ER Stress Drives Lipogenesis and Steatohepatitis via Caspase-2 Activation of S1P

Ju Youn Kim, Ricard Garcia-Carbonell, Shinichiro Yamachika, Peng Zhao, Debanjan Dhar, Rohit Loomba, Randal J. Kaufman, Alan R. Saltiel, Michael Karin

Research output: Contribution to journalArticlepeer-review

148 Scopus citations

Abstract

Nonalcoholic fatty liver disease (NAFLD) progresses to nonalcoholic steatohepatitis (NASH) in response to elevated endoplasmic reticulum (ER) stress. Whereas the onset of simple steatosis requires elevated de novo lipogenesis, progression to NASH is triggered by accumulation of hepatocyte-free cholesterol. We now show that caspase-2, whose expression is ER-stress inducible and elevated in human and mouse NASH, controls the buildup of hepatic-free cholesterol and triglycerides by activating sterol regulatory element-binding proteins (SREBP) in a manner refractory to feedback inhibition. Caspase-2 colocalizes with site 1 protease (S1P) and cleaves it to generate a soluble active fragment that initiates SCAP-independent SREBP1/2 activation in the ER. Caspase-2 ablation or pharmacological inhibition prevents diet-induced steatosis and NASH progression in ER-stress-prone mice. Caspase-2 inhibition offers a specific and effective strategy for preventing or treating stress-driven fatty liver diseases, whereas caspase-2-generated S1P proteolytic fragments, which enter the secretory pathway, are potential NASH biomarkers. Caspase-2 inhibition could present a specific and effective strategy for preventing or treating stress-driven fatty liver diseases.

Original languageEnglish (US)
Pages (from-to)133-145.e15
JournalCell
Volume175
Issue number1
DOIs
StatePublished - Sep 20 2018
Externally publishedYes

Keywords

  • caspase-2
  • DNL
  • hepatic steatosis
  • lipogenesis
  • liver fibrosis
  • NASH
  • site 1 protease
  • SREBP

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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