Fellowship for Ahern: Myocardial Rad Modulation of the L-type Calcium Channel Provides Cardioprotection

Calcium is an essential component of cardiac muscle contraction, and its concentration must be tightly controlled to avoid dysfunction in the heart. The L-Type Calcium channel (LTCC) acts as a gateway for calcium to enter into cardiac muscle cells to initiate contraction. The LTCC is strictly regulated to prevent too much calcium from overloading the cell, which could lead to cardiac hypertrophy and potential heart failure. One such regulator of the LTCC is Rad. Previous data showed that overexpression of Rad leads to complete block of the LTCC; conversely, deletion of Rad increases calcium influx through the channel without promoting progression to hypertrophy. Deletion of Rad also resembles a tonic â-adrenergic receptor-like stimulation, a response normally induced by the sympathetic nervous system on the heart. The mechanism by which Rad affects the calcium current through the LTCC remains unknown. Understanding how Rad affects calcium influx through the LTCC will provide insight into a specific target for treating cardiac hypertrophy. The proposed studies will test the overall hypothesis that Rad is a negative modulator of calcium current through the LTCC, which can be removed through phosphorylation. Specific Aim 1 will determine the effect of Rad modulation on LTCC calcium current by testing the hypothesis that phosphorylation of Rad will cause changes in association with the LTCC, thereby increasing calcium current. This will be accomplished through immunocytochemistry and patch clamping of isolated cardiomyocytes from a Rad Flag-tagged model in conditions that promote or inhibit kinase activity. Specific Aim 2 will determine structural remodeling of the heart by Rad by testing the hypothesis that phosphorylation of Rad will provide protection from cardiac hypertrophy in a thoracic aorta constriction model. This will be completed through echocardiography, live cell calcium imaging, and analysis of genetic markers through molecular assays. These aims will provide training in handling various mammalian models, critical techniques in cardiovascular research, and in professional development to endow an enthusiastic trainee with a foundation necessary to succeed as an independent scientist.