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

J Biol Chem. 2002 Aug 30;277(35):31567-76. doi: 10.1074/jbc.M202723200. Epub 2002 Jun 20.

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.

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Animals
  • Base Sequence
  • Binding Sites
  • COS Cells
  • Casein Kinase II
  • Chlorocebus aethiops
  • DNA Primers
  • Enzyme Inhibitors / pharmacology
  • G-Protein-Coupled Receptor Kinases
  • Inositol Phosphates / metabolism
  • Ligands
  • Models, Molecular
  • Polymerase Chain Reaction
  • Protein Conformation
  • Protein Kinase C / metabolism
  • Protein-Serine-Threonine Kinases / chemistry*
  • Protein-Serine-Threonine Kinases / metabolism*
  • Receptors, Leukotriene B4 / chemistry*
  • Receptors, Leukotriene B4 / genetics
  • Receptors, Leukotriene B4 / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Staurosporine / pharmacology
  • Tetradecanoylphorbol Acetate / pharmacology
  • Threonine*
  • Transfection

Substances

  • DNA Primers
  • Enzyme Inhibitors
  • Inositol Phosphates
  • Ligands
  • Receptors, Leukotriene B4
  • Recombinant Proteins
  • Threonine
  • Casein Kinase II
  • Protein-Serine-Threonine Kinases
  • Protein Kinase C
  • G-Protein-Coupled Receptor Kinases
  • G-protein-coupled receptor kinase 6
  • Staurosporine
  • Tetradecanoylphorbol Acetate