Regulation of the proapoptotic factor Bax by Ku70-dependent deubiquitylation

Amsel, Avigail D.; Rathaus, M.; Kronman, Noam; Cohen, Haim Y.

doi:10.1073/pnas.0706700105

Cited by 94 publications

(87 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition to Mcl-1, a slight decrease in Bax expression was observed in Ku70 À / À MEF cells (Figure 1a), which supports a previous report showing that Ku70 may also function as Bax deubiquitinase. 20 However, the effect of Ku70 on Bax is relatively weak in our system. The Ku70 protein contains several functional domains, including the Ku86-binding sites (aa 1-115 and aa 378-482), DNA-binding domain (aa 277-341) and the C-terminal portion (aa 536-609).…”

Section: Discussionmentioning

confidence: 67%

“…21,22 Ku proteins have been reported to support cell survival but the mechanism(s) involved is not fully understood. 20 Figure 1c, left panel). ABT-737 is a known inhibitor of Bcl2, Bcl-XL and Bcl-w but not of Mcl-1.…”

Section: Resultsmentioning

confidence: 97%

“…16,17 The N-terminal portion (aa 1-535) is important for Ku70 to heterodimerize with Ku86 and bind to DNA to mediate its DSB repair capacity. The C terminus of Ku70 is mainly responsible for its antiapoptotic function, 20 through mechanism(s) that were not fully understood. Our studies here demonstrated that Ku70 interacts with Mcl-1 via its C terminus (aa 536-609) ( Figure 5).…”

Section: Discussionmentioning

confidence: 99%

“…For direct in vitro deubiquitylation activity assay, 40 ng of K48-linked tetraubiquitin chains was incubated with purified Ku70/80 complex or BSA (negative control) at 30 1C for 1 or 2 h as described. 20 The reaction products were separated by SDS/PAGE, and the hydrolysis of ubiquitin chains into monoubiquitin units was detected by silver staining.…”

Section: Discussionmentioning

confidence: 99%

“…For example, a recent report revealed that Ku70 regulates the proapoptotic function of Bax by sequestering Bax from the mitochondria and mediating Bax deubiquitylation. 20 Here we discovered that Ku70 functions as a novel Mcl-1 deubiquitinase that directly removes polyubiquitin chains from Mcl-1 protein, leading to reduced Mcl-1 ubiquitination/degradation, enhanced stability and suppression of apoptosis. …”

mentioning

confidence: 99%

See 4 more Smart Citations

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

Wang

Xie

et al. 2014

Cell Death Differ

View full text Add to dashboard Cite

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) Mcl-1 is an antiapoptotic molecule that is overexpressed in various types of cancers, including lung cancer, 1 leukemia, 2 lymphoma, 3 hepatocellular carcinoma 4 and so on. In addition to its antiapoptotic function, Mcl-1 is also an oncoprotein that promotes the development of cancer. 5 In contrast to other Bcl2 family members such as Bcl2 and Bcl-XL, Mcl-1 is unique in its short half-life (30 min-3 h) and short-term prosurvival function, which probably relates to the presence of a long proline-, glutamic acid-, serine-and threonine-rich (PEST) region upstream of the Bcl2 homology (BH) domain. 1 The mechanism(s) that stabilizes the Mcl-1 protein are critical for its long-term survival function. Mcl-1 protein can be phosphorylated at multiple sites that distinctly regulate Mcl-1 protein turnover. For example, extracellular signal-regulated kinase 1/2-mediated T163 site phosphorylation enhances the half-life and antiapoptotic function of Mcl-1. 1,6 In contrast, S159 phosphorylation by GSK-3b facilitates Mcl-1 ubiquitination and degradation to reduce its survival activity. 7 Ubiquitination and deubiquitination are two reversible processes that can control protein stability. E3 ligases and deubiquitinases (deubiquitinating enzymes (DUBs)) are two groups of regulatory enzymes that orchestrate the ubiquitination levels of target proteins in eukaryotic cells. 8 Recently, Mule and FBW7 have been identified as Mcl-1 ubiquitin E3 ligases that can directly induce polyubiquitination and degradation of Mcl-1. 9,10 Inversely, USP9X has been demonstrated as the Mcl-1 deubiquitinase that removes the Lys 48-linked polyubiquitin chains that normally mark Mcl-1 for proteasomal degradation, leading to stabilization of Mcl-1. 3 Therefore, the stability of Mcl-1 in cells is tightly regulated by its E3 ligases and deubiquitinase, which is dependent on Mcl-1 phosphorylation status. 3,11 Ku70 is a protein that binds to DNA double-strand break (DSB) ends and is required for the non-homologous endjoining pathway of DSB repair. 12-15 The Ku70 protein consists of three structural domains, including the N-terminal, central (that is, DNA binding) and C-terminal domains. 16,17 Ku70 usually heterodimerizes with Ku86, which forms a functional complex for DSB repair. By forming a bridge between the broken DNA ends, the Ku70/Ku86 heterodimer acts to structurally support and align the DNA ends, to protect them from degradation and to prevent promiscuous binding to unbroken DNA. Ku70/Ku86 effectively aligns the DNA, while still allowing access of polymerases, nucleases and ligases to the broken DNA ends to promote end joining. 18 In some cases, a fourth domain is present at the C terminus of Ku86, which binds to the DNA-dependent protein kinase catalytic subunit...

show abstract

Section: Discussionmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

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

Wang

Xie

et al. 2014

Cell Death Differ

View full text Add to dashboard Cite

show abstract

The PI3K/AKT pathway promotes gefitinib resistance in mutant KRAS lung adenocarcinoma by a deacetylase‐dependent mechanism

Jeannot

Busser

Brambilla

et al. 2013

Intl Journal of Cancer

View full text Add to dashboard Cite

To select the appropriate patients for treatment with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), it is important to gain a better understanding of the intracellular pathways leading to EGFR-TKI resistance, which is a common problem in patients with lung cancer. We recently reported that mutant KRAS adenocarcinoma is resistant to gefitinib as a result of amphiregulin and insulin-like growth factor-1 receptor overexpression. This resistance leads to inhibition of Ku70 acetylation, thus enhancing the BAX/Ku70 interaction and preventing apoptosis. Here, we determined the intracellular pathways involved in gefitinib resistance in lung cancers and explored the impact of their inhibition. We analyzed the activation of the phosphatidyl inositol-3-kinase (PI3K)/AKT pathway and the mitogen-activated protein kinase/extracellular-signal regulated kinase (MAPK/ERK) pathway in lung tumors. The activation of AKT was associated with disease progression in tumors with wild-type EGFR from patients treated with gefitinib (phase II clinical trial IFCT0401). The administration of IGF1R-TKI or amphiregulin-directed shRNA decreased AKT signaling and restored gefitinib sensitivity in mutant KRAS cells. The combination of PI3K/AKT inhibition with gefitinib restored apoptosis via Ku70 downregulation and BAX release from Ku70. Deacetylase inhibitors, which decreased the BAX/Ku70 interaction, inhibited AKT signaling and induced gefitinib-dependent apoptosis. The PI3K/AKT pathway is thus a major pathway contributing to gefitinib resistance in lung tumors with KRAS mutation, through the regulation of the BAX/Ku70 interaction. This finding suggests that combined treatments could improve the outcomes for this subset of lung cancer patients, who have a poor prognosis.

show abstract

Impact of curcumin on sirtuins: A review

Zendedel

Butler

Atkin

et al. 2018

J of Cellular Biochemistry

View full text Add to dashboard Cite

Curcumin is a bioactive phytochemical that modulates several physiological and cellular processes leading to therapeutic effects against different diseases. Sirtuins are highly conserved nicotine adenine dinucleotide-dependent proteins that regulate the activity of target enzymes and transcription factors by deacetylation. Curcumin possesses both antioxidant and anti-inflammatory properties and has been shown to increase sirtuin-1 (SIRT1) by activating small molecules. Upregulation of SIRT1 by curcumin has been reported to confer protective effects against a range of neurological disorders including glutamate excitotoxicity, β-amyloid-induced cell death in cortical neurons, cerebral ischemic damage, and stroke. Activation of AMPK and SIRT1 by curcumin has also been noted to mediate the protective effects of curcumin against ischemia/reperfusion injury, cardiac fibrosis, diabetes, and lipid metabolism abnormalities. These protective effects of SIRT1 activation are partly mediated by the deacetylation of p53 and reduction of apoptosis. In this review, we summarize the role of SIRT1 in mediating the pharmacological effects of curcumin in several diseases.

show abstract

Regulation of the proapoptotic factor Bax by Ku70-dependent deubiquitylation

Abstract: The DNA end-joining protein Ku70 is one of several proteins that inhibit apoptosis by sequestering the proapoptotic factor Bax from the mitochondria. However, the molecular mechanism underlying Ku70-dependent inhibition of Bax is not fully understood. Here

Cited by 94 publications

References 34 publications

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

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

The PI3K/AKT pathway promotes gefitinib resistance in mutant KRAS lung adenocarcinoma by a deacetylase‐dependent mechanism

Impact of curcumin on sirtuins: A review

Contact Info

Product

Resources

About