# Modulation of Cardiac Function by Myosin Light Chain Kinases and Phosphatases

> **NIH NIH R01** · UT SOUTHWESTERN MEDICAL CENTER · 2021 · $405,000

## Abstract

PROJECT SUMMARY
Cardiac contraction depends on the molecular motor myosin in sarcomeres where maintenance of contractile
performance is achieved in part by the constitutive phosphorylation of myosin regulatory light chain (RLC)
through the respective activities of myosin light chain kinase (MLCK) and phosphatase (MLCP). Dilated cardiac
myopathy in mice and humans results in decreased cardiac MLCK (cMLCK) expression and RLC
phosphorylation while animal models with increased phosphorylation have enhanced cardiac performance with
resistance to heart failure. Although it is well established that RLC phosphorylation is important for normal cardiac
function, surprisingly little is known about signaling mechanisms regulating cMLCK and MLCP activities,
respectively. We propose investigations on cardiac-specific signaling mechanisms for these two enzymes that
affect myosin phosphorylation to elucidate cellular mechanisms for normal function as well as potential causes
of decreased RLC phosphorylation in heart failure. Specific Aim 1: Having recently discovered cMLCK is
phosphorylated in vivo, we plan to identify roles of specific phosphorylation sites in regulating cMLCK activity
using cMLCK expression and assay systems I developed to test the hypothesis that cMLCK phosphorylation
enhances its activity. These studies will be extended to intact cardiac muscle to define signaling mechanisms
involved in cMLCK phosphorylation, including responsible protein kinases. Additionally, we will test the
hypothesis that other forms of heart failure involve reduced RLC phosphorylation to identify potentially common
signaling derangements. Specific Aim 2. Determine the roles of myosin-targeted and soluble phosphatase
activities in mediating RLC dephosphorylation. Using conditional knockout models for cardiac MYPT2 and the
related, ubiquitously expressed subunit MYPT1 in adult mice, we will assess the effects of specific gene ablation
on cardiac function. Intact cardiac muscle trabeculae from wildtype and knockout hearts will be used to
quantitatively measure contributions of distinct pools of phosphatases to maintenance of half-maximal RLC
phosphorylation. Cardiomyocytes from MYPT1 and MYPT2 as well as PP1cδ knockout mice will be used to
identify the regulatory subunit for the soluble phosphatase. These studies will test the hypothesis that PP1cδ
bound and unbound to MYPT2 specifically dephosphorylates RLC, providing insights into the physiological role
of myosin phosphatases in the heart. These results will also set the stage for future studies on aberrant signaling
pathways that cause cardiac muscle dysfunction through effects on RLC phosphorylation.

## Key facts

- **NIH application ID:** 10191016
- **Project number:** 5R01HL146757-03
- **Recipient organization:** UT SOUTHWESTERN MEDICAL CENTER
- **Principal Investigator:** Audrey N Chang
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $405,000
- **Award type:** 5
- **Project period:** 2019-05-01 → 2024-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10191016

## Citation

> US National Institutes of Health, RePORTER application 10191016, Modulation of Cardiac Function by Myosin Light Chain Kinases and Phosphatases (5R01HL146757-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10191016. Licensed CC0.

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