CHIP controls necroptosis through ubiquitylation- and lysosome-dependent degradation of RIPK3

Abstract

Receptor-interacting protein kinase 3 (RIPK3) functions as a key regulator of necroptosis. Here, we report that the RIPK3 expression level is negatively regulated by CHIP (carboxyl terminus of Hsp70-interacting protein; also known as STUB1) E3 ligase-mediated ubiquitylation. Chip(-/-) mouse embryonic fibroblasts and CHIP-depleted L929 and HT-29 cells exhibited higher levels of RIPK3 expression, resulting in increased sensitivity to necroptosis induced by TNF (also known as TNFα). These phenomena are due to the CHIP-mediated ubiquitylation of RIPK3, which leads to its lysosomal degradation. Interestingly, RIPK1 expression is also negatively regulated by CHIP-mediated ubiquitylation, validating the major role of CHIP in necrosome formation and sensitivity to TNF-mediated necroptosis. Chip(-/-) mice (C57BL/6) exhibit inflammation in the thymus and massive cell death and disintegration in the small intestinal tract, and die within a few weeks after birth. These phenotypes are rescued by crossing with Ripk3(-/-) mice. These results imply that CHIP is a bona fide negative regulator of the RIPK1-RIPK3 necrosome formation leading to desensitization of TNF-mediated necroptosis.

C-terminus of HSC70-Interacting Protein (CHIP) Inhibits Adipocyte Differentiation via Ubiquitin- and Proteasome-Mediated Degradation of PPARγ

“…Based on these observations, the systemic effects of CHIP should be further assessed in the future. Since the whole-body CHIP knockout mouse of the C57BL/6 strain does not survive for more than one month, a conditional knockout system must be established to investigate the physiological roles of CHIP in association with PPARγ3547. Additional studies should examine whether the E3 ligases identified so far are expressed in adipocyte tissues and whether their expression levels are regulated by a high-fat diet.…”

“…The mice were maintained in accordance with the approved guidelines and regulations for experimental animals provided by Yonsei Laboratory Animal Research Center. Using C57BL/6 J mice, heterogeneous CHIP male and female mice were mated to produce wild type and knockout CHIP mice, as previously reported35. Mouse embryos were obtained 13.5 days after verifying plug formation.…”

“…CHIP (C-terminus of HSC70-interacting protein) is an E3 ligase with a variety of target proteins, including p53, PTEN (Phosphatase and tensin homolog), Tau, and RIPK3 (Receptor-interacting serine/threonine-protein kinase 3)32333435. It contains a U-box domain responsible for ubiquitylation activities and a tetratricopeptide repeat (TPR) domain required for protein interactions.…”

Necroptosis: Mechanisms and Relevance to Disease

“…RIPK1 and RIPK3 mutually interact via their RIP homotypic interaction motif (RHIM) (38) and undergo trans- or autophosphorylation, endowing the necrosome with the ability to activate MLKL (9, 33). According to two recent reports, protein phosphatase, Mg2+/Mn2+ dependent 1B (PPM1B) and the E3 ubiquitin ligase STIP1 homology and U-Box containing protein 1 (Stub1; also known as Chip) exert prominent necroptosis-inhibitory functions by catalyzing the dephosphorylation of RIPK3 (39) or its ubiquitination and proteasomal degradation of Ripk3 (40), respectively. These findings, however, have not been confirmed by independent investigators yet.…”

Molecular mechanism and therapy application of necrosis during myocardial injury

“…Recent work showed that CHIP ablation generally accelerated TNF‐a‐mediated necrosis 44. CHIP knockout mice showed post‐natal lethality which was rescued by simultaneous knockout of RIP3.…”