Human Immunodeficiency Virus Type 1 Tat Protein Directly Activates Neuronal N -methyl- D -aspartate Receptors at an Allosteric Zinc-Sensitive Site

The human immunodeficiency virus type 1 (HIV-1) regulatory protein Tat is neurotoxic and may be involved in the neuropathogenesis of HIV-1 dementia, in part via N -methyl- D -aspartate (NMDA) receptor activation. Here, in acutely isolated rat hippocampal neurons, Tat evoked inward currents reversing near 0 mV, with a negative slope conductance region characteristic of NMDA receptor activation. Although the NMDA receptor antagonist ketamine blocked Tat's actions, competitive glutamate- and glycine-binding site antagonists were ineffective (AP-5 and 5,7-dichlorokynurenate, respectively). Evidence for Tat acting at a distinct modulatory site on the NR1 subunit of NMDA receptors was provided by findings that 1 &#119 M Zn 2+ abolished Tat-evoked responses in all neurons tested. Thus, Tat appears to excite neurons via direct activation of the NMDA receptor at an allosteric Zn 2+ -sensitive site.