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The ubiquitin-specific protease USP2a prevents endocytosis-mediated EGFR degradation.

ABSTRACT: Ubiquitination of epidermal growth factor receptor (EGFR) is required for downregulation of the receptor by endocytosis. Impairment of this pathway results in constitutively active EGFR, which is associated with carcinogenesis, particularly in lung cancer. We previously demonstrated that the deubiquitinating enzyme ubiquitin-specific protease 2a (USP2a) has oncogenic properties. Here, we show a new role for USP2a as a regulator of EGFR endocytosis. USP2a localizes to early endosomes and associates with EGFR, stabilizing the receptor, which retains active downstream signaling. HeLa cells transiently expressing catalytically active, but not mutant (MUT), USP2a show increased plasma membrane-localized EGFR, as well as decreased internalized and ubiquitinated EGFR. Conversely, USP2a silencing reverses this phenotype. Importantly, USP2a prevents the degradation of MUT in addition to wild-type EGFR. Finally, we observed that USP2a and EGFR proteins are coordinately overexpressed in non-small cell lung cancers. Taken together, our data indicate that USP2a antagonizes EGFR endocytosis and thus amplifies signaling activity from the receptor. Our findings suggest that regulation of deubiquitination could be exploited therapeutically in cancers overexpressing EGFR.

SUBMITTER: Liu Z

PROVIDER: S-EPMC3866888 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature

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The ubiquitin-specific protease USP2a prevents endocytosis-mediated EGFR degradation.

Liu Z Z Zanata S M SM Kim J J Peterson M A MA Di Vizio D D Chirieac L R LR Pyne S S Agostini M M Freeman M R MR Loda M M

Oncogene 20120618 13

Ubiquitination of epidermal growth factor receptor (EGFR) is required for downregulation of the receptor by endocytosis. Impairment of this pathway results in constitutively active EGFR, which is associated with carcinogenesis, particularly in lung cancer. We previously demonstrated that the deubiquitinating enzyme ubiquitin-specific protease 2a (USP2a) has oncogenic properties. Here, we show a new role for USP2a as a regulator of EGFR endocytosis. USP2a localizes to early endosomes and associat ...[more]

PMID: 22710717

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Project description:Glioblastoma multiforme (GBM) is the most malignant glioma, with a 30-60% epidermal growth factor receptor (EGFR) mutation. This mutation is associated with unrestricted cell growth and increases the possibility of cancer invasion. Patients with EGFR-mutated GBM often develop resistance to the available treatment modalities and higher recurrence rates. The drug resistance observed is associated with multiple genetic or epigenetic factors. The ubiquitin-specific protease 6 N-terminal-like protein (USP6NL) is a GTPase-activating protein that functions as a deubiquitinating enzyme and regulates endocytosis and signal transduction. It is highly expressed in many cancer types and may promote the growth and proliferation of cancer cells. We hypothesized that USP6NL affects GBM chemoresistance and tumorigenesis, and that its inhibition may be a novel therapeutic strategy for GBM treatment. The USP6NL level, together with EGFR expression in human GBM tissue samples and cell lines associated with therapy resistance, tumor growth, and cancer invasion, were investigated. Its pivotal roles and potential mechanism in modulating tumor growth, and the key mechanism associated with therapy resistance of GBM cells, were studied, both in vitro and in vivo. Herein, we found that deubiquitinase USP6NL and growth factor receptor EGFR were strongly associated with the oncogenicity and resistance of GBM, both in vitro and in vivo, toward temozolomide, as evidenced by enhanced migration, invasion, and acquisition of a highly invasive and drug-resistant phenotype by the GBM cells. Furthermore, abrogation of USP6NL reversed the properties of GBM cells and resensitized them toward temozolomide by enhancing autophagy and reducing the DNA damage repair response. Our results provide novel insights into the probable mechanism through which USP6NL/EGFR signaling might suppress the anticancer therapeutic response, induce cancer invasiveness, and facilitate reduced sensitivity to temozolomide treatment in GBM in an autolysosome-dependent manner. Therefore, controlling the USP6NL may offer an alternative, but efficient, therapeutic strategy for targeting and eradicating otherwise resistant and recurrent phenotypes of aggressive GBM cells.

Project description:ObjectiveAndrogen deprivation therapy (ADT) is still the principal treatment option for prostate cancer (PCa). In addition to reactivation of androgen receptor signaling, the resistance of PCa to apoptosis during ADT also contributes to castration resistant PCa (CRPC). A previous study reported that gene transfer of IL-13Rα2 into PCa cells sensitized the cells to the IL-13R-targeted cytotoxin IL13Rα1, leading to apoptosis. Compared with IL-13Rα2, IL13Rα1 is more constitutively expressed in PCa cells, but its function in PCa remains to be established.MethodsWe determined the role and expression of IL13Rα1 in PCa cancer cells using western blotting, flow cytometry, and cell proliferation assays. Co-immunoprecipitation and mass spectrometry were used to identify the proteins that interacted with IL13Rα1, to elucidate its function.ResultsIn this study, we showed that IL13Rα1 was selectively suppressed in androgen-deprived PCa cells and that its suppression tended to be associated with poor prognoses of PCa patients. IL13Rα1 overexpression promoted apoptosis and inhibited tumor growth under androgen-deprived or castrated conditions (P < 0.01). Mechanistically, IL13Rα1 recruited and facilitated ubiquitin protein ligase E3C-mediated ubiquitination and degradation of hexokinase 2 (HK2), resulting in glycolytic inhibition and eventually leading to PCa cell apoptosis. Furthermore, our data revealed that mutated ataxia-telangiectasia kinase phosphorylated and facilitated the selective ubiquitin proteasome-mediated degradation of HK2. Notably, IL13Rα1-overexpressing PCa cells were more susceptible to apoptosis and exhibited reduced tumor growth after exposure to the HK2 inhibitor, 2-deoxy-D-glucose (P < 0.01).ConclusionsOur data identified a tumor suppressor role for IL13Rα1 in preventing the resistance of PCa cells to apoptosis during androgen deprivation by inhibiting glycolysis. IL13Rα1-mediated signaling involving HK2 may therefore provide a novel treatment target and strategy for CRPC.

Dataset Information

The ubiquitin-specific protease USP2a prevents endocytosis-mediated EGFR degradation.

Publications

The ubiquitin-specific protease USP2a prevents endocytosis-mediated EGFR degradation.

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