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PTP1B inhibition promotes cell death in hypoxia by triggering RNF213-dependent pyroptosis

ABSTRACT: The tumor microenvironment (TME) typically includes hypoxic regions. Hypoxic cancer cells are resistant to many anti-neoplastic therapies and can seed recurrence; consequently, understanding how they survive could yield new therapeutic strategies. In response to decreasing oxygen, cells are known to successively activate hypoxia-inducible factor 1-alpha (HIF1alpha), endoplasmic reticulum (ER) stress, and AMP-dependent protein kinase (AMPK). We previously identified an additional pathway in which the protein-tyrosine phosphatase PTP1B (encoded by PTPN1) prevents the death of HER2+ breast cancer cells exposed to severe hypoxia (O2<1%) by inhibiting RNF213, a large (~600 kDa) E3 ubiquitin ligase containing two functional AAA-ATPase domains and two ubiquitin ligase domains (RING and RZ) that also is implicated in Moyamoya disease (MMD), lipotoxicity, and innate immunity. These findings provided a potential explanation for earlier observations that Ptpn1-/- mice are resistant to Neu (rodent HER2)-induced breast cancer, but how PTP1B regulates RNF213, the identity(ies) of RNF213 targets, the mechanism of cell death, and the relevance to other RNF213 actions remained unclear. Via proximity-based proteomics, we identified the CYLD-SPATA2 complex, a major negative regulator of NF-kappaB activation, as an RNF213 substrate critical for hypoxia-induced cell death. Here we show that PTP1B and ABL1/2 reciprocally control the phosphorylation of RNF213 on Tyrosine-1275. Phosphorylation of this site promotes RNF213 oligomerization, resulting in RZ domain activation, LUBAC complex-dependent ubiquitylation and degradation of the CYLD/SPATA2 deubiquitinase complex, and NF-kappaB activation. NF-kappaB induces NLRP3 inflammasome priming, and concomitant hypoxia-induced ER stress triggers inflammasome activation, resulting in pyroptotic cell death. Mutagenesis experiments show that the RNF213 RING negatively regulates the RZ domain, and RING domain mutants, including those associated with MMD, catalyze LUBAC-independent CYLD/SPATA2 degradation. Our results identify a novel PTP1B/RNF213/CYLD/SPATA2 pathway responsible for the pyroptotic death of hypoxic tumor cells, reveal new insights into RNF213 regulation, and have potentially important implications for the pathogenesis of MMD, atherosclerosis, and inflammatory and auto-immune disorders. The mass spectrometry raw files for the phosphorylation identification and proximity labeling results are included here.

INSTRUMENT(S): Orbitrap Eclipse, Q Exactive

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Beatrix Ueberheide

PROVIDER: MSV000092191 | MassIVE | Fri Jun 16 08:27:00 BST 2023

SECONDARY ACCESSION(S): PXD043060

REPOSITORIES: MassIVE

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Project description:Breast cancers with HER2 overexpression are sensitive to drugs targeting the receptor or its kinase activity. HER2-targeting drugs are initially effective against HER2- positive breast cancer, but resistance inevitably occurs. We previously found that nuclear factor kappa B is hyper-activated in the subset of HER-2 positive breast cancer cells and tissue specimens. In this study, we report that constitutively active NF-ÎºB rendered HER2-positive cancer cells resistant to anti-HER2 drugs, and cells selected for Lapatinib resistance up-regulated NF-ÎºB. In both circumstances, cells were anti-apoptotic and grew rapidly as xenografts. Lapatinib-resistant cells were refractory to HER2 and NF-ÎºB inhibitors alone but were sensitive to their combination, suggesting a novel therapeutic strategy. A subset of NF-ÎºB-responsive genes was overexpressed in HER2-positive and triple-negative breast cancers, and patients with this NF-ÎºB signature had poor clinical outcome. Anti-HER2 drug resistance may be a consequence of NF-ÎºB activation, and selection for resistance results in NF-ÎºB activation, suggesting this transcription factor is central to oncogenesis and drug resistance. Clinically, the combined targeting of HER2 and NF-ÎºB suggests a potential treatment paradigm for patients who relapse after anti-HER2 therapy. Patients with these cancers may be treated by simultaneously suppressing HER2 signaling and NF-ÎºB activation. We used microarrays to detail the gene expression differences underlying the characterictic survival differences between the SKR6, SKR6-Vector, SKR6CA, and SKR6LR cell lines, which are defined as follows: SKR6: A clonal derivative of SKBR3 cells isolated by fluorescence-activated cell sorting (FACS) to enrich for elevated HER2 levels, SKR6CA: SKR6 cells retrovirally transduced with constitutively active NF-ÎºB relA/p65 (CAp65) and selected with puromycin, SKR6 vector: SKR6 cells transduced with the pQCXIP empty retroviral vector and selected with puromycin, and SKR6LR: SKR6 cells treated with increasing lapatinib concentrations (0.2 to 5 Î¼M) for several months. We sorted SKBR-3 cells by fluorescence-activated cell sorting (FACS) to enriched for cell population with elevated HER2 expression, which we termed SKR6. The following cell lines were then created from SKR6 cells: SKR6CA: SKR6 cells retrovirally transduced with constitutively active NF-ÎºB relA/p65 (CAp65), SKR6 vector: SKR6 cells transduced with the pQCXIP empty retroviral vector and selected with puromycin, and SKR6LR: SKR6 cells treated with increasing lapatinib concentrations (0.2 to 5 Î¼M) for several months.

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PTP1B inhibition promotes cell death in hypoxia by triggering RNF213-dependent pyroptosis

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