HIV-1 Tat Protein-Induced Rapid and Reversible Decrease in [3H]Dopamine Uptake: Dissociation of [3H]Dopamine Uptake and [3H]2 -Carbomethoxy-3- -(4-fluorophenyl)tropane (WIN 35,428) Binding in Rat Striatal Synaptosomes

Program in Behavioral Neuroscience, Department of Psychology, University of South Carolina, 1512 Pendleton St., Columbia, SC 29208, USA.
Journal of Pharmacology and Experimental Therapeutics (Impact Factor: 3.97). 04/2009; 329(3):1071-83. DOI: 10.1124/jpet.108.150144
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Human immunodeficiency virus (HIV)-1 Tat protein plays a key role in the pathogenesis of both HIV-1-associated cognitive-motor disorder and drug abuse. Dopamine (DA) transporter (DAT) function is strikingly altered in patients with HIV-1-associated dementia and a history of chronic drug abuse. This study is the first in vitro evaluation of potential mechanisms underlying the effects of Tat protein on DAT function. Rat striatal synaptosomes were incubated with recombinant Tat(1-86) protein, and [(3)H]DA uptake and the binding of [(3)H]2beta-carbomethoxy-3-beta-(4-fluorophenyl)tropane (WIN 35,428) and [(3)H]1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)-piperazine (GBR 12935) were determined. Tat decreased [(3)H]DA uptake, [(3)H]WIN 35,428 binding, and [(3)H]GBR 12935 binding in a time-dependent manner. The potency of Tat for inhibiting [(3)H]DA uptake (K(i) = 1.2 microM) was the same as that for inhibiting [(3)H]GBR 12935 binding but 3-fold less than that for inhibiting [(3)H]WIN 35,428 binding. Mutant Tat proteins did not alter [(3)H]DA uptake. Kinetic analysis of [(3)H]DA uptake revealed that Tat (1 or 10 microM) decreased the V(max) value and increased the K(m) value in a dose-dependent manner. The V(max) value, decreased by Tat (1 microM), returned to the control level after washout of Tat, indicating that the inhibitory effect of Tat on DA uptake was reversible. Saturation studies revealed that Tat decreased the B(max) value and increased the K(d) value of [(3)H]WIN 35,428 binding, whereas Tat decreased the B(max) value of [(3)H]GBR 12935 binding, without a change in the K(d) value. These findings provide new insight into understanding the pharmacological mechanisms of Tat-induced dysfunction of the DAT in the dopaminergic system in HIV-infected patients.

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Available from: David Wallace, Aug 12, 2014
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    • " Midde et al . , 2013 ) and NMDA receptor ( Li et al . , 2008 ) . Since experimental rodents cannot be infected with HIV - 1 , several approaches are utilized to study the effects of viral proteins on HIV - 1 associated neurobiological and behavioral deficits : ( 1 ) rodent brain synaptosomes and in vitro exposure to Tat ( Wallace et al . , 2006 ; Zhu et al . , 2009 ) ; ( 2 ) direct microinjection of Tat into the brain ( Harrod et al . , 2008 ; Ferris et al . , 2010 ; Fitting et al . , 2010 ) ; ( 3 ) transgenic mice that express Tat protein ( Kim et al . , 2003 ; Duncan et al . , 2008 ) ; and ( 4 ) the HIV - 1 transgenic rat model , which carries a gag - pol - deleted HIV - 1 provirus regulated by "
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    Frontiers in Microbiology 06/2015; 6:540. DOI:10.3389/fmicb.2015.00540 · 3.99 Impact Factor
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    • "Vpr Cyclophilin A mM range Solbak et al., 2010 280 Solbak et al., 2011 Adenine nucleotide translocator 10–100 Sabbah et al., 2006 9.7 Jacotot et al., 2001 Importin-a 4300–8900 Takeda et al., 2011 Tat IB-a 178 Vitagliano et al. 2011 Dopamine transporter nd Zhu et al., 2009 Reverse transcriptase Topoisomerase I nd Takahashi et al., 2004 Adenoviruses "
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    Critical Reviews in Microbiology 09/2013; 41(2). DOI:10.3109/1040841X.2013.826177 · 6.02 Impact Factor
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    • "Consistent with these results, exogenous microinjection of a 72-amino-acid Tat protein directly into the nucleus accumbens (NAc) of rats increased acute locomotor responding to cocaine (Harrod et al, 2008). These results are logical, given reports that Tat protein allosterically modulates DAT in a dose-dependent and reversible manner (Aksenov et al, 2001; 2006; Ferris et al, 2009; Zhu et al, 2009, 2011), inhibiting [ 3 H]DA uptake into striatal synaptosomes time-and concentration-dependently (Zhu et al, 2009). These actions may directly contribute to decreased DA recycling, subsequently increasing extracellular DA in the NAc to potentiate the psychostimulant effects of cocaine when both are present (Ferris et al, 2009, 2010). "
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    ABSTRACT: As a major neuropathogenic factor associated with human immunodeficiency virus (HIV) infection, HIV-1 Tat protein is known to synergize with psychostimulant drugs of abuse to cause neurotoxicity and exacerbate the progression of central nervous system pathology. However, the functional consequences of the interaction between HIV-1 Tat and abused drugs on behavior are little known. We tested the hypothesis that HIV-1 Tat expression in brain would modulate the psychostimulant effects of cocaine. Using the GT-tg bigenic mouse model, where brain-selective Tat expression is induced by activation of a doxycycline (Dox) promotor, we tested the effects of Tat on cocaine (10 mg/kg, s.c.) induced locomotion and conditioned place preference (CPP). Compared to uninduced littermates or C57BL/6 J controls, cocaine-induced hyperlocomotion was sustained for a significantly longer duration among Tat-induced mice. Moreover, although all groups displayed similar saline-CPP, Tat-induced GT-tg mice demonstrated a 3-fold increase in cocaine-CPP over the response of either uninduced littermates or Dox-treated C57BL/6 J control mice. Induction of Tat also increased the magnitude of a previously-established cocaine-CPP after an additional cycle of cocaine place conditioning. Despite Tat-induced potentiation, extinction of place preference occurred within 21 days, commensurate with cocaine-extinction among saline-treated littermates and C57BL/6 J controls. Re-exposure to cocaine produced reinstatement of an equivalent place preference in Tat-induced GT-tg, or C57BL/6 J, mice; however, induction of Tat protein after the extinction of CPP also produced reinstatement without additional exposure to cocaine. Together, these data suggest that central HIV-1 Tat expression can potentiate the psychostimulant behavioral effects of cocaine in mice.Neuropsychopharmacology accepted article preview online, 15 August 2013. doi:10.1038/npp.2013.201.
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