Conacyt, Population Health Research Center, National Institute of Public Health, Cuernavaca, Mexico.
School of Medicine FES Iztacala, National Autonomous University of Mexico (UNAM), Tlalnepantla, Mexico.
J Neurophysiol. 2022 Dec 1;128(6):1555-1564. doi: 10.1152/jn.00287.2022. Epub 2022 Nov 9.
Neuronal L-type Ca channels of the Ca1.3 subclass are transmembrane protein complexes that contribute to the pacemaker activity in the adult substantia nigra dopaminergic neurons. The altered function of these channels may play a role in the development and progress of neurodegenerative mechanisms implicated in Parkinson's disease (PD). Although L-type channel expression is precisely regulated, an increased functional expression has been observed in PD. Previously, we showed that Parkin, an E3 enzyme of the ubiquitin-proteasome system (UPS) interacts with neuronal Ca2.2 channels promoting their ubiquitin-mediated degradation. In addition, previous studies show an increase in Ca1.3 channel activity in dopaminergic neurons of the SNc and that Parkin expression is reduced in PD. These findings suggest that the decrease in Parkin may affect the proteasomal degradation of Ca1.3, which helps explain the increase in channel activity. Therefore, the present report aims to gain insight into the degradation mechanisms of the neuronal Ca1.3 channel by the UPS. Immunoprecipitation assays showed the interaction between Parkin and the Ca1.3 channels expressed in HEK-293 cells and neural tissues. Likewise, Parkin overexpression reduced the total and membrane channel levels and decreased the current density. Consistent with this, patch-clamp recordings in the presence of an inhibitor of the UPS, MG132, prevented the effects of Parkin, suggesting enhanced channel proteasomal degradation. In addition, the half-life of the pore-forming Ca1.3α protein was significantly reduced by Parkin overexpression. Finally, electrophysiological recordings using a knockout HEK-293 cell line generated by CRISPR/Cas9 showed increased current density. These results suggest that Parkin promotes the proteasomal degradation of Ca1.3, which may be a relevant aspect for the pathophysiology of PD. The increased expression of Ca1.3 calcium channels is a crucial feature of Parkinson's disease (PD) pathophysiology. However, the mechanisms that determine this increase are not yet defined. Parkin, an enzyme of the ubiquitin-proteasome system, is known to interact with neuronal channels promoting their ubiquitin-mediated degradation. Interestingly, Parkin mutations also play a role in PD. Here, the degradation mechanisms of Ca1.3 channels and their relationship with the pathophysiology of PD are studied in detail.
神经元 L 型钙通道的 Ca1.3 亚类是跨膜蛋白复合物,有助于成年黑质多巴胺能神经元的起搏活动。这些通道功能的改变可能在帕金森病 (PD) 中涉及的神经退行性机制的发展和进展中发挥作用。尽管 L 型通道的表达受到精确调节,但在 PD 中观察到其功能表达增加。先前,我们发现泛素-蛋白酶体系统 (UPS) 的 E3 酶 Parkin 与神经元 Ca2.2 通道相互作用,促进其泛素介导的降解。此外,先前的研究表明,SNc 中的多巴胺能神经元中 Ca1.3 通道活性增加,并且 PD 中 Parkin 的表达减少。这些发现表明 Parkin 的减少可能会影响 Ca1.3 的蛋白酶体降解,这有助于解释通道活性的增加。因此,本报告旨在深入了解 UPS 对神经元 Ca1.3 通道的降解机制。免疫沉淀测定显示 Parkin 与在 HEK-293 细胞和神经组织中表达的 Ca1.3 通道之间的相互作用。同样,Parkin 的过表达降低了总通道和膜通道水平,并降低了电流密度。与此一致,在 UPS 抑制剂 MG132 的存在下进行的膜片钳记录阻止了 Parkin 的作用,表明通道的蛋白酶体降解增强。此外,通过 Parkin 过表达,孔形成 Ca1.3α 蛋白的半衰期显着缩短。最后,使用通过 CRISPR/Cas9 生成的 Ca1.3 敲除 HEK-293 细胞系进行的电生理记录显示电流密度增加。这些结果表明 Parkin 促进 Ca1.3 的蛋白酶体降解,这可能是 PD 病理生理学的一个重要方面。钙通道 Ca1.3 的表达增加是帕金森病 (PD) 病理生理学的一个关键特征。然而,确定这种增加的机制尚不清楚。泛素-蛋白酶体系统的酶 Parkin 已知与神经元通道相互作用,促进其泛素介导的降解。有趣的是,Parkin 突变也在 PD 中起作用。在这里,详细研究了 Ca1.3 通道的降解机制及其与 PD 病理生理学的关系。
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