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Proc Natl Acad Sci U S A. 2018 Jun 26;115(26):E5944-E5953. doi: 10.1073/pnas.1806973115. Epub 2018 Jun 11.

Regulation of a distinct activated RIPK1 intermediate bridging complex I and complex II in TNFα-mediated apoptosis.

Author information

1
Department of Cell Biology, Harvard Medical School, Boston, MA 02115.
2
Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, PuDong District, 201203 Shanghai, China.
3
Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115.
4
Department of Cell Biology, Harvard Medical School, Boston, MA 02115; junying_yuan@hms.harvard.edu.

Abstract

Stimulation of cells with TNFα can promote distinct cell death pathways, including RIPK1-independent apoptosis, necroptosis, and RIPK1-dependent apoptosis (RDA)-the latter of which we still know little about. Here we show that RDA involves the rapid formation of a distinct detergent-insoluble, highly ubiquitinated, and activated RIPK1 pool, termed "iuRIPK1." iuRIPK1 forms after RIPK1 activation in TNF-receptor-associated complex I, and before cytosolic complex II formation and caspase activation. To identify regulators of iuRIPK1 formation and RIPK1 activation in RDA, we conducted a targeted siRNA screen of 1,288 genes. We found that NEK1, whose loss-of-function mutations have been identified in 3% of ALS patients, binds to activated RIPK1 and restricts RDA by negatively regulating formation of iuRIPK1, while LRRK2, a kinase implicated in Parkinson's disease, promotes RIPK1 activation and association with complex I in RDA. Further, the E3 ligases APC11 and c-Cbl promote RDA, and c-Cbl is recruited to complex I in RDA, where it promotes prodeath K63-ubiquitination of RIPK1 to lead to iuRIPK1 formation. Finally, we show that two different modes of necroptosis induction by TNFα exist which are differentially regulated by iuRIPK1 formation. Overall, this work reveals a distinct mechanism of RIPK1 activation that mediates the signaling mechanism of RDA as well as a type of necroptosis.

KEYWORDS:

RIPK1; TNF; apoptosis; necroptosis; ubiquitination

PMID:
29891719
PMCID:
PMC6042106
DOI:
10.1073/pnas.1806973115
[Indexed for MEDLINE]
Free PMC Article

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