O-glycosylation modulates proprotein convertase activation of angiopoietin-like protein 3: possible role of polypeptide GalNAc-transferase-2 in regulation of concentrations of plasma lipids.
The angiopoietin-like protein 3 (ANGPTL3) is an important inhibitor of the endothelial and lipoprotein lipases and a promising drug target. ANGPTL3 undergoes proprotein convertase processing (RAPR(224)↓TT) for activation, and the processing site contains two potential GalNAc O-glycosylation sites immediately C-terminal (TT(226)). We developed an in vivo model system in CHO ldlD cells that was used to show that O-glycosylation in the processing site blocked processing of ANGPTL3. Genome-wide SNP association studies have identified the polypeptide GalNAc-transferase gene, GALNT2, as a candidate gene for low HDL and high triglyceride blood levels. We hypothesized that the GalNAc-T2 transferase performed critical O-glycosylation of proteins involved in lipid metabolism. Screening of a panel of proteins known to affect lipid metabolism for potential sites glycosylated by GalNAc-T2 led to identification of Thr(226) adjacent to the proprotein convertase processing site in ANGPTL3. We demonstrated that GalNAc-T2 glycosylation of Thr(226) in a peptide with the RAPR(224)↓TT processing site blocks in vitro furin cleavage. The study demonstrates that ANGPTL3 activation is modulated by O-glycosylation and that this step is probably controlled by GalNAc-T2.
Schjoldager
Katrine T-B G
KT
Center for Glycomics, Department of Cellular and Molecular Medicine and School of Dentistry, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark.
Vester-Christensen
Malene B
MB
Bennett
Eric Paul
EP
Levery
Steven B
SB
Schwientek
Tilo
T
Yin
Wu
W
Blixt
Ola
O
Clausen
Henrik
H
D000091303:Angiopoietin-Like Protein 3; D000075802:Angiopoietin-like Proteins; D042682:Angiopoietins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D045683:Furin / Q000378:metabolism; D006020:Glycopeptides / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D008055:Lipids / Q000097:blood*; D017350:N-Acetylgalactosaminyltransferases / Q000378:metabolism*; D043484:Proprotein Convertases / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D000097763:Polypeptide N-acetylgalactosaminyltransferase
D000091303:Angiopoietin-Like Protein 3; D000075802:Angiopoietin-like Proteins; D042682:Angiopoietins; D045683:Furin; D006020:Glycopeptides; D008055:Lipids; D017350:N-Acetylgalactosaminyltransferases; D043484:Proprotein Convertases; D000097763:Polypeptide N-acetylgalactosaminyltransferase; C479896:ANGPTL3 protein, human