Dataset Information

Structural basis for SMAC-mediated antagonism of caspase inhibition by the giant ubiquitin ligase BIRC6

ABSTRACT: Certain Inhibitors of apoptosis (IAP) family members are sentinel proteins preventing untimely cell death by inhibiting caspases. Antagonists including second mitochondria-derived activator of caspase (SMAC) regulate IAPs, driving cell death. Baculoviral IAP repeat-containing protein 6 (BIRC6), a giant IAP with dual E2/E3 ubiquitin ligase activity, regulates programmed cell death through unknown mechanisms. We show BIRC6 directly restricts executioner caspases-3 and -7, and ubiquitinates caspases-3, -7 and -9 working exclusively with non canonical E1, UBA6. Importantly, we show SMAC supresses both mechanisms. Cryo-electron microscopy structures of BIRC6 alone and in complex with SMAC reveals BIRC6 is an anti parallel dimer juxtaposing the substrate-binding module against the catalytic domain. Furthermore, we discover SMAC multi-site binding to BIRC6 results in a sub-nanomolar affinity interaction, enabling SMAC to competitively displace caspases thus antagonising BIRC6 anti-caspase function.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Adan Pinto-Fernandez

LAB HEAD: Adan Pinto-Fernandez

PROVIDER: PXD039954 | Pride | 2023-03-08

REPOSITORIES: Pride

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Publications

Structural basis for SMAC-mediated antagonism of caspase inhibition by the giant ubiquitin ligase BIRC6.

Dietz Larissa L Ellison Cara J CJ Riechmann Carlos C Cassidy C Keith CK Felfoldi F Daniel FD Pinto-Fernández Adán A Kessler Benedikt M BM Elliott Paul R PR

Science (New York, N.Y.) 20230209 6637

Certain inhibitor of apoptosis (IAP) family members are sentinel proteins that prevent untimely cell death by inhibiting caspases. Antagonists, including second mitochondria-derived activator of caspases (SMAC), regulate IAPs and drive cell death. Baculoviral IAP repeat-containing protein 6 (BIRC6), a giant IAP with dual E2 and E3 ubiquitin ligase activity, regulates programmed cell death through unknown mechanisms. We show that BIRC6 directly restricts executioner caspase-3 and -7 and ubiquitin ...[more]

PMID: 36758106

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Project description:Metastatic malignant melanoma is the deadliest skin cancer type, and it is characterized by its high resistance to apoptosis. The main driving mutations in melanoma cause hyperactivation of genes within the ERK pathway, with BRAF mutations being the most frequent ones, followed by NRAS, NF1 and MEK mutations. Increasing evidence shows that the MST2/Hippo pathway is also deregulated in this cancer type. While mutations are rare, MST2/Hippo pathway core proteins expression levels are often dysregulated in melanoma. The expression of the tumour suppressor RASSF1A, a bona fide activator of the pro-apoptotic MST2 pathway, is silenced by promoter methylation in over half of melanomas and correlates with poor prognosis. Here, using mass spectrometry-based interaction proteomics we identified Second Mitochondria-derived Activator of Caspases (SMAC) as a novel LATS1 interactor. We show that RASSF1A-dependent activation of the pro-apoptotic MST2 pathway promotes LATS1-SMAC interaction and negatively regulates the anti-apoptotic signal mediated by the members of the IAP family. Moreover, proteomic experiments identified a common cluster of the apoptotic regulator that bind to SMAC and LATS1. Mechanistic analysis show that the LATS1-SMAC complex promotes XIAP ubiquitination and its subsequent degradation which ultimately results apoptosis. Importantly, we show that the oncogenic BRAFV600E mutant prevents the pro-apoptotic signal mediated by the LAST1-SMAC complex while treatment of melanoma cell lines with BRAF inhibitors promotes this complex, indicating that inhibition of the LATS1-SMAC might be necessary for BRAFV600E-driven melanoma. Finally, we show that LATS1-SMAC interaction is regulated by the SMAC mimetic Birinapant which requires the inhibition of C-IAP1 and the degradation of XIAP, indicating that the MST2/Hippo pathway is part of the mechanism of action of Birinapant. Overall, the current work shows SMAC-dependent apoptosis is regulated by the LATS1 tumour suppressor and supports the idea that LATS1 is a signalling hub that regulates the crosstalk between the MST2 pathway, the apoptotic network and the RAF/ERK pathway.

Dataset Information

Structural basis for SMAC-mediated antagonism of caspase inhibition by the giant ubiquitin ligase BIRC6

Publications

Structural basis for SMAC-mediated antagonism of caspase inhibition by the giant ubiquitin ligase BIRC6.

Similar Datasets

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