Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, Lund SE-221 84, Sweden.
Glycobiology. 2023 May 17;33(4):325-341. doi: 10.1093/glycob/cwad013.
In Parkinson's disease, there is an accumulation of α-synuclein (SYN) aggregates in neurons, which is promoted by neuroinflammation. In neural cells, cytokine-induced SYN aggregation is modulated by heparan sulfate (HS) derived from glypican-1 (GPC1) by amyloid precursor protein (APP) and nitric oxide (NO)-dependent cleavage. We have explored possible interplay between APP, GPC1, and SYN in undifferentiated and differentiated neural progenitor cells (NPCs) by modulating APP and GPC1 processing. Effects were monitored by immunofluorescence microscopy and slot immunoblotting using antibodies recognizing APP degradation products, HS released from GPC1, and SYN aggregates (filamentous SYN [SYNfil]). Suppression of HS release from GPC1 by inhibition of β-secretase or by NO deprivation resulted in no or slight increase in SYNfil aggregation. Stimulation of HS release by ascorbate did not further increase SYNfil staining. Interleukin-6 (IL-6) induced increased APP and GPC1 processing and SYNfil formation, which was reduced when β-secretase was inhibited and when HS release was impeded by NO deprivation. Ascorbate restored APP and GPC1 processing but did not affect SYNfil formation. Ascorbate-dependent differentiation of NPC resulted in the expression of tyrosine hydroxylase (TH) which colocalized with SYNfil. Suppression of APP processing by inhibition of β-secretase greatly disturbed the differentiation process. IL-6 induced coclustering of APP-degradation products, TH, HS, and SYNfil, which could be reversed by stimulation of HS release from GPC1 by excess ascorbate. We suggest that continuous release of HS from GPC1 moderates SYN aggregation and supports differentiation of NPC to dopaminergic neurons.
在帕金森病中，α-突触核蛋白（SYN）聚集体在神经元中积累，这是由神经炎症促进的。在神经细胞中，细胞因子诱导的 SYN 聚集受糖蛋白聚糖-1（GPC1）衍生的肝素硫酸盐（HS）调节，由淀粉样前体蛋白（APP）和一氧化氮（NO）依赖性切割调节。我们通过调节 APP 和 GPC1 处理，探索了未分化和分化神经祖细胞（NPC）中 APP、GPC1 和 SYN 之间可能的相互作用。通过免疫荧光显微镜和 Slot 免疫印迹监测效应，使用识别 APP 降解产物、从 GPC1 释放的 HS 和 SYN 聚集体（丝状 SYN [SYNfil]）的抗体。抑制 GPC1 的 HS 释放β-分泌酶或剥夺 NO 导致 SYNfil 聚集无或轻微增加。抗坏血酸刺激 HS 释放不会进一步增加 SYNfil 染色。白细胞介素-6（IL-6）诱导 APP 和 GPC1 处理和 SYNfil 形成增加，当抑制β-分泌酶和剥夺 NO 阻碍 HS 释放时，这种增加减少。抗坏血酸恢复了 APP 和 GPC1 的处理，但不影响 SYNfil 的形成。NPC 的抗坏血酸依赖性分化导致酪氨酸羟化酶（TH）的表达，其与 SYNfil 共定位。抑制 APP 处理β-分泌酶极大地扰乱了分化过程。IL-6 诱导 APP 降解产物、TH、HS 和 SYNfil 的共聚类，这可以通过过量抗坏血酸刺激 GPC1 从 HS 释放来逆转。我们认为，GPC1 持续释放 HS 可调节 SYN 聚集并支持 NPC 向多巴胺能神经元的分化。
