An inhibitory role of the G-protein regulator AGS3 in mTOR-dependent macroautophagy

GPSM1 in POMC neurons impairs brown adipose tissue thermogenesis and provokes diet-induced obesity

OBJECTIVE

G-protein-signaling modulator 1 (GPSM1) has been proved the potential role in brain tissues, however, whether GPSM1 in hypothalamic nuclei, especially in POMC neurons is essential for the proper regulation of whole-body energy balance remains unknown. The aim of our current study was to explore the role of GPSM1 in POMC neurons in metabolic homeostasis.

METHODS

We generated POMC neuron specific GPSM1 deficiency mice and subjected them to a High Fat Diet to monitor metabolic phenotypes in vivo. By using various molecular, biochemical, immunofluorescent, immunohistochemical analyses, and cell culture studies to reveal the pathophysiological role of GPSM1 in POMC neurons and elucidate the underlying mechanisms of GPSM1 regulating POMC neurons activity.

RESULTS

We demonstrated that mice lacking GPSM1 in POMC neurons were protected against diet-induced obesity, glucose dysregulation, insulin resistance, and hepatic steatosis. Mechanistically, GPSM1 deficiency in POMC neurons induced enhanced autophagy and improved leptin sensitivity through PI3K/AKT/mTOR signaling, thereby increasing POMC expression and α-MSH production, and concurrently enhancing sympathetic innervation and activity, thus resulting in decreased food intake and increased brown adipose tissue thermogenesis.

CONCLUSIONS

Our findings identify a novel function of GPSM1 expressed in POMC neurons in the regulation of whole-body energy balance and metabolic homeostasis by regulating autophagy and leptin sensitivity, which suggests that GPSM1 in the POMC neurons could be a promising therapeutic target to combat obesity and obesity-related metabolic disorders.

G-protein signaling modulator 1 promotes colorectal cancer metastasis by PI3K/AKT/mTOR signaling and autophagy

BACKGROUND

Colorectal cancer is the second most common malignant tumor worldwide. A deeper insight into the mechanisms underlying colorectal cancer metastasis is urgently needed. G-protein signaling modulator 1 and autophagy play critical roles in tumor migration and invasion. However, the biological functions and regulatory networks of G-protein signaling modulator 1 and autophagy have not yet been fully studied.

METHODS

We performed immunohistochemistry and clinic-pathological characteristic analysis in 328 human colorectal cancer specimens to identify the clinical role of G-protein signaling modulator 1 in colorectal cancer. An in vitro coculture system and a tumor metastasis mouse model were used to explore the biological function of G-protein signaling modulator 1 on tumor metastasis. Autophagic flux detection like GFP-LC3B signal immunofluorescence and electron microscope observation of autophagic vesicles and confocal microscope detection were used to gain insights into the underlying role of G-protein signaling modulator 1 in autophagy.

RESULTS

We found that G-protein signaling modulator 1 was abundantly expressed in colorectal cancer tissues and was associated with lymph node metastasis and poor prognosis. Furthermore, our bioinformatic and functional studies demonstrated that G-protein signaling modulator 1 significantly promoted cell migration and invasion, both in vitro and in vivo. Mechanistically, we demonstrated that G-protein signaling modulator 1 could promote colorectal cancer cell migration and invasion and inhibit autophagy and by activating the PI3K/AKT/mTOR pathway.

CONCLUSIONS

We proposed that G-protein signaling modulator 1 promotes colorectal cancer metastasis by modulating autophagy through the PI3K/AKT/mTOR pathway.

Intersection of two key signal integrators in the cell: activator of G-protein signaling 3 and dishevelled-2

Activator of G-protein signaling 3 (AGS3, encoded by GPSM1) was discovered as a one of several receptor-independent activators of G-protein signaling, which are postulated to provide a platform for divergence between canonical and noncanonical G-protein signaling pathways. Similarly, Dishevelled (DVL) proteins serve as a point of divergence for β-catenin-dependent and -independent signaling pathways involving the family of Frizzled (FZD) ligands and cell-surface WNT receptors. We recently discovered the apparent regulated localization of dishevelled-2 (DVL2) and AGS3 to distinct cellular puncta, suggesting that the two proteins interact as part of various cell signaling systems. To address this hypothesis, we asked the following questions: (1) do AGS3 signaling pathways influence the activation of β-catenin (CTNNB1)-regulated transcription through the WNT-Frizzled-Dishevelled axis, and (2) is the AGS3 and DVL2 interaction regulated? The interaction of AGS3 and DVL2 was regulated by protein phosphorylation, subcellular distribution, and a cell-surface G-protein-coupled receptor. These data, and the commonality of functional system impacts observed for AGS3 and DVL2, suggest that the AGS3-DVL2 complex presents an unexpected path for functional integration within the cell.This article has an associated First Person interview with the first author of the paper.

Role of G-proteins and phosphorylation in the distribution of AGS3 to cell puncta

Activator of G-protein signaling 3 (AGS3, also known as GPSM1) exhibits broad functional diversity and oscillates among different subcellular compartments in a regulated manner. AGS3 consists of a tetratricopeptide repeat (TPR) domain and a G-protein regulatory (GPR) domain. Here, we tested the hypothesis that phosphorylation of the AGS3 GPR domain regulates its subcellular distribution and functionality. In contrast to the cortical and/or diffuse non-homogeneous distribution of wild-type (WT) AGS3, an AGS3 construct lacking all 24 potential phosphorylation sites in the GPR domain localized to cytosolic puncta. This change in localization was revealed to be dependent upon phosphorylation of a single threonine amino acid (T602). The punctate distribution of AGS3-T602A was rescued by co-expression of Gα_i and Gα_o but not Gα_s or Gα_q Following treatment with alkaline phosphatase, both AGS3-T602A and WT AGS3 exhibited a gel shift in SDS-PAGE as compared to untreated WT AGS3, consistent with a loss of protein phosphorylation. The punctate distribution of AGS3-T602A was lost in an AGS3-A602T conversion mutant, but was still present upon T602 mutation to glutamate or aspartate. These results implicate dynamic phosphorylation as a discrete mechanism to regulate the subcellular distribution of AGS3 and associated functionality.

Choose Delicately and Reuse Adequately: The Newly Revealed Process of Autophagy

Autophagy is a degradation system for intracellular components. One of the roles of autophagy is the prompt removal of damaged organelles. Another unique role is to supply resources that maintain metabolism in response to the cellular nutritional state. Precise management of all the components in the autophagic system is essential for cellular health. Especially important are the selectivity of target cargos for autophagy, and the coordination of autophagy with the lysosomal catabolic process. This review outlines our current understanding of autophagy and discusses potential therapeutic perspectives. Emphasis will be given to lysosomal function as a central controller of metabolism, and to selective autophagy as a key mechanism for the efficient removal of dysfunctional organelles.

Activator of G-Protein Signaling 3-Induced Lysosomal Biogenesis Limits Macrophage Intracellular Bacterial Infection

Many intracellular pathogens cause disease by subverting macrophage innate immune defense mechanisms. Intracellular pathogens actively avoid delivery to or directly target lysosomes, the major intracellular degradative organelle. In this article, we demonstrate that activator of G-protein signaling 3 (AGS3), an LPS-inducible protein in macrophages, affects both lysosomal biogenesis and activity. AGS3 binds the Gi family of G proteins via its G-protein regulatory (GoLoco) motif, stabilizing the Gα subunit in its GDP-bound conformation. Elevated AGS3 levels in macrophages limited the activity of the mammalian target of rapamycin pathway, a sensor of cellular nutritional status. This triggered the nuclear translocation of transcription factor EB, a known activator of lysosomal gene transcription. In contrast, AGS3-deficient macrophages had increased mammalian target of rapamycin activity, reduced transcription factor EB activity, and a lower lysosomal mass. High levels of AGS3 in macrophages enhanced their resistance to infection by Burkholderia cenocepacia J2315, Mycobacterium tuberculosis, and methicillin-resistant Staphylococcus aureus, whereas AGS3-deficient macrophages were more susceptible. We conclude that LPS priming increases AGS3 levels, which enhances lysosomal function and increases the capacity of macrophages to eliminate intracellular pathogens.

Activator of G-protein Signaling 3 Controls Renal Epithelial Cell Survival and ERK5 Activation

Activator of G-protein signaling 3 (AGS3) is an accessory protein that functions to regulate the activation status of heterotrimeric G-protein subunits. To date, however, the downstream signaling pathways regulated by AGS3 remain to be fully elucidated, particularly in renal epithelial cells. In the present study, normal rat kidney (NRK-52E) proximal tubular epithelial cells were genetically modified to regulate the expression of AGS3 to investigate its role on MAPK and mTOR signaling to control epithelial cell number. Knockdown of endogenous AGS3 protein was associated with a reduced phosphorylated form of ERK5 and increased apoptosis as determined by elevated cleaved caspase-3. In the presence of the ERK5 inhibitor, BIX02189, a significant 2-fold change (P < 0.05) in G2/M transition state was detected compared to control conditions. Neither of the other MAPK, ERK1/2 or p38 MAPK, nor another pro-survival pathway, mTOR, was significantly altered by the changes in AGS3 protein levels in the renal epithelial cells. The selective ERK5 inhibitor, BIX02189, was found to dose-dependently reduce NRK cell number by up to 41% (P < 0.05) compared to control cells. In summary, these findings demonstrated that cell viability was regulated by AGS3 and was associated with ERK5 activation in renal epithelial cells.

Accessory proteins for heterotrimeric G-proteins in the kidney

Heterotrimeric G-proteins play a fundamentally important role in regulating signal transduction pathways in the kidney. Accessory proteins are being identified as direct binding partners for heterotrimeric G-protein α or βγ subunits to promote more diverse mechanisms by which G-protein signaling is controlled. In some instances, accessory proteins can modulate the signaling magnitude, localization, and duration following the activation of cell membrane-associated receptors. Alternatively, accessory proteins complexed with their G-protein α or βγ subunits can promote non-canonical models of signaling activity within the cell. In this review, we will highlight the expression profile, localization and functional importance of these newly identified accessory proteins to control the function of select G-protein subunits under normal and various disease conditions observed in the kidney.

Heterotrimeric G protein-mediated signaling and its non-canonical regulation in the heart

Heterotrimeric guanine nucleotide-binding proteins (G proteins) regulate a multitude of signaling pathways in mammalian cells by transducing signals from G protein-coupled receptors (GPCRs) to effectors, which in turn regulate cellular function. In the myocardium, G protein signaling occurs in all cardiac cell types and is centrally involved in the regulation of heart rate, pump function, and vascular tone and in the response to hemodynamic stress and injury. Perturbations in G protein-mediated signaling are well known to contribute to cardiac hypertrophy, failure, and arrhythmias. Most of the currently used drugs for cardiac and other diseases target GPCR signaling. In the canonical G protein signaling paradigm, G proteins that are located at the cytoplasmic surface of the plasma membrane become activated after an agonist-induced conformational change of GPCRs, which then allows GTP-bound Gα and free Gβγ subunits to activate or inhibit effector proteins. Research over the past two decades has markedly broadened the original paradigm with a GPCR-G protein-effector at the cell surface at its core by revealing novel binding partners and additional subcellular localizations for heterotrimeric G proteins that facilitate many previously unrecognized functional effects. In this review, we focus on non-canonical and epigenetic-related mechanisms that regulate heterotrimeric G protein expression, activation, and localization and discuss functional consequences using cardiac examples where possible. Mechanisms reviewed involve microRNAs, histone deacetylases, chaperones, alternative modes of G protein activation, and posttranslational modifications. Some of these newly characterized mechanisms may be further developed into novel strategies for the treatment of cardiac disease and beyond.

Overexpression of activator of G-protein signaling 3 decreases the proliferation of esophageal squamous cell carcinoma

BACKGROUND

Activator of G-protein Signaling 3 (AGS3, also known as GPSM1), is related to cell cycle progression. We investigated the expression of AGS3 in human esophageal squamous cell carcinoma (ESCC) and the therapeutic effect of chemotherapy drugs.

METHODS

Immunohistochemistry and Western blot analysis were performed for AGS3 in 85ESCC samples. The data were correlated with clinicopathological features. The univariate and multivariate survival analyses were also performed to determine its prognostic significance. The effect of overexpression of AGS3 on proliferation of esophageal carcinoma TE1 cells was analyzed by serum starvation.

RESULTS

AGS3 was down regulated in ESCC as compared with the adjacent normal tissue. Low expression of AGS3 was associated with tumor grade (P=0.002), and AGS3 was negatively correlated with proliferation marker Ki-67 (P<0.01). Univariate analysis showed that AGS3 expression did have a remarkable prediction for poor prognosis (P=0.004), while in vitro, the expression of AGS3 was down regulated with release from serum starvation of TE1 cells.

CONCLUSIONS

This study shows that AGS3 is an important regulator of ESCC proliferation.

Activators of G protein signaling in the kidney

Heterotrimeric G proteins play a crucial role in regulating signal processing to maintain normal cellular homeostasis, and subtle perturbations in its activity can potentially lead to the pathogenesis of renal disorders or diseases. Cell-surface receptors and accessory proteins, which normally modify and organize the coupling of individual G protein subunits, contribute to the regulation of heterotrimeric G protein activity and their convergence and/or divergence of downstream signaling initiated by effector systems. Activators of G protein signaling (AGS) are a family of accessory proteins that intervene at multiple distinct points during the activation-inactivation cycle of G proteins, even in the absence of receptor stimulation. Perturbations in the expression of individual AGS proteins have been reported to modulate signal transduction pathways in a wide array of diseases and disorders within the brain, heart, immune system, and more recently, the kidney. This review will provide an overview of the expression profile, localization, and putative biologic role of the AGS family in the context of normal and diseased states of the kidney.

Activators of G protein signaling exhibit broad functionality and define a distinct core signaling triad

Activators of G protein signaling (AGS), initially discovered in the search for receptor-independent activators of G protein signaling, define a broad panel of biologic regulators that influence signal transfer from receptor to G-protein, guanine nucleotide binding and hydrolysis, G protein subunit interactions, and/or serve as alternative binding partners for Gα and Gβγ independently of the classic heterotrimeric Gαβγ. AGS proteins generally fall into three groups based upon their interaction with and regulation of G protein subunits: group I, guanine nucleotide exchange factors (GEF); group II, guanine nucleotide dissociation inhibitors; and group III, entities that bind to Gβγ. Group I AGS proteins can engage all subclasses of G proteins, whereas group II AGS proteins primarily engage the Gi/Go/transducin family of G proteins. A fourth group of AGS proteins with selectivity for Gα16 may be defined by the Mitf-Tfe family of transcription factors. Groups I-III may act in concert, generating a core signaling triad analogous to the core triad for heterotrimeric G proteins (GEF + G proteins + effector). These two core triads may function independently of each other or actually cross-integrate for additional signal processing. AGS proteins have broad functional roles, and their discovery has advanced new concepts in signal processing, cell and tissue biology, receptor pharmacology, and system adaptation, providing unexpected platforms for therapeutic and diagnostic development.

Normal autophagic activity in macrophages from mice lacking Gαi3, AGS3, or RGS19

In macrophages autophagy assists antigen presentation, affects cytokine release, and promotes intracellular pathogen elimination. In some cells autophagy is modulated by a signaling pathway that employs Gαi3, Activator of G-protein Signaling-3 (AGS3/GPSM1), and Regulator of G-protein Signaling 19 (RGS19). As macrophages express each of these proteins, we tested their importance in regulating macrophage autophagy. We assessed LC3 processing and the formation of LC3 puncta in bone marrow derived macrophages prepared from wild type, Gnai3(-/-), Gpsm1(-/-), or Rgs19(-/-) mice following amino acid starvation or Nigericin treatment. In addition, we evaluated rapamycin-induced autophagic proteolysis rates by long-lived protein degradation assays and anti-autophagic action after rapamycin induction in wild type, Gnai3(-/-), and Gpsm1(-/-) macrophages. In similar assays we compared macrophages treated or not with pertussis toxin, an inhibitor of GPCR (G-protein couple receptor) triggered Gαi nucleotide exchange. Despite previous findings, the level of basal autophagy, autophagic induction, autophagic flux, autophagic degradation and the anti-autophagic action in macrophages that lacked Gαi3, AGS3, or RGS19; or had been treated with pertussis toxin, were similar to controls. These results indicate that while Gαi signaling may impact autophagy in some cell types it does not in macrophages.

Translocation of activator of G-protein signaling 3 to the Golgi apparatus in response to receptor activation and its effect on the trans-Golgi network

Group II activators of G-protein signaling play diverse functional roles through their interaction with Gαi, Gαt, and Gαo via a G-protein regulatory (GPR) motif that serves as a docking site for Gα-GDP. We recently reported the regulation of the AGS3-Gαi signaling module by a cell surface, seven-transmembrane receptor. Upon receptor activation, AGS3 reversibly dissociates from the cell cortex, suggesting that it may function as a signal transducer with downstream signaling implications, and this question is addressed in the current report. In HEK-293 and COS-7 cells expressing the α2A/D-AR and Gαi3, receptor activation resulted in the translocation of endogenous AGS3 and AGS3-GFP from the cell cortex to a juxtanuclear region, where it co-localized with markers of the Golgi apparatus (GA). The agonist-induced translocation of AGS3 was reversed by the α2-AR antagonist rauwolscine. The TPR domain of AGS3 was required for agonist-induced translocation of AGS3 from the cell cortex to the GA, and the translocation was blocked by pertussis toxin pretreatment or by the phospholipase Cβ inhibitor U73122. Agonist-induced translocation of AGS3 to the GA altered the functional organization and protein sorting at the trans-Golgi network. The regulated movement of AGS3 between the cell cortex and the GA offers unexpected mechanisms for modulating protein secretion and/or endosome recycling events at the trans-Golgi network.

Adiponectin knockout accentuates high fat diet-induced obesity and cardiac dysfunction: role of autophagy

Adiponectin (APN), an adipose-derived adipokine, offers cardioprotective effects although the precise mechanism of action remains unclear. This study was designed to examine the role of APN in high fat diet-induced obesity and cardiac pathology. Adult C57BL/6 wild-type and APN knockout mice were fed a low or high fat diet for 22weeks. After 40day feeding, mice were treated with 2mg/kg rapamycin or vehicle every other day for 42days on respective fat diet. Cardiomyocyte contractile and Ca(2+) transient properties were evaluated. Myocardial function was evaluated using echocardiography. Dual energy X-ray absorptiometry was used to evaluate adiposity. Energy expenditure, metabolic rate and physical activity were monitored using a metabolic cage. Lipid deposition, serum triglyceride, glucose tolerance, markers of autophagy and fatty acid metabolism including LC3, p62, Beclin-1, AMPK, mTOR, fatty acid synthase (FAS) were evaluated. High fat diet intake induced obesity, systemic glucose intolerance, cardiac hypertrophy, dampened metabolic ability, cardiac and intracellular Ca(2+) derangements, the effects of which were accentuated by APN knockout. Furthermore, APN deficiency augmented high fat diet-induced upregulation in the autophagy adaptor p62 and the decline in AMPK without affecting high fat diet-induced decrease in LC3II and LC3II-to-LC3I ratio. Neither high fat diet nor APN deficiency altered Beclin-1. Interestingly, rapamycin negated high fat diet-induced/APN-deficiency-accentuated obesity, cardiac hypertrophy and contractile dysfunction as well as AMPK dephosphorylation, mTOR phosphorylation and p62 buildup. Our results collectively revealed that APN deficiency may aggravate high fat diet-induced obesity, metabolic derangement, cardiac hypertrophy and contractile dysfunction possibly through decreased myocardial autophagy.

Regulation of the G-protein regulatory-Gαi signaling complex by nonreceptor guanine nucleotide exchange factors

Group II activators of G-protein signaling (AGS) serve as binding partners for Gα(i/o/t) via one or more G-protein regulatory (GPR) motifs. GPR-Gα signaling modules may be differentially regulated by cell surface receptors or by different nonreceptor guanine nucleotide exchange factors. We determined the effect of the nonreceptor guanine nucleotide exchange factors AGS1, GIV/Girdin, and Ric-8A on the interaction of two distinct GPR proteins, AGS3 and AGS4, with Gα(il) in the intact cell by bioluminescence resonance energy transfer (BRET) in human embryonic kidney 293 cells. AGS3-Rluc-Gα(i1)-YFP and AGS4-Rluc-Gα(i1)-YFP BRET were regulated by Ric-8A but not by Gα-interacting vesicle-associated protein (GIV) or AGS1. The Ric-8A regulation was biphasic and dependent upon the amount of Ric-8A and Gα(i1)-YFP. The inhibitory regulation of GPR-Gα(i1) BRET by Ric-8A was blocked by pertussis toxin. The enhancement of GPR-Gα(i1) BRET observed with Ric-8A was further augmented by pertussis toxin treatment. The regulation of GPR-Gα(i) interaction by Ric-8A was not altered by RGS4. AGS3-Rluc-Gα(i1)-YFP and AGS4-Rluc-G-Gα(i1)-YFP BRET were observed in both pellet and supernatant subcellular fractions and were regulated by Ric-8A in both fractions. The regulation of the GPR-Gα(i1) complex by Ric-8A, as well as the ability of Ric-8A to restore Gα expression in Ric8A(-/-) mouse embryonic stem cells, involved two helical domains at the carboxyl terminus of Ric-8A. These data indicate a dynamic interaction between GPR proteins, Gα(i1) and Ric-8A, in the cell that influences subcellular localization of the three proteins and regulates complex formation.

Group II activators of G-protein signalling and proteins containing a G-protein regulatory motif

Beyond the core triad of receptor, Gαβγ and effector, there are multiple accessory proteins that provide alternative modes of signal input and regulatory adaptability to G-protein signalling systems. Such accessory proteins may segregate a signalling complex to microdomains of the cell, regulate the basal activity, efficiency and specificity of signal propagation and/or serve as alternative binding partners for Gα or Gβγ independent of the classical heterotrimeric Gαβγ complex. The latter concept led to the postulate that Gα and Gβγ regulate intracellular events distinct from their role as transducers for cell surface seven-transmembrane span receptors. One general class of such accessory proteins is defined by AGS proteins or activators of G-protein signalling that refer to mammalian cDNAs identified in a specific yeast-based functional screen. The discovery of AGS proteins and related entities revealed a number of unexpected mechanisms for regulation of G-protein signalling systems and expanded functional roles for this important signalling system.

Regulation of the AGS3·G{alpha}i signaling complex by a seven-transmembrane span receptor

G-protein signaling modulators (GPSM) play diverse functional roles through their interaction with G-protein subunits. AGS3 (GPSM1) contains four G-protein regulatory motifs (GPR) that directly bind Gα(i) free of Gβγ providing an unusual scaffold for the "G-switch" and signaling complexes, but the mechanism by which signals track into this scaffold are not well understood. We report the regulation of the AGS3·Gα(i) signaling module by a cell surface, seven-transmembrane receptor. AGS3 and Gα(i1) tagged with Renilla luciferase or yellow fluorescent protein expressed in mammalian cells exhibited saturable, specific bioluminescence resonance energy transfer indicating complex formation in the cell. Activation of α(2)-adrenergic receptors or μ-opioid receptors reduced AGS3-RLuc·Gα(i1)-YFP energy transfer by over 30%. The agonist-mediated effects were inhibited by pertussis toxin and co-expression of RGS4, but were not altered by Gβγ sequestration with the carboxyl terminus of GRK2. Gα(i)-dependent and agonist-sensitive bioluminescence resonance energy transfer was also observed between AGS3 and cell-surface receptors typically coupled to Gα(i) and/or Gα(o) indicating that AGS3 is part of a larger signaling complex. Upon receptor activation, AGS3 reversibly dissociates from this complex at the cell cortex. Receptor coupling to both Gαβγ and GPR-Gα(i) offer additional flexibility for systems to respond and adapt to challenges and orchestrate complex behaviors.

Identification of a deubiquitinating enzyme as a novel AGS3-interacting protein

Activator of G protein Signaling 3 (AGS3) is a receptor-independent G protein activator that has been implicated in multiple biological events such as brain development, neuroplasticity and addiction, cardiac function, Golgi structure/function, macroautophagy and metabolism. However, how AGS3 is regulated is little known. We demonstrate here that AGS3 interacts with a ubiquitin specific protease USP9x, and this interaction is at least partially mediated through the C-terminal G protein regulatory domain of AGS3. Knockdown of USP9x causes a moderate reduction in the level of AGS3. In contrast, overexpression of either USP9x or its deubiquitinating domain UCH increases the amount of AGS3, whereas expression of the mutant UCH domain that lacks deubiquitinating activity does not have the same effect. As previously observed in AGS3 knockdown cells, the localization of several marker proteins of the late Golgi compartments is disturbed in cells depleted of USP9x. Taken together, our study suggests that USP9x can modulate the level of a subpopulation of AGS3, and this modulation plays a role in regulating the structure of the late Golgi compartments. Finally, we have found that levels of AGS3 and USP9x are co-regulated in the prefrontal cortex of rats withdrawn from repeated cocaine treatment. In conjunction with the above data, this observation indicates a potential role of USP9X in the regulation of the AGS3 level during cocaine-induced neuroplasticity.