The Effects of MRTF-A Phosphorylation State on TGFβ1-induced Epithelial-to-Mesenchymal Transition
Open Access
- Author:
- Phan, Steven
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Esther Gomez, Thesis Supervisor
Michael John Janik, Thesis Honors Advisor - Keywords:
- MRTF-A
EMT
Epithelial-Mesenchymal Transition
TGFβ1
Erk - Abstract:
- Epithelial-mesenchymal transition (EMT) is a biological process that results in the loss of cell-cell junctions and increased cell motility, invasiveness, and resistance to apoptosis1-4. Myocardin-related transcription factor (MRTF)-A is a G-actin-binding RPEL protein that works with serum response factor (SRF) to regulate cytoskeletal gene expression, contributing to transforming growth factor beta 1 (TGFβ1)-induced EMT. The polymerization of G-actin to F-actin frees the MRTF-A molecule from the G-actin and allows MRTF-A to enter the nucleus, where it can aid in promoting gene expression. MRTF-A subcellular localization can also be regulated by its phosphorylation state, which can be controlled by a variety of signaling molecules including extracellular signal-regulated kinase (Erk)3,12,13. To understand the effects of MRTF-A phosphorylation on TGFβ1-induced EMT, we examined cells transfected with MRTF-A and the MRTF-A mutants, S454A, which mimics the non-phosphorylated state, and S454E, which mimics the phosphorylated state. Using western blotting and immunofluorescence staining, we compared protein expression and localization and determined if cells underwent TGFβ1-induced EMT. We find that MRTF-A S454A promotes higher α-SMA expression than MRTF-A S454E. The results show that phosphorylation of MRTF-A decreases the expression of α-SMA, which is upregulated during EMT, while the de-phosphorylation of MRTF-A decreases the expression of E-cadherin, which is downregulated during EMT. Furthermore, treatment of cells with the inhibitor U0126, which blocks Erk activity, resulted in a decrease in the expression of the epithelial marker E-cadherin. These findings offer preliminary analysis toward future work to understand the mechanisms regulating MRTF-A phosphorylation and EMT.