Abstract 336: Conservation of Cardiac L-type Ca2+ Channels and Their Modulation in Drosophila: a Novel Genetically Pliable Channelopathic Model

Abstract

Misregulation of L-type Ca 2+ channels (LTCCs) underlies numerous cardiac pathologies. For example, heart failure features blunted protein kinase A (PKA) upregulation of the LTCCs. However, studying LTCC regulation in mammalian systems is challenging due to complex physiology and lack of genetic manipulability while recombinant channels expressed in heterologous systems, which lack key auxiliary elements, poorly represent the native context. Drosophila , however, has a simple heart with many conserved genes and is genetically pliable. Thus, we pinpointed the signature of Ca 2+ channels (CCs) in the fly cardiac tubes. First, RNAi-mediated selective knockdown of Dmca1D, homologous to the human LTCCs, abolished cardiac contraction (B, as compared to ctrl in A), establishing this channel isoform as the primary CC in fly hearts. Second, we successfully isolated viable single fly cardiomyocytes (C, inset) and recorded robust Ca 2+ currents using patch clamp electrophysiology (C), a feat never before accomplished for the fly cardiac system. Moreover, recording Ca 2+ currents in distinct hypomorphic CC lines, we confirmed the CC type in the fly heart. We also observed pharmacological responses of the CCs that were strikingly similar to those seen in humans. Current through Dmca1D is blocked by a dihydropiridine, nifedipine (C), and is readily upregulated by forskolin, a downstream activator of the PKA pathway (C). In all, we have established the existence of a conserved compendium of cardiac CCs in fly heart tubes, suggesting that Drosophila may serve as a robust and effective platform to study the pathophysiology of diseases involving cardiac CCs and to devise therapeutic strategies.