Heart disease is the leading cause of death in the United States and worldwide, with a worsening trajectory due to increasingly aging populations. A deep and precise understanding of the molecular mechanisms underlying normal cardiac physiology, and how they go awry in disease, is key for identifying new drug targets and developing effective new therapeutics to combat heart disease. Ca2+ cycling involving local signaling between surface L-type Ca2+ (CaV1.2) channels and intracellular ryanodine receptors (RYR2) is responsible for the Ca2+-induced Ca2+ release (CICR) that underlies cardiac excitation-contraction coupling. Dysregulation of both CaV1.2 and RYR2 contributes prominently to the deranged cardiomyocyte Ca2+ signaling that is an adverse attribute of heart disease. Sympathetic activation of cardiac contractility, which is crucial for the fight-or-flight response, involves augmented CaV1.2 current and sensitization of RYR2; yet, excessive activation of this pathway under conditions of chronic stress results in post-translational modifications of RYR2 channels that cause them to become ‘leaky’ and cause cardiac pathology. There are significant gaps in knowledge regarding CaV1.2 and RYR2 functional organization and regulation in heart under both and disease conditions; how their dysregulation or dysfunction contributes to heart disease progression; and whether and how they can be targeted for effective treatment of heart failure (HF) and other cardiac diseases.
This Program Project Grant (PPG) comprises four Projects and two Scientific Cores that have been put together to help address these critical gaps. The overarching goal is to define the mechanisms that regulate local Ca2+ signaling by CaV1.2 and RYR2 in normal and failing hearts with unprecedented precision. While each project stands on its own footing as far as being comprised of innovative and exciting research, all are dependent on the expertise provided by the Cores and are enriched by interproject collaborations that are greatly enhanced by the PPG structure. All four Projects leverage the Pakistan Genome Resource (PGR) (Core A), a unique cohort of individuals with extensive phenotype data and high rates of consanguinity that result in a prevalence of genetic mutations.
Moreover, all four Projects involve experiments that span fundamental studies on single molecules and cells to animal models (Core B; Mouse Cardiac Physiology Core). Combining human missense mutations found in the PGR cohort in CaV1.2, RYR2 or key regulatory proteins with in-depth structure-function experiments promises to advance new understanding of genotype-phenotype relationships in human cardiovascular diseases involving Ca2+ cycling proteins in the heart. We expect the proposed studies to: yield fundamental new insights into structure-function and regulation of CaV1.2 and RYR2; elucidate how their dysregulation contributes to heart diseases; and advance their utility as therapeutic targets for cardiac dysfunction.
The PIs of the four projects have a strong history of collaboration and a track record of developing innovative approaches for fundamental studies of CaV1.2 and RYR2 molecular physiology and structural biology. The four Projects and two Cores are highly complementary and synergistic. The Projects and Specific Aims are:
PROJECT 1: Tools to Probe Trafficking, Function and Regulation of Calcium Channel Signaling Complexes in Heart
PROJECT 2: Roles of Rad and Other CaV1.2 Neighboring Proteins in Regulating Cardiac Function in Health and Disease
PROJECT 3: Illuminating the function regulome of cardiac L-type Ca2+ channels in health and disease
PROJECT 4: Molecular dissection of stress-induced dysregulation of SR calcium release in disorders of cardiac muscle