Platform : Ion Channel Regulatory Mechanisms

1836-Plat Coupling of Distinct Ion Channel Types in Neurons Mediated by AKAP79/ 150 Jie Zhang, Mark S. Shapiro. Physiology, UT Health Science Center, San Antonio, TX, USA. M-type Kþ channels, comprised of KCNQ2-5 (Kv7.2-7.5) subunits, play key roles in the regulation of neuronal excitability in the nervous system. In diverse neurons, L-type Ca2þ channels (LTCCs) drive transcriptional regulation via NFAT transcription factors, and in sensory neurons, TRPV1 cation channels excite neurons in response to heat, acidity or chemical ligands, driving nociception. The A-kinase-anchoring protein (AKAP)79/150 has been shown to orchestrate regulation of all three types of channels by PKC, PKA, calcineurin and NFATs. Using stochastic optical reconstruction microscopy (STORM) super-resolution microscopy, we have directly visualized individual signaling complexes containing AKAP79/150, these three ion channels and G proteincoupled receptors in neurons and tissue-culture cells. Using multi-color STORM, we observe AKAP150-mediated clustering of KCNQ, LTCCs and TRPV1 channels at the single-complex level. Thus, AKAP79/150 links different channel types together, raising the possibility of their functional, as well as physical, coupling. In sensory neurons, capsaicin caused PIP2 hydrolysis by TRPV1 activation. In neurons isolated from AKAP150þ/þ mice, brief application of low concentrations of capsaicin (100 nM), which we believe triggers only local PIP2 depletion, induced ~40% suppression of M-current (IM), suggesting close localization of TRPV1 and M-channels, the latter thus suppressed by TRPV1-induced local PIP2 depletion. However, in AKAP150-/neurons, IM was not affected by this modest activation of TRPV1 channels, implying the critical role of AKAP79/150. Application of the LTCC blocker, nifedipine, but not the N-type Ca2þ channel blocker, u-conotoxin GVIA, significantly suppressed desensitization and tachyphylaxis of TRPV1 currents, suggesting the functional coupling of LTCCs with TRPV1 channels, consistent with their physical coupling at the single-complex level seen with STORM.We thus find AKAP79/150 mediates physical and functional coupling of these three ion channels in sensory neurons, indicating physiological roles in tuning the nociceptive response to painful stimuli.