Baciu P C, Acaster C, Goetinck P F
Cutaneous Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Charlestown 02129.
J Biol Chem. 1994 Jan 7;269(1):696-703.
We have cloned and determined the genomic organization of the core protein of the chicken transmembrane proteoglycan, syndecan-4. Identification of the initial cDNA was accomplished using polyclonal antibodies directed against the cytoplasmic domain of murine syndecan-1 core protein. The cDNA for chicken syndecan-4 encodes a putative core protein of 197 amino acids which consists of a 19-amino acid signal peptide, a 125-amino acid ectodomain, a 25-amino acid transmembrane domain, and a 28-amino acid cytoplasmic domain. The predicted molecular mass of the mature core protein is 19,639 daltons. The ectodomain of chicken syndecan-4 core protein contains three potential sites for glycosaminoglycan attachment, two sites for N-glycosylation, and lacks a dibasic protease cleavage site proximal to the membrane-spanning region found in other syndecan family members. Comparison of the complete amino acid sequence with human syndecan-4 (amphlican (David, G., van der Schueren, B., Marynen, P., Cassiman, J. J., and van den Berghe, H. (1992) J. Cell Biol. 118, 961-969)) and rat syndecan-4 (ryudocan (Kojima, T., Shworak, N. W., and Rosenberg, R. D. (1992) J. Biol. Chem. 267, 4870-4877)) indicates an overall identity of 58 and 56%, respectively, with a 91 and 92% identity in the highly conserved transmembrane and cytoplasmic domains. The core protein of chicken syndecan-4 synthesized by chicken cells is modified with heparan sulfate side chains yielding a proteoglycan with a molecular mass of > 200 kDa in LMH cells (immortalized male leghorn LM strain hepatocytes) and primary skin fibroblasts. Syndecan-4 isolated from chondrocyte cultures runs as a diffuse band between 100 and 200 kDa. Northern analysis of chicken syndecan-4 indicates three messages with distinct sizes of 0.9, 1.3, and 2.9 kb and a wide mRNA tissue distribution. The chicken syndecan-4 gene is divided into 5 exons encoding distinct regions which contain the signal peptide, the glycosaminoglycan attachment sites, a small spacer of unknown function, the glycosylation sites and the transmembrane and cytoplasmic domains.
我们已经克隆并确定了鸡跨膜蛋白聚糖syndecan-4核心蛋白的基因组结构。最初的cDNA是利用针对鼠syndecan-1核心蛋白胞质结构域的多克隆抗体鉴定出来的。鸡syndecan-4的cDNA编码一个由197个氨基酸组成的推定核心蛋白，该蛋白由一个19个氨基酸的信号肽、一个125个氨基酸的胞外结构域、一个25个氨基酸的跨膜结构域和一个28个氨基酸的胞质结构域组成。成熟核心蛋白的预测分子量为19,639道尔顿。鸡syndecan-4核心蛋白的胞外结构域含有三个潜在的糖胺聚糖附着位点、两个N-糖基化位点，并且在跨膜区域附近缺少其他syndecan家族成员中发现的双碱性蛋白酶切割位点。将完整氨基酸序列与人syndecan-4（amphlican（David, G., van der Schueren, B., Marynen, P., Cassiman, J. J., and van den Berghe, H. (1992) J. Cell Biol. 118, 961-969））和大鼠syndecan-4（ryudocan（Kojima, T., Shworak, N. W., and Rosenberg, R. D. (1992) J. Biol. Chem. 267, 4870-4877））进行比较，结果表明总体同一性分别为58%和56%，在高度保守的跨膜和胞质结构域中的同一性分别为91%和92%。鸡细胞合成的鸡syndecan-4核心蛋白被硫酸乙酰肝素侧链修饰，在LMH细胞（永生化雄性来航鸡LM品系肝细胞）和原代皮肤成纤维细胞中产生分子量>200 kDa的蛋白聚糖。从软骨细胞培养物中分离出的syndecan-4在100至200 kDa之间呈现为一条弥散带。对鸡syndecan-4的Northern分析表明有三种大小分别为0.9、1.3和2.9 kb的不同信息，并且mRNA在组织中的分布广泛。鸡syndecan-4基因被分为5个外显子，编码不同的区域，这些区域包含信号肽、糖胺聚糖附着位点、一个功能未知的小间隔区、糖基化位点以及跨膜和胞质结构域。
