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
Source: PubMed


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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    Full-text · Article · Sep 2013 · Critical Reviews in Microbiology
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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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