Structure Studies of ERK Inhibitor-Resistant ERK2 Mutants

Abstract

Extracellular regulatory kinase (ERK) is a serine-threonine kinase that is involved in the regulation of cellular signals. Because ERK is involved in regulating cell proliferation, differentiation and survival, tight control is required. Therefore, many ERK inhibitors have been tested. ERK inhibitors have been studied in a way that inhibits B-Raf Proto-Oncogene (BRAF)/ RasGTPase (Ras) mutant tumors and overcomes BRAF/Mitogen-activated protein kinase kinase (MEK) inhibitor resistance. However as ERK-specific inhibitors were developed and used, the identification of mutations resistant to ERK inhibitors also increased. Nevertheless, the mechanism of inhibitor-resistant mutations occurring in ERK has not been sufficiently studied. So here, I studied the Y34H and G35C mutants that maintain ERK2 activity and are resistant to several ERK inhibitors among the mutants that occur in ERK2 when ERK inhibitors are continuously used in ERK2. Y34H and G35C ERK2 mutants were overexpressed in E.coli competent cell and crystallized. Additionally, X-ray crystallography was used to determine the crystal structure of the Y34H and G35C mutations. The structure of each mutant was different from that of wild type ERK2. In addition, the structure was compared with the previously known inhibitor complex ERK2. Y34H obtained resistance to inhibitors and maintained activity by altering the conformation of the Gly-rich loop and C-helix. On the other hand, G35C gained resistance to inhibitors under the influence of the Cys residue. Additionally, both mutants did not change the structure of the activation loop. As a result, I identified the mechanism by which the Y34H and G35C mutations are resistant to inhibitors. Additionally, the mechanism by which the mutants remain active was identified.