Neurotoxicity of the human immunodeficiency virus type 1 Tat transactivator to PC12 cells requires the Tat amino acid 49-58 basic domain
✍ Scribed by B. S. Weeks; D. M. Lieberman; B. Johnson; E. Roque; M. Green; P. Loewenstein; E. H. Oldfield; H. K. Kleinman
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 804 KB
- Volume
- 42
- Category
- Article
- ISSN
- 0360-4012
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✦ Synopsis
The acquired immunodeficiency syndrome (AIDS) frequently involves the central nervous system (CNS) and manifests as dementia due to encephalitis or diffuse neurodegeneration. Human immunodeficiency virus type 1 (HIV-1) proteins, potentially transported into the CNS by mononuclear inflammatory cells, have been implicated in the etiology of this HIV-1 associated neurological dysfunction. Here we investigate the neurotoxicity of the essential HIV-1 regulator protein Tat in vivo after microinfusion into the rat brain and in vitro using PC12, NG108-15, and GT17 neuronal cell lines. Infusion of either chemically synthesized Tat (Tat86) or recombinant Tat (rTat) into the striatal gray matter in Sprague-Dawley rats resulted in postural deviation ipsilateral to the infusion, a clinical presentation in rats associated with complete striatal dysfunction. Histologic examination 3 days after infusion revealed massive necrosis in the area of the distribution of the infusion. Infusion of heat denatured rTat, peptide Tat49-58, or peptide Tat57-86 did not result in clinically or histologically detectable brain damage. After 3 days incubation in vitro, the lethal dose for half (LD50) of PC12 cells due to rTat was 5 pg/ml. The LD50 for Tat86 under the same conditions was 10 pg/ml. Tat49-58 and Tat57-86 peptides were not toxic in vitro even at 10fold higher doses. At 5 pg/ml, rTat was toxic to 100% of GT17 cells after 24 hr. At 5 pg/ml, Tat86 was toxic to 90% of' the NG108-15 cells after 7 days of treatment. Prior experiments have shown Tat4948 is specifically recognized by a cell surface protein that mediates Tat uptake. Here we show that Tat toxicity is inhibited by cotreatment with excess Tat49-58, suggesting Tat neurotoxicity requires binding to its surface ligand. Chloroquine, which increases nuclear accumulation of Tat, enhances Tat toxicity to PC12 cells, suggesting that Tat internalization is a required step in the mechanism of its toxicity.