ISC10, an Inhibitor of the SMK1 MAPK, Prevents Activation Loop Autophosphorylation and Substrate Phosphorylation Through Separate Mechanisms

Authors

Abhimannyu Rimal, Thomas Jefferson UniversityFollow
Thomas M Swayne, Thomas Jefferson UniversityFollow
Zeal P Kamdar, Thomas Jefferson UniversityFollow
Madison A Tewey, Thomas Jefferson UniversityFollow
Edward Winter, edward.winter@jefferson.edu

Document Type

Article

Publication Date

9-3-2022

Comments

This article is the author’s final published version in Journal of Biological Chemistry, Volume 298, Issue 10, September 2022, Article number 102450.

The published version is available at https://doi.org/10.1016/j.jbc.2022.102450. Copyright © Rimal et al.

Abstract

Many eukaryotic protein kinases are activated by the intramolecular autophosphorylation of activation loop residues. Smk1 is a meiosis-specific mitogen-activated protein kinase (MAPK) in yeast that autophosphorylates its activation loop tyrosine and thereby upregulates catalytic output. This reaction is controlled by an inhibitor, Isc10, that binds the MAPK during meiosis I and an activator, Ssp2, that binds Smk1/Isc10 during meiosis II. Upon completion of the meiotic divisions, Isc10 is degraded, and Smk1 undergoes autophosphorylation to generate the high activity form of the MAPK that controls spore formation. How Isc10 inhibits Smk1 is not clear. Here, we use a bacterial coexpression/reconstitution system to define a domain in the carboxy-terminal half of Isc10 that specifically inhibits Smk1 autophosphorylation. Nevertheless, Smk1 bound by this domain is able to phosphorylate other substrates, and it phosphorylates the amino-terminal half of Isc10 on serine 97. In turn, the phosphorylated motif in Isc10 inhibits the Smk1 active site. These data show that Isc10 inhibits autophosphorylation and the phosphorylation of substrates by separate mechanisms. Furthermore, we demonstrate Isc10 can inhibit the autophosphorylation of the mammalian intestinal cell kinase ICK1 (also known as CILK1), suggesting a conserved mechanism of action. These findings define a novel class of developmentally regulated molecules that prevent the self-activation of MAPKs and MAPK-like enzymes.

Recommended Citation

Rimal, Abhimannyu; Swayne, Thomas M; Kamdar, Zeal P; Tewey, Madison A; and Winter, Edward, "ISC10, an Inhibitor of the SMK1 MAPK, Prevents Activation Loop Autophosphorylation and Substrate Phosphorylation Through Separate Mechanisms" (2022). Department of Biochemistry and Molecular Biology Faculty Papers. Paper 223.
https://jdc.jefferson.edu/bmpfp/223

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

PubMed ID

36063999

Language

English