Objective:To examine the role of heat shock protein 90(Hsp90) in the maintenance of actin cytoskeleton in human neuroblastoma tumor cells.Methods:Co-precipitation experiments were performed to examine Hsp90 interaction with actin.Hsp90 and actin interactions were evaluated by protein refolding and acto-myosin motility assays.17-(AUylamino)-17- demethoxygeldanamycin(17AAG) induced actin-cytoskeleton re-organization was examined by laser scanning confocal microcopy.Results:It was shown that inhibition of Hsp90 by 17AAC accelerates detergent induced cell lysis of neuroblastoma tumor cells through destabilization of actin cytoskeleton.The in vitro co-precipitation experiments showed that functional but not mutant Hsp90 binds with F-actin.Among biochemical modifications,phopshorylation and oligomerization enhanced Hsp90 binding with F-actin.F-actin binding to Hsp90 interfered with Hsp90 chaperone activity in protein refolding assays,and Hsp90 binding to F-actin interfered with actin motility on myosin coated flow cell.In the combination treatment,17AAG irreversibly augmented the effect of cytochalasin D,an inhibitor of actin polymerization.Conclusions:It can be concluded that Hsp90 binds to F-actin in tumor cells and maintains the cellular integrity. The results display a novel element of Hsp90 inhibition in destabilizing the actin cytoskeleton of tumor cells,therefore suggest that 17AAG combination with cytoskeletal disruptor may be effective in combating cancer. Objective: To examine the role of heat shock protein 90 (Hsp90) in the maintenance of actin cytoskeleton in human neuroblastoma tumor cells. Methods: Co-precipitation experiments were performed to examine Hsp90 interaction with actin. Hsp90 and actin interactions were evaluated by protein refolding and acto-myosin motility assays.17- (AUylamino) -17- demethoxygeldanamycin (17AAG) induced actin-cytoskeleton re-organization was examined by laser scanning confocal microcopy. Results: It was shown that inhibition of Hsp90 by 17AAC accelerates detergent induced cell lysis of neuroblastoma tumor cells through destabilization of actin cytoskeleton. in vitro co-precipitation experiments showed that functional but not mutant Hsp90 binds with F-actin. Am bi biochemical modifications, phopshorylation and oligomerization enhanced Hsp90 binding with F-actin. F-actin binding to Hsp90 interfered with Hsp90 chaperone activity in protein refolding assays, and Hsp90 binding to F-actin interfered with actin motilit y on myosin coated flow cell. the combination treatment, 17 AAG irreversibly augmented the effect of cytochalasin D, an inhibitor of actin polymerization. Conlusions: It can be concluded that Hsp90 binds to F-actin in tumor cells and maintains the cellular integrity. results display a novel element of Hsp90 inhibition in destabilizing the actin cytoskeleton of tumor cells, therefore suggesting that 17 AAG combination with cytoskeletal disruptor may be effective in combating cancer.