Functional modulation of vascular adhesion protein-1 by a novel splice variant.
Vascular Adhesion Protein-1 (VAP-1) is an endothelial adhesion molecule belonging to the primary amine oxidases. Upon inflammation it takes part in the leukocyte extravasation cascade facilitating transmigration of leukocytes into the inflamed tissue. Screening of a human lung cDNA library revealed the presence of an alternatively spliced shorter transcript of VAP-1, VAP-1Δ3. Here, we have studied the functional and structural characteristics of VAP-1Δ3, and show that the mRNA for this splice variant is expressed in most human tissues studied. In comparison to the parent molecule this carboxy-terminally truncated isoform lacks several of the amino acids important in the formation of the enzymatic groove of VAP-1. In addition, the conserved His684, which takes part in coordinating the active site copper, is missing from VAP-1Δ3. Assays using the prototypic amine substrates methylamine and benzylamine demonstrated that VAP-1Δ3 is indeed devoid of the semicarbazide-sensitive amine oxidase (SSAO) activity characteristic to VAP-1. When VAP-1Δ3-cDNA is transfected into cells stably expressing VAP-1, the surface expression of the full-length molecule is reduced. Furthermore, the SSAO activity of the co-transfectants is diminished in comparison to transfectants expressing only VAP-1. The observed down-regulation of both the expression and enzymatic activity of VAP-1 may result from a dominant-negative effect caused by heterodimerization between VAP-1 and VAP-1Δ3, which was detected in co-immunoprecipitation studies. This alternatively spliced transcript adds thus to the repertoire of potential regulatory mechanisms through which the cell-surface expression and enzymatic activity of VAP-1 can be modulated.
MediCity Research Laboratory, University of Turku, Turku, Finland.
Sam
S
Kaitaniemi
Kirsi
K
Grön
Heli
H
Elovaara
Marko
M
Salmi
Sirpa
S
Jalkanen
Kati
K
Elima
D000328:Adult; D017398:Alternative Splicing; D006631:Amine Oxidase (Copper-Containing) / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001596:Benzylamines / Q000378:metabolism; D016466:CHO Cells; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D005333:Fetus / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D057809:HEK293 Cells; D006801:Humans; D008744:Methylamines / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013379:Substrate Specificity / Q000235:genetics
D001596:Benzylamines; D015815:Cell Adhesion Molecules; D008744:Methylamines; D020033:Protein Isoforms; C030796:benzylamine; C027451:methylamine; C076668:AOC3 protein, human; D006631:Amine Oxidase (Copper-Containing)