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MAP4K4 expression in cardiomyocytes: multiple isoforms, multiple phosphorylations and interactions with striatins.

Fuller, SJ; Edmunds, NS; McGuffin, LJ; Hardyman, MA; Cull, JJ; Alharbi, HO; Meijles, DN; Sugden, PH; Clerk, A (2021) MAP4K4 expression in cardiomyocytes: multiple isoforms, multiple phosphorylations and interactions with striatins. Biochem J, 478 (11). pp. 2121-2143. ISSN 1470-8728 https://doi.org/10.1042/BCJ20210003
SGUL Authors: Meijles, Daniel Nathan

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Abstract

The Ser/Thr kinase MAP4K4, like other GCKIV kinases, has N-terminal kinase and C-terminal citron homology (CNH) domains. MAP4K4 can activate c-Jun N-terminal kinases (JNKs), and studies in the heart suggest it links oxidative stress to JNKs and heart failure. In other systems, MAP4K4 is regulated in striatin-interacting phosphatase and kinase (STRIPAK) complexes, in which one of three striatins tethers PP2A adjacent to a kinase to keep it dephosphorylated and inactive. Our aim was to understand how MAP4K4 is regulated in cardiomyocytes. The rat MAP4K4 gene was not properly defined. We identified the first coding exon of the rat gene using 5'-RACE, we cloned the full-length sequence and confirmed alternative-splicing of MAP4K4 in rat cardiomyocytes. We identified an additional α-helix C-terminal to the kinase domain important for kinase activity. In further studies, FLAG-MAP4K4 was expressed in HEK293 cells or cardiomyocytes. The Ser/Thr protein phosphatase inhibitor calyculin A (CalA) induced MAP4K4 hyperphosphorylation, with phosphorylation of the activation loop and extensive phosphorylation of the linker between the kinase and CNH domains. This required kinase activity. MAP4K4 associated with myosin in untreated cardiomyocytes, and this was lost with CalA-treatment. FLAG-MAP4K4 associated with all three striatins in cardiomyocytes, indicative of regulation within STRIPAK complexes and consistent with activation by CalA. Computational analysis suggested the interaction was direct and mediated via coiled-coil domains. Surprisingly, FLAG-MAP4K4 inhibited JNK activation by H2O2 in cardiomyocytes and increased myofibrillar organisation. Our data identify MAP4K4 as a STRIPAK-regulated kinase in cardiomyocytes, and suggest it regulates the cytoskeleton rather than activates JNKs.

Item Type: Article
Additional Information: © 2021 The Author(s) This is an open access article published by Portland Press Limited on behalf of the Biochemical Society and distributed under the Creative Commons Attribution License 4.0 (CC BY). Open access for this article was enabled by the participation of University of Reading in an all-inclusive Read & Publish pilot with Portland Press and the Biochemical Society under a transformative agreement with JISC.
Keywords: cardiac myocytes, protein phosphatases, protein-serine-threonine kinases, Biochemistry & Molecular Biology, 06 Biological Sciences, 11 Medical and Health Sciences, 03 Chemical Sciences
SGUL Research Institute / Research Centre: Academic Structure > Molecular and Clinical Sciences Research Institute (MCS)
Journal or Publication Title: Biochem J
ISSN: 1470-8728
Language: eng
Dates:
DateEvent
11 June 2021Published
25 May 2021Accepted
Publisher License: Creative Commons: Attribution 4.0
Projects:
Project IDFunderFunder ID
PG/13/71/30460British Heart Foundationhttp://dx.doi.org/10.13039/501100000274
PG/15/41/31560British Heart Foundationhttp://dx.doi.org/10.13039/501100000274
PG/15/24/31367British Heart Foundationhttp://dx.doi.org/10.13039/501100000274
FS/18/33/33621British Heart Foundationhttp://dx.doi.org/10.13039/501100000274
CV05-02Fondation Leducqhttp://dx.doi.org/10.13039/501100001674
BB/T018496/1Biotechnology and Biological Sciences Research Councilhttp://dx.doi.org/10.13039/501100000268
PubMed ID: 34032269
Go to PubMed abstract
URI: https://openaccess.sgul.ac.uk/id/eprint/113385
Publisher's version: https://doi.org/10.1042/BCJ20210003

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