title: Hsp72 chaperone function is dispensable for protection against stress-induced apoptosis.
abstract: In addition to its role as a molecular chaperone, heat shock protein 72 (Hsp72) protects cells against a wide range of apoptosis inducing stresses. However, it is unclear if these two roles are functionally related or whether Hsp72 inhibits apoptosis by a mechanism independent of chaperone activity. The N-terminal adenosine triphosphatase domain, substrate-binding domain and the C-terminal EEVD regulatory motif of Hsp72 are all essential for chaperone activity. In this study, we show that Hsp72 mutants with a functional substrate-binding domain but lacking chaperone activity retain their ability to protect cells against apoptosis induced by heat and tumor necrosis factor alpha. In contrast, a deletion mutant lacking a functional substrate-binding domain has no protective capacity. The ability of the Hsp72 substrate-binding domain to inhibit apoptosis independent of the regulatory effects of the adenosine triphosphate-binding domain indicates that the inhibition of apoptosis may involve a stable binding interaction with a regulatory substrate rather than Hsp72 chaperone activity.
authors.affiliation: Peter MacCallum Cancer Centre, St. Andrews Place, East Melbourne, 3002, Australia.
authors.forename: Ari M
authors.initials: AM
authors.lastname: Chow
authors.forename: Rohan
authors.initials: R
authors.lastname: Steel
authors.forename: Robin L
authors.initials: RL
authors.lastname: Anderson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D050884:HSP72 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009154:Mutation; D013312:Stress, Physiological / Q000502:physiology*
chemical_list: D050884:HSP72 Heat-Shock Proteins