Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, United States.
Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, United States.
ASN Neuro. 2021 Jan-Dec;13:17590914211022089. doi: 10.1177/17590914211022089.
People infected with HIV (PWH) are highly susceptible to striatal and hippocampal damage. Motor and memory impairments are common among these patients, likely as behavioral manifestations of damage to these brain regions. GABAergic dysfunction from HIV infection and viral proteins such as transactivator of transcription (Tat) have been well documented. We recently demonstrated that the neuron specific Cl extruder, K Cl cotransporter 2 (KCC2), is diminished after exposure to HIV proteins, including Tat, resulting in disrupted GABAR-mediated hyperpolarization and inhibition. Here, we utilized doxycycline (DOX)-inducible, GFAP-driven HIV-1 Tat transgenic mice to further explore this phenomenon. After two weeks of Tat expression, we found no changes in hippocampal KCC2 levels, but a significant decrease in the striatum that was associated with hyperlocomotion in the open field assay. We were able to restore KCC2 activity and baseline locomotion with the KCC2 enhancer, CLP290. Additionally, we found that CLP290, whose mechanism of action has yet to be described, acts to restore phosphorylation of serine 940 resulting in increased KCC2 membrane localization. We also examined neuronal subpopulation contributions to the noted effects and found significant differences. Dopamine D2 receptor-expressing medium spiny neurons (MSNs) were selectively vulnerable to Tat-induced KCC2 loss, with no changes observed in dopamine D1 receptor-expressing MSNs. These results suggest that disinhibition/diminished hyperpolarization of dopamine D2 receptor-expressing MSNs can manifest as increased locomotion in this context. They further suggest that KCC2 activity might be a therapeutic target to alleviate motor disturbances related to HIV.
感染 HIV 的人(PWH)极易受到纹状体和海马体损伤。这些患者通常会出现运动和记忆障碍,这可能是这些大脑区域受损的行为表现。HIV 感染和病毒蛋白(如转录激活物(Tat))引起的 GABA 能功能障碍已有充分的记录。我们最近表明,神经元特异性 Cl 外排体,K-Cl 共转运蛋白 2(KCC2),在暴露于 HIV 蛋白(包括 Tat)后减少,导致 GABA 介导的超极化和抑制作用中断。在这里,我们利用强力霉素(DOX)诱导、GFAP 驱动的 HIV-1 Tat 转基因小鼠进一步探索了这一现象。在 Tat 表达两周后,我们没有发现海马体 KCC2 水平的变化,但纹状体的水平显著下降,这与旷场试验中的过度运动有关。我们能够通过 KCC2 增强剂 CLP290 恢复 KCC2 活性和基础运动。此外,我们发现 CLP290 的作用机制尚未描述,它可以恢复丝氨酸 940 的磷酸化,从而增加 KCC2 的膜定位。我们还检查了神经元亚群对所观察到的影响的贡献,发现了显著差异。多巴胺 D2 受体表达的中型多棘神经元(MSNs)对 Tat 诱导的 KCC2 缺失特别敏感,而多巴胺 D1 受体表达的 MSNs 则没有观察到变化。这些结果表明,多巴胺 D2 受体表达的 MSNs 的去抑制/去极化减少可能表现为在此背景下运动增加。它们进一步表明,KCC2 活性可能是一种治疗靶点,可以缓解与 HIV 相关的运动障碍。