# Signaling Pathways and Regulators of Calcium Channels in Heart

> **NIH NIH F31** · COLUMBIA UNIVERSITY HEALTH SCIENCES · 2020 · $45,000

## Abstract

In the heart, calcium influx via Cav1.2 channels has a key role in excitation-contraction coupling, and in
determining the plateau phase of the action potential. Although CaV1.2 channels are known to associate with
proteins that regulate channel trafficking, localization, turnover, and function, the components of these protein
complexes have not yet been fully identified. Physiologic b-adrenergic activation of PKA during the sympathetic
“fight or flight” response increases calcium influx through CaV1.2 in cardiomyocytes, leading to increased cardiac
contractility. In pathological conditions, increased CaV1.2 currents can trigger electrical instability, early after-
depolarizations, arrhythmias, and sudden death, frequently in the setting of adrenergic stimulation or decreased
repolarizing currents. The molecular mechanisms of b-adrenergic regulation of CaV1.2 in cardiomyocytes are
incompletely known, but up-regulation of CaV1.2 mediated by activation of PKA is required for this process.
Based upon the failure to identify the regulatory sites in the heart, the difficulties in reconstituting the regulation
using heterologous expression, and the challenges in creating knock-in mice or using adenoviral-based
expression, the Marx laboratory developed the straightforward but rigorous approach of using doxycycline-
inducible, tissue-specific, transgenic-mice-expressing FLAG-epitope-tagged, dihydropyridine (DHP)-resistant
pore-forming a1C subunits. Recent data suggest that b-adrenergic regulation of CaV1.2 does not require any
combination of potential PKA phosphorylation sites conserved in human, guinea pig, rabbit, rat, and mouse a1C
subunits. b-adrenergic regulation of a1C may require, however, a unique combination of species-specific
phospho-regulatory sites in a1C. To test this hypothesis, I generated transgenic mice with doxycycline-inducible
expression of rabbit a1C with alanine-substitutions of all conserved and non-conserved potential PKA sites in the
intracellular regions (N-terminal, intracellular loops, and C-terminal regions). If b-adrenergic regulation is
preserved in these mice, I will cross these mice with mice expressing a mutant b2b subunit in which consensus
PKA phosphorylation sites are substituted with alanines. This study will test whether prior failures to identify a
mechanism is because of redundancy between the a and b subunits and will provide the definitive answer about
whether PKA phosphorylation of any a1C or b2 residues is necessary. Since it appears that the a1C and b2
subunits may not the primary functional PKA targets and due to the inability to reconstitute adrenergic regulation
when the primary subunits are heterologously expressed, I further hypothesize that additional proteins expressed
in cardiomyocytes may be required for adrenergic regulation of CaV1.2. In Aim 2, I seek to identify and test these
novel regulators of CaV1.2 in the heart. The two Aims will provide new insights the mechanisms responsible for
b-adrenerg...

## Key facts

- **NIH application ID:** 9856138
- **Project number:** 5F31HL142178-02
- **Recipient organization:** COLUMBIA UNIVERSITY HEALTH SCIENCES
- **Principal Investigator:** Daniel Dennis Roybal
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $45,000
- **Award type:** 5
- **Project period:** 2018-12-20 → 2021-12-19

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9856138

## Citation

> US National Institutes of Health, RePORTER application 9856138, Signaling Pathways and Regulators of Calcium Channels in Heart (5F31HL142178-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9856138. Licensed CC0.

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