Department of Chemistry, Université du Québec à Montréal, Montreal, QC, Canada.
Center of Excellence in Research on Orphan Diseases - Courtois Foundation, Montreal, Canada.
FASEB J. 2021 Feb;35(2):e21306. doi: 10.1096/fj.202001845R.
Glycosaminoglycans (GAGs) are long and unbranched anionic heteropolysaccharides that have been associated with virtually all amyloid deposits. Soluble sulfated GAGs are known for their propensity to promote the self-assembly of numerous amyloidogenic proteins and to modulate their cytotoxicity. Nonetheless, although GAGs are prevalent on the outer leaflet of eukaryotic cell plasma membrane as part of proteoglycans, their contributions in the perturbation of lipid bilayer induced by amyloid polypeptides remain unknown. Herein, we investigate the roles of GAGs in the cytotoxicity and plasma membrane perturbation induced by the islet amyloid polypeptide (IAPP), whose deposition in the pancreatic islets is associated with type II diabetes. Cellular assays using GAG-deficient cells reveal that GAGs exacerbate IAPP-induced cytotoxicity and permeabilization of the plasma membrane. Confocal microscopy and flow cytometry analyses show that IAPP sequestration at the cell surface is dependent of GAGs and of the aggregation propensity of the peptide. Using giant plasma membrane vesicles (GPMVs) prepared from GAG-deficient cells, we investigate the direct contributions of membrane-embedded proteoglycans in IAPP-induced membrane disassembly. In sharp contrast to soluble sulfated GAGs, kinetics of amyloid self-assembly expose that the presence of GAGs on GPMVs does not significantly modulate in vitro amyloid formation. Overall, this study indicates that cell surface GAGs increase the local concentration of IAPP in the vicinity of the plasma membrane, promoting lipid bilayer perturbation and cell death.
糖胺聚糖 (GAGs) 是长而无分支的阴离子杂多糖，与几乎所有的淀粉样沉积物都有关联。可溶性硫酸化 GAGs 以促进许多淀粉样蛋白原纤维形成的倾向和调节其细胞毒性而闻名。尽管 GAGs 作为糖蛋白的一部分存在于真核细胞膜的外叶，但它们在淀粉样多肽引起的脂质双层扰动中的贡献仍不清楚。本文中，我们研究了 GAGs 在胰岛淀粉样多肽 (IAPP) 引起的细胞毒性和质膜扰动中的作用，IAPP 在胰腺胰岛中的沉积与 II 型糖尿病有关。使用 GAG 缺陷细胞进行的细胞测定表明，GAGs 会加剧 IAPP 诱导的细胞毒性和质膜通透性。共聚焦显微镜和流式细胞术分析表明，IAPP 在细胞表面的隔离依赖于 GAGs 和肽的聚集倾向。使用从 GAG 缺陷细胞制备的巨大质膜囊泡 (GPMVs)，我们研究了膜嵌入糖蛋白聚糖在 IAPP 诱导的膜解组装中的直接作用。与可溶性硫酸化 GAGs 形成鲜明对比的是，淀粉样自组装的动力学表明，GPMVs 上 GAGs 的存在不会显著调节体外淀粉样形成。总的来说，这项研究表明，细胞表面 GAGs 增加了 IAPP 在质膜附近的局部浓度，促进了脂质双层的扰动和细胞死亡。
