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

ABSTRACT: 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.

SUBMITTER: Subramanian BC

PROVIDER: S-EPMC6176921 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Low-dose alcohol possesses multiple bioactivities. Accordingly, we investigated the protective effect and related molecular mechanism of low-dose alcohol against acute stress- (AS-) induced renal injury. Herein, exhaustive swimming for 15 min combined with restraint stress for 3 h was performed to establish a rat acute stress model, which was verified by an open field test. Evaluation of renal function (blood creatinine and urea nitrogen), urine test (urine leukocyte esterase and urine occult blood), renal histopathology, oxidative stress, inflammation, and apoptosis was performed. The key indicators of the cytochrome P450 (CYP) 4A1/20-hydroxystilbenetetraenoic acid (20-HETE) pathway, cyclooxygenase (COX)/prostaglandin E2 (PGE2) pathway, and leukotriene B4 (LTB4)/leukotriene B4 receptor 1 (BLT1) pathway were measured by real-time PCR and ELISA. We found that low-dose alcohol (0.05 g/kg, i.p.) ameliorated AS-induced renal dysfunction and histological damage. Low-dose alcohol also attenuated AS-induced oxidative stress and inflammation, presenting as reduced malondialdehyde and hydrogen peroxide formation, increased superoxide dismutase and glutathione activity, and decreased myeloperoxidase, interleukin-6, interleukin-1β, and monocyte chemoattractant protein-1 levels (P < 0.05). Moreover, low-dose alcohol alleviated AS-induced apoptosis by downregulating Bax and cleaved caspase 3 protein expression and reduced numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick-end label-positive cells (P < 0.01). Correlation analysis indicated that 20-HETE was strongly correlated with oxidative stress, while LTB4 was strongly correlated with inflammation. Low-dose alcohol inhibited AS-induced increases in CYP4A1, CYP4A2, CYP4A3, CYP4A8, and BLT1 mRNA levels and LTB4 and 20-HETE content (P < 0.01). Interestingly, low-dose alcohol had no effect on COX1 or COX2 mRNA expression or the concentration of PGE2. Furthermore, low-dose alcohol reduced calcium-independent phospholipase A2 mRNA expression, but did not affect secreted phospholipase A2 or cytosolic phospholipase A2 mRNA expression. Together, these results indicate that low-dose alcohol ameliorated AS-induced renal injury by inhibiting CYP4A/20-HETE and LTB4/BLT1 pathways, but not the COX/PGE2 pathway.

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

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

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