PMID:17202348

Citation	Norman, JP, Perry, SW, Kasischke, KA, Volsky, DJ and Gelbard, HA (2007) HIV-1 trans activator of transcription protein elicits mitochondrial hyperpolarization and respiratory deficit, with dysregulation of complex IV and nicotinamide adenine dinucleotide homeostasis in cortical neurons. J. Immunol. 178:869-76
Abstract	HIV-1 causes a common, progressive neurological disorder known as HIV-associated dementia (HAD). The prevalence of this disorder has increased despite the use of highly active antiretroviral therapy, and its underlying pathogenesis remains poorly understood. However, evidence suggests that some aspects of HAD may be reversible. To model the reversible aspects of HAD, we have used the HIV-1 neurotoxin trans activator of transcription protein (Tat) to investigate nonlethal changes in cultured neurons. Exposure of rodent cortical neurons to sublethal concentrations of Tat elicits mitochondrial hyperpolarization. In this study, we used the cationic lipophilic dye rhodamine 123 to confirm this observation, and then performed follow-up studies to examine the mechanism involved. In intact neurons, we found Tat elicited a rapid drop in internal mitochondrial pH, and addition of Tat to purified mitochondrial extracts inhibited complex IV of the electron transport chain. To correlate enzyme activity in mitochondrial extracts with results in intact cells, we measured neuronal respiration following Tat exposure. Cortical neurons demonstrated decreased respiration upon Tat treatment, consistent with inhibition of complex IV. We examined mitochondrial Ca(2+) homeostasis using a mitochondrial targeted enhanced yellow fluorescent protein-calmodulin construct. We detected a decrease in mitochondrial calcium concentration following exposure to Tat. Finally, we measured the energy intermediate NAD(P)H after Tat treatment, and found a 20% decrease in the autofluorescence. Based on these findings, we suggest that decreased NADPH and calcium concentration contribute to subsequent respiratory decline after exposure to Tat, with detrimental effects on neuronal signaling.
Links	PubMed
Keywords	Animals; Cell Respiration/drug effects; Cells, Cultured; Cerebral Cortex/cytology; Electron Transport Complex IV/metabolism; Gene Products, tat/pharmacology; HIV-1; Homeostasis/drug effects; Hydrogen-Ion Concentration; Membrane Potential, Mitochondrial/drug effects; Mitochondria/drug effects; Mitochondria/metabolism; NAD/metabolism; NADP/metabolism; Neurons/cytology; Neurons/drug effects; Neurons/metabolism; Rats; Rats, Sprague-Dawley; Transcription, Genetic; tat Gene Products, Human Immunodeficiency Virus
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HV1BR:TAT	involved_in	GO:0060081: membrane hyperpolarization	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete
HV1BR:TAT		GO:0060081: membrane hyperpolarization	ECO:0000314:		P		Figure 1 shows that adding tat protein to cortical neurons caused a 10% loss in rhod123 fluorescence which is a measurement method of mitochondrial membrane potential. This result proves that the tat protein induces mitochondrial hyperpolarization.	complete CACAO 6382
HV1BR:TAT		GO:1901856: negative regulation of cellular respiration	ECO:0000314:		P		Figure 3 demonstrates the inhibiting effect of the tat protein on mitochondrial complexes III and IV while having no effect on complexes I and II. The ETC activity of an isolated mitochondrial protein was monitored after adding tat protein, and the graph (A) shows the effect that the tat treatment had on each complex. Complexes III and IV show inhibited activity once the tat protein was introduced. (B) shows the concentration dependent inhibition of complex IV activity.	complete CACAO 6406
HV1BR:TAT	involved_in	GO:1901856: negative regulation of cellular respiration	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete

References

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