title: Proteomic analysis of polymeric salivary mucins: no evidence for MUC19 in human saliva.
abstract: MUC5B is the predominant polymeric mucin in human saliva [Thornton, Khan, Mehrotra, Howard, Veerman, Packer and Sheehan (1999) Glycobiology 9, 293-302], where it contributes to oral cavity hydration and protection. More recently, the gene for another putative polymeric mucin, MUC19, has been shown to be expressed in human salivary glands [Chen, Zhao, Kalaslavadi, Hamati, Nehrke, Le, Ann and Wu (2004) Am. J. Respir. Cell Mol. Biol. 30, 155-165]. However, to date, the MUC19 mucin has not been isolated from human saliva. Our aim was therefore to purify and characterize the MUC19 glycoprotein from human saliva. Saliva was solubilized in 4 M guanidinium chloride and the high-density mucins were purified by density-gradient centrifugation. The presence of MUC19 was investigated using tandem MS of tryptic peptides derived from this mucin preparation. Using this approach, we found multiple MUC5B-derived tryptic peptides, but were unable to detect any putative MUC19 peptides. These results suggest that MUC19 is not a major component in human saliva. In contrast, using the same experimental approach, we identified Muc19 and Muc5b glycoproteins in horse saliva. Moreover, we also identified Muc19 from pig, cow and rat saliva; the saliva of cow and rat also contained Muc5b; however, due to the lack of pig Muc5b genomic sequence data, we were unable to identify Muc5b in pig saliva. Our results suggest that unlike human saliva, which contains MUC5B, cow, horse and rat saliva are a heterogeneous mixture of Muc5b and Muc19. The functional consequence of these species differences remains to be elucidated.
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The Michael Smith Building, University of Manchester, Manchester M13 9PT, UK.
authors.forename: Karine
authors.initials: K
authors.lastname: Rousseau
authors.forename: Sara
authors.initials: S
authors.lastname: Kirkham
authors.forename: Lindsay
authors.initials: L
authors.lastname: Johnson
authors.forename: Brian
authors.initials: B
authors.lastname: Fitzpatrick
authors.forename: Marj
authors.initials: M
authors.lastname: Howard
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Adams
authors.forename: Duncan F
authors.initials: DF
authors.lastname: Rogers
authors.forename: David
authors.initials: D
authors.lastname: Knight
authors.forename: Peter
authors.initials: P
authors.lastname: Clegg
authors.forename: David J
authors.initials: DJ
authors.lastname: Thornton
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D006736:Horses; D006801:Humans; D008969:Molecular Sequence Data; D055257:Mucin-5B; D009077:Mucins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics / Q000379:methods*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012463:Saliva / Q000378:metabolism*; D012471:Salivary Proteins and Peptides / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013552:Swine; D053719:Tandem Mass Spectrometry
chemical_list: C482349:MUC19 protein, human; C524578:MUC5B protein, human; D055257:Mucin-5B; D009077:Mucins; D012333:RNA, Messenger; D012471:Salivary Proteins and Peptides