Hildebrand, Michael E.David, Laurence S.Hamid, JawedMulatz, Kirk J.García, EsperanzaZamponi, Gerald W.Snutch, Terrance Preston2018-06-062018-06-062007-07-20Hildebrand, M. E., David, L. S., Hamid, J., Mulatz, K., Garcia, E., Zamponi, G. W., & Snutch, T. P. (2007). Selective inhibition of Cav3.3 T-type calcium channels by Galphaq/11-coupled muscarinic acetylcholine receptors. The Journal of Biological Chemistry, 282(29), 21043–55. https://doi.org/10.1074/jbc.M6118092000021-9258http://hdl.handle.net/1880/106727https://doi.org/10.11575/PRISM/43799T-type calcium channels play critical roles in controlling neuronal excitability, including the generation of complex spiking patterns and the modulation of synaptic plasticity, although the mechanisms and extent to which T-type Ca(2+) channels are modulated by G-protein-coupled receptors (GPCRs) remain largely unexplored. To examine specific interactions between T-type Ca(2+) channel subtypes and muscarinic acetylcholine receptors (mAChRS), the Cav3.1 (alpha(1G)), Cav3.2 (alpha(1H)), and Cav3.3 (alpha) T-type Ca(2+)(1I)channels were co-expressed with the M1 Galpha(q/11)-coupled mAChR. Perforated patch recordings demonstrate that activation of M1 receptors has a strong inhibitory effect on Cav3.3 T-type Ca(2+) currents but either no effect or a moderate stimulating effect on Cav3.1 and Cav3.2 peak current amplitudes. This differential modulation was observed for both rat and human T-type Ca(2+) channel variants. The inhibition of Cav3.3 channels by M1 receptors is reversible, use-independent, and associated with a concomitant increase in inactivation kinetics. Loss-of-function experiments with genetically encoded antagonists of Galpha and Gbetagamma proteins and gain-of-function experiments with genetically encoded Galpha subtypes indicate that M1 receptor-mediated inhibition of Cav3.3 occurs through Galpha(q/11). This is supported by experiments showing that activation of the M3 and M5 Galpha(q/11)-coupled mAChRs also causes inhibition of Cav3.3 currents, although Galpha(i)-coupled mAChRs (M2 and M4) have no effect. Examining Cav3.1-Cav3.3 chimeric channels demonstrates that two distinct regions of the Cav3.3 channel are necessary and sufficient for complete M1 receptor-mediated channel inhibition and represent novel sites not previously implicated in T-type channel modulation.enjournal articlehttp://dx.doi.org/10.1074/jbc.M611809200