Molecular interactions of the type 1 human immunodeficiency virus transregulatory protein Tat with N-methyl-d-aspartate receptor subunits.
We investigated the effect of type 1 human immunodeficiency virus (HIV-1) regulatory protein Tat on N-methyl-d-aspartate (NMDA) receptors expressed in Xenopus oocytes by voltage-clamp recording and its role in NMDA-mediated neurotoxicity using cultured rat hippocampal neurons. Tat (0.01-1muM) potentiated NMDA-induced currents of recombinant NMDA receptors. However, in the presence of Zn(2+), the potentiating effect of Tat was much more pronounced, indicating an additional Zn(2+)-related effect on NMDA receptors. Consistently, Tat potentiated currents of the particularly Zn(2+)-sensitive NR1/NR2A NMDA receptor with a higher efficacy, whereas currents from a Zn(2+)-insensitive mutant were only marginally augmented. In addition, chemical-modified Tat, deficient for metal binding, did not reverse Zn(2+)-mediated inhibition of NMDA responses, demonstrating that Tat disinhibits NMDA receptors from Zn(2+)-mediated antagonism by complexing the cation. We therefore investigated the interplay of Tat and Zn(2+) in NMDA-mediated neurotoxicity using cultures of rat hippocampal neurons. Zn(2+) exhibited a prominent rescuing effect when added together with the excitotoxicant NMDA, which could be reverted by the Zn(2+)-chelator tricine. Similar to tricine, Tat enhanced NMDA-mediated neurotoxicity in the presence of neuroprotective Zn(2+) concentrations. Double-staining with antibodies against Tat and the NR1 subunit of the NMDA receptor revealed partial colocalization of the immunoreactivities in membrane patches of hippocampal neurons, supporting the idea of a direct interplay between Tat and glutamatergic transmission. We therefore propose that release of Zn(2+)-mediated inhibition of NMDA receptors by HIV-1 Tat contributes to the neurotoxic effect of glutamate and may participate in the pathogenesis of AIDS-associated dementia.
Chandra
T
T
Abteilung Neurochemie, Max-Planck-Institut für Hirnforschung, Deutschordenstr. 46, 60528 Frankfurt, Germany.
Maier
W
W
König
H-G
HG
Hirzel
K
K
Kögel
D
D
Schüler
T
T
Chandra
A
A
Demirhan
I
I
Laube
B
B
D000818:Animals; D000831:Animals, Newborn; D002843:Chromatin; D004347:Drug Interactions; D015696:Gene Products, tat / Q000378:metabolism* / Q000494:pharmacology*; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008845:Microinjections / Q000379:methods; D018613:Microscopy, Confocal / Q000379:methods; D016296:Mutagenesis / Q000502:physiology; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000528:radiation effects; D009865:Oocytes; D018408:Patch-Clamp Techniques / Q000379:methods; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000096:biosynthesis / Q000378:metabolism*; D014121:Toxoids / Q000494:pharmacology; D014981:Xenopus; D015032:Zinc / Q000378:metabolism / Q000494:pharmacology
D002843:Chromatin; D015696:Gene Products, tat; D021122:Protein Subunits; D016194:Receptors, N-Methyl-D-Aspartate; D014121:Toxoids; D016202:N-Methylaspartate; D015032:Zinc; D005998:Glycine; C100184:tricine