12-O-Tetradecanoylphorbol 13-Acetate Stimulates Human T-Lymphocyte Adherence to the Fibronectin RGD Domain and the Laminin IKVAV Domain

In order for T cells to exit the circulatory system, these cells must attach to extracellular matrix proteins. We have used 12-O-tetradecanoylphorbol 13-acetate (TPA) to study the ability of human T cells to adhere to fibronectin or laminin or to specific domains on these extracellular matrix proteins. Both primary human T-lymphocytes and a T-cell line (H-9) adhered and spread well on solid-phase fibronectin and laminin in the presence of TPA, with maximum activity at 3 hr of treatment. Furthermore, attachment of both cell populations to fibronectin was inhibited using a soluble RGD-containing synthetic peptide or by pretreating the fibronectin with antibodies that block the RGD domain. A synthetic peptide from the CSI alternatively spliced region of fibronectin did not inhibit attachment to fibronectin. The H-9 cells also attached to the laminin A chain IKVAV-containing synthetic peptide, but not to the laminin-derived YIGSR- or RGD-containing sequences. Immunoprecipitation of 32 P-labeled H-9 cells with antibodies to the β1 integrin subunit demonstrated phosphorylation of an α integrin subunit after treatment with TPA. These data demonstrate that TPA activates T-cell adherence to laminin and to fibronectin via specific sites on each protein and that this adhesion may be associated with integrin phosphorylation.