# cAMP Compartmentation in Cardiac Myocytes

> **NIH NIH R01** · UNIVERSITY OF NEVADA RENO · 2021 · $360,000

## Abstract

The cAMP signaling pathway plays a critical role in regulating many different aspects of cardiac myocyte
function, including gene transcription, cell metabolism, and excitation-contraction coupling. However, not
all G-protein coupled receptors that stimulate cAMP production produce the same responses. Subcellular
compartmentation of cAMP is essential to explain how different receptors can utilize the same diffusible
second messenger to elicit unique functional responses. Furthermore, disruption of cAMP
compartmentation has been linked to various disease states, including cardiac hypertrophy, heart failure,
and arrhythmias. Yet, a complete picture of the mechanisms contributing to cAMP compartmentation
remains a mystery. Most work has focused on the role of phosphodiesterases (PDEs), which breakdown
cAMP and are commonly thought to act as either functional barriers or active sinks that define different
signaling domains. However, a number of studies indicate that PDE activity alone is not sufficient. The
results suggest that, in addition to PDE activity, unique receptor-dependent responses can only be
explained if the movement of intracellular cAMP is somehow limited by other mechanisms. Using a
sophisticated new approach, we have directly measured the diffusion coefficient of cAMP in intact
myocytes and found that it does indeed move dramatically slower than previously thought. Furthermore,
our preliminary data have identified two factors critical to explaining this behavior. The first is buffering of
cAMP by protein kinase A (PKA) immobilized by A kinase anchoring proteins (AKAPs). The second are
subcellular restricted spaces. In this proposal, we will address the following specific questions: 1) Does
buffering by PKA anchored to the outer membrane of mitochondria contribute to cAMP
compartmentation? and 2) Does the restricted space associated with dyadic clefts contribute to cAMP
compartmentation. To answer these questions, we will use a combination of molecular, biochemical, and
biophysical techniques. These include raster image correlation spectroscopy (RICS) to directly measure
cAMP diffusion, fluorescence resonance energy transfer (FRET)-based biosensors targeted to different
subcellular locations to measure cAMP compartmentation; and patch clamp electrophysiology, Ca2+
fluorometry, and myocyte shortening to measure compartmentalized cAMP-dependent functional
responses. The answers to these questions could lead to the development of novel approaches to halting
the progression of cardiovascular disease and preventing the deadly consequences.

## Key facts

- **NIH application ID:** 10079026
- **Project number:** 5R01HL145778-03
- **Recipient organization:** UNIVERSITY OF NEVADA RENO
- **Principal Investigator:** ROBERT D HARVEY
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $360,000
- **Award type:** 5
- **Project period:** 2019-01-15 → 2022-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10079026

## Citation

> US National Institutes of Health, RePORTER application 10079026, cAMP Compartmentation in Cardiac Myocytes (5R01HL145778-03). Retrieved via AI Analytics 2026-06-11 from https://api.ai-analytics.org/grant/nih/10079026. Licensed CC0.

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