Functional modulation of vascular adhesion protein-1 by a novel splice variant.
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Kaitaniemi S, Gron K, Elovaara H, Salmi M, Jalkanen S, Elima K
Functional modulation of vascular adhesion protein-1 by a novel splice variant.
PLoS One. 2013;8(1):e54151. doi: 10.1371/journal.pone.0054151. Epub 2013 Jan 18.
- PubMed ID
- 23349812 [ View in PubMed]
- Abstract
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-1Delta3. Here, we have studied the functional and structural characteristics of VAP-1Delta3, 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-1Delta3. Assays using the prototypic amine substrates methylamine and benzylamine demonstrated that VAP-1Delta3 is indeed devoid of the semicarbazide-sensitive amine oxidase (SSAO) activity characteristic to VAP-1. When VAP-1Delta3-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-1Delta3, 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.