Endo180半胱氨酸富集区与I型胶原蛋白C末端分子的体外相互作用

In vitro Interaction of the Cysteine-rich Domain of Endo180 with the C-terminal Region of Type I Collagen

I型胶原蛋白（type I collagen）是由2条α1链和1条α2链构成的纤维状异源三聚体.它是构成细胞外基质最主要的成分.I型胶原蛋白和内吞胶原蛋白受体Endo180（Endocytic 180）之间的相互作用在细胞基质的粘附和降解过程中起着关键性作用.但内吞胶原蛋白受体Endo180与胶原蛋白的结合区域尚未有相关的报道.本研究在体外通过酶联免疫吸附、蛋白免疫沉淀和Western印迹等多种定量分析实验发现,用碱性磷酸酶（alkaline phosphatase,AP）标记I型胶原蛋白C末端（氨基酸1151~1464）后形成的分泌型三聚体融合蛋白AP-Coll-S,可与用抗体恒定区（antibody constant fragment,Fc）标记的Endo180的半胱氨酸富集区（CysR）结合.从而表明,AP-Coll-S和CysR-Fc之间存在相互作用.本研究结果为进一步研究胶原蛋白和其受体Endo180的分子间相互作用提供新依据.

Type I collagen is a fibril-forming hetero trimer which constitutes of two α1 and one α2chains. It makes up the most abundant component of extracellular matrices. The interaction of collagen with its receptor Endo180 plays an important role in cell adhesion and matrix turnover. However,the nature of their molecular interaction remains to be determined. In this study,regions of human collage α1encompassing part of the C-terminal glycine repeats and the C-prodomain（ amino acids 1151 ~ 1454）were affinity-labeled with human placental alkaline phosphatase（ AP）. The resulting secreted trimeric AP-collagen fusion protein（ designated as AP-Coll-S） were showed to be able to bind to the cysteine-rich domain of Endo180（ Cys R） fused to human Ig G1 constant fragment（ Fc） via various quantitative analyses in vitro. These results suggested that the cysteine-rich domain of Endo180 alone could directly bind to the C- terminal region of type I collagen. Thus,our study provides a method validation for further dissection and understanding of the molecular interaction between collagen and Endo180.