PROJECT 3
Manu Ben Johny
Illuminating the functional regulome of cardiac L-type Ca2+ channels in health and disease
CaV1.2 channels and their modulation figure crucially in the normal function and pathophysiology of the heart. Disruption of CaV1.2 function and regulation results in electrical and Ca2+ disturbances that underlie life-threatening cardiac diseases including arrhythmias, cardiomyopathies, and heart failure (HF). CaV1.2 serves as the primary portal for Ca2+ influx into cardiomyocytes (CMs) that initiates excitation-contraction coupling, sculpts the action potential (AP), underlies inotropy, and supports activity-dependent gene transcription. To fulfill diverse cellular functions, these channels recruit a rich repertoire of regulatory proteins, yielding heterogeneous macromolecular complexes that tune channel activity and localization. Indeed, the canonical CaV1.2 auxiliary subunits (α2δ and β2) and regulatory proteins such as calmodulin and Rad are now well-established as vital players in orchestrating trafficking, gating, and adrenergic regulation. Intriguingly, proximity proteomic analysis from Dr. Marx suggests that the CaV1.2 neighborhood is staggering and extends beyond these conventional subunits12, including proteins linked to cardiomyopathies, such as leucine rich repeat contain protein 10 (Lrrc10) and junctophilin 2 (Jph2). Yet, discerning functionally-relevant channel modulators amidst the CaV1.2 neighborhood is a long-standing challenge. Furthermore, how non-canonical modulators tune CaV1.2 function, and how channel mis-regulation contribute to pathophysiology are largely unknown. This gap impedes forward progress in our understanding of CaV1.2 in cardiac physiology and thwarts the development of new therapies. The overall objective of this project is to construct a next-generation blueprint of functionally-relevant cardiac CaV1.2 modulators, and to determine how channel mis-regulation by non-canonical regulators contributes to heart failure. We develop a novel functional screening approach to systematically identify CaV1.2 modulators. We further leverage the Pakistan Genome Resource, ( PGR , Core A ,
Dr. Saleheen) that provides genome sequencing data from >80000 individuals with extensive cardio-metabolic phenotyping data and who are from consanguineous unions, enabling identification of extensive loss-of-function mutations. We will conduct in depth mechanistic analysis to probe the pathophysiological relevance of CaV1.2 mis-regulation by Lrrc10 and Jph2, two emerging modulators linked to cardiomyopathies and HF.
1: Identify functionally-relevant non-canonical modulators of CaV1.2.
2: Elucidate the mechanism of Lrrc10 modulation of CaV1.2 and effects of DCM-linked mutations.
3: Identify mechanism of Jph2 modulation of CaV1.2 and effects of human mutations.