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Proc Natl Acad Sci U S A. 2018 Sep 18;115(38):E8996-E9005. doi: 10.1073/pnas.1804379115. Epub 2018 Sep 4.

PKCε contributes to lipid-induced insulin resistance through cross talk with p70S6K and through previously unknown regulators of insulin signaling.

Author information

1
Department of Cellular and Molecular Physiology, Yale University, New Haven, CT 06520.
2
Systems Biology Institute, Yale University, West Haven, CT 06516.
3
Internal Medicine, Yale University, New Haven, CT 06520.
4
Howard Hughes Medical Institute, Yale University, New Haven, CT 06519.
5
Yale Center for Molecular Discovery, Yale University, West Haven, CT 06516.
6
Section of Endocrinology, Veterans Affairs Medical Center, West Haven, CT 06516.
7
Department of Cellular and Molecular Physiology, Yale University, New Haven, CT 06520; jesse.rinehart@yale.edu.

Abstract

Insulin resistance drives the development of type 2 diabetes (T2D). In liver, diacylglycerol (DAG) is a key mediator of lipid-induced insulin resistance. DAG activates protein kinase C ε (PKCε), which phosphorylates and inhibits the insulin receptor. In rats, a 3-day high-fat diet produces hepatic insulin resistance through this mechanism, and knockdown of hepatic PKCε protects against high-fat diet-induced hepatic insulin resistance. Here, we employed a systems-level approach to uncover additional signaling pathways involved in high-fat diet-induced hepatic insulin resistance. We used quantitative phosphoproteomics to map global in vivo changes in hepatic protein phosphorylation in chow-fed, high-fat-fed, and high-fat-fed with PKCε knockdown rats to distinguish the impact of lipid- and PKCε-induced protein phosphorylation. This was followed by a functional siRNA-based screen to determine which dynamically regulated phosphoproteins may be involved in canonical insulin signaling. Direct PKCε substrates were identified by motif analysis of phosphoproteomics data and validated using a large-scale in vitro kinase assay. These substrates included the p70S6K substrates RPS6 and IRS1, which suggested cross talk between PKCε and p70S6K in high-fat diet-induced hepatic insulin resistance. These results identify an expanded set of proteins through which PKCε may drive high-fat diet-induced hepatic insulin resistance that may direct new therapeutic approaches for T2D.

KEYWORDS:

PKCε; cross talk; insulin resistance; phosphoproteomics; systems biology

Comment in

PMID:
30181290
PMCID:
PMC6156646
DOI:
10.1073/pnas.1804379115
[Indexed for MEDLINE]
Free PMC Article

Conflict of interest statement

The authors declare no conflict of interest.

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