Medical Proteomics Unit, Office for Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, 6th Floor-SiMR Building, 2 Wanglang Road, Bangkoknoi, Bangkok, 10700, Thailand.
J Biol Inorg Chem. 2019 Mar;24(2):235-246. doi: 10.1007/s00775-019-01641-w. Epub 2019 Jan 30.
Fibronectin, an extracellular matrix (ECM) protein, has been thought to be involved in pathogenic mechanisms of kidney stone disease, especially calcium oxalate (CaOx) type. Nevertheless, its precise roles in modulation of CaOx crystal remained unclear. We thus performed a systematic evaluation of effects of fibronectin on CaOx monohydrate (COM) crystal (the major causative chemical crystal in kidney stone formation) in various stages of kidney stone pathogenesis, including crystallization, crystal growth, aggregation, adhesion onto renal tubular cells, and invasion through ECM in renal interstitium. The data showed that fibronectin significantly decreased crystallization, growth and adhesive capability of COM crystals in a dose-dependent manner. In contrast, COM crystal aggregation and invasion through ECM migration chamber were significantly enhanced by fibronectin in a dose-dependent fashion. Sequence analysis revealed three calcium-binding and six oxalate-binding domains in fibronectin. Immunofluorescence study confirmed binding of fibronectin to COM crystals. Additionally, calcium- and oxalate-affinity assays confirmed depletion of both calcium and oxalate ions after incubation with fibronectin. Moreover, calcium-saturated and oxalate-saturated forms of fibronectin markedly reduced the modulatory activities of fibronectin on COM crystallization, crystal growth, aggregation, and adhesion onto the cells. These data strongly indicate the dual functions of fibronectin, which serves as an inhibitor for COM crystallization, crystal growth and adhesion onto renal tubular cells, but on the other hand, acts as a promoter for COM crystal aggregation and invasion through ECM. Finally, its COM crystal modulatory activities are most likely mediated through binding with calcium and oxalate ions on the crystals and in their environment.
纤连蛋白是一种细胞外基质（ECM）蛋白，被认为参与肾结石疾病的发病机制，尤其是草酸钙（CaOx）型。然而，其在调节 CaOx 晶体方面的确切作用仍不清楚。因此，我们系统评估了纤连蛋白在肾结石发病的各个阶段对 CaOx 一水合物（COM）晶体（肾结石形成的主要致化学晶体）的影响，包括结晶、晶体生长、聚集、黏附到肾小管细胞以及通过 ECM 侵入肾间质。数据表明，纤连蛋白以剂量依赖性方式显著降低 COM 晶体的结晶、生长和黏附能力。相比之下，COM 晶体的聚集和通过 ECM 迁移室的侵入则被纤连蛋白以剂量依赖性方式显著增强。序列分析显示纤连蛋白中有三个钙结合和六个草酸盐结合结构域。免疫荧光研究证实了纤连蛋白与 COM 晶体的结合。此外，钙和草酸盐亲和性测定证实，与纤连蛋白孵育后，钙和草酸盐离子均被耗尽。此外，钙饱和和草酸盐饱和形式的纤连蛋白显著降低了纤连蛋白对 COM 结晶、晶体生长、聚集和黏附到细胞上的调节活性。这些数据强烈表明纤连蛋白具有双重功能，一方面作为 COM 结晶、晶体生长和黏附到肾小管细胞的抑制剂，但另一方面作为 COM 晶体聚集和通过 ECM 侵入的促进剂。最后，其对 COM 晶体的调节活性很可能是通过与晶体及其环境中的钙和草酸盐离子结合介导的。
