How activating mutations affect MEK1 regulation and function.

TitleHow activating mutations affect MEK1 regulation and function.
Publication TypeJournal Article
Year of Publication2017
AuthorsJindal, GA, Goyal, Y, Humphreys, JM, Yeung, E, Tian, K, Patterson, VL, He, H, Burdine, RD, Goldsmith, EJ, Shvartsman, SY
JournalJ Biol Chem
Volume292
Issue46
Pagination18814-18820
Date Published2017 11 17
ISSN1083-351X
KeywordsAnimals, Crystallography, X-Ray, Enzyme Activation, Humans, MAP Kinase Kinase 1, Mitogen-Activated Protein Kinase 1, Models, Molecular, Neoplasms, Phosphorylation, Point Mutation, Protein Conformation, raf Kinases, Zebrafish
Abstract

<p>The MEK1 kinase directly phosphorylates ERK2, after the activation loop of MEK1 is itself phosphorylated by Raf. Studies over the past decade have revealed a large number of disease-related mutations in the gene that lead to tumorigenesis and abnormal development. Several of these mutations result in MEK1 constitutive activity, but how they affect MEK1 regulation and function remains largely unknown. Here, we address these questions focusing on two pathogenic variants of the Phe-53 residue, which maps to the well-characterized negative regulatory region of MEK1. We found that these variants are phosphorylated by Raf faster than the wild-type enzyme, and this phosphorylation further increases their enzymatic activity. However, the maximal activities of fully phosphorylated wild-type and mutant enzymes are indistinguishable. On the basis of available structural information, we propose that the activating substitutions destabilize the inactive conformation of MEK1, resulting in its constitutive activity and making it more prone to Raf-mediated phosphorylation. Experiments in zebrafish revealed that the effects of activating variants on embryonic development reflect the joint control of the negative regulatory region and activating phosphorylation. Our results underscore the complexity of the effects of activating mutations on signaling systems, even at the level of a single protein.</p>

DOI10.1074/jbc.C117.806067
Alternate JournalJ. Biol. Chem.
PubMed ID29018093
PubMed Central IDPMC5704466
Grant ListR01 GM086537 / GM / NIGMS NIH HHS / United States
T32 GM007388 / GM / NIGMS NIH HHS / United States