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J Biol Chem. 2017 Mar 3;292(9):3581-3590. doi: 10.1074/jbc.M116.769208. Epub 2017 Jan 17.

A Phosphoproteomic Screen Identifies a Guanine Nucleotide Exchange Factor for Rab3A Protein as a Mitogen-activated Protein (MAP) Kinase Phosphatase-5-regulated MAP Kinase Target in Interleukin 6 (IL-6) Secretion and Myogenesis.

Author information

1
From the Department of Pharmacology and.
2
the Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24060.
3
the Department of Biology Education, College of Education, Pusan National University, Busan 609-735, Republic of Korea, and.
4
Program in Public Health, University of California, Irvine, California 92697.
5
From the Department of Pharmacology and anton.bennett@yale.edu.
6
Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University, New Haven, Connecticut 06520.

Abstract

The mitogen-activated protein kinases (MAPKs) have been shown to regulate skeletal muscle function. Previously, we showed that MAPK phosphatase-5 (MKP-5) negatively regulates myogenesis and regeneration of skeletal muscle through inhibition of p38 MAPK and c-Jun N-terminal kinase (JNK). However, the identity and contribution of MKP-5-regulated MAPK targets in the control of skeletal muscle function and regenerative myogenesis have not been established. To identify MKP-5-regulated MAPK substrates in skeletal muscle, we performed a global differential phospho-MAPK substrate screen in regenerating skeletal muscles of wild type and MKP-5-deficient mice. We discovered a novel MKP-5-regulated MAPK substrate called guanine nucleotide exchange factor for Rab3A (GRAB) that was hyperphosphorylated on a phospho-MAPK motif in skeletal muscle of MKP-5-deficient mice. GRAB was found to be phosphorylated by JNK on serine 169. Myoblasts overexpressing a phosphorylation-defective mutant of GRAB containing a mutation at Ser-169 to Ala-169 (GRAB-S169A) inhibited the ability of C2C12 myoblasts to differentiate. We found that GRAB phosphorylation at Ser-169 was required for the secretion of the promyogenic cytokine interleukin 6 (IL-6). Consistent with this observation, MKP-5-deficient mice exhibited increased circulating IL-6 expression as compared with wild type mice. Collectively, these data demonstrate a novel mechanism whereby MKP-5-mediated regulation of JNK negatively regulates phosphorylation of GRAB, which subsequently controls secretion of IL-6. These data support the notion that MKP-5 serves as a negative regulator of MAPK-dependent signaling of critical skeletal muscle signaling pathways.

KEYWORDS:

cytokine; dual specificity phosphoprotein phosphatase; mitogen-activated protein kinase (MAPK); myogenesis; phosphoproteomics; skeletal muscle

PMID:
28096466
PMCID:
PMC5339744
DOI:
10.1074/jbc.M116.769208
[Indexed for MEDLINE]
Free PMC Article

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