Activity-regulated Cytoskeleton-associated Gene Research Articles

Suppression of activity-regulated cytoskeleton-associated gene expression in the dorsal striatum attenuates extinction of cocaine-seeking

The caudate putamen (CPu) has been implicated in habit learning and neuroadaptive changes that mediate the compulsive nature of drug-seeking following chronic cocaine self-administration. Re-exposure to an operant chamber previously associated with cocaine, but not yoked-saline, increases activity-regulated cytoskeleton-associated (Arc) gene mRNA expression within the dorsolateral (dl) CPu following prolonged abstinence. In this study, we tested the hypothesis that antisense gene knockdown of Arc within the dlCPu would alter cocaine-seeking. Initial studies showed that a single infusion of Arc antisense oligodeoxynucleotide (ODN) into the dlCPu significantly attenuated the induction of Arc mRNA and Arc protein by a single cocaine exposure (20 mg/kg i.p.) compared to scrambled-ODN-infused controls. In cocaine self-administering rats, infusion of Arc antisense ODN into the dlCPu 3 h prior to a test of context-driven drug-seeking significantly attenuated Arc protein induction, but failed to alter responding during testing, suggesting striatal Arc does not facilitate context-induced drug-seeking following prolonged abstinence. However, Arc antisense ODN infusion blunted the decrease in responding during subsequent 1-h extinction tests 24 and 48 h later. Following re-exposure to a cocaine-paired context, surface expression of the AMPA-type glutamate receptor GluR1 was significantly reduced whereas GluR2 was significantly increased in the dlCPu, independent of Arc antisense ODN infusion. Together, these findings indicate an important role for Arc in neuroadaptations within brain regions responsible for drug-seeking after abstinence and direct attention to changes occurring within striatal circuitry that are necessary to break down the habitual behaviour that leads to relapse.

Persistent neural activity regulates Arc/Arg3.1 transcription in the dentate gyrus

The activity-regulated cytoskeleton-associated gene (Arc, also known as Arg3.1) is an effector immediate-early gene rapidly induced by strong neural activity. Although a number of studies have revealed significant functions of Arc and Arc has come into widespread use as a neural activity marker in behavioral studies, the mechanisms regulating Arc transcription remain unclear. Here, we examined the conditions of Arc transcription in acute slices of dentate gyrus. Surprisingly, kainic acid (1 μM to 10 mM) application to slices did not induce Arc transcription, although intraperitoneal injection of kainic acid (20 mg/kg) induced robust Arc transcription. No types of high-frequency stimulation examined induced Arc transcription in acute slices. These findings indicate that Arc transcription is dramatically suppressed in acute slices of the dentate gyrus, in which background neural activity is markedly reduced. Burst stimulation increased the number of Arc-expressing cells in the presence of picrotoxin, in which excitation was maintained even after the end of stimulation. Moreover, the involvement of background neural activity in Arc transcription was tested by application of carbachol, a muscarinic receptor agonist. Carbachol also increased the number of Arc-expressing cells, which was blocked by atropine, a muscarinic receptor antagonist. Taken together, these findings suggest that persistent background activity is critical for Arc transcription.

Context-driven cocaine-seeking in abstinent rats increases activity-regulated gene expression in the basolateral amygdala and dorsal hippocampus differentially following short and long periods of abstinence

In this study, the expression patterns of zif268 and activity-regulated cytoskeleton-associated gene (arc) were investigated in the basolateral amygdala (BLA) and dorsal hippocampal (dHPC) subregions during context-induced drug-seeking following 22 h or 15 d abstinence from cocaine self-administration. Arc and zif/268 mRNA in BLA and dHPC increased after re-exposure to the cocaine-paired chamber at both timepoints; however, only the BLA increases (with one exception-see below) were differentially affected by the presence or absence of the cocaine-paired lever in the chamber. Following 22 h of abstinence, arc mRNA was significantly increased in the BLA of cocaine-treated rats re-exposed to the chamber only with levers extended, whereas following 15 d of abstinence, arc mRNA in the BLA was increased in cocaine-treated rats returned to the chamber with or without levers extended. In contrast, zif268 mRNA in the BLA was greater in cocaine-treated rats returned to the chamber with levers extended vs. levers retracted only after 15 d of abstinence. In the dentate gyrus (DG) following 22 h of abstinence, zif268 mRNA was greater in rats returned to the chamber where levers were absent regardless of drug treatment whereas arc mRNA was increased in CA1 (cell bodies and dendrites) and CA3 only in cocaine-treated groups. Following 15 d of abstinence, arc mRNA was significantly greater in CA1 and CA3 of both cocaine-treated groups returned to the chamber than in those placed into a familiar, non-salient alternate environment; however, only in CA1 cell bodies the cocaine context-induced increases significantly greater than in yoked-saline controls. In contrast, zif/268 mRNA in all dHPC regions was significantly greater in both cocaine-treated groups returned to the cocaine context than in the cocaine-treated group returned to an alternative environment or saline-treated groups. These data suggest that the temporal dynamics of arc and zif268 gene expression in the BLA and dHPC encode different key elements of drug context-induced cocaine-seeking.

NEURALIZED MESSENGER RIBONUCLEIC ACID IS LOCALIZED IN DENDRITES BUT IS NOT TARGETED TO ACTIVE SYNAPSES.

Previous studies have revealed that a small subset of mRNAs expressed by neurons are transported into dendrites. One of these (the mRNA for activity-regulated cytoskeleton-associated gene Arc) has a unique property in that it is rapidly targeted to active synapses, but only a few of the known dendritic mRNAs have been tested. Here we assess whether the mRNA for a transcription factor (Neuralized), which has been shown to be present in dendrites, localizes to active synapses in the way that Arc does. A cloned cDNA encompassing 1.71 kilobases of the Neuralized gene was generated by RT-PCR and inserted into expression vectors for producing c-RNA probes for in situ hybridization. The probe was used for in situ hybridization of Sprague-Dawley rat brain sections collected from rats in which afferent pathways to the hippocampus had been strongly activated in a manner that causes Arc mRNA localization at the active dendrites. We found that stimulation patterns that induced dramatic reorganization of Arc mRNA did not cause any detectable alteration in the distribution of Neuralized mRNA. The expression pattern for Neuralized mRNA seems to resemble other mRNAs whose dendritic distribution is not affected by synaptic activation, including the mRNAs for CAM kinase II and dendrin. These results suggest that Arc mRNA possesses unique characteristics not shared by other dendritic mRNAs that have been tested to date. Supported by NIH-NS12333 to OS.

Amyloid-β at sublethal level impairs BDNF-induced arc expression in cortical neurons

Alzheimer's disease (AD) is characterized by progressive memory loss and cognitive dysfunction that probably due to a deficit in synaptic plasticity. One member of neurotrophins, brain-derived neurotrophic factor (BDNF), is known to be involved in the hippocampal long-term potentiation (LTP), a cellular model for learning and memory. Moreover, activity-regulated cytoskeleton-associated gene ( Arc), an immediate early gene, is found to be a downstream effector of the BDNF signaling cascade. Inhibition of Arc protein synthesis impairs both the maintenance of LTP and the consolidation of long-term memory. In addition, the formation of senile plaques is a pathological feature in AD and mainly consists of the deposition of amyloid-β (Aβ), a proteolytic product of amyloid precursor protein. Several studies concerning neurobehavioral performance have suggested that Aβ at sublethal levels interfere with the signaling cascades critical for synaptic plasticity and thus lead to the cognitive impairment in early stage of AD. Whether the BDNF-mediated Arc synthesis is impaired by sublethal Aβ in early AD is still unclear. Therefore, in the present study, primary cultures of neonatal rat cortical neurons were used to evaluate the effect of sublethal Aβ on the BDNF-induced Arc protein expression. Consistent with the literature, Arc, an indicator of synaptic plasticity, was induced by BDNF (25 ng/ml) in both dose- and time-dependent manners. After treating cultures with sublethal Aβ (5 μM), a significant suppression was observed on the level of BDNF-induced Arc protein expression. This result indicates that Aβ at sublethal level impairs the BDNF-mediated signaling in cortical neurons and thus underlies the deficits of synaptic plasticity occurred at the early stage of AD before significant neuronal loss.

Arc interacts with microtubules/microtubule-associated protein 2 and attenuates microtubule-associated protein 2 immunoreactivity in the dendrites.

Arc, activity-regulated cytoskeleton-associated gene, is an immediate early gene, and its expression is regulated by a variety of stimuli, such as electric stimulation and methamphetamine. The function of Arc, however, is unknown. To explore this function, we carried out expression experiments by transfecting green fluorescent protein (GFP)-Arc constructs or by using a protein transduction system in hippocampal cultured neurons. We found that the overexpression of Arc as well as Arc induction by seizure in vivo decreased microtubule-associated protein 2 (MAP2) staining in the dendrites by immunocytochemistry, although MAP2 content was not changed on Western blot. Furthermore, Arc interacted with newly polymerized microtubules and MAP2, leading to blocking of the epitope of MAP2. The data suggest that Arc increased by synaptic activities would trigger dendritic remodeling by interacting with cytoskeletal proteins.

Muscarinic acetylcholine receptor stimulation induces expression of the activity-regulated cytoskeleton-associated gene (ARC)

Muscarinic acetylcholine receptors (mAChR) are involved in learning and memory but their molecular function in these processes is not fully understood. In this study, the signal transduction pathway coupling mAChR activation to induction of the activity-regulated cytoskeleton-associated gene (ARC) was examined. ARC was first identified as an effector immediate early gene induced by neuronal activity and ARC protein is thought to play a role in synaptic plasticity. In rats, intraperitoneal injection of pilocarpine, a potent agonist of mAChR, led to increased ARC expression in the brain. In human SH-SY5Y neuroblastoma cells mAChR stimulation with carbachol caused a rapid and robust induction of ARC expression. This effect was inhibited by atropine, a nonselective muscarinic receptor antagonist as well as by M1/M3 subtype-specific antagonists. Analysis of mAChR downstream effectors revealed that protein kinase C (PKC) and tyrosine kinases of the src family are key molecules in the signal cascade leading to ARC expression. Our data suggest, for the first time, that a correlation exists among mAChR-controlled signal cascades, the induction of the effector immediate early gene ARC and synaptic plasticity.

Memory function and brain glucose metabolism.

Memory formation and memory retrieval are subject to complex cellular and molecular processes. Increasing evidence exists that neuronal glucose metabolism and its control by the insulin signal transduction cascade are the main players in such processes. Acetylcholine synthesis depends on the availability of acetyl CoA, provided from glucose breakdown, and insulin, which controls the activity of acetylcholine transferase. ATP is necessary for both synaptic activity and plasticity. This is also true for APPs, the secreted derivative of APP. Trafficking of the latter protein is controlled by insulin and insulin receptor function also acting on activity-regulated cytoskeleton-associated gene expression, which induces biochemical stimuli involved in synaptic activity and plasticity. Any damage in neuronal glucose metabolism and its control may, therefore, cause disturbances in memory function--as is found for example in sporadic Alzheimer's disease. Mimicking these metabolic and behavioral abnormalities in experimental animals, it was found that EGb 761 (definition see editorial) shows beneficial effects both on brain glucose and energy metabolism and on behavior.

Insulin-induced expression of the activity-regulated cytoskeleton-associated gene (ARC) in human neuroblastoma cells requires p21ras, mitogen-activated protein kinase/extracellular regulated kinase and src tyrosine kinases but is protein kinase C-independent

We examined the effect of insulin on the expression of the activity-regulated cytoskeleton-associated gene (ARC), an effector immediate early gene with a proposed role in memory formation. In human SH-SY5Y neuroblastoma cells, application of insulin leads to dramatic increase in ARC mRNA and protein levels. Inhibition experiments reveal, that p21ras, mitogen-activated protein kinase/extracellular regulated kinase and tyrosine kinase (src) activity are required for the insulin-induced ARC expression in SH-SY5Y cells, whereas protein kinase C is not involved in the signal transduction pathway. Our data indicated for the first time a correlation of the insulin-controlled signal cascade and the induction of synaptic plasticity-associated immediate early genes.

Mutation screening of the chromosome 8q24.3-human activity-regulated cytoskeleton-associated gene (ARC) in idiopathic generalized epilepsy

Idiopathic generalized epilepsy (IGE) comprises a heterogeneous group of disorders, in which a high genetic predisposition and a complex mode of inheritance have been suggested. However, genes, which confer liability to common IGE subtypes including juvenile myoclonic epilepsy (JME) and childhood absence epilepsy (CAE) have not been identified so far. Here, we tested the hypothesis that genetic variation in the human homolog of the ««activity-regulated cytoskeleton-associated gene»» (ARC) contributes to the etiology of common IGE disorders. The gene has recently been mapped to chromosome 8q24.3, a region which spans previously identified major IGE susceptibility loci. A systematic search for mutations was performed in 143 patients with a known family history of IGE. However, no evidence for functional variants was found in theARC coding sequence. Nevertheless, we detected a novel common C489T single nucleotide polymorphism, which provides a useful marker in genetic linkage and association studies. By performing a population- and family-based study we however failed to show significant association between this novel single nucleotide polymorphism and IGE, a finding, which most likely rules out that genetic variation in or close to the ARC gene confers liability to common IGE subtypes.

Effect of atypical antipsychotics on phencyclidine-induced expression of arc in rat brain.

The effect of atypical antipsychotics on the immediate-early gene, arc (activity-regulated cytoskeleton-associated gene), expression was investigated in phencyclidine (PCP)-treated rats using RT-PCR. Administration of PCP (10 mg/kg) increased arc mRNA levels in the prefrontal cortex, nucleus accumbens and posterior cingulate cortex. Pretreatment with clozapine (20 mg/kg), olanzapine (10 mg/kg) and risperidone (2 mg/kg), but not haloperidol (2 mg/kg), prevented PCP-induced arc expression in the prefrontal cortex and nucleus accumbens. Pretreatment of haloperidol increased the striatal arc mRNA levels. Clozapine, olanzapine and haloperidol inhibited the PCP-induced arc expression in the posterior cingulate cortex. These results suggest that the effects of antipsychotic drugs on PCP-induced arc expression in the prefrontal cortex and nucleus accumbens are useful for distinguishing atypical antipsychotic properties of the drugs.