The ubiquitin-related BAG-1 provides a link between the molecular chaperones Hsc70/Hsp70 and the proteasome.
The BAG-1 protein modulates the chaperone activity of Hsc70 and Hsp70 in the mammalian cytosol and nucleus. Remarkably, BAG-1 possesses a ubiquitin-like domain at its amino terminus, suggesting a link to the ubiquitin/proteasome system. Here we show that BAG-1 is indeed associated with the 26 S proteasome in HeLa cells. Binding of the chaperone cofactor to the proteolytic complex is regulated by ATP hydrolysis and is not mediated by Hsc70 and Hsp70. The presented findings reveal a role of BAG-1 as a physical link between the Hsc70/Hsp70 chaperone system and the proteasome. In fact, targeting of BAG-1 to the proteasome promotes an association of the chaperones with the proteolytic complex in vitro and in vivo. A regulatory function of the chaperone cofactor at the interface between protein folding and protein degradation is thus indicated.
Lüders
J
J
Department of Molecular Cell Biology, Max Planck Institute for Biochemistry, Am Klopferspitz 18a, D-82152 Martinsried, Germany.
Demand
J
J
Höhfeld
J
J
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004268:DNA-Binding Proteins; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors; D014452:Ubiquitins / Q000378:metabolism*
C091732:BCL2-associated athanogene 1 protein; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D009097:Multienzyme Complexes; D020033:Protein Isoforms; D014157:Transcription Factors; D014452:Ubiquitins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex