A-kinase anchoring proteins (AKAPs) organize numerous intracellular signaling pathways by bringing together their molecular components into discrete sub-cellular microdomains. One such AKAP, AKAP79/150 interacts with protein kinase A, protein kinase C (PKC), calmodulin (CaM), calcineurin, and phosphatidylinositol 4,5- bisphosphate (PIP2), along with effectors such as M-type (KCNQ, Kv7) K+ channels and certain G protein- coupled receptors. In this project, we will study which KCNQ1-5 subunits are targets of AKAP79/150, and which Gq/11-coupled receptors of sympathetic and nodose ganglia neurons (muscarinic M1, bradykinin B2, angiotensin AT1 and purinergic P2Y) use AKAP79/150 to modulate M-type channels. We will also investigate the interactions between the CaM and PIP2 molecules with AKAP79/150 that are critical to the function of both M channels and AKAP79/150. The role of AKAP79/150 in Gq/11-coupled receptor control of neuronal discharge properties of the neurons, and on their release of neurotransmitter will be explored, both at the single-cell level, and via an in vitro model of the chronotropic response of cardiomyocytes to sympathetic neuron activity. We will use a heterologous expression system in which M-channels, receptors and signaling molecules are expressed in Chinese hamster ovary (CHO) cells, preparations of rat and mouse superior cervical ganglia (SCG) and nodose ganglia (NG) neurons, and a co-culture of SCG neurons and ventricular cardiomyocytes. Techniques to be used include fluorescence resonance energy transfer (FRET), total internal reflection fluorescence (TIRF), confocal microscopy, patch-clamp electrophysiology, carbon-fiber amperometry and video imaging. We aspire to discover the mechanisms endowing AKAP79/150 in specificity towards receptors and M-type K+ channels, and its functional role in shaping the neurophysiological and neurotransmitter release properties of neurons.
The signaling pathways that comprise a common motif in biological signaling underlie how the nervous system is regulated, including alterations in emotional state and mood, personality and the acquisition and use of memories. We will study the regulation of the M-type potassium ion channel, which plays dominant role in regulation of nerve-cell excitability, mediated by the A-kinase Anchoring Protein, AKAP79/150. The elucidation of the mechanisms and functional role of AKAP79/150 in M-channel activity will shed light on how the nervous system functions in health and disease.
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