Interaction with Neuronal Calcium Sensor NCS-1 Mediates Desensitization of the D2 Dopamine Receptor

Abstract

Dopaminergic transmission within limbic regions of the brain is highly dependent on the regulation of D2 receptor activity. Here we show that the neuronal calcium sensor-1 (NCS-1) can mediate desensitization of D2 dopamine receptors. Analysis of D2 receptors expressed in human embryonic kidney 293 cells indicates that NCS-1 attenuates agonist-induced receptor internalization via a mechanism that involves a reduction in D2 receptor phosphorylation. This effect of NCS-1 was accompanied by an increase in D2 receptor-mediated cAMP inhibition after dopamine stimulation. The ability of NCS-1 to modulate D2 receptor signaling was abolished after a single amino acid mutation in NCS-1 that has been shown to impair the calcium-binding properties of NCS-1. Coimmunoprecipitation experiments from striatal neurons reveal that NCS-1 is found in association with both the D2 receptor and G-protein-coupled receptor kinase 2, a regulator of D2 receptor desensitization. Colocalization of NCS-1 and D2 receptors was examined in both primate and rodent brain. In striatum, NCS-1 and D2 receptors were found to colocalize within sites of synaptic transmission and in close proximity to intracellular calcium stores. NCS-1-D2 receptor interaction may serve to couple dopamine and calcium signaling pathways, thereby providing a critical component in the regulation of dopaminergic signaling in normal and diseased brain.

Interaction between variation in the D2 dopamine receptor (DRD2) and the neuronal calcium sensor-1 (FREQ) genes in predicting response to nicotine replacement therapy for tobacco dependence

“…Consistent with the role of NCS-1 in modulating dopamine D2 receptor signaling, 12 we found evidence for a statistically significant interaction between a common variant in the FREQ gene (rs1054879) and a functional variant in the DRD2 promoter, DRD2 À141 Ins/Del. This finding builds upon our previous report indicating that smokers with at least one copy of the DRD2 À141 Del allele have higher abstinence rates when treated with NRT, 5 and suggests that this enhanced response to treatment is present only for the subset of smokers who also are homozygous for the A allele of FREQ rs1054879; 62% of these smokers were abstinent at EOT compared with abstinence rates of 29-38% among other groups of smokers.…”

“…In vitro studies have shown that NCS-1 attenuates dopamine-induced D2 receptor desensitization and internalization in a calcium-dependent manner. 12 Genetic variation in the FREQ gene leading to altered NCS-1 protein levels or function would be expected to alter the rate of D2 receptor desensitization and internalization. Because nicotine stimulates dopamine release from striatal neurons, 14 changes in D2 signaling associated with genetic variation in FREQ could modulate liability to relapse and/or response to NRT.…”

“…In addition, based on the results of this study, it will be important to analyze variation in genes encoding additional DRIPs. One interesting candidate DRIP is the gene encoding G-protein-coupled receptor kinase 2 (ADRBK1), because this enzyme has been shown to interact with both NCS-1 and DRD2 proteins 12 and functions to regulate DRD2 receptor desensitization. 15,16 It should be noted that we also examined whether the FREQ SNPs modified the effect of the DRD2 À141 Ins/Del on response to bupropion in a placebo-controlled bupropion trial for smoking cessation.…”

“…In mammalian cells, NCS-1 has been shown to promote exocytosis from dense core vesicles of neuroendocrine cells and plays a prominent role in D2 dopamine receptor desensitization via a direct interaction with the receptor. 12 Given the established role for NCS-1 in regulating D2 receptor signaling, these studies present the intriguing possibility that alterations in NCS-1 activity and/ or expression may contribute to the dopaminergic pathophysiology of nicotine dependence and response to nicotine replacement medications.…”

Regulation of neuromodulator receptor efficacy—implications for whole-neuron and synaptic plasticity

“…Calcium indirectly reduces desensitization, via the calcium-dependent protein calmodulin, which inhibits GRKs (31). Another pathway for calcium to prevent desensitization has recently been detected in the calcium sensor NCS-1, which reduces phosphorylation and internalization of the D2 receptor (32). Arrestins can increase the effects of GRKs, for instance, overexpression of arrestins reduces the ability of β-adrenergic receptors to activate G S by > 75% (33).…”