Sharpin prevents skin inflammation by inhibiting TNFR1-induced keratinocyte apoptosis

Elife. 2014 Dec 2;3:e03422. doi: 10.7554/eLife.03422.

Abstract

Linear Ubiquitin chain Assembly Complex (LUBAC) is an E3 ligase complex that generates linear ubiquitin chains and is important for tumour necrosis factor (TNF) signaling activation. Mice lacking Sharpin, a critical subunit of LUBAC, spontaneously develop inflammatory lesions in the skin and other organs. Here we show that TNF receptor 1 (TNFR1)-associated death domain (TRADD)-dependent TNFR1 signaling in epidermal keratinocytes drives skin inflammation in Sharpin-deficient mice. Epidermis-restricted ablation of Fas-associated protein with death domain (FADD) combined with receptor-interacting protein kinase 3 (RIPK3) deficiency fully prevented skin inflammation, while single RIPK3 deficiency only delayed and partly ameliorated lesion development in Sharpin-deficient mice, showing that inflammation is primarily driven by TRADD- and FADD-dependent keratinocyte apoptosis while necroptosis plays a minor role. At the cellular level, Sharpin deficiency sensitized primary murine keratinocytes, human keratinocytes, and mouse embryonic fibroblasts to TNF-induced apoptosis. Depletion of FADD or TRADD in Sharpin-deficient HaCaT cells suppressed TNF-induced apoptosis, indicating the importance of FADD and TRADD in Sharpin-dependent anti-apoptosis signaling in keratinocytes.

Keywords: LUBAC; Sharpin; TNFR1; apoptosis; cell biology; immunology; mouse; skin inflammation; ubiquitin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis* / drug effects
  • Epidermis / metabolism
  • Epidermis / pathology
  • Fas-Associated Death Domain Protein / metabolism
  • HEK293 Cells
  • Humans
  • Inflammation / pathology*
  • Keratinocytes / drug effects
  • Keratinocytes / metabolism*
  • Keratinocytes / pathology*
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Nerve Tissue Proteins / deficiency
  • Nerve Tissue Proteins / metabolism*
  • Phenotype
  • Receptor-Interacting Protein Serine-Threonine Kinases / deficiency
  • Receptor-Interacting Protein Serine-Threonine Kinases / metabolism
  • Receptors, Tumor Necrosis Factor, Type I / deficiency
  • Receptors, Tumor Necrosis Factor, Type I / metabolism*
  • Signal Transduction / drug effects
  • Skin / pathology*
  • TNF Receptor-Associated Death Domain Protein / metabolism
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • Fas-Associated Death Domain Protein
  • Nerve Tissue Proteins
  • Receptors, Tumor Necrosis Factor, Type I
  • TNF Receptor-Associated Death Domain Protein
  • Tumor Necrosis Factor-alpha
  • sharpin
  • Receptor-Interacting Protein Serine-Threonine Kinases
  • Ripk3 protein, mouse