Hsp90 inhibition depletes Chk1 and sensitizes tumor cells to replication stress.
DNA damage and replication stress activate the Chk1 signaling pathway, which blocks S phase progression, stabilizes stalled replication forks, and participates in G2 arrest. In this study, we show that Chk1 interacts with Hsp90, a molecular chaperone that participates in the folding, assembly, maturation, and stabilization of specific proteins known as clients. Consistent with Chk1 being an Hsp90 client, we also found that Chk1 but not Chk2 is destabilized in cells treated with the Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG). 17-AAG-mediated Chk1 loss blocked the ability of Chk1 to target Cdc25A for proteolytic destruction, demonstrating that the Chk1 signaling pathway was disrupted in the 17-AAG-treated cells. Finally, 17-AAG-mediated disruption of Chk1 activation dramatically sensitized various tumor cells to gemcitabine, an S phase-active chemotherapeutic agent. Collectively, our studies identify Chk1 as a novel Hsp90 client and suggest that pharmacologic inhibition of Hsp90 may sensitize tumor cells to chemotherapeutic agents by disrupting Chk1 function during replication stress.
Arlander
Sonnet J H
SJ
Department of Molecular Pharmacology, Mayo Graduate School, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
Eapen
Alex K
AK
Vroman
Benjamin T
BT
McDonald
Robert J
RJ
Toft
David O
DO
Karnitz
Larry M
LM
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D016227:Benzoquinones; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival; D000071877:Checkpoint Kinase 1; D004249:DNA Damage; D004261:DNA Replication; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D047029:Lactams, Macrocyclic; D011233:Precipitin Tests; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D017828:Rifabutin / Q000031:analogs & derivatives* / Q000494:pharmacology; D016196:S Phase; D015398:Signal Transduction; D013997:Time Factors; D020687:cdc25 Phosphatases / Q000378:metabolism; D000093542:Gemcitabine
D000964:Antimetabolites, Antineoplastic; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D003841:Deoxycytidine; D017828:Rifabutin; C112765:tanespimycin; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases; C517004:CDC25A protein, human; D020687:cdc25 Phosphatases; D000093542:Gemcitabine