Mechanism and functional role of AKAP79/150 in M current control

University Of Texas Hlth Science Center, San Antonio TX

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Abstract

DESCRIPTION (provided by applicant): 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 (CaN), ion channels such as M-type (KCNQ, Kv7) K+ channels, L-type Ca2+ channels and G protein-coupled receptors. The nuclear factor of activated T-cells (NFAT) family of transcription factors has been shown to underlie activity-dependent regulation of gene transcription in excitable cells, including central and peripheral neurons. Sensory neurons of the nodose ganglia are responsible for sending afferents from the visceral organs to the brainstem, where body organs are controlled. In this project, we will study the transcriptional regulation of KCNQ2-3 channels in superior cervical ganglion (SCG) sympathetic neurons via NFATc1-c4 members, which are activated by intracellular Ca2+ (Ca2+i) signals, such as those generated by activity-dependent depolarization. We hypothesize the Ca2+i signals are sensed by CaN, anchored by AKAP79/150 to L-type CaV1.3 Ca2+ channels, followed by dephosphorylation of NFATs, their import into the nucleus, and up-regulation of M-channel gene expression that acts as a negative feedback on excitability in physiological and pathophysiological states. We will test this hypothesis using a variety of cutting-edge approaches. We further hypothesize AKAP79/150 to orchestrate modulation of M current in NG neurons by a variety of Gq/11-linked receptor types that are critical to pain and inflammation, including bradykinin, PAR-2, histamine, angiotensin II and purinergic receptors. We will determine which Gq/11-coupled receptors modulate NG neurons, and the role of AKAP79/150 in coupling the receptors to the M-type channels. Techniques to be used include patch-clamp electrophysiology of native SCG and NG neurons, single live-cell imaging, confocal microscopy, luciferase gene-reporter assays, genetically-altered mice and live-animal airway plethysmography. We aspire to discover the mechanisms endowing AKAP79/150 in organizing the transcriptional regulation of M-type K+ channels, and in orchestrating the receptor signaling towards these channels in sensory neurons that are pivotal in control of visceral sensation.