Expression of cargo receptor ERGIC-53 with defferernt sugar-binding specificities and the effect on carbohydrate structures attached on secretory and membrane proteins.

在分泌途径中，新合成的分泌蛋白和膜蛋白在内质网通过高尔基体转运的过程中经历折叠和糖基化。沿着这一途径运输蛋白质的分选是由货物受体完成的。ERGIC-53是一种具有豆状凝集素结构域的受体，其胞浆尾部含有ER-RETRIVE信号肽。将ERGIC-53编码的凝集素结构域替换为半乳糖结合型紫荆花凝集素(BPA)或唾液酸结合型紫荆凝集素(MAH)。其羧基末端的信号肽也被其他反式高尔基体定位蛋白TGN38、CI-MPR和Furin所取代。在MDCK细胞中表达嵌合的Cargo受体，并分析其对细胞分泌途径的影响。根据Western blotting和流式细胞仪分析的数据，BPA位于凝集素结构域，TGN38位于细胞质尾部的嵌合体ERGIC-53将富含半乳糖的蛋白质运送到细胞表面。

In secretory pathway newly synthesized secretory and membrane proteins undergo folding and glycosylation during the transport from the ER, through the Golgi. Transport along this pathway sorting of proteins are occurred by cargo receptors. ERGIC-53 is one of the cargo receptors with a leguminous lectin domain on its lumenal side and ER-retrieve signal peptide on its cytoplasmic tail. We constructed the cDNA coding ERGIC-53 substituted of its lectin domain into galactose-binding Bauhinia purpurea lectin (BPA) or sialic acid-binding Maackia amurensis lectin (MAH). Signal peptide on its carboxy terminus was also substituted into those of other trans Golgi localized proteins, TGN38, CI-MPR and furin. Chimeric cargo receptors were expressed in MDCK cells and the effect on the secretory pathway of the cells were analyzed, respectively. Based on the data of western blotting and flow cytometric analyses, chimeric ERGIC-53 with BPA at its lectin domain and TGN38 at cytoplasmic tail transported proteins rich in galactose to the surface of the cells and rich in galactose.