Deletion of clustered O-linked carbohydrates does not impair function of low density lipoprotein receptor in transfected fibroblasts.

作者：Claire Davis, Åke P. Elhammer, David W. Russell, Wolfgang J. Schneider, Stuart A. Kornfeld, Michael S. Brown, Joseph L. Goldstein · 发表于：Journal of Biological Chemistry · 年份：1986 · DOI：10.1016/s0021-9258(17)35862-3 · 被引用次数：207 · 研究领域：Glycosylation and Glycoproteins Research、Ubiquitin and proteasome pathways、Peptidase Inhibition and Analysis

A single exon in the gene for the receptor for plasma low density lipoprotein (LDL) encodes a region of clustered serine and threonine residues that is immediately external to the membrane-spanning sequence. This region has been proposed as the site of clustered O-linked carbohydrate chains. In the current studies we have deleted the 144 base pairs (48 amino acids) that encode this serine- and threonine-rich region from the cDNA for the human LDL receptor. Upon transfection into receptor-deficient hamster fibroblasts, this mutated cDNA encoded a shortened receptor that no longer showed an anomalously high molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Labeling with [3H]glucosamine confirmed the lack of clustered O-linked sugars and further revealed that the shortened receptor and the normal receptor both contained isolated O-linked carbohydrate chains attached to the NH2-terminal portion of the protein. The ratio of clustered to isolated O-linked sugar chains in the normal receptor was estimated to be approximately 4-6 to 1. Despite the loss of clustered O-linked carbohydrate, the LDL receptor encoded by the deletion-bearing cDNA bound and internalized LDL normally. It also recycled normally and exhibited a normal half-life. We conclude that: 1) the serine- and threonine-rich region of the LDL receptor is the site for addition of clustered O-linked carbohydrates; 2) the receptor contains a small number of isolated chains of O-linked carbohydrat...