E3 Ubiquitin Ligase HOIP Attenuates Apoptotic Cell Death Induced by Cisplatin

Abstract

The genotoxin cisplatin is commonly used in chemotherapy to treat solid tumors, yet our understanding of the mechanism underlying the drug response is limited. In a focused siRNA screen, using an siRNA library targeting genes involved in ubiquitin and ubiquitin-like signaling, we identified the E3 ubiquitin ligase HOIP as a key regulator of cisplatin-induced genotoxicity. HOIP forms, with SHARPIN and HOIL-1L, the linear ubiquitin assembly complex (LUBAC). We show that cells deficient in the HOIP ligase complex exhibit hypersensitivity to cisplatin. This is due to a dramatic increase in caspase-8/caspase-3-mediated apoptosis that is strictly dependent on ATM-, but not ATR-mediated DNA damage checkpoint activation. Moreover, basal and cisplatininduced activity of the stress response kinase JNK is enhanced in HOIP-depleted cells and, conversely, JNK inhibition can increase cellular resistance to cisplatin and reverse the apoptotic hyperactivation in HOIP-depleted cells. Furthermore, we show that HOIP depletion sensitizes cancer cells, derived from carcinomas of various origins, through an enhanced apoptotic cell death response. We also provide evidence that ovarian cancer cells classified as cisplatin-resistant can regain sensitivity following HOIP downregulation. Cumulatively, our study identifies a HOIP-regulated antiapoptotic signaling pathway, and we envisage HOIP as a potential target for the development of combinatorial chemotherapies to potentiate the efficacy of platinum-based anticancer drugs. Cancer Res; 74(8); 2246-57. Ó2014 AACR.

Regulation of Linear Ubiquitin Chain Assembly Complex by Caspase-Mediated Cleavage of RNF31

“…Although it has been reported that the LUBAC plays a critical role in the activation of NF-B signaling, previous studies have suggested that the LUBAC plays a role in the process of apoptosis. Sharpin-deficient cpdm mouse embryonic fibroblasts (MEFs) have increased sensitivity to TNF-␣-induced apoptosis (3,5), and RNF31-silenced ovarian cancer cells are more sensitive to cisplatin-induced death (17). Although the mechanism of apoptosis regulation has not been completely demonstrated, these previous studies support our finding that LUBAC inhibition by caspase-dependent RNF31 cleavage sensitizes cancer cells to apoptosis.…”

SHARPIN-mediated regulation of protein arginine methyltransferase 5 controls melanoma growth

“…LUBAC forms linear-type ubiquitin chains through methionine 1-glycine 76 linkages (1)(2)(3). Linear ubiquitination has been implicated in the regulation of canonical NF-κB signaling; accordingly, defects in this process are associated with inflammatory immune disorders and cancer (4,5). Similarly, altered expression of HOIP or OTULIN, a linear ubiquitin chain-specific deubiquitinase, plays a role in autoimmunity and lymphomagenesis (4,6).…”

Linear ubiquitin chain assembly complex coordinates late thymic T-cell differentiation and regulatory T-cell homeostasis

“…These signals involve the linear ubiquitination of NEMO to reinforce canonical NF-κB signalling, although it is likely to be that other LUBAC substrates exist. Loss of LUBAC activity drives cells into apoptosis or necroptosis following exposure to TNF, lymphotoxin α or genotoxic stress1516171819. All three LUBAC components are required for maximal linear ubiquitination; however, not all components are equal.…”