title: Characterization of posttranslational modifications of human A33 antigen, a novel palmitoylated surface glycoprotein of human gastrointestinal epithelium.
abstract: Monoclonal antibody (mAb) A33 recognizes a differentiation antigen (A33) expressed in normal human gastrointestinal epithelium and in 95% of human colon cancers. Murine mAb A33 shows specific targeting of colon cancer in humans and a humanized A33 antibody is currently being evaluated in the clinic. The cDNA for the human A33 antigen has recently been cloned, and sequence comparison indicated that the A33 antigen is a novel human cell surface molecule of the immunoglobulin superfamily. Because mAb A33 recognizes a conformational epitope, only a partial characterization of the A33 antigen has been carried out to date. In this report we show that the A33 antigen is (I) N-glycosylated, containing approximately 8 K of N-linked carbohydrate and there is no evidence for O-glycosylation, sialylation or glycophosphatidylinositol, and (ii) S-acylated in vitro, incorporating [3H] palmitic acid linked through a hydroxylamine-sensitive thioester bond. The S-palmitoylation may be involved in regulating the internalization process initiated by binding of mAb A33 to cell surface A33 antigen.
authors.affiliation: Ludwig Institute for Cancer Research, New York Branch at Memorial Sloan-Kettering Cancer Center, New York 10021, USA. ritterg@mskcc.org
authors.forename: G
authors.initials: G
authors.lastname: Ritter
authors.forename: L S
authors.initials: LS
authors.lastname: Cohen
authors.forename: E C
authors.initials: EC
authors.lastname: Nice
authors.forename: B
authors.initials: B
authors.lastname: Catimel
authors.forename: A W
authors.initials: AW
authors.lastname: Burgess
authors.forename: R L
authors.initials: RL
authors.lastname: Moritz
authors.forename: H
authors.initials: H
authors.lastname: Ji
authors.forename: J K
authors.initials: JK
authors.lastname: Heath
authors.forename: S J
authors.initials: SJ
authors.lastname: White
authors.forename: S
authors.initials: S
authors.lastname: Welt
authors.forename: L J
authors.initials: LJ
authors.lastname: Old
authors.forename: R J
authors.initials: RJ
authors.lastname: Simpson
mesh_terms: D000215:Acylation; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm / Q000378:metabolism*; D015153:Blotting, Western; D003110:Colonic Neoplasms / Q000276:immunology; D004064:Digestive System / Q000276:immunology*; D004591:Electrophoresis, Polyacrylamide Gel; D004848:Epithelium / Q000276:immunology; D006031:Glycosylation; D006801:Humans; D007163:Immunosorbent Techniques; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D019308:Palmitic Acid / Q000378:metabolism*; D011499:Protein Processing, Post-Translational
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; C104258:GPA33 protein, human; C504395:Gpa33 protein, mouse; D008562:Membrane Glycoproteins; D019308:Palmitic Acid