Arc/Arg3.1 Translation Is Controlled by Convergent N-Methyl-D-aspartate and Gs-coupled Receptor Signaling Pathways

Abstract

Arc/Arg3.1 is an immediate early gene whose expression is necessary for the late-phase of long-term potentiation (LTP) and memory consolidation. Whereas pathways regulating Arc transcription have been extensively investigated, less is known about the role of post-transcriptional mechanisms in Arc expression. Fluorescence microscopy experiments in cultured hippocampal neurons revealed that Arc protein level was dramatically increased by activation of the cAMP-dependent protein kinase (PKA) pathway, which is implicated in long-term memory. A PKA-dependent increase in Arc protein level was observed after pharmacological or synaptic activation of N-methyl-D-aspartate (NMDA) receptors, which play a critical role in both LTP induction and learning. Arc protein was also up-regulated by activation of PKA through G s -coupled dopamine and ␤-adrenergic receptors, which regulate the late-phase of LTP and memory. When agonists for the NMDA and G scoupled receptors were co-applied, they had an additive effect on Arc protein expression. Interestingly, G s -coupled receptor stimulation was ineffective in the presence of an NMDA receptor antagonist, suggesting calcium influx through the NMDA receptor plays a gating role in this pathway. Stimulation of the cAMP/PKA pathway did not affect Arc mRNA level or protein stability, identifying translational efficacy as the main determinant of Arc protein expression level. It is concluded that efficient Arc translation requires NMDA receptor activity, whereas a further enhancement can be achieved with activation of G s -coupled receptors. These experiments have, therefore, revealed remarkable similarities in the signaling pathways that control Arc expression and those that regulate LTP, learning, and memory.Activity-regulated, cytoskeletal-associated protein Arc, also known as Arg3.1, was identified as an immediate early gene, whose mRNA is induced by patterns of synaptic activity that elicit LTP (1, 2). After transcription Arc mRNA is transported into neuronal dendrites, where it localizes specifically to activated synapses (3). Experiments using antisense or genetic knockdown have shown that Arc expression is necessary for both the late phase of LTP and memory consolidation (4, 5). Thus far, studies of the regulation of Arc expression have focused mainly on mechanisms controlling gene transcription. Arc mRNA levels are increased after treatment with stimulants or growth factors as well as by exposing animals to novel environments (6 -13). The signaling pathways controlling Arc transcription include several receptors (for NMDA, 2 dopamine, serotonin, brain-derived neurotrophic factor, insulin, adrenaline, and acetylcholine), second messengers (Ca 2ϩ and cAMP), protein kinases (cAMP-dependent protein kinases A and C (PKA and PKC), Src, extracellular signal-regulated kinase), and transcription factors (Egr1 and Egr3) (6, 13-21).Post-transcriptional regulation of Arc protein expression has not been studied in as much detail. Brain-derived neurotrophic factor and reelin-integrin receptor si...

Activation of Intracellular Metabotropic Glutamate Receptor 5 in Striatal Neurons Leads to Up-regulation of Genes Associated with Sustained Synaptic Transmission Including Arc/Arg3.1 Protein

“…In cortical and hippocampal neurons, NMDA receptors are required for group I mGluR-dependent Arc transcription (14,20,42), whereas in striatal neurons mGluR5-mediated Arc induction is unaffected by NMDA antagonists (Fig. 4B).…”

Dendritic protein synthesis in the normal and diseased brain

“…However, many neuromodulatory inputs to the hippocampus and cerebral cortex regulate protein synthesis-dependent plasticity. These afferents include dopaminergic inputs from the ventral tegmental area (Huang and Kandel, 1995, Kudoh et al, 2002, Tischmeyer et al, 2003, Huang et al, 2004, Smith et al, 2005, Nagai et al, 2007, Navakkode et al, 2007, Bloomer et al, 2008, Schicknick et al, 2008, Wang et al, 2010a), cholinergic inputs from the medial septal nucleus and the nucleus basalis magnocellularis (Frey et al, 2001, Massey et al, 2001, Frey et al, 2003, Bergado et al, 2007, McCoy and McMahon, 2007, Volk et al, 2007), and noradrenergic inputs from the locus ceoruleus (Straube et al, 2003, Walling and Harley, 2004, Gelinas and Nguyen, 2005, Gelinas et al, 2007, Bloomer et al, 2008). …”

Blockade of α2-adrenoceptors induces Arc gene expression in rat brain in a glutamate receptor-dependent manner: A combined qPCR, in situ hybridisation and immunocytochemistry study

“…For example, 5-HT agonist-induced increase in Arc mRNA was blocked by GYKI 52466 (Pei et al, 2004). Also, NMDA activation increased Arc mRNA, an effect prevented by NMDA receptor antagonists including MK 801 (Steward and Worley, 2001;Bloomer et al, 2008). Moreover, it has been reported that Group I (mGluR5) receptor activation increased Arc gene expression both in cultured neurones in vitro and brain tissue in vivo (Brackmann et al, 2004;Waung et al, 2008;Wang et al, 2009).…”

“…First, the selective AMPA receptor antagonist, GYKI 52466 (Nikam and Kornberg, 2001) was utilised given its role in defining 5-HT-glutamate interactions (Pei et al, 2004). Second, MK 801 and MPEP, selective antagonists at NMDA and mGluR5 receptors respectively, were used since evidence implicates a role for these co-excitatory receptors in the regulation of Arc expression (Steward and Worley, 2001;Brackmann et al, 2004;Lea and Faden, 2006;Bloomer et al, 2008;Bramham et al, 2010;Wang et al, 2009;Waung et al, 2008). Finally, the mGluR2/3 receptor antagonist, LY341495 was utilised in control experiments since activation of mGluR2/3 receptors inhibits neuronal activity and glutamate release, but does not recruit Arc expression (Cartmell and Schoepp, 2000;Bramham et al, 2010;Nicoletti et al, 2011;Linden et al, 2009 …”