Publication Date
2025
Document Type
Thesis
Committee Members
Weiwen Long, Ph.D. (Advisor); Michael Craig, Ph.D. (Committee Member); Hongmei Ren, Ph.D. (Committee Member)
Degree Name
Master of Science (MS)
Abstract
Extracellular signal-regulated kinase 3 (ERK3) is a member of the atypical mitogen-activated protein kinase (MAPK) family. While ERK3’s role in promoting cell migration and invasion in multiple types of cancer has been well-documented, its activation and regulation remain poorly understood. Unlike other typical MAPK proteins, whose activation is regulated via the phosphorylation of an upstream kinase, ERK3 is regulated through its abundance, as it is constitutively phosphorylated when present in the cell. While USP20 has been established as a deubiquitinating protein that stabilizes ERK3 by preventing its degradation, both TRIM21 and FBXW7 have been identified as E3 ligases that target ERK3, thereby destabilizing it. In this study, we investigate a novel regulator of ERK3, F-Box and Leucine-Rich Repeat Protein 16 (FBXL16). While we originally proposed that FBXL16 may be an E3 ligase of ERK3, we later found that it instead had an opposite and stabilizing effect. In order to characterize FBXL16’s ability to stabilize ERK3, we generated several constructs of ERK3 and then overexpressed them in H1299 cells with or without overexpression of FBXL16. Intriguingly, we found that FBXL16 can stabilize ERK3 through both the C-terminus and the C34 domain. To further examine whether FBXL16’s ability to stabilize ERK3 is dependent on an E3 ligase, we developed a series of mutants in an attempt to abolish E3 ligase recruitment via phosphodegrons in both the C-terminus and C34 domain. Notably, we found that simultaneous mutation of both T417/421 and S684/688 phosphodegrons could increase the half-life of ERK3, but mutation of each phosphodegron independently could not stabilize ERK3. Finally, we found that rescuing ERK3 in the absence of FBXL16 could partially restore cell migration, and overexpression of FBXL16 in cells with diminished ERK3 could also partially restore cell migration. In conclusion, our study identifies FBXL16 as a novel positive regulator of ERK3 whose interaction can be mediated at multiple regions of ERK3. Furthermore, while intertwined, the ability of FBXL16 and ERK3 to upregulate cell migration and invasion is likely complex, involving multiple downstream targets.
Page Count
78
Department or Program
Department of Biochemistry and Molecular Biology
Year Degree Awarded
2025
Copyright
Copyright 2025, all rights reserved. My ETD will be available under the "Fair Use" terms of copyright law.
