Stepwise phosphorylation of leukotriene B4 receptor 1 defines cellular responses to leukotriene B4.

Nakanishi,Y., Tan,M., Ichiki,T., Inoue,A. Yoshihara,J., Maekawa,N., Takenoshita.I., Yanagida,K., Yamahira,S., Yamaguchi,S., Aoki,J. Nagamune,T., Yokomizo,T., Shimizu,T., and Nakamura,M.

Leukotriene B4 (LTB4) receptor type 1 (BLT1) is abundantly expressed in phagocytic and immune cells and plays crucial roles in various inflammatory diseases. Although many reports demonstrate that BLT1 is phosphorylated at several Ser and Thr residues upon stimulation with LTB4, the precise functions of this modification remain elusive. Here, we determined two types of BLT1 phosphorylation, basal and ligand-induced, in the C-terminus of human BLT1 using the Phos-tag SDS-PAGE technique. Ligand-induced phosphorylation occurred at different LTB4 concentrations, and this modification facilitated basal phosphorylation. Because neutrophils migrate through the LTB4 gradient toward inflammatory sites, the degree of phosphorylation could be enhanced in parallel with an increase in LTB4. At high concentrations of LTB4, deficiencies in these two types of phosphorylation impaired chemotaxis and b-hexosaminidase release in Chinese hamster ovary (CHO-K1) and rat basophilic leukemia (RBL-2H3) cells, respectively. These results suggest that an LTB4 gradient around inflammatory regions boosts BLT1 phosphorylation in a stepwise manner to facilitate the precise migration of phagocytic and immune cells, and the initiation of local responses, including degranulation. 

Science Signaling

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