title: Targeting β-tubulin:CCT-β complexes incurs Hsp90- and VCP-related protein degradation and induces ER stress-associated apoptosis by triggering capacitative Ca2+ entry, mitochondrial perturbation and caspase overactivation.
abstract: We have previously demonstrated that interrupting the protein-protein interaction (PPI) of β-tubulin:chaperonin-containing TCP-1β (CCT-β) induces the selective killing of multidrug-resistant cancer cells due to CCT-β overexpression. However, the molecular mechanism has not yet been identified. In this study, we found that CCT-β interacts with a myriad of intracellular proteins involved in the cellular functions of the endoplasmic reticulum (ER), mitochondria, cytoskeleton, proteasome and apoptosome. Our data show that the targeted cells activate both the heat-shock protein 90 (Hsp90)-associated protein ubiquitination/degradation pathway to eliminate misfolded proteins in the cytoplasm and the valosin-containing protein (VCP)-centered ER-associated protein degradation pathway to reduce the excessive levels of unfolded polypeptides from the ER, thereby mitigating ER stress, at the onset of β-tubulin:CCT-β complex disruption. Once ER stress is expanded, ER stress-associated apoptotic signaling is enforced, as exhibited by cellular vacuolization and intracellular Ca2+ release. Furthermore, the elevated intracellular Ca2+ levels resulting from capacitative Ca2+ entry augments apoptotic signaling by provoking mitochondrial perturbation and caspase overactivation in the targeted cells. These findings not only provide a detailed picture of the apoptotic signaling cascades evoked by targeting the β-tubulin:CCT-β complex but also demonstrate a strategy to combat malignancies with chemoresistance to Hsp90- and VCP-related anticancer agents.
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan, ROC.
authors.forename: Y-F
authors.initials: YF
authors.lastname: Lin
authors.forename: Y-F
authors.initials: YF
authors.lastname: Lee
authors.forename: P-H
authors.initials: PH
authors.lastname: Liang
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D056404:Chaperonin Containing TCP-1 / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress; D060746:Endoplasmic Reticulum-Associated Degradation; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D059748:Proteolysis; D014404:Tubulin / Q000235:genetics / Q000378:metabolism*; D000074405:Valosin Containing Protein
chemical_list: C533298:CCT2 protein, human; D018797:Cell Cycle Proteins; D018841:HSP90 Heat-Shock Proteins; D014404:Tubulin; D020169:Caspases; D000251:Adenosine Triphosphatases; D056404:Chaperonin Containing TCP-1; C000614178:VCP protein, human; D000074405:Valosin Containing Protein; D002118:Calcium