Nuclear alpha1-Adrenergic Receptor Signaling in Adult Mouse Cardiace Myocytes

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DESCRIPTION (provided by applicant): The objective of this research is to define the molecular mechanisms of a1-adrenergic receptor (a1-AR) survival signaling in adult mouse cardiac myocytes. Recent evidence suggests that a1-ARs are required for normal growth and development of the heart and myocardial adaptation to stress. Additionally, clinical trials with a1-AR antagonists, or a1-blockers, led to significant increases in heart failure. Ongoing research in this lab has revealed that the previously described a1A-AR-ERK survival signal is initiated by a1A-AR localized on the nuclear membrane that, when activated, induce accumulation of phosphorylated ERK in caveolae at the plasma membrane. This signaling pathway is unique because it does not fit the classical models of G- protein coupled receptor signaling and presents a provocative model for a1 A-AR-ERK survival signaling in adult cardiac myocytes. We hypothesize that activated nuclear a1-AR initiate signaling thru Gaq and PLCP1 leading to activation of PKC within the nucleus, PKC translocates to caveolae at the plasma membrane and activates the known kinase pathway (Ras, Raf, and MEK) upstream of ERK. Furthermore we hypothesize that caveolin-3 is a regulator of a1-AR induced ERK signaling, and that Bad and/or FOXO1 are downstream targets of a1-AR-ERK survival signal. We will test these hypotheses by determining the signaling proteins involved in transducing the a1-AR survival signal from the nucleus to the plasma membrane, what regulatory role caveolin-3 might have on the survival signal, and what the down stream targets of phosphorylated ERK is/are. I propose the following specific aims to achieve these goals. Aim 1: Determine how caveolin-3 regulates a1A-ERK mediated survival signaling and the downstream targets of activated ERK in adult mouse cardiac myocytes. Aim 2: Determine the signal transduction pathway from activated nuclear a1-AR that leads to activated ERK at the plasma membrane in adult mouse cardiac myocytes. Our goal is to determine the molecular mechanisms behind a1-AR-ERK survival signal in adult cardiac myocytes. Using Western blot of ERK phosphorylation and cell death assays on isolated cardiac myocytes with varying expression of caveolin-3 will determine the regulatory role of caveolin-3. Using Western blot analysis of the phosphorylation status of Bad and FOXO1 we will determine if either protein is a downstream target of activated ERK. Immunocytochemistry, inhibition of PKC isozymes and Western blot analysis of ERK phosphorylation will be used to determine how the a1-AR survival signal reaches caveolae at the plasma membrane.