Muscarinic modulation of Ca_v2.3 (R-type) calcium channels is antagonized by RGS3 and RGS3T

Abstract

Ca(2+) influx through voltage-gated R-type (Ca(V)2.3) Ca(2+) channels is important for hormone and neurotransmitter secretion and other cellular events. Previous studies have shown that Ca(V)2.3 is both inhibited and stimulated through signaling mechanisms coupled to muscarinic ACh receptors. We previously demonstrated that muscarinic stimulation of Ca(V)2.3 is blocked by regulator of G protein signaling (RGS) 2. Here we investigated whether muscarinic inhibition of Ca(V)2.3 is antagonized by RGS3. RGS3 is particularly interesting because it contains a lengthy ( approximately 380 residue) amino-terminal domain of uncertain physiological function. Ca(V)2.3, M(2) muscarinic ACh receptors (M(2)R), and various deletion mutants of RGS3, including its native isoform RGS3T, were expressed in HEK293 cells, and agonist-dependent inhibition of Ca(V)2.3 was quantified using whole cell patch-clamp recordings. Full-length RGS3, RGS3T, and the core domain of RGS3 were equally effective in antagonizing inhibition of Ca(V)2.3 through M(2)R. These results identify RGS3 and RGS3T as potential physiological regulators of R-type Ca(2+) channels. Furthermore, they suggest that the signaling activity of RGS3 is unaffected by its extended amino-terminal domain. Confocal microscopy was used to examine the intracellular locations of four RGS3-enhanced green fluorescent protein fusion proteins. The RGS3 core domain was uniformly distributed throughout both cytoplasm and nucleus. By contrast, full-length RGS3, RGS3T, and the amino-terminal domain of RGS3 were restricted to the cytoplasm. These observations suggest that the amino terminus of RGS3 may serve to confine it to the cytoplasmic compartment where it can interact with cell surface receptors, heterotrimeric G proteins, and other signaling proteins.

Inhibitory Signaling to Ion Channels in Hippocampal Neurons Is Differentially Regulated by Alternative Macromolecular Complexes of RGS7

“…The role of RGS complexes in this process is less clear, with only few RGS proteins across the entire nervous system implicated in regulation of Ca V 2-mediated calcium influx. For example, RGS2 and RGS3 disinhibit Ca V 2 channels and increase transmitter release (Han et al, 2006;Toro-Castillo et al, 2007), whereas RGS4 and RGS12 accelerate the time course of desensitization of norepinephrine-mediated current inhibition (Diversé-Pierluissi et al, 1999;Schiff et al, 2000). In this report, we reveal RGS7 to be a key player in regulation of Ca V function in hippocampal CA1 neurons.…”

“…In the axons, G␤␥, released by the GABA B Rs, binds and inhibits Ca V 2 voltage-gated channels (N and P/Q types), suppressing neurotransmitter release and thereby inhibiting the synaptic output of CA1 neurons (Zamponi and Currie, 2013). The inhibitory signaling by GABA B Rs via GIRK and Ca V 2 is important for hippocampal synaptic plasticity and memory formation (Davies et al, 1991;Wagner and Alger, 1995;Schuler et al, 2001) and its dysfunctions are thought to contribute to a variety of neuropsychiatric conditions including epilepsy, Down syndrome, and motor and cognitive impairments (Schuler et al, 2001;Alonso et al, 2008;Cramer et al, 2010;Zamponi et al, 2010;Victoria et al, 2016) A critical role in controlling the strength and timing of GABA B R signaling to GIRK in CA1 neurons belongs to the RGS7/ G␤5 protein complex Ostrovskaya et al, 2014). Being a constitutive dimer, RGS7/G␤5 functions as a GTPase activating protein (GAP) that accelerates G-protein inactivation (Anderson et al, 2009) to limit G␤␥mediated GIRK activation and facilitate current deactivation upon termination of the GABA B R signaling.…”

Voltage-Gated Calcium Channels: Classification and Pharmacological Properties (Part I)

“…Як і для інших ПКК-каналів, α1-субодиниця утворює пору, через яку іони кальцію проникають у клітину, і визначає більшу частину властивостей каналу. За будовою α1-субодиниці, цей тип каналів також відомий як Ca v 2.3, і експресується в основному у корі головного мозку, дендритах пірамідальних клітин гіпокампа, стріатумі, мигдалині і міжніжкових ядрах [79], також, разом з каналами Q-типу, описані в гранулярних клітинах мозочка [80].…”

RGS3 controls T lymphocyte migration in a model of Th2-mediated airway inflammation

“…RGS3 belongs to the R4/B subfamily and selectively interacts with G i ␣ and G q ␣ 11 , but not G s ␣ or G␣ 12/13 (14,40). Ectopic expression of RGS3 in various cell types demonstrated its ability to regulate G i -or G q -mediated signaling pathways induced by agonists such as gonadotropinreleasing hormone (7,33,34), lysophospohatidic acid (8,19), endothelin-1 (14), carbachol and angiontensin II (47), acetylcholine (24,25,46), and various chemokines (6,39). Functionally, expression of RGS3 inhibited LPA-and chemokineinduced migration in renal tubular cells (19) and lymphoid cells (6,39), respectively.…”