Glycosaminoglycans (GAGs) are essential functional components of the extracellular matrix (ECM). Artificial GAGs like sulfated hyaluronan (sHA) exhibit pro-osteogenic properties and boost healing processes. Hence, they are of high interest for supporting bone regeneration and wound healing. Although sulfated GAGs (sGAGs) appear intracellularly, the knowledge about intracellular effects and putative interaction partners is scarce. Here we used an affinity-purification mass spectrometry-based (AP-MS) approach to identify novel and particularly intracellular sGAG-interacting proteins in human bone marrow stromal cells (hBMSC). Overall, 477 proteins were found interacting with at least one of four distinct sGAGs. Enrichment analysis for protein localization showed that mainly intracellular and cell-associated interacting proteins were identified. The interaction of sGAG with α2-macroglobulin receptor-associated protein (LRPAP1), exportin-1 (XPO1), and serine protease HTRA1 (HTRA1) was confirmed in reverse assays. Consecutive pathway and cluster analysis led to the identification of biological processes, namely processes involving binding and processing of nucleic acids, LRP1-dependent endocytosis, and exosome formation. Respecting the preferentially intracellular localization of sGAG in vesicle-like structures, also the interaction data indicate sGAG-specific modulation of vesicle-based transport processes. By identifying many sGAG-specific interacting proteins, our data provide a resource for upcoming studies aimed at molecular mechanisms and understanding of sGAG cellular effects.

中文翻译：

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通过亲和纯化质谱法鉴定细胞内糖胺聚糖相互作用蛋白


糖胺聚糖 (GAG) 是细胞外基质 (ECM) 的重要功能成分。硫酸化透明质酸 (sHA) 等人工 GAG 具有促成骨特性并促进愈合过程。因此，它们在支持骨再生和伤口愈合方面受到高度关注。尽管硫酸化 GAG (sGAG) 出现在细胞内，但有关细胞内效应和假定的相互作用伙伴的知识却很少。在这里，我们使用基于亲和纯化质谱 (AP-MS) 的方法来鉴定人骨髓基质细胞 (hBMSC) 中新型的、特别是细胞内 sGAG 相互作用的蛋白。总体而言，发现 477 种蛋白质与四种不同 sGAG 中的至少一种相互作用。蛋白质定位的富集分析表明，主要鉴定出细胞内和细胞相关的相互作用蛋白质。反向测定证实了 sGAG 与 α2-巨球蛋白受体相关蛋白 (LRPAP1)、输出蛋白-1 (XPO1) 和丝氨酸蛋白酶 HTRA1 (HTRA1) 的相互作用。连续的通路和聚类分析导致了生物过程的鉴定，即涉及核酸结合和加工、LRP1依赖性内吞作用和外泌体形成的过程。考虑到 sGAG 在囊泡样结构中的优先细胞内定位，相互作用数据也表明基于囊泡的运输过程的 sGAG 特异性调节。通过识别许多 sGAG 特异性相互作用蛋白，我们的数据为即将开展的旨在分子机制和了解 sGAG 细胞效应的研究提供了资源。