title: Down-regulation of monocytic VLA-4 leads to a decreased adhesion to VCAM-1.
abstract: The alpha 4 beta 1 integrin VLA-4 is expressed on practically all leukocytes, except on mature granulocytes. Here we show that in vitro treatment of monocytic cells with phorbol-12-myristate-13-acetate (PMA) leads to a selective decrease in the VLA-4 alpha-chain expression, both at the RNA and protein level. Meanwhile the expression of beta 1 and that of alpha 5, another alpha-chain associating with beta 1, was seen to increase. The decrease of alpha 4 expression was restricted to monocytic cells, and was not observed on other VLA-4-positive cells tested (MOLT-4 T cells and HOS sarcoma cells). The down-regulation of the VLA-4 alpha-chain was followed by a decreased binding capacity of the cells to recombinant VCAM-1. This data indicates that while previous findings show that the integrin-dependent adhesion may rapidly be regulated by altering the avidity of the interacting molecules, their quantitative modulation also has a clear impact on adhesion.
authors.affiliation: Department of Bacteriology and Immunology, University of Helsinki, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Tiisala
authors.forename: M
authors.initials: M
authors.lastname: Hakkarainen
authors.forename: M L
authors.initials: ML
authors.lastname: Majuri
authors.forename: P S
authors.initials: PS
authors.lastname: Mattila
authors.forename: P
authors.initials: P
authors.lastname: Mattila
authors.forename: R
authors.initials: R
authors.lastname: Renkonen
mesh_terms: D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D015536:Down-Regulation; D006801:Humans; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016029:Receptors, Very Late Antigen / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D019010:Vascular Cell Adhesion Molecule-1
chemical_list: D015815:Cell Adhesion Molecules; D016029:Receptors, Very Late Antigen; D019010:Vascular Cell Adhesion Molecule-1; D013755:Tetradecanoylphorbol Acetate