CRN2M Centre de Recherche Neurobiologie-Neurophysiologie, CNRS, UMR7286, Aix-Marseille Université, 13015 Marseille, France.
Institut de Microbiologie de la Méditerranée (IMM), CNRS, Aix-Marseille Université, 13009 Marseille, France.
Cells. 2024 May 30;13(11):944. doi: 10.3390/cells13110944.
Pacemaking activity in substantia nigra dopaminergic neurons is generated by the coordinated activity of a variety of distinct somatodendritic voltage- and calcium-gated ion channels. We investigated whether these functional interactions could arise from a common localization in macromolecular complexes where physical proximity would allow for efficient interaction and co-regulations. For that purpose, we immunopurified six ion channel proteins involved in substantia nigra neuron autonomous firing to identify their molecular interactions. The ion channels chosen as bait were Cav1.2, Cav1.3, HCN2, HCN4, Kv4.3, and SK3 channel proteins, and the methods chosen to determine interactions were co-immunoprecipitation analyzed through immunoblot and mass spectrometry as well as proximity ligation assay. A macromolecular complex composed of Cav1.3, HCN, and SK3 channels was unraveled. In addition, novel potential interactions between SK3 channels and sclerosis tuberous complex (Tsc) proteins, inhibitors of mTOR, and between HCN4 channels and the pro-degenerative protein Sarm1 were uncovered. In order to demonstrate the presence of these molecular interactions in situ, we used proximity ligation assay (PLA) imaging on midbrain slices containing the substantia nigra, and we could ascertain the presence of these protein complexes specifically in substantia nigra dopaminergic neurons. Based on the complementary functional role of the ion channels in the macromolecular complex identified, these results suggest that such tight interactions could partly underly the robustness of pacemaking in dopaminergic neurons.
在黑质多巴胺能神经元中,起搏活动是由多种不同的体树突电压和钙门控离子通道的协调活动产生的。我们研究了这些功能相互作用是否可以来自于大分子复合物中的共同定位,在这种复合物中,物理接近度可以允许有效的相互作用和共同调节。为此,我们免疫纯化了六种参与黑质神经元自主放电的离子通道蛋白,以鉴定它们的分子相互作用。选择作为诱饵的离子通道是 Cav1.2、Cav1.3、HCN2、HCN4、Kv4.3 和 SK3 通道蛋白,选择的方法来确定相互作用是通过免疫印迹和质谱分析以及接近连接测定来进行共免疫沉淀分析。揭示了一个由 Cav1.3、HCN 和 SK3 通道组成的大分子复合物。此外,还发现了 SK3 通道和硬化结节性复合物(Tsc)蛋白之间、mTOR 抑制剂之间以及 HCN4 通道和促退化蛋白 Sarm1 之间的新的潜在相互作用。为了证明这些分子相互作用在原位的存在,我们在含有黑质的中脑切片上使用了接近连接测定(PLA)成像,并且可以确定这些蛋白质复合物特异性地存在于黑质多巴胺能神经元中。基于鉴定的大分子复合物中离子通道的互补功能作用,这些结果表明,这种紧密的相互作用可能部分地构成了多巴胺能神经元起搏的稳健性。
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