A mouse molecular mimic of human vascular adhesion protein-1.
Human vascular adhesion protein-1 (VAP-1) is an endothelial sialoglycoprotein which exists in forms of Mr 90000 and 170000 and mediates lymphocyte binding to vessels under shear. VAP-1 is functionally defined by an inhibitory mouse mAb 1B2. A large-scale immunoaffinity purification of VAP-1 from human tonsil lysates was performed to determine the protein sequence for VAP-1 cDNA cloning. A dominant protein of molecular weight 90000 was obtained which yielded an N-terminal sequence of 20 amino acids which bore no significant identity to any protein sequence in the data banks. A mouse mAb (5B11) against a synthetic peptide from this sequence was raised and found to stain tissues in an identical manner to mAb 1B2, to inhibit lymphocyte adhesion to endothelial cells and to recognize VAP-1. Later, the N-terminal sequence obtained from the 1B2 immunoprecipitations was found to be identical to a mouse cyclophilin C associated protein (mCyCAP) subsequently published by others. We show here by several criteria at the protein and DNA level that VAP-1 is distinct from mCyCAP. Moreover, we elucidate the mechanism which results in binding of mCyCAP to mAb 1B2 during antibody synthesis in hybridoma cells and the sequelae of co-precipitation of mCyCAP during the immunoaffinity chromatography. Binding of mCyCAP to a mouse mAb has not been described before and suggests a new function for this molecule in immunoglobulin synthesis and/or secretion. Moreover, these data indicate that the N-terminal peptide of mCyCAP is a molecular mimic of a functionally important epitope of VAP-1.
Salmi
M
M
National Public Health Institute and MediCity Research Laboratory, University of Turku, Finland.
Smith
D J
DJ
Bono
P
P
Leu
T
T
Hellman
J
J
Matikainen
M T
MT
Jalkanen
S
S
D006631:Amine Oxidase (Copper-Containing); D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000918:Antibody Specificity; D015815:Cell Adhesion Molecules / Q000276:immunology*; D006801:Humans; D016056:Immunodominant Epitopes / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D012795:Sialoglycoproteins / Q000276:immunology*
D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D016056:Immunodominant Epitopes; D012795:Sialoglycoproteins; C076668:AOC3 protein, human; D006631:Amine Oxidase (Copper-Containing)