Phan Trong-Nhat, Wong Ee Lin, Park Sun Young, Kim Hae Jong, Yang Beom-Seok
a Chemical Kinomics Research Center , Korea Institute of Science and Technology , Seoul , Korea.
Biosci Biotechnol Biochem. 2015;79(4):574-80. doi: 10.1080/09168451.2014.987208. Epub 2014 Dec 4.
An X-ray crystallographic study has suggested that vertebrate discoidin domain receptors (DDRs) have a conserved Ca(2+) binding site. DDR1 and DDR2 transfected in HEK293 cells were expressed mainly as 120 and 130 kDa forms, respectively, as they are sufficiently N-glycosylated. However, both of them showed the molecular weight of 110 kDa predominantly in the cells cultured with Ca(2+)-depleted media. DDR2-carrying D234A mutation at the conserved Ca(2+)-binding site expressed the 110 kDa form dominantly even in normal culture condition. DDR2 becomes 100 kDa form in glucose-depleted culture condition and its molecular weight increases up to 130 kDa with re-feeding glucose. However, in the mutant DDR2, the increase came to a halt at 110 kDa. The 110 kDa form had premature N-glycosyl carbohydrates and located predominantly within the endoplasmic reticulum. These results suggest that DDRs require Ca(2+)-binding to complete their N-glycan processing and generate the form targeted to cell membrane.
一项X射线晶体学研究表明，脊椎动物盘状结构域受体（DDRs）具有一个保守的Ca(2+)结合位点。转染到HEK293细胞中的DDR1和DDR2分别主要以120 kDa和130 kDa的形式表达，因为它们具有充分的N-糖基化。然而，在用缺乏Ca(2+)的培养基培养的细胞中，它们两者主要显示为110 kDa的分子量。在保守的Ca(2+)结合位点携带D234A突变的DDR2即使在正常培养条件下也主要表达110 kDa的形式。在缺乏葡萄糖的培养条件下，DDR2变为100 kDa的形式，而再添加葡萄糖后其分子量增加到130 kDa。然而，在突变的DDR2中，分子量增加在110 kDa处停止。110 kDa的形式具有过早的N-糖基碳水化合物，并且主要位于内质网内。这些结果表明，DDRs需要Ca(2+)结合来完成其N-聚糖加工并产生靶向细胞膜的形式。
