Gould S E, Upholt W B, Kosher R A
Department of Anatomy, School of Medicine, University of Connecticut Health Center, Farmington 06030.
Proc Natl Acad Sci U S A. 1992 Apr 15;89(8):3271-5. doi: 10.1073/pnas.89.8.3271.
A partial cDNA that encodes a newly discovered member of the syndecan family of integral membrane proteoglycans, which we have termed syndecan 3, has been isolated from an embryonic chicken limb bud cDNA library. Syndecan 3 is distinct from but structurally related to syndecan and fibroglycan, two previously characterized members of this family of membrane-intercalated proteoglycans. Syndecan 3 contains a cytoplasmic domain potentially associated with the cytoskeleton that is 85% identical in amino acid sequence to the cytoplasmic domain of syndecan. Syndecan 3 also possesses a hydrophobic transmembrane domain and an extracellular domain containing several clustered potential glycosaminoglycan attachment sites. Like syndecan, the ectodomain of syndecan 3 has a single dibasic protease-susceptible site adjacent to the transmembrane domain, which might be involved in shedding the ectodomain from the cell surface. A striking feature of syndecan 3 is an extensive (182 amino acid) threonine, serine, and proline (T+S+P)-rich domain that closely resembles T+S+P-rich regions in several mucin-like proteins in which O-linked oligosaccharides are bound to the threonine and serine residues. Syndecan 3 is expressed in high amounts during a critical phase of chicken limb chondrogenesis in which limb mesenchymal cells condense, round up, and interact with one another before depositing a cartilage matrix. The multiple functional domains of syndecan 3 provide potential sites for mediating the adhesive cell-matrix interactions and cytoskeletal reorganization involved in this critical condensation process.
我们从一个胚胎鸡肢芽cDNA文库中分离出了一个部分cDNA，它编码一种新发现的整合膜蛋白聚糖syndecan家族成员，我们将其命名为syndecan 3。Syndecan 3与syndecan和fibroglycan不同，但在结构上相关，syndecan和fibroglycan是该膜插入蛋白聚糖家族中两个先前已被鉴定的成员。Syndecan 3含有一个可能与细胞骨架相关的胞质结构域，其氨基酸序列与syndecan的胞质结构域有85%的同源性。Syndecan 3还具有一个疏水跨膜结构域和一个胞外结构域，该胞外结构域包含几个成簇的潜在糖胺聚糖附着位点。与syndecan一样，syndecan 3的胞外结构域在跨膜结构域附近有一个单一的双碱性蛋白酶敏感位点，这可能参与将胞外结构域从细胞表面脱落。Syndecan 3的一个显著特征是一个广泛的（182个氨基酸）富含苏氨酸、丝氨酸和脯氨酸（T+S+P）的结构域，它与几种粘蛋白样蛋白中富含T+S+P的区域非常相似，在这些蛋白中，O-连接寡糖与苏氨酸和丝氨酸残基结合。Syndecan 3在鸡肢软骨形成的关键阶段大量表达，在这个阶段，肢间充质细胞聚集、变圆并在沉积软骨基质之前相互作用。Syndecan 3 的多个功能结构域为介导参与这一关键聚集过程的粘附性细胞-基质相互作用和细胞骨架重组提供了潜在位点。
