title: Threonine 308 within a putative casein kinase 2 site of the cytoplasmic tail of leukotriene B(4) receptor (BLT1) is crucial for ligand-induced, G-protein-coupled receptor-specific kinase 6-mediated desensitization.
abstract: Desensitization of G-protein-coupled receptors may involve phosphorylation of serine and threonine residues. The leukotriene B(4) (LTB(4)) receptor (BLT1) contains 14 intracellular serines and threonines, 8 of which are part of consensus target sequences for protein kinase C (PKC) or casein kinase 2. In this study, we investigated the importance of PKC and GPCR-specific kinase (GRK) phosphorylation in BLT1 desensitization. Pretreatment of BLT1-transfected COS-7 cells with PKC activators caused a decrease of LTB(4)-induced inositol phosphate (IP) accumulation. This reduction was prevented with the PKC inhibitor, staurosporine, and not observed in cells expressing a BLT1 deletion mutant (G291stop) lacking the cytoplasmic tail. Moreover LTB(4)-induced IP accumulation was significantly inhibited by overexpression of GRK2, GRK5, and especially GRK6, in cells expressing wild type BLT1 but not in those expressing G291stop. GRK6-mediated desensitization correlated with increased phosphorylation of BLT1. The G319stop truncated BLT1 mutant displayed functional characteristics comparable with wild type BLT1 in terms of desensitization by GRK6, but not by PKC. Substitution of Thr(308) within a putative casein kinase 2 site to proline or alanine in the full-length BLT1 receptor prevented most of GRK6-mediated inhibition of LTB(4)-induced IP production but only partially affected LTB(4)-induced BLT1 phosphorylation. Our findings thus suggest that Thr(308) is a major residue involved in GRK6-mediated desensitization of BLT1 signaling.
authors.affiliation: Immunology Division, Department of Pediatrics, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.
authors.forename: Remi
authors.initials: R
authors.lastname: Gaudreau
authors.forename: Christian
authors.initials: C
authors.lastname: Le Gouill
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Venne
authors.forename: Jana
authors.initials: J
authors.lastname: Stankova
authors.forename: Marek
authors.initials: M
authors.lastname: Rola-Pleszczynski
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D019556:COS Cells; D047390:Casein Kinase II; D002522:Chlorocebus aethiops; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000494:pharmacology; D054768:G-Protein-Coupled Receptor Kinases; D007295:Inositol Phosphates / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D018102:Receptors, Leukotriene B4 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013912:Threonine; D014162:Transfection
chemical_list: D017931:DNA Primers; D004791:Enzyme Inhibitors; D007295:Inositol Phosphates; D008024:Ligands; D018102:Receptors, Leukotriene B4; D011994:Recombinant Proteins; D013912:Threonine; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D054768:G-Protein-Coupled Receptor Kinases; C089176:G-protein-coupled receptor kinase 6; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate