Neurons and glia modify receptor protein-tyrosine phosphatase ζ (RPTPζ)/phosphacan with cell-specific O-mannosyl glycans in the developing brain.
Protein O-mannosylation is a glycan modification that is required for normal nervous system development and function. Mutations in genes involved in protein O-mannosyl glycosylation give rise to a group of neurodevelopmental disorders known as congenital muscular dystrophies (CMDs) with associated CNS abnormalities. Our previous work demonstrated that receptor protein-tyrosine phosphatase ζ (RPTPζ)/phosphacan is hypoglycosylated in a mouse model of one of these CMDs, known as muscle-eye-brain disease, a disorder that is caused by loss of an enzyme (protein O-mannose β-1,2-N-acetylglucosaminyltransferase 1) that modifies O-mannosyl glycans. In addition, monoclonal antibodies Cat-315 and 3F8 were demonstrated to detect O-mannosyl glycan modifications on RPTPζ/phosphacan. Here, we show that O-mannosyl glycan epitopes recognized by these antibodies define biochemically distinct glycoforms of RPTPζ/phosphacan and that these glycoforms differentially decorate the surface of distinct populations of neural cells. To provide a further structural basis for immunochemically based glycoform differences, we characterized the O-linked glycan heterogeneity of RPTPζ/phosphacan in the early postnatal mouse brain by multidimensional mass spectrometry. Structural characterization of the O-linked glycans released from purified RPTPζ/phosphacan demonstrated that this protein is a significant substrate for protein O-mannosylation and led to the identification of several novel O-mannose-linked glycan structures, including sulfo-N-acetyllactosamine containing modifications. Taken together, our results suggest that specific glycan modifications may tailor the function of this protein to the unique needs of specific cells. Furthermore, their absence in CMDs suggests that hypoglycosylation of RPTPζ/phosphacan may have different functional consequences in neurons and glia.
From the Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, New York 13210 and.
Chrissa A
CA
Dwyer
the Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602.
Toshihiko
T
Katoh
the Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602.
Michael
M
Tiemeyer
From the Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, New York 13210 and matthewr@upstate.edu.
Russell T
RT
Matthews
D000606:Amino Sugars / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D000911:Antibodies, Monoclonal / Q000737:chemistry; D001921:Brain / Q000201:enzymology* / Q000254:growth & development / Q000473:pathology; D002240:Carbohydrate Sequence; D004195:Disease Models, Animal; D018507:Gene Expression Regulation, Developmental; D006031:Glycosylation; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008358:Mannose / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000172:deficiency / Q000235:genetics*; D009457:Neuroglia / Q000201:enzymology* / Q000473:pathology; D009474:Neurons / Q000201:enzymology* / Q000473:pathology; D009928:Organ Specificity; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D058494:Walker-Warburg Syndrome / Q000201:enzymology / Q000235:genetics* / Q000473:pathology
D000606:Amino Sugars; D000911:Antibodies, Monoclonal; D007527:Isoenzymes; C000458:N-acetyllactosamine; D017351:N-Acetylglucosaminyltransferases; C443106:protein O-mannose beta-1,2-N-acetylglucosaminyltransferase; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5; D008358:Mannose
Brain; Cat-315; Extracellular Matrix; Glycosylation; Muscular Dystrophy; O-Glycan; O-Mannose; POMGnT1; Proteoglycan; RPTPzeta/Phosphacan