The LTB₄-BLT1 axis regulates the polarized trafficking of chemoattractant GPCRs during neutrophil chemotaxis

Neutrophils sense and respond to diverse chemotactic cues through G-protein-coupled receptors (GPCRs). However, the precise trafficking dynamics of chemoattractant GPCRs during neutrophil activation and chemotaxis remain unclear. Here, by using small-molecule inhibitors and CRISPR-based knockouts, we establish that two primary chemoattractant GPCRs - formyl peptide receptor 1 (FPR1) and complement component 5a (C5a) receptor 1 (C5aR1) - internalize in a CDC42-actin-dependent manner. Through live-cell imaging, we demonstrate that, upon stimulation, FPR1 rapidly clusters and re-distributes along the plasma membrane to the trailing edge, where it internalizes and is directionally trafficked towards the front of migrating primary human neutrophils. In contrast to FPR1 and C5aR1, the leukotriene B₄ (LTB₄) receptor (BLT1, also known as LTB4R), which relays LTB₄ signals in response to primary chemoattractants during neutrophil chemotaxis, fails to internalize upon physiological stimulation with LTB₄, N-formyl-Met-Leu-Phe (fMLF) or C5a. Importantly, we report that blocking the LTB₄-BLT1 axis or downstream myosin activation enhances the internalization of FPR1 and C5aR1, thus reducing downstream signaling and impairing chemotaxis to primary chemoattractants. The polarized trafficking of chemoattractant GPCRs and its regulation by the BLT1-mediated myosin activation therefore drives persistent chemotactic signaling in neutrophils.This article has an associated First Person interview with the first author of the paper.