Initiation of the decorin glycosaminoglycan chain in the endoplasmic reticulum-Golgi intermediate compartment.
We have transiently expressed decorin with a C-terminal KDEL endoplasmic reticulum retention signal peptide in COS-7 cells to study initiation of galactosaminoglycan synthesis in the endoplasmic reticulum-Golgi intermediate compartment. All decorin-KDEL molecules were substituted with N-linked oligosaccharides sensitive to endoglycosidase H, indicating that the core protein was located proximal to the medial-Golgi. O-Linked glycosylation was only initiated in a minor fraction of the molecules. The O-linked saccharides were characterized by gel filtration after stepwise degradations using chondroitin ABC/AC-I lyases, beta1-3-glycuronidase, beta-galactosidase, and alkaline phosphatase. The major O-linked saccharide was the linkage region pentasaccharide GalNAcbeta1-4GlcUAbeta1-3Galbeta1-3Galbeta1-4Xyl-2-phosphate, demonstrating initiation of chondroitin synthesis in the endoplasmic reticulum-Golgi intermediate compartment. In the presence of brefeldin A, partial elongation of a chondroitin chain took place, indicating retrieval of polymerases but not of sulfotransferases.
Jönsson
Mats
M
Department of Cell and Molecular Biology, Lund University, BMC C13, SE-221 84, Lund, Sweden.
Eklund
Erik
E
Fransson
Lars-Ake
LA
Oldberg
Ake
A
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002807:Chondroitin / Q000737:chemistry; D019765:Chondroitin ABC Lyase / Q000378:metabolism; D002845:Chromatography; D058575:Decorin; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D016326:Extracellular Matrix Proteins; D005822:Genetic Vectors; D005966:Glucuronidase / Q000378:metabolism; D006025:Glycosaminoglycans / Q000737:chemistry*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism*; D008024:Ligands; D009844:Oligosaccharides / Q000737:chemistry; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011509:Proteoglycans / Q000737:chemistry*; D051381:Rats; D001616:beta-Galactosidase / Q000378:metabolism
D058575:Decorin; D016326:Extracellular Matrix Proteins; D006025:Glycosaminoglycans; D008024:Ligands; D009844:Oligosaccharides; D010710:Phosphates; D011509:Proteoglycans; D002807:Chondroitin; D000469:Alkaline Phosphatase; D001616:beta-Galactosidase; D005966:Glucuronidase; D019765:Chondroitin ABC Lyase