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Nepal B, Das S, Reith ME, Kortagere S. Overview of the structure and function of the dopamine transporter and its protein interactions. Front Physiol 2023; 14:1150355. [PMID: 36935752 PMCID: PMC10020207 DOI: 10.3389/fphys.2023.1150355] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 02/21/2023] [Indexed: 03/06/2023] Open
Abstract
The dopamine transporter (DAT) plays an integral role in dopamine neurotransmission through the clearance of dopamine from the extracellular space. Dysregulation of DAT is central to the pathophysiology of numerous neuropsychiatric disorders and as such is an attractive therapeutic target. DAT belongs to the solute carrier family 6 (SLC6) class of Na+/Cl- dependent transporters that move various cargo into neurons against their concentration gradient. This review focuses on DAT (SCL6A3 protein) while extending the narrative to the closely related transporters for serotonin and norepinephrine where needed for comparison or functional relevance. Cloning and site-directed mutagenesis experiments provided early structural knowledge of DAT but our contemporary understanding was achieved through a combination of crystallization of the related bacterial transporter LeuT, homology modeling, and subsequently the crystallization of drosophila DAT. These seminal findings enabled a better understanding of the conformational states involved in the transport of substrate, subsequently aiding state-specific drug design. Post-translational modifications to DAT such as phosphorylation, palmitoylation, ubiquitination also influence the plasma membrane localization and kinetics. Substrates and drugs can interact with multiple sites within DAT including the primary S1 and S2 sites involved in dopamine binding and novel allosteric sites. Major research has centered around the question what determines the substrate and inhibitor selectivity of DAT in comparison to serotonin and norepinephrine transporters. DAT has been implicated in many neurological disorders and may play a role in the pathology of HIV and Parkinson's disease via direct physical interaction with HIV-1 Tat and α-synuclein proteins respectively.
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Affiliation(s)
- Binod Nepal
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Sanjay Das
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Maarten E. Reith
- Department of Psychiatry, New York University School of Medicine, New York City, NY, United States
| | - Sandhya Kortagere
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
- *Correspondence: Sandhya Kortagere,
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SRI-32743, a novel allosteric modulator, attenuates HIV-1 Tat protein-induced inhibition of the dopamine transporter and alleviates the potentiation of cocaine reward in HIV-1 Tat transgenic mice. Neuropharmacology 2022; 220:109239. [PMID: 36126727 DOI: 10.1016/j.neuropharm.2022.109239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 08/09/2022] [Accepted: 09/01/2022] [Indexed: 11/21/2022]
Abstract
Cocaine abuse increases the incidence of HIV-1-associated neurocognitive disorders. We have demonstrated that HIV-1 transactivator of transcription (Tat) allosterically modulates dopamine (DA) reuptake through the human DA transporter (hDAT), potentially contributing to Tat-induced cognitive impairment and potentiation of cocaine conditioned place preference (CPP). This study determined the effects of a novel allosteric modulator of DAT, SRI-32743, on the interactions of HIV-1 Tat, DA, cocaine, and [3H]WIN35,428 with hDAT in vitro. SRI-32743 (50 nM) attenuated Tat-induced inhibition of [3H]DA uptake and decreased the cocaine-mediated dissociation of [3H]WIN35,428 binding in CHO cells expressing hDAT, suggesting a SRI-32743-mediated allosteric modulation of the Tat-DAT interaction. In further in vivo studies utilizing doxycycline-inducible Tat transgenic (iTat-tg) mice, 14 days of Tat expression significantly reduced the recognition index by 31.7% in the final phase of novel object recognition (NOR) and potentiated cocaine-CPP 2.7-fold compared to responses of vehicle-treated control iTat-tg mice. The Tat-induced NOR deficits and potentiation of cocaine-CPP were not observed in saline-treated iTat-tg or doxycycline-treated G-tg (Tat-null) mice. Systemic administration (i.p.) of SRI-32743 prior to behavioral testing ameliorated Tat-induced impairment of NOR (at a dose of 10 mg/kg) and the Tat-induced potentiation of cocaine-CPP (at doses of 1 or 10 mg/kg). These findings demonstrate that Tat and cocaine interactions with DAT may be regulated by compounds interacting at the DAT allosteric modulatory sites, suggesting a potential therapeutic intervention for HIV-infected patients with concurrent cocaine abuse.
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Du C, Hua Y, Clare K, Park K, Allen CP, Volkow ND, Hu XT, Pan Y. Memantine Attenuates Cocaine and neuroHIV Neurotoxicity in the Medial Prefrontal Cortex. Front Pharmacol 2022; 13:895006. [PMID: 35694269 PMCID: PMC9174902 DOI: 10.3389/fphar.2022.895006] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Accepted: 04/20/2022] [Indexed: 11/30/2022] Open
Abstract
Individuals with substance use disorder are at a higher risk of contracting HIV and progress more rapidly to AIDS as drugs of abuse, such as cocaine, potentiate the neurotoxic effects of HIV-associated proteins including, but not limited to, HIV-1 trans-activator of transcription (Tat) and the envelope protein Gp120. Neurotoxicity and neurodegeneration are hallmarks of HIV-1-associated neurocognitive disorders (HANDs), which are hypothesized to occur secondary to excitotoxicity from NMDA-induced neuronal calcium dysregulation, which could be targeted with NMDA antagonist drugs. Multiple studies have examined how Gp120 affects calcium influx and how cocaine potentiates this influx; however, they mostly focused on single cells and did not analyze effects in neuronal and vascular brain networks. Here, we utilize a custom multi-wavelength imaging platform to simultaneously study the neuronal activity (detected using genetically encoded Ca2+ indicator, GcaMP6f, expressed in neurons) and hemodynamic changes (measured by total hemoglobin and oxygenated hemoglobin within the tissue) in the prefrontal cortex (PFC) of HIV-1 Tg rats in response to cocaine and evaluate the effects of the selective NMDA antagonist drug memantine on cocaine and HIV neurotoxicity compared to those of non-HIV-1 Tg animals (controls). Our results show that memantine improved cocaine-induced deficit in cerebral blood volume while also attenuating an abnormal increase of the neuronal calcium influx and influx duration in both control rats and HIV-1 Tg rats. Cocaine-induced neuronal and hemodynamic dysregulations were significantly greater in HIV-1 Tg rats than in control rats. With memantine pretreatment, HIV-1 Tg rats showed attenuated cocaine’s effects on neuronal and hemodynamic responses, with responses similar to those observed in control rats. These imaging results document an enhancement of neuronal Ca2+ influx, hypoxemia, and ischemia with cocaine in the PFC of HIV-1 Tg rats that were attenuated by memantine pretreatment. Thus, the potential utility of memantine in the treatment of HAND and of cocaine-induced neurotoxicity deserves further investigation.
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Affiliation(s)
- Congwu Du
- Department of Biomedical Engineering, Stony Brook University, New York, NY, United States
- *Correspondence: Congwu Du, ; Nora D. Volkow, ; Xiu-Ti Hu,
| | - Yueming Hua
- Department of Biomedical Engineering, Stony Brook University, New York, NY, United States
| | - Kevin Clare
- Department of Biomedical Engineering, Stony Brook University, New York, NY, United States
| | - Kicheon Park
- Department of Biomedical Engineering, Stony Brook University, New York, NY, United States
| | - Craig P. Allen
- Department of Biomedical Engineering, Stony Brook University, New York, NY, United States
| | - Nora D. Volkow
- National Institute on Drug Abuse, Bethesda, MD, United States
- *Correspondence: Congwu Du, ; Nora D. Volkow, ; Xiu-Ti Hu,
| | - Xiu-Ti Hu
- Department of Microbial Pathogens and Immunity, Rush University Medical Center, Chicago, IL, United States
- *Correspondence: Congwu Du, ; Nora D. Volkow, ; Xiu-Ti Hu,
| | - Yingtian Pan
- Department of Biomedical Engineering, Stony Brook University, New York, NY, United States
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League AF, Gorman BL, Hermes DJ, Johnson CT, Jacobs IR, Yadav-Samudrala BJ, Poklis JL, Niphakis MJ, Cravatt BF, Lichtman AH, Ignatowska-Jankowska BM, Fitting S. Monoacylglycerol Lipase Inhibitor MJN110 Reduces Neuronal Hyperexcitability, Restores Dendritic Arborization Complexity, and Regulates Reward-Related Behavior in Presence of HIV-1 Tat. Front Neurol 2021; 12:651272. [PMID: 34484091 PMCID: PMC8415271 DOI: 10.3389/fneur.2021.651272] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Accepted: 07/12/2021] [Indexed: 12/01/2022] Open
Abstract
While current therapeutic strategies for people living with human immunodeficiency virus type 1 (HIV-1) suppress virus replication peripherally, viral proteins such as transactivator of transcription (Tat) enter the central nervous system early upon infection and contribute to chronic inflammatory conditions even alongside antiretroviral treatment. As demand grows for supplemental strategies to combat virus-associated pathology presenting frequently as HIV-associated neurocognitive disorders (HAND), the present study aimed to characterize the potential utility of inhibiting monoacylglycerol lipase (MAGL) activity to increase inhibitory activity at cannabinoid receptor-type 1 receptors through upregulation of 2-arachidonoylglycerol (2-AG) and downregulation of its degradation into proinflammatory metabolite arachidonic acid (AA). The MAGL inhibitor MJN110 significantly reduced intracellular calcium and increased dendritic branching complexity in Tat-treated primary frontal cortex neuron cultures. Chronic MJN110 administration in vivo increased 2-AG levels in the prefrontal cortex (PFC) and striatum across Tat(+) and Tat(–) groups and restored PFC N-arachidonoylethanolamine (AEA) levels in Tat(+) subjects. While Tat expression significantly increased rate of reward-related behavioral task acquisition in a novel discriminative stimulus learning and cognitive flexibility assay, MJN110 altered reversal acquisition specifically in Tat(+) mice to rates indistinguishable from Tat(–) controls. Collectively, our results suggest a neuroprotective role of MAGL inhibition in reducing neuronal hyperexcitability, restoring dendritic arborization complexity, and mitigating neurocognitive alterations driven by viral proteins associated with latent HIV-1 infection.
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Affiliation(s)
- Alexis F League
- Department of Psychology and Neuroscience, University of North Carolina Chapel Hill, Chapel Hill, NC, United States
| | - Benjamin L Gorman
- Department of Psychology and Neuroscience, University of North Carolina Chapel Hill, Chapel Hill, NC, United States
| | - Douglas J Hermes
- Department of Psychology and Neuroscience, University of North Carolina Chapel Hill, Chapel Hill, NC, United States
| | - Clare T Johnson
- Department of Psychology and Neuroscience, University of North Carolina Chapel Hill, Chapel Hill, NC, United States
| | - Ian R Jacobs
- Department of Psychology and Neuroscience, University of North Carolina Chapel Hill, Chapel Hill, NC, United States
| | - Barkha J Yadav-Samudrala
- Department of Psychology and Neuroscience, University of North Carolina Chapel Hill, Chapel Hill, NC, United States
| | - Justin L Poklis
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, United States
| | - Micah J Niphakis
- Department of Chemistry, Scripps Research Institute, La Jolla, CA, United States
| | - Benjamin F Cravatt
- Department of Chemistry, Scripps Research Institute, La Jolla, CA, United States
| | - Aron H Lichtman
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, United States
| | | | - Sylvia Fitting
- Department of Psychology and Neuroscience, University of North Carolina Chapel Hill, Chapel Hill, NC, United States
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