Syndecans是I型跨膜蛋白,有一个n端外结构域,包含几个糖胺聚糖(GAG)附着的一致序列和一个短的c端胞质结构域。Syndecan-1和-3 GAG附着位点出现在两个不同的簇中,一个在n端附近,另一个在膜附着位点附近,被一个富含脯氨酸和苏氨酸的“间隔体”隔开。Syndecan外结构域在家族和种间的保守性较差,但跨膜结构域和细胞质结构域的保守性较高。Syndecan-1和-3形成一个亚家族。Syndecan核心蛋白形成二聚体(Choi et al. 2007),至少Syndecan -3和-4形成低聚体(Asundi & Carey 1995, Shin et al. 2012)。syndecan -1是包括血管内皮在内的主要上皮细胞syndecan。Syndecan-2主要存在于间充质细胞、神经元和平滑肌细胞中。syndecan- 3是神经系统主要的syndecan,而syndecan-4普遍表达,但水平低于其他syndecan(参考Alexopoulou et al. 2007)。核心syndecan蛋白有3 - 5条硫酸肝素或硫酸软骨素链,它们与多种配体相互作用,包括成纤维细胞生长因子、血管内皮生长因子、转化生长因子- β、纤维连接蛋白、胶原蛋白、维连蛋白和几种整合素。Syndecans可作为整合素共受体。 Interactions between fibronectin and syndecans are modulated by tenascin-C. Syndecans bind a wide variety of soluble and insoluble ligands, inckluding extracellular matrix components, cell adhesion molecules, growth factors, cytokines, and proteinases. As the cleaved ectodomains of syndecans retain the ability to bind ligands, ectodomain shedding is a mechanism for releasing soluble effectors that may compete for ligands with their cell-bound counterparts (Kainulainen et al. 1998). Shed ectodomains are found in inflammatory fluids (Subramanian et al. 1997) and may induce the proliferation of cancer cells (Maeda et al. 2004).