title: Evaluation of the specific structures of IgA1 hinge glycopeptide in 30 IgA nephropathy patients by mass spectrometry.
abstract: BACKGROUND
  Although many reports have described the abnormal structures of O-glycan in the IgA1 hinge region in IgA nephropathy (IgAN), the specific glycopeptide that can be used as a diagnostic biomarker for IgAN has not yet been identified. To pursue this diagnostic approach, we used mass spectrometric analysis to search for specific structures in IgA1 hinge glycopeptides in 30 IgAN patients contrasted with 30 healthy controls.
  
  
  METHODS
  IgA1 hinge glycopeptides were individually purified from the sera of 30 biopsy-proven IgAN patients and 30 healthy controls. The structure of each glycopeptide was analyzed by ion trap mass spectrometry. Sugar conformations in each glycopeptide were estimated by collision-induced dissociation tandem mass spectrometry. Furthermore, to search for specific O-glycans in IgAN patients with a statistical significance, the identified hinge glycopeptides were analyzed by Fisher exact test.
  
  
  RESULTS
  A total of 57 hinge glycopeptides were identified from each of the 2 sample groups. Among the structures of the hinge glycopeptides identified, statistical significance was found for 6 glycopeptides (O-glycan compositions were 33-mer hinge core peptides + xGalNAc + yGal + zNeu5Ac; x:y:z = 5:3:3, 5:3:0, 5:2:1, 4:2:2, 3:1:1, 3:1:0) by Fisher exact test (p<0.05). In these 6 O-glycan compositions, 3 compositions (x:y:z = 4:2:2, 3:1:1, 3:1:0) were only observed in IgAN patients and were absent in the 30 controls.
  
  
  CONCLUSIONS
  Statistically specific O-glycans were identified in 30 IgAN patients compared with 30 controls. These results open the possibility for preparation of lectin and/or antibodies binding to specific glycopeptides in IgAN.
authors.affiliation: Department of Nephrology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan. hirokoo@or2.fiberbit.net
authors.forename: Hiroko
authors.initials: H
authors.lastname: Odani
authors.forename: Koichiro
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Sachiko
authors.initials: S
authors.lastname: Iwayama
authors.forename: Hitoo
authors.initials: H
authors.lastname: Iwase
authors.forename: Akihiko
authors.initials: A
authors.lastname: Takasaki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Takahashi
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Fujita
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sugiyama
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Hiki
mesh_terms: D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D003404:Creatinine / Q000097:blood; D005260:Female; D005922:Glomerulonephritis, IGA / Q000097:blood*; D006020:Glycopeptides / Q000097:blood*; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry; D055815:Young Adult
chemical_list: D015415:Biomarkers; D006020:Glycopeptides; D007070:Immunoglobulin A; D003404:Creatinine