Sun Yuyang, Zhang Haopeng, Selvaraj Senthil, Sukumaran Pramod, Lei Saobo, Birnbaumer Lutz, Singh Brij B
Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58201, and.
National Institute of Environmental Health Sciences, Durham, North Carolina 27709.
J Neurosci. 2017 Mar 22;37(12):3364-3377. doi: 10.1523/JNEUROSCI.3010-16.2017. Epub 2017 Mar 3.
Loss of dopaminergic (DA) neurons leads to Parkinson's disease; however, the mechanism(s) for the vulnerability of DA neurons is(are) not fully understood. We demonstrate that TRPC1 regulates the L-type Ca channel that contributes to the rhythmic activity of adult DA neurons in the substantia nigra region. Store depletion that activates TRPC1, via STIM1, inhibits the frequency and amplitude of the rhythmic activity in DA neurons of wild-type, but not in TRPC1, mice. Similarly, TRPC1 substantia nigra neurons showed increased L-type Ca currents, decreased stimulation-dependent STIM1-Ca1.3 interaction, and decreased DA neurons. L-type Ca currents and the open channel probability of Ca1.3 channels were also reduced upon TRPC1 activation, whereas increased Ca1.3 currents were observed upon STIM1 or TRPC1 silencing. Increased interaction between Ca1.3-TRPC1-STIM1 was observed upon store depletion and the loss of either TRPC1 or STIM1 led to DA cell death, which was prevented by inhibiting L-type Ca channels. Neurotoxins that mimic Parkinson's disease increased Ca1.3 function, decreased TRPC1 expression, inhibited Tg-mediated STIM1-Ca1.3 interaction, and induced caspase activation. Importantly, restoration of TRPC1 expression not only inhibited Ca1.3 function but increased cell survival. Together, we provide evidence that TRPC1 suppresses Ca1.3 activity by providing an STIM1-based scaffold, which is essential for DA neuron survival. Ca entry serves critical cellular functions in virtually every cell type, and appropriate regulation of Ca in neurons is essential for proper function. In Parkinson's disease, DA neurons are specifically degenerated, but the mechanism is not known. Unlike other neurons, DA neurons depend on Ca1.3 channels for their rhythmic activity. Our studies show that, in normal conditions, the pacemaking activity in DA neurons is inhibited by the TRPC1-STIM1 complex. Neurotoxins that mimic Parkinson's disease target TRPC1 expression, which leads to an abnormal increase in Ca1.3 activity, thereby causing degeneration of DA neurons. These findings link TRPC1 to Ca1.3 regulation and provide important indications about how disrupting Ca balance could have a direct implication in the treatment of Parkinson's patients.
多巴胺能（DA）神经元的丧失会导致帕金森病；然而，DA神经元易损性的机制尚未完全明确。我们证明，瞬时受体电位通道蛋白1（TRPC1）调节L型钙通道，该通道有助于黑质区域成年DA神经元的节律性活动。通过基质相互作用分子1（STIM1）激活TRPC1的内质网钙库耗竭，会抑制野生型小鼠而非TRPC1基因敲除小鼠DA神经元的节律性活动频率和幅度。同样，TRPC1基因敲除小鼠的黑质神经元L型钙电流增加，刺激依赖性STIM1-Ca1.3相互作用减少，DA神经元数量减少。TRPC1激活后，L型钙电流以及Ca1.3通道的开放概率也降低，而STIM1或TRPC1基因沉默后则观察到Ca1.3电流增加。内质网钙库耗竭时，Ca1.3-TRPC1-STIM1之间的相互作用增强，TRPC1或STIM1缺失均导致DA细胞死亡，而抑制L型钙通道可预防这种情况。模拟帕金森病的神经毒素会增加Ca1.3功能，降低TRPC1表达，抑制毒胡萝卜素（Tg）介导的STIM1-Ca1.3相互作用，并诱导半胱天冬酶激活。重要的是，恢复TRPC1表达不仅会抑制Ca1.3功能，还能提高细胞存活率。总之，我们提供的证据表明，TRPC1通过提供基于STIM1的支架来抑制Ca1.3活性，这对DA神经元的存活至关重要。钙内流在几乎每种细胞类型中都发挥着关键的细胞功能，而神经元中钙的适当调节对其正常功能至关重要。在帕金森病中，DA神经元会特异性退化，但其机制尚不清楚。与其他神经元不同，DA神经元的节律性活动依赖于Ca1.3通道。我们的研究表明，在正常情况下，DA神经元的起搏活动受到TRPC1-STIM1复合体的抑制。模拟帕金森病的神经毒素靶向TRPC1表达，导致Ca1.3活性异常增加，从而引起DA神经元退化。这些发现将TRPC1与Ca1.3调节联系起来，并为破坏钙平衡如何直接影响帕金森病患者的治疗提供了重要线索。
