# Regulation of Endothelial Nitric Oxide Synthase mRNA Stability

> **NIH NIH R01** · THOMAS JEFFERSON UNIVERSITY · 2020 · $390,000

## Abstract

Project Summary
Endothelial nitric oxide synthase (eNOS) is a key enzyme involved in the regulation of vascular tone and
altered eNOS activity leads to endothelial dysfunction and atherosclerosis. Post-transcriptional modulation of
eNOS mRNA stability is a major determinant of eNOS expression in vascular endothelium. The molecular
mechanisms regulating eNOS mRNA stability remain poorly understood and represent an important gap in
knowledge. This competitive renewal application proposes to investigate the molecular mechanisms by which
eNOS mRNA stability is regulated. Preliminary studies suggest that the binding of Polypyrimidine Tract Binding
Protein 1 (PTB1) to the eNOS mRNA 3’-UTR leads to decreased eNOS mRNA stability and expression.
Moreover, we found that PTB1 specifically interacts with the mammalian Ste20-like kinase 1 (Mst1), an
upstream serine/threonine-specific protein kinase of the Hippo pathway, which leads to PTB1 phosphorylation
and decreased eNOS mRNA stability and protein expression in vascular endothelial cells. Our preliminary data
further demonstrate that Mst1 kinase is activated in the atherosclerotic lesions and blocking Mst1 activation by
overexpression of dominant negative protein (DN-Mst1) (K59R) in vascular endothelial cells markedly
increased eNOS mRNA stability and expression, implicating a functional significance of Mst1 kinase in
regulating endothelial functions. We therefore hypothesize that hyperlipidemia-induced activation of Mst1
promotes the binding of PTB1 to eNOS 3’-UTR, which in turn downregulates eNOS expression and causes
endothelial dysfunction in the atherogenesis. Accordingly, we propose three comprehensive specific aims to
delineate how the regulation of PTB1 by Mst1 kinase affects eNOS mRNA stability and expression, and the
extent to which this contributes to the pathogenesis of endothelial dysfunction and vascular disease. Specific
aim 1 will examine the functional significance of Mst1 in regulating eNOS mRNA stability by PTB1. We will
identify the Mst1 specific phosphorylation site(s) on PTB1 and then determine whether phosphorylation of
PTB1 by Mst1 alters the binding affinity of PTB1 to the eNOS 3’-UTR, leading to decreased eNOS mRNA
stability and protein expression in vascular endothelial cells. Specific aim 2 will determine whether PTB1
induces eNOS mRNA instability by inhibiting 3’-polyadenylation of eNOS mRNA and/or by increasing the
binding of microRNAs to the eNOS 3’-UTR. Specific aim 3 will determine whether the Mst1/PTB1 pathway
regulates endothelial dysfunction in vivo. By using our newly generated endothelial specific DN-Mst1
transgenic and Mst1 knockout mice, we will investigate whether eNOS expression, endothelium-dependent
vascular relaxation, and atherosclerosis are altered by specifically blocking Mst1 activation in vascular
endothelial cells. We envision these will establish the importance of Mst1 as a therapeutic target for improving
endothelial function and decreasing cardiovascula...

## Key facts

- **NIH application ID:** 9840496
- **Project number:** 5R01HL103869-10
- **Recipient organization:** THOMAS JEFFERSON UNIVERSITY
- **Principal Investigator:** Jianxin Sun
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $390,000
- **Award type:** 5
- **Project period:** 2010-08-01 → 2021-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9840496

## Citation

> US National Institutes of Health, RePORTER application 9840496, Regulation of Endothelial Nitric Oxide Synthase mRNA Stability (5R01HL103869-10). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9840496. Licensed CC0.

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