title: GrpE-like regulation of the hsc70 chaperone by the anti-apoptotic protein BAG-1.
abstract: The BAG-1 protein appears to inhibit cell death by binding to Bcl-2, the Raf-1 protein kinase, and certain growth factor receptors, but the mechanism of inhibition remains enigmatic. BAG-1 also interacts with several steroid hormone receptors which require the molecular chaperones Hsc70 and Hsp90 for activation. Here we show that BAG-1 is a regulator of the Hsc70 chaperone. BAG-1 binds to the ATPase domain of Hsc70 and, in cooperation with Hsp40, stimulates Hsc70's steady-state ATP hydrolysis activity approximately 40-fold. Similar to the action of the GrpE protein on bacterial Hsp70, BAG-1 accelerates the release of ADP from Hsc70. Thus, BAG-1 regulates the Hsc70 ATPase in a manner contrary to the Hsc70-interacting protein Hip, which stabilizes the ADP-bound state. Intriguingly, BAG-1 and Hip compete in binding to the ATPase domain of Hsc70. Our results reveal an unexpected diversity in the regulation of Hsc70 and raise the possibility that the observed anti-apoptotic function of BAG-1 may be exerted through a modulation of the chaperone activity of Hsc70 on specific protein folding and maturation pathways.
authors.affiliation: ZMBH, Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany. j-hoehfeld@sun0.urz.uni-heidelberg.de
authors.forename: J
authors.initials: J
authors.lastname: Höhfeld
authors.forename: S
authors.initials: S
authors.lastname: Jentsch
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D004268:DNA-Binding Proteins; D050883:HSC70 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D018832:Molecular Chaperones / Q000378:metabolism; D011485:Protein Binding; D014157:Transcription Factors
chemical_list: C091732:BCL2-associated athanogene 1 protein; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C494647:DNAJB1 protein, human; C484657:GRPEL1 protein, human; C109172:GrpE-like 1 mitochondrial protein, vertebrate; D050883:HSC70 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D006360:Heat-Shock Proteins; C105426:Hip chaperone; D018832:Molecular Chaperones; D014157:Transcription Factors; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases