Hahn Yun Kyung, Masvekar Ruturaj R, Xu Ruqiang, Hauser Kurt F, Knapp Pamela E
Department of Anatomy & Neurobiology, MCV Campus, Virginia Commonwealth University, P.O. Box 980709, Richmond, VA 23298-0709, USA.
Curr HIV Res. 2015;13(1):10-20. doi: 10.2174/1570162x13666150311163733.
The NeuN antibody has been widely used to identify and quantify neurons in normal and disease situations based on binding to a nuclear epitope in most types of neurons. This epitope was recently identified as the RNA-binding, feminizing locus on X-3 (Rbfox3), a member of the larger, mammalian Fox1 family of RNA binding proteins. Fox1 proteins recognize a unique UGCAUG mRNA motif and regulate alternative splicing of precursor mRNA to control post-transcriptional events important in neuronal differentiation and central nervous system development. Recent clinical findings show that Rbfox3/NeuN gene dosage is altered in certain human neurodevelopmental disorders, and redistribution has been noted in HIV(+) tissue. We hypothesized that HIV-1 Tat might affect Rbfox3/NeuN expression, and examined this question in vivo using inducible transgenic mice, and in vitro using human mesencephalic-derived neurons. Rbfox3/NeuN expression and localization in HIV+ basal ganglia and hippocampus was also examined. Chronic Tat exposure reduced Rbfox3/NeuN protein levels and increased cytoplasmic localization, similar to the effect of HIV exposure. Cytoplasmic Rbfox3/NeuN signal has occasionally been reported, although the meaning or function of cytoplasmic versus nuclear localization remains speculative. Importantly, Rbfox3/NeuN reductions were more significant in male mice. Although Rbfox3/NeuN-expressing cells were significantly decreased by Tat exposure, stereology showed that Nissl(+) neuron numbers remained normal. Thus, loss of Rbfox3/NeuN may relate more to functional change than to neuron loss. The effects of Tat by itself are highly relevant to HIV(+) individuals maintained on antiretroviral therapy, since Tat is released from infected cells even when viral replication is inhibited.
NeuN抗体已被广泛用于在正常和疾病情况下基于与大多数类型神经元中的核表位结合来鉴定和定量神经元。该表位最近被鉴定为X-3上的RNA结合、雌性化位点（Rbfox3），它是更大的哺乳动物RNA结合蛋白Fox1家族的成员。Fox1蛋白识别独特的UGCAUG mRNA基序，并调节前体mRNA的可变剪接，以控制在神经元分化和中枢神经系统发育中重要的转录后事件。最近的临床研究结果表明，在某些人类神经发育障碍中，Rbfox3/NeuN基因剂量发生改变，并且在HIV(+)组织中已注意到重新分布。我们假设HIV-1 Tat可能影响Rbfox3/NeuN的表达，并使用诱导型转基因小鼠在体内以及使用人源中脑神经元在体外研究了这个问题。还检查了HIV+基底神经节和海马中Rbfox3/NeuN的表达和定位。与HIV暴露的影响类似，长期暴露于Tat会降低Rbfox3/NeuN蛋白水平并增加细胞质定位。虽然偶尔有关于细胞质Rbfox3/NeuN信号的报道，但细胞质与细胞核定位的意义或功能仍属推测。重要的是，Rbfox3/NeuN的减少在雄性小鼠中更为显著。虽然Tat暴露使表达Rbfox3/NeuN的细胞显著减少，但体视学显示尼氏（Nissl）阳性神经元数量保持正常。因此，Rbfox3/NeuN的丧失可能更多地与功能变化而非神经元丧失有关。Tat本身的作用与接受抗逆转录病毒治疗的HIV(+)个体高度相关，因为即使病毒复制受到抑制，Tat也会从受感染的细胞中释放出来。
