Initiation of mammalian O-mannosylation in vivo is independent of a consensus sequence and controlled by peptide regions within and upstream of the alpha-dystroglycan mucin domain.
To reveal insight into the initiation of mammalian O-mannosylation in vivo, recombinant glycosylation probes containing sections of human alpha-dystroglycan (hDG) were expressed in epithelial cell lines. We demonstrate that O-mannosylation within the mucin domain of hDG occurs preferentially at Thr/Ser residues that are flanked by basic amino acids. Protein O-mannosylation is independent of a consensus sequence, but strictly dependent on a peptide region located upstream of the mucin domain. This peptide region cannot be replaced by other N-terminal peptides, however, it is not sufficient to induce O-mannosylation on a structurally distinct mucin domain in hybrid constructs. The presented in vivo evidence for a more complex regulation of mammalian O-mannosylation contrasts with a recent in vitro study of O-mannosylation in human alpha-dystroglycan peptides indicating the existence of an 18-meric consensus sequence. We demonstrate in vivo that the entire region p377-417 is necessary and sufficient for O-mannosylation initiation of hDG, but not of MUC1 tandem repeats. The feature of a doubly controlled initiation process distinguishes mammalian O-mannosylation from other types of O-glycosylation, which are largely controlled by structural properties of the substrate positions and their local peptide environment.
Breloy
Isabelle
I
Institute of Biochemistry II, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Köln, Germany.
Schwientek
Tilo
T
Gries
Barbara
B
Razawi
Hanieh
H
Macht
Marcus
M
Albers
Christian
C
Hanisch
Franz-Georg
FG
D000595:Amino Acid Sequence / Q000502:physiology; D002460:Cell Line; D049030:Dystroglycans / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D008358:Mannose / Q000235:genetics / Q000378:metabolism*; D018396:Mucin-1 / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D046188:Protein Modification, Translational / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000502:physiology
C060192:MUC1 protein, human; D018396:Mucin-1; D010455:Peptides; D049030:Dystroglycans; D008358:Mannose