Selective Inhibition of Cav3.3 T-type Calcium Channels by Gαq/11-coupled Muscarinic Acetylcholine Receptors

• Published in: The Journal of biological chemistry 2007-07, Vol.282 (29), p.21043-21055
• Main Authors: Hildebrand, Michael E., David, Laurence S., Hamid, Jawed, Mulatz, Kirk, Garcia, Esperanza, Zamponi, Gerald W., Snutch, Terrance P.
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M611809200

T-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 Ca2+ channels are modulated by G-protein-coupled receptors (GPCRs) remain largely unexplored. To examine specific interactions between T-type Ca2+ channel subtypes and muscarinic acetylcholine receptors (mAChRS), the Cav3.1 (α1G), Cav3.2 (α1H), and Cav3.3 (α) T-type Ca2+1Ichannels were co-expressed with the M1 Gαq/11-coupled mAChR. Perforated patch recordings demonstrate that activation of M1 receptors has a strong inhibitory effect on Cav3.3 T-type Ca2+ 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 Ca2+ 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 Gα and Gβγ proteins and gain-of-function experiments with genetically encoded Gα subtypes indicate that M1 receptor-mediated inhibition of Cav3.3 occurs through Gαq/11. This is supported by experiments showing that activation of the M3 and M5 Gαq/11-coupled mAChRs also causes inhibition of Cav3.3 currents, although Gαi-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.