RGS9-2 modulates D ₂ dopamine receptor-mediated Ca ²⁺ channel inhibition in rat striatal cholinergic interneurons

Abstract

Regulator of G protein signaling (RGS) proteins negatively regulate receptor-mediated second messenger responses by enhancing the GTPase activity of G␣ subunits. We describe a receptor-specific role for an RGS protein at the level of an individual brain neuron. RGS9-2 and G␤5 mRNA and protein complexes were detected in striatal cholinergic and ␥-aminobutyric acidergic neurons. Dialysis of cholinergic neurons with RGS9 constructs enhanced basal Ca 2؉ channel currents and reduced D2 dopamine receptor modulation of Cav2.2 channels. These constructs did not alter M2 muscarinic receptor modulation of Cav2.2 currents in the same neuron. The noncatalytic DEP-GGL domain of RGS9 antagonized endogenous RGS9-2 activity, enhancing D2 receptor modulation of Ca 2؉ currents. In vitro, RGS9 constructs accelerated GTPase activity, in agreement with electrophysiological measurements, and did so more effectively at Go than Gi. These results implicate RGS9-2 as a specific regulator of dopamine receptor-mediated signaling in the striatum and identify a role for GAP activity modulation by the DEP-GGL domain.calcium ͉ GTPase activating protein ͉ receptor-specific ͉ basal ganglia ͉ indirect pathway R egulators of G protein signaling (RGS) are a diverse family of proteins identified by the presence of a 120-aa domain termed the RGS box. In cell lines or in purified in vitro assays, most RGS proteins enhance the GTPase activity of heterotrimeric G protein ␣ subunits and thereby accelerate the deactivation of receptor-initiated second messenger responses. Many RGS proteins also contain one or more putative protein-protein interaction domains. These noncatalytic domains have been suggested to regulate catalytic activity, signal transduction pathway specificity, and͞or subcellular targeting of RGS proteins.One subfamily of RGS proteins (RGS6, -7, -9, and -11) all share homologous DEP (Dishevelled, Egl-10, Pleckstrin), GGL (G protein Gamma subunit Like), and RGS domains. The DEP domain of the retinal isoform of RGS9 (RGS9-1) has been shown to confer localization to a retinal membrane protein termed R9AP, and this localization has been shown to be necessary for proper RGS9-1 function in the retina (1). Several investigators have demonstrated that the GGL domain interacts with the G␤ 5 subunit (2-6). In vitro, G␤ 5 binding to RGS6, -7, or -11 increases the GAP specificity of these RGS proteins for G␣ (2, 3). In addition, G␤ 5 binding to either RGS7 or RGS9 enhances RGS-mediated acceleration of G protein gated inwardly rectifying K ϩ (Kir3) channel activation and deactivation kinetics in an oocyte expression system. This enhancement may result from G␤ 5 -mediated increased stability of the RGS protein or enhanced GAP activity (7).Despite the functional similarities among RGS6, -7, -9, and -11 in heterologous expression systems or when analyzed in vitro, each of these RGS proteins is likely to play a unique role in the central nervous system because they are differentially localized within the brain (8, 9). In contrast to the more ubiquitous loc...

Coexpressed D1- and D2-Like Dopamine Receptors Antagonistically Modulate Acetylcholine Release in Caenorhabditis elegans

“…Furthermore, Gao is regulated by RGS9-2 in medium spiny neurons (Cabrera-Vera et al 2004), and we have found that the homologous protein EGL-10 regulates GOA-1/Gao coupled to DOP-3 in C. elegans ( Figure 1A and Chase et al 2004). Finally, D1-like receptors in the mammalian brain can couple to Gaq (Wang et al 1995), and we have shown that the C. elegans DOP-1 receptor also couples to Gaq (this work and Chase et al 2004).…”

Macromolecular Composition Dictates Receptor and G Protein Selectivity of Regulator of G Protein Signaling (RGS) 7 and 9-2 Protein Complexes in Living Cells

“…Several studies have demonstrated that the long splice isoform of RGS9 (RGS9-2) serves as a critical GAP in these neurons (9,10). In particular, RGS9-2 has been shown to regulate signaling downstream from D2 dopamine (D2R) and -opioid (MOR) receptors and has been implicated in drug addiction and movement disorders (11)(12)(13)(14)(15). However, no studies directly examined the impact of RGS9-2 on G protein dynamics activated by D2R and MOR.…”

β-Arrestin2 Plays Permissive Roles in the Inhibitory Activities of RGS9-2 on G Protein-Coupled Receptors by Maintaining RGS9-2 in the Open Conformation

“…RGS2, RGS4, and RGS9-2 are known to be closely related to the dopaminergic nervous system and drug addiction (45). RGS9-2 is highly enriched in the striatum and nucleus accumbens, where it regulates the functional responses of D2-like receptors in vivo (6,28,35). Regulatory roles for RGS2 and RGS4 in the signaling of D2-like receptors have not been reported.…”

“…It was reported that D2-like receptors are functionally regulated by RGS9-2. For example, viral expression of RGS9-2 in the nucleus accumbens or dialysis of RGS9-2 proteins into striatal cholinergic interneurons reduced the behavioral or electrophysiological response to stimulation of the D2-like receptor (6,35). On the other hand, knockout of RGS9-2 enhanced behavioral responses to the activation of D2-like receptors (28,35).…”