Institute of Biotechnology, HiLIFE, University of Helsinki, Viikinkaari 5D, 00790 Helsinki, Finland.
Drug Research Program, Faculty of Pharmacy, University of Helsinki, Viikinkaari 5E, 00014 Helsinki, Finland.
Biomolecules. 2022 Apr 9;12(4):563. doi: 10.3390/biom12040563.
There are several links between insulin resistance and neurodegenerative disorders such as Parkinson's disease. However, the direct influence of insulin signaling on abnormal α-synuclein accumulation-a hallmark of Parkinson's disease-remains poorly explored. To our best knowledge, this work is the first attempt to investigate the direct effects of insulin signaling on pathological α-synuclein accumulation induced by the addition of α-synuclein preformed fibrils in primary dopaminergic neurons. We found that modifying insulin signaling through (1) insulin receptor inhibitor GSK1904529A, (2) SHIP2 inhibitor AS1949490 or (3) PTEN inhibitor VO-OHpic failed to significantly affect α-synuclein aggregation in dopaminergic neurons, in contrast to the aggregation-reducing effects observed after the addition of glial cell line-derived neurotrophic factor. Subsequently, we tested different media formulations, with and without insulin. Again, removal of insulin from cell culturing media showed no effect on α-synuclein accumulation. We observed, however, a reduced α-synuclein aggregation in neurons cultured in neurobasal medium with a B27 supplement, regardless of the presence of insulin, in contrast to DMEM/F12 medium with an N2 supplement. The effects of culture conditions were present only in dopaminergic but not in primary cortical or hippocampal cells, indicating the unique sensitivity of the former. Altogether, our data contravene the direct involvement of insulin signaling in the modulation of α-synuclein aggregation in dopamine neurons. Moreover, we show that the choice of culturing media can significantly affect preformed fibril-induced α-synuclein phosphorylation in a primary dopaminergic cell culture.
胰岛素抵抗与神经退行性疾病之间存在多种联系，如帕金森病。然而，胰岛素信号对帕金森病标志性的异常α-突触核蛋白积累的直接影响仍未得到充分探索。据我们所知，这项工作是首次尝试研究胰岛素信号对原代多巴胺能神经元中添加α-突触核蛋白原纤维诱导的病理性α-突触核蛋白积累的直接影响。我们发现，通过（1）胰岛素受体抑制剂 GSK1904529A、（2）SHIP2 抑制剂 AS1949490 或（3）PTEN 抑制剂 VO-OHpic 改变胰岛素信号，不能显著影响多巴胺能神经元中α-突触核蛋白的聚集，而添加胶质细胞系源性神经营养因子则观察到聚集减少的效果。随后，我们测试了不同的培养基配方，有无胰岛素。同样，从细胞培养培养基中去除胰岛素对α-突触核蛋白的积累没有影响。然而，我们观察到在含有 B27 补充剂的神经基础培养基中培养的神经元中α-突触核蛋白聚集减少，无论培养基中是否含有胰岛素，与含有 N2 补充剂的 DMEM/F12 培养基相比。培养条件的影响仅存在于多巴胺能神经元中，而不存在于原代皮质或海马细胞中，表明前者的独特敏感性。总之，我们的数据与胰岛素信号直接参与调节多巴胺神经元中α-突触核蛋白聚集的观点相矛盾。此外，我们还表明，培养介质的选择可以显著影响原代多巴胺能细胞培养中诱导的α-突触核蛋白原纤维形成的磷酸化。
