# Post-translational modification of the thin filament leads to progressive pump dysfunction

> **NIH NIH R01** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 2021 · $390,000

## Abstract

ABSTRACT
 Heart disease remains the leading cause of death in the United States. Patients and animal
models of heart failure consistently develop elevated protein kinase C activity and downstream
phosphorylation of the myofilament molecular switch protein, cardiac troponin I (cTnI) at Ser43/45
(S43/45). Previously, we showed contractile dysfunction is linked to chronic phosphorylation of this cTnI
cluster and it impairs both contraction and relaxation in isolated myocytes. The working hypothesis
guiding this application is that cTnI p-S43/45 is a master brake for short-term modulation of steady state
function, but chronically it causes cardiac dysfunction, and serves a non-traditional role as a sarcomere
stress signal. This type of sarcomere stress communicates with mitochondria to activate reactive oxygen
species production and initiate mitochondrial remodeling prior to significant contractile dysfunction. This
communication lays the foundation for the progressive downward spiral of cardiac dysfunction and
remodeling that leads to heart failure The objectives are to demonstrate cTnIS43/45 acts as a rapid in
vivo master brake, causes dose-dependent contractile dysfunction under chronic conditions and also
communicates sarcomere stress by causing early mitochondrial ROS production, altered energetics and
remodeling. For the approach, transgenic mice with a range of phospho-mimetic cTnIS43/45D or a
novel phospho-null cTnIS43/45N were generated to achieve dose-dependent replacement of
endogenous cTnI. In Aim 1, in vivo and cellular cardiac structure and contractile function are integrated
with analysis of myofilament and Ca2+ signaling to gain insight into the role played by this cluster. This
approach will show that dose-dependent cTnIS43/45D replacement produces in vivo cardiac and
myocyte dysfunction that leads to later remodeling, progressively impaired function and heart failure.
Studies in this aim also will prove that prior the significant remodeling, this cluster acts as a brake on the
positive inotropic and lusitropic response to β-adrenergic receptor stimulation, and in vivo replacement
with cTnIS43/45N is a functionally conservative substitution. Preliminary studies show oxidative stress
and downstream mitochondrial alterations develop in adult cTnIS43/45D mice prior to detection of
significant dysfunction. Thus, Aim 2 examines the novel idea that cTnIS43/45D plays a non-canonical
role to stimulate downstream mitochondrial reactive oxygen species (ROS) production, followed by
altered energetics and remodeling as an early route for triggering progressively impaired cardiac
performance. Studies in each aim also include proof-of-concept experiments to show that early targeting
of cTnI and/or downstream mitochondria prevents and/or attenuates the downward spiral of dysfunction
and remodeling to heart failure.

## Key facts

- **NIH application ID:** 10138003
- **Project number:** 5R01HL144777-02
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **Principal Investigator:** Margaret V Westfall
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $390,000
- **Award type:** 5
- **Project period:** 2020-04-05 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10138003

## Citation

> US National Institutes of Health, RePORTER application 10138003, Post-translational modification of the thin filament leads to progressive pump dysfunction (5R01HL144777-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10138003. Licensed CC0.

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