Glycobiology Advance Access originally published online on April 3, 2006
Glycobiology 2006 16(7):623-634; doi:10.1093/glycob/cwj110
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N-Glycosylation of the MUC1 mucin in epithelial cells and secretions
3 Paediatric Molecular Genetics, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK; 4 Division of Molecular Biosciences, Imperial College London, South Kensington, London SW7 2AZ, UK; 5 Center of Biochemistry, Medical Faculty and Center for Molecular Medicine Cologne, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Köln, Germany; and 6 M-SCAN Mass Spectrometry Research and Training Centre, Silwood Park, Ascot SL5 7PZ, UK
1 To whom correspondence should be addressed; e-mails: ann-harris{at}northwestern.edu; akd10{at}uni-koeln.de
2 Present address: Human Molecular Genetics Program, Children’s Memorial Research Center, Northwestern University, 2300 Children’s Plaza, Box 211, Chicago, IL 60614-3394
Received on December 14, 2005; revised on February 28, 2006; accepted on March 26, 2006
The MUC1 mucin is an important tumor-associated antigen that shows extensive glycosylation in vivo. The O-glycosylation of this molecule, which has been well characterized in many cell types and tissues, is important in conferring the unusual biochemical and biophysical properties on a mucin. N-Glycosylation is crucial to the folding, sorting, membrane trafficking, and secretion of many proteins. Here, we evaluated the N-glycosylation of MUC1 derived from two sources: endogenous MUC1 isolated from human milk and a recombinant epitope-tagged MUC1F overexpressed in Caco2 colon carcinoma cells. N-Glycans on purified MUC1F/MUC1 were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), gas chromatography-mass spectrometry (GC-MS), and CAD-ESI-MS/MS. The spectra indicate that MUC1F N-glycans have compositions consistent with high-mannose structures (Hex5-9HexNAc2) and complex/hybrid-type glycans (NeuAc0-3Fuc0-3Hex3-8HexNAc3-7). Many of the N-glycan structures are identical on MUC1F and native MUC1; however, a marked difference is seen between the N-glycans on membrane-bound and secreted forms of the native molecule.
Key words: epithelia / MUC1 / mucin / N-glycosylation