Helix 8 of leukotriene B4 receptor 1 inhibits ligand-induced internalization.
Recent crystallographic studies revealed that G-protein-coupled receptors (GPCRs) possess a putative cytoplasmic helical domain, termed helix 8, at the proximal region of the C-terminal tail. However, the significance of helix 8 in GPCR functions and signaling is not fully understood. Helix 8 mutants of leukotriene B4 receptor type 1 (BLT1) ... exhibit prolonged activation after ligand stimulation, suggesting some regulatory roles of helix 8 in GPCR signaling. Here, we report the inhibitory role of BLT1 helix 8 on ligand-dependent internalization using BLT1 and platelet-activating factor receptor as model GPCRs. Mutating the dileucine motif in helix 8 of BLT1 to alanines (BLT1 LLAA) enhanced LTB4-dependent internalization of BLT1, whereas wild-type (WT) BLT1 exhibited minimal internalization. Mutational studies revealed that phosphorylation of 5 serine/threonine residues between amino acids 308 and 319 of BLT1 was responsible for enhanced ligand-dependent internalization of BLT1 LLAA. BLT1 LLAA showed enhanced basal and ligand-dependent phosphorylation compared to WT BLT1. Taken together, helix 8 of BLT1 inhibits receptor internalization by suppressing the excessive phosphorylation of the C-terminal tail.
Mesh Terms:
Animals, Blotting, Western, CHO Cells, Cricetinae, Endocytosis, Immunoprecipitation, Leukotriene B4, Microscopy, Confocal, Microscopy, Immunoelectron, Phosphorylation, Protein Binding, Protein Structure, Secondary, Receptors, Leukotriene B4, Structure-Activity Relationship
Animals, Blotting, Western, CHO Cells, Cricetinae, Endocytosis, Immunoprecipitation, Leukotriene B4, Microscopy, Confocal, Microscopy, Immunoelectron, Phosphorylation, Protein Binding, Protein Structure, Secondary, Receptors, Leukotriene B4, Structure-Activity Relationship
FASEB J.
Date: Oct. 01, 2012
PubMed ID: 22707565
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