Fetal Cardiomyocyte Plasma Membrane Calcium Handling

The long term goal of my research is to elucidate the connection between cardiac excitability and the regulation of cardiac development and pathogenesis. Over the past three years myself and colleagues focused on the function of the T-type Ca channel (CaV3.1). We recently showed that CaV3.1 is expressed embryonic ventricular myocytes (EVM) at embyronic day 14 (E14). T-type Ca channel current (IT) is also re-expressed during pathogenesis in the adult; however, the functional relevance of CaV3.1 expression is an enigma. Recent data from our lab suggests that CaV3.1 mediates steady-state Ca entry, and this Ca entry dependent on active CamK11.We postulate that long term, low amplitude Ca entry via CaV3.1 contributes to cardiac development and adult pathogenesis. We will test the hypothesis that CaV3.1 provides a Ca entry pathway at diastolic potentials. Moreover, we will test whether this pathway is modulated by Ca-calmodulin activated kinase II (CamKII). The majority of this proposal will concentrate on the first aim: To characterize and determine the regulation of plasma membrane Ca entry in EVM. Aim 1 is divided into four parts: 1) To characterize the voltage-dependent Ca current in EVM; 2) To determine the extent of CamKIl modulation of EVM PM Ca currents; 3) To explore a detailed molecular mechanism of Ca channel modulation of CamK II; and, 4) To determine the fetal development of internal Ca stores and relative contibutions of Ca efflux pathways. Aim 2 considers cell proliferation as an endpoint assay for transcriptional regulation resulting from altered Ca PM conductances. The rationale is that EVM express the unique property of cell division, and Ca regulates cell cycle events in a variety of somatic and cancerous cells. The logic behind the rational for these studies is straightforward: IT is re-expressed in pressure-overload induced hypertrophy; CaV3.1 allows steady-state Ca entry; Ca entry is known to regulate transcription; therefore, it is plausible that an over active Ca entry pathway via CaV3.1 may regulate the development of cardiac pathology. Most intriguing, support this hypothesis would suggest a novel therapeutic target (CaV3.1) for the management of heart disease.