Self Rachel L, Mulholland Patrick J, Nath Avindra, Harris Barton R, Prendergast Mark A
Department of Psychology, University of Kentucky, 115 Kastle Hall, Lexington, KY 40506-0044, USA.
Brain Res. 2004 Jan 2;995(1):39-45. doi: 10.1016/j.brainres.2003.09.052.
Human immunodeficiency virus type-1 (HIV-1) infection is commonly associated with neuronal loss, as well as, cognitive and motor deficits collectively termed HIV-1-associated dementia (HAD). Function of the HIV-1 transcription factor Tat, activation of N-methyl-D-aspartate (NMDA)-type glutamate receptors, and subsequent rapid rises in free intracellular Ca2+ have been implicated in the development of this neurological disorder. However, the role of specific NMDA receptor modulatory sites in mediating effects of Tat has not been examined. The present studies examined the ability of two variants of Tat protein (1-100 nM), Tat 1-72 and Tat 1-86, to produce rapid rises in intracellular Ca2+ in organotypic slice cultures of rat hippocampus. Further, these studies evaluated the role of an NMDA receptor polyamine-sensitive site in mediating Tat-induced elevations in intracellular Ca2+. Brief exposure (10 min) to each variant of Tat protein (>1 nM) markedly increased levels of intracellular Ca2+ in each region of the hippocampus to as much as 145% of controls. In contrast, exposure of cultures to a deletion mutant of Tat protein devoid of amino acids 31-61 (Tat Delta31-61) did not produce changes in intracellular Ca2+ levels. Most significantly, exposure to the NMDA receptor antagonist dizocilpine (MK801 20 microM) and the polyamine site antagonist arcaine (10 microM) significantly attenuated increases in intracellular Ca2+ levels when co-administered with either the Tat 1-72 or Tat 1-86 amino acid variant of Tat. Thus, exposure of the hippocampus to Tat produces increases in intracellular Ca2+ levels that require function of an NMDA receptor polyamine-sensitive site and this may well contribute to the neurotoxic effects of HIV-1 infection. Polyamine-sensitive portions of this receptor may then represent novel therapeutic targets in the pharmacologic treatment of HAD-related neurotoxicity.
1型人类免疫缺陷病毒（HIV-1）感染通常与神经元丧失以及认知和运动功能缺陷相关，这些统称为HIV-1相关痴呆（HAD）。HIV-1转录因子Tat的功能、N-甲基-D-天冬氨酸（NMDA）型谷氨酸受体的激活以及随后细胞内游离Ca2+的快速升高与这种神经疾病的发展有关。然而，特定NMDA受体调节位点在介导Tat效应中的作用尚未得到研究。本研究检测了Tat蛋白的两种变体（1 - 100 nM），即Tat 1 - 72和Tat 1 - 86，在大鼠海马器官型脑片培养物中引起细胞内Ca2+快速升高的能力。此外，这些研究评估了NMDA受体多胺敏感位点在介导Tat诱导的细胞内Ca2+升高中的作用。短暂暴露（10分钟）于每种Tat蛋白变体（>1 nM）可使海马各区域的细胞内Ca2+水平显著升高，达到对照水平的145%。相比之下，将培养物暴露于缺失氨基酸31 - 61的Tat蛋白缺失突变体（Tat Delta31 - 61）并未引起细胞内Ca2+水平的变化。最显著的是，当与Tat的Tat 1 - 72或Tat 1 - 86氨基酸变体共同给药时，暴露于NMDA受体拮抗剂地佐环平（MK801 20 microM）和多胺位点拮抗剂阿卡因（10 microM）可显著减弱细胞内Ca2+水平的升高。因此，海马暴露于Tat会导致细胞内Ca2+水平升高，这需要NMDA受体多胺敏感位点的功能，这很可能导致HIV-1感染的神经毒性作用。该受体的多胺敏感部分可能代表了HAD相关神经毒性药物治疗中的新治疗靶点。
