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Disrupting CCT-β : β-tubulin selectively kills CCT-β overexpressed cancer cells through MAPKs activation.

ABSTRACT: We have previously demonstrated the ability of I-Trp to disrupt the protein-protein interaction of β-tubulin with chaperonin-containing TCP-1β (CCT-β). This caused more severe apoptosis in multidrug-resistant MES-SA/Dx5, compared to MES-SA, due to its higher CCT-β overexpression. In this study, we screened a panel of cancer cell lines, finding CCT-β overexpression in the triple-negative breast cancer cell line MDA-MB-231, colorectal cancer cell lines Colo205 and HCT116, and a gastric cancer cell line MKN-45. Thus, I-Trp killed these cancers with sub- to low-μM EC₅₀, whereas it was non-toxic to MCF-10A. We then synthesized analogs of I-Trp and evaluated their cytotoxicity. Furthermore, apoptotic mechanism investigations revealed the activation of both protein ubiquitination/degradation and ER-associated protein degradation pathways. These pathways proceeded through activation of MAPKs at the onset of CCT-β : β-tubulin complex disruption. We thus establish an effective strategy to treat CCT-β overexpressed cancers by disrupting the CCT-β : β-tubulin complex.

SUBMITTER: Liu YJ

PROVIDER: S-EPMC5636972 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The ciliated protozoan Tetrahymena thermophila contains two distinct nuclei within a single cell-the mitotic micronucleus and the amitotic macronucleus. Although microtubules are required for proper division of both nuclei, macronuclear chromosomes lack centromeres and the role of microtubules in macronuclear division has not been established. Here we describe nuclear division defects in cells expressing a mutant beta-tubulin allele that confers hypersensitivity to the microtubule-stabilizing drug paclitaxel. Macronuclear division is profoundly affected by the btu1-1 (K350M) mutation, producing cells with widely variable DNA contents, including cells that lack macronuclei entirely. Protein expressed by the btu1-1 allele is dominant over wild-type protein expressed by the BTU2 locus. Normal macronuclear division is restored when the btu1-1 allele is inactivated by targeted disruption or expressed as a truncated protein. Immunofluorescence studies reveal elongated microtubular structures that surround macronuclei that fail to migrate to the cleavage furrows. In contrast, other cytoplasmic microtubule-dependent processes, such as cytokinesis, cortical patterning, and oral apparatus assembly, appear to be unaffected in the mutant. Micronuclear division is also perturbed in the K350M mutant, producing nuclei with elongated early-anaphase spindle configurations that persist well after the initiation of cytokinesis. The K350M mutation affects tubulin dynamics, as the macronuclear division defect is exacerbated by three treatments that promote microtubule polymerization: (i) elevated temperatures, (ii) sublethal concentrations of paclitaxel, and (iii) high concentrations of dimethyl sulfoxide. Inhibition of phosphatidylinositol 3-kinase (PI 3-kinase) with 3-methyladenine or wortmannin also induces amacronucleate cell formation in a btu1-1-dependent manner. Conversely, the myosin light chain kinase inhibitor ML-7 has no effect on nuclear division in the btu1-1 mutant strain. These findings provide new insights into microtubule dynamics and link the evolutionarily conserved PI 3-kinase signaling pathway to nuclear migration and/or division in Tetrahymena.

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Disrupting CCT-β : β-tubulin selectively kills CCT-β overexpressed cancer cells through MAPKs activation.

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