Neurotoxic mechanisms of transactivating protein Tat of Maedi-Visna virus.
Infection by lentiviruses such as human immunodeficiency virus (HIV) and Maedi-Visna virus (MVV) is associated with neurodegenerative disorders. We have investigated the neurotoxic mechanisms of a synthetic peptide of transactivating protein tat of MVV in striatal neuronal cultures. Tat peptide (but not control peptide) caused neuronal death, without affecting glial viability, in a time- and dose-dependent manner. Significant neuronal death was not observed until 6-8 h after tat peptide application (2.35-2350 nM), whereas half maximal and maximal cell death was observed after 12 and 24 h respectively. Tat peptide neurotoxicity could be partially inhibited by blockade of either N-methyl-D-aspartate (NMDA)- or non-NMDA receptors, suggesting that excessive neuroexcitation by glutamate or its analogues may contribute to tat-neurotoxicity. Furthermore, when both these glutamate receptor subtypes were blocked simultaneously, an increased degree of neuroprotection was observed. Finally, tat peptide toxicity was also reduced by blockade of L-type calcium channels. Calcium imaging revealed that intracellular calcium increases slowly upon tat application, predominantly due to entry of extracellular calcium. These results indicate that cellular calcium entry through voltage-gated calcium channels following activation of both NMDA and non-NMDA receptors, and subsequent accumulation of intracellular calcium may contribute to the neuronal death induced by tat protein.
Strijbos
P J
PJ
Department of Molecular Pharmacology, Wellcome Research Laboratories, Beckenham, Kent, UK.
Zamani
M R
MR
Rothwell
N J
NJ
Arbuthnott
G
G
Harkiss
G
G
D000818:Animals; D002118:Calcium / Q000378:metabolism; D016923:Cell Death; D002478:Cells, Cultured; D003342:Corpus Striatum / Q000166:cytology; D004305:Dose-Response Relationship, Drug; D015696:Gene Products, tat / Q000494:pharmacology*; D007150:Immunohistochemistry; D009410:Nerve Degeneration; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009498:Neurotoxins / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014790:Visna-maedi virus
D015696:Gene Products, tat; D009498:Neurotoxins; D002118:Calcium