TNFR1-dependent cell death drives inflammation in Sharpin-deficient mice.

James A Rickard,John Silke,Chunzi Huang,Jason Corbin,Aleks Bankovacki,Nieves Peltzer,Najoua Lalaoui,Wendy Wei-Lynn Wong,Holly Anderton,Ueli Nachbur,Cathrine Hall,Nima Etemadi,Lahiru Gangoda,Maurice Darding,Henning Walczak,Hannah K Vanyai ,David L Vaux ,Edward S Mocarski ,James M Murphy ,William J Kaiser ,Anne K Voss ,Kate E Lawlor ,Warren S Alexander

doi:10.7554/elife.03464

Abstract

SHARPIN regulates immune signaling and contributes to full transcriptional activity and prevention of cell death in response to TNF in vitro. The inactivating mouse Sharpin cpdm mutation causes TNF-dependent multi-organ inflammation, characterized by dermatitis, liver inflammation, splenomegaly, and loss of Peyer's patches. TNF-dependent cell death has been proposed to cause the inflammatory phenotype and consistent with this we show Tnfr1, but not Tnfr2, deficiency suppresses the phenotype (and it does so more efficiently than Il1r1 loss). TNFR1-induced apoptosis can proceed through caspase-8 and BID, but reduction in or loss of these players generally did not suppress inflammation, although Casp8 heterozygosity significantly delayed dermatitis. Ripk3 or Mlkl deficiency partially ameliorated the multi-organ phenotype, and combined Ripk3 deletion and Casp8 heterozygosity almost completely suppressed it, even restoring Peyer's patches. Unexpectedly, Sharpin, Ripk3 and Casp8 triple deficiency caused perinatal lethality. These results provide unexpected insights into the developmental importance of SHARPIN.

Highlights

Chronic proliferative dermatitis mutation mice are deficient in SHARPIN (Sharpincpdm/cpdm: referred to as Shpnm/m; protein: SHARPIN) and develop dermatitis, multi-organ pathology and an immunological phenotype including disrupted lymphoid architecture, splenomegaly, liver inflammation and a loss of Peyer's patches in the gut (HogenEsch et al, 1993, 1999; Seymour et al, 2007)
Since the dermatitis and inflammatory phenotype were shown to be tumour necrosis factor (TNF) dependent, and because the only TNF signaling output that was aberrantly increased in the absence of SHARPIN was cell death, we previously proposed TNF/TNFR1-mediated cell death to be causative of the cpdm phenotype (Gerlach et al, 2011)
We found that HaCaT keratinocytes stably expressing catalytically inactive HOIPC885S were sensitive to TNF-induced cell death (Figure 5B), indicating a requirement for linear ubiquitin chain assembly complex (LUBAC) and its linear-ubiquitinchain-forming activity in preventing TNF-induced keratinocyte death

Summary

Introduction

Chronic proliferative dermatitis mutation (cpdm) mice are deficient in SHARPIN (Sharpincpdm/cpdm: referred to as Shpnm/m; protein: SHARPIN) and develop dermatitis, multi-organ pathology and an immunological phenotype including disrupted lymphoid architecture, splenomegaly, liver inflammation and a loss of Peyer's patches in the gut (HogenEsch et al, 1993, 1999; Seymour et al, 2007). Cell biology | Developmental biology and stem cells eLife digest In response to an injury or infection, areas of the body can become inflamed as the immune system attempts to repair the damage and/or destroy any microbes or toxins that have entered the body. At the level of individual cells inflammation can involve cells being programmed to die in one of two ways: apoptosis and necroptosis

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Conclusion