HOIP Deficiency Causes Embryonic Lethality by Aberrant TNFR1-Mediated Endothelial Cell Death

Nieves Peltzer,Eva Rieser,Lucia Taraborrelli,Peter Draber,Maurice Darding,Barbara Pernaute,Yutaka Shimizu,Aida Sarr,Helena Draberova,Antonella Montinaro,Juan Pedro Martinez-Barbera,John Silke,Tristan A Rodriguez,Henning Walczak

doi:10.1016/j.celrep.2014.08.066

Abstract

Linear ubiquitination is crucial for innate and adaptive immunity. The linear ubiquitin chain assembly complex (LUBAC), consisting of HOIL-1, HOIP, and SHARPIN, is the only known ubiquitin ligase that generates linear ubiquitin linkages. HOIP is the catalytically active LUBAC component. Here, we show that both constitutive and Tie2-Cre-driven HOIP deletion lead to aberrant endothelial cell death, resulting in defective vascularization and embryonic lethality at midgestation. Ablation of tumor necrosis factor receptor 1 (TNFR1) prevents cell death, vascularization defects, and death at midgestation. HOIP-deficient cells are more sensitive to death induction by both tumor necrosis factor (TNF) and lymphotoxin-α (LT-α), and aberrant complex-II formation is responsible for sensitization to TNFR1-mediated cell death in the absence of HOIP. Finally, we show that HOIP's catalytic activity is necessary for preventing TNF-induced cell death. Hence, LUBAC and its linear-ubiquitin-forming activity are required for maintaining vascular integrity during embryogenesis by preventing TNFR1-mediated endothelial cell death.

Highlights

Ubiquitination is the covalent attachment of ubiquitin to a target protein
Using cleaved caspase-3 as a marker of apoptotic cells, we found that apoptosis was increased in HoipÀ/À yolk sacs at E9.5 (Figure S2B) and that this increase was even more pronounced at E10.5 (Figures 2C and 2D)
We found that murine embryonic fibroblasts (MEFs) obtained from TnfÀ/ÀHoipÀ/À embryos were rendered sensitive to death induction by both tumor necrosis factor (TNF) and LT-a (Figure 5A), in line with the recently reported finding that SHARPIN-deficient cells are sensitized to TNF and LT-a (Etemadi et al, 2013)

Summary

Introduction

Ubiquitination is the covalent attachment of ubiquitin to a target protein. When ubiquitin itself is the target, interubiquitin linkages are formed. The linear ubiquitin chain assembly complex (LUBAC) is currently the only known E3 ligase that generates linear linkages under physiological conditions and is composed of three proteins—heme-oxidized iron-responsive element-binding protein 2 (IRP2) ubiquitin ligase-1 (HOIL-1; known as RanBP-type and C3HC4-type zinc finger-containing protein 1 [RBCK1]), HOIL-1 interacting protein (HOIP; known as ring finger protein 31 [RNF31]), and SH3 and multiple ankyrin repeat domains protein (SHANK)-associated RBCK1 homology (RH)-domain-interacting protein (SHARPIN; known as SHANK-interacting protein-like 1 [SIPL1]) (Gerlach et al, 2011; Ikeda et al, 2011; Tokunaga et al, 2011)—with HOIP being the catalytically active component of this complex (Tokunaga et al, 2009)

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