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

Abstract

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 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 (␣ 1G ), Cav3.2 (␣ 1H ), and Cav3.3 (␣ 1I ) T-type Ca 2؉ channels were co-expressed with the M1 G␣ 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 G␣ and G␤␥ proteins and gain-of-function experiments with genetically encoded G␣ subtypes indicate that M1 receptor-mediated inhibition of Cav3.3 occurs through G␣ q/11 . This is supported by experiments showing that activation of the M3 and M5 G␣ q/11 -coupled mAChRs also causes inhibition of Cav3.3 currents, although G␣ 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.

Functional Coupling between mGluR1 and Cav3.1 T-Type Calcium Channels Contributes to Parallel Fiber-Induced Fast Calcium Signaling within Purkinje Cell Dendritic Spines

“…1), potentiating Ca v 3.1 and Ca v 3.2 isoforms while inhibiting Ca v 3.3 T-type channels. The latter is consistent with the known inhibition of Ca v 3.3 channels by G␣ q/11 -coupled mAChRs (Hildebrand et al, 2007 . Inset, Representative EPSP recorded at the soma after PF stimulation.…”

“…The Ca v 3.2 isoform is regulated by G␤ 2 ␥-proteins, CAMKII, and redox changes (Welsby et al, 2003;Wolfe et al, 2003;Joksovic et al, 2006), whereas G␣ q/11 -coupled muscarinic acetylcholine receptors (mAChRs) inhibit Ca v 3.3 channels but not Ca v 3.1 or Ca v 3.2 channels (Hildebrand et al, 2007). Hence, T-type channel function may be finely tuned in various cell types according to the combined repertoire of channel isoforms and modulatory pathways.…”

“…Leak subtraction of capacitance and leakage current was performed online using a P/6 protocol with reverse polarity pulses for channel kinetics experiments and with Clampfit9 (MDS Analytical Technologies) during offline analysis for all other experiments. Current-voltage relationships and channel activation and inactivation kinetics were analyzed as described previously (Hildebrand et al, 2007). All voltage-clamp recordings were performed at room temperature (20 -24°C) except for the subset of experiments shown in supplemental Figure 1 (available at www.jneurosci.org as supplemental material) (31°C).…”

Protein Kinase C-Mediated Inhibition of Recombinant T-Type CaV3.2 Channels by Neurokinin 1 Receptors

“…4, D-F) is consistent with other studies in which PMA and other activators of PKC (i.e., 1-oleoyl-2-acetyl-sn-glycerol, phorbol-12,13-dibutyrate, and phorbol- 12,13-didecanoate) inhibited natively expressed T-type currents in neuronal (Marchetti and Brown, 1988;Schroeder et al, 1990;Cheong et al, 2008) and non-neuronal cells . However, our data are also in contrast with studies in which Ca V 3.2 channels were either unaffected (Park et al, 2003) or were significantly stimulated by PMA (Park et al, 2003Hildebrand et al, 2007). It is also interesting to mention the temperature-dependence of PMA effects.…”

T-Type Calcium Channel Inhibition Underlies the Analgesic Effects of the Endogenous Lipoamino Acids

“…Three T-channel subunits have been identified: Cav3.1, Cav3.2, and Cav3.3 (Perez-Reyes, 2003), which are implicated in distinct physiological functions, as recently supported by knock-out (KO) mice studies (Kim et al, 2001;Chen et al, 2003;Lee et al, 2004;Mangoni et al, 2006;Choi et al, 2007). Over the past few years, intracellular messenger pathways (Wolfe et al, 2003;Chemin et al, 2006;Park et al, 2006;Chemin et al, 2007b;Hildebrand et al, 2007;Iftinca et al, 2007;Tao et al, 2008) and endogenous ligands (Nelson et al, 2007a,b;Traboulsie et al, 2007;Maeda et al, 2009) regulating Cav3 activity were identified, including bioactive lipids (Chemin et al, 2001(Chemin et al, , 2007aRoss et al, 2008Ross et al, , 2009.…”