCTION AND REDISTRIBUTION DURING ACTIN REORGANIZATION AFTER RENAL ISCHEMIA

The small heat-shock proteins appear to have a regulatory role in acti n dynamics. Since cytoskeletal disruption is integral to ischemic rena l injury, we evaluated expression and intracellular distribution of he at-shock protein 25 (HSP-25) in rat renal cortex after 45 min of renal ischemia. HSP-25 was constitutively expressed and induced by ischemia with peak levels reached by 6 h reflow. Ischemia caused a shift of HS P-25 from the detergent-soluble into the insoluble cytoskeletal fracti on. By 2 h reflow, the majority of HSP-25 had redistributed into the s oluble fraction. HSP-25 was predominantly localized in a subapical dis tribution in control proximal tubules, a pattern intermediate between deoxyribonuclease (DNase)-reactive and filamentous actin. After ischem ia, HSP-25 dispersed through the cytoplasm with small punctate accumul ations similar to DNase-reactive actin. During later reflow, all three proteins were found in coarse intracytoplasmic accumulations; however , HSP-25 and DNase-reactive actin were in separate accumulations. HSP- 25 and microfilamentous actin staining returned to the subapical domai n. Thus the temporal and spatial patterns of HSP-25 induction and dist ribution suggest specific interactions between HSP-25 and actin during the early postischemic reorganization of the cytoskeleton. HSP-25 may have additional roles distinct from actin dynamics later in the cours e of postischemic recovery.