Role of Ku70 in deubiquitination of Mcl-1 and suppression of apoptosis.

Abstract

Mcl-1 is a unique antiapoptotic Bcl2 family member with a short half-life due to its rapid turnover through ubiquitination. We discovered that Ku70, a DNA double-strand break repair protein, functions as a deubiquitinase to stabilize Mcl-1. Ku70 knockout in mouse embryonic fibroblast (MEF) cells or depletion from human lung cancer H1299 cells leads to the accumulation of polyubiquitinated Mcl-1 and a reduction in its half-life and protein expression. Conversely, expression of exogenous Ku70 in Ku70(-/-) MEF cells restores Mcl-1 expression. Subcellular fractionation indicates that Ku70 extensively colocalizes with Mcl-1 in mitochondria, endoplasmic reticulum and nucleus in H1299 cells. Ku70 directly interacts with Mcl-1 via its C terminus (that is, aa 536-609), which is required and sufficient for deubiquitination and stabilization of Mcl-1, leading to suppression of apoptosis. Purified Ku70 protein directly deubiquitinates Mcl-1 by removing K48-linked polyubiquitin chains. Ku70 knockdown not only promotes Mcl-1 turnover but also enhances antitumor efficacy of the BH3-mimetic ABT-737 in human lung cancer xenografts. These findings identify Ku70 as a novel Mcl-1 deubiquitinase that could be a potential target for cancer therapy by manipulating Mcl-1 deubiquitination.

• Authors: B Wang, M Xie, R Li, T K Owonikoko, S S Ramalingam, F R Khuri, W J Curran, Y Wang, X Deng
• Journal: Cell death and differentiation (Cell Death Differ) Vol. 21 Issue 7 Pg. 1160-9 (Jul 2014) ISSN: 1476-5403 [Electronic] England
• PMID: 24769731 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• ABT-737
• Antigens, Nuclear
• Antineoplastic Agents
• Biphenyl Compounds
• DNA-Binding Proteins
• MCL1 protein, human
• Myeloid Cell Leukemia Sequence 1 Protein
• Nitrophenols
• Piperazines
• Sulfonamides
• Xrcc6 protein, human
• Xrcc6 protein, mouse
• Ku Autoantigen
• Staurosporine

Topics

• Animals
• Antigens, Nuclear (physiology)
• Antineoplastic Agents (pharmacology)
• Apoptosis
• Biphenyl Compounds (pharmacology)
• Cell Survival
• DNA-Binding Proteins (physiology)
• HCT116 Cells
• HEK293 Cells
• Half-Life
• Humans
• Ku Autoantigen
• Mice
• Mice, Nude
• Myeloid Cell Leukemia Sequence 1 Protein (metabolism)
• Nitrophenols (pharmacology)
• Piperazines (pharmacology)
• Protein Interaction Domains and Motifs
• Protein Stability
• Protein Transport
• Staurosporine (pharmacology)
• Sulfonamides (pharmacology)
• Ubiquitination
• Xenograft Model Antitumor Assays