Phospholipid flippases attenuate LPS-induced TLR4 signaling by mediating endocytic retrieval of Toll-like receptor 4

Abstract

P4-ATPases are lipid flippases that catalyze the transport of phospholipids to create membrane phospholipid asymmetry and to initiate the biogenesis of transport vesicles. Here we show, for the first time, that lipid flippases are essential to dampen the inflammatory response and to mediate the endotoxin-induced endocytic retrieval of Toll-like receptor 4 (TLR4) in human macrophages. Depletion of CDC50A, the β-subunit that is crucial for the activity of multiple P4-ATPases, resulted in endotoxin-induced hypersecretion of proinflammatory cytokines, enhanced MAP kinase signaling and constitutive NF-κB activation. In addition, CDC50A-depleted THP-1 macrophages displayed reduced tolerance to endotoxin. Moreover, endotoxin-induced internalization of TLR4 was strongly reduced and coincided with impaired endosomal MyD88-independent signaling. The phenotype of CDC50A-depleted cells was also induced by separate knockdown of two P4-ATPases, namely ATP8B1 and ATP11A. We conclude that lipid flippases are novel elements of the innate immune response that are essential to attenuate the inflammatory response, possibly by mediating endotoxin-induced internalization of TLR4.Electronic supplementary materialThe online version of this article (doi:10.1007/s00018-016-2360-5) contains supplementary material, which is available to authorized users.

C. quinoa and S. hispanica L. Seeds Provide Immunonutritional Agonists to Selectively Polarize Macrophages

“…Said interaction, seemed to depend on TLR4 since pretreatment of cell cultures with C34 blunted PPIs-induced changes in the activity of these compartments. Endocytic retrieval of TLR4 is mediated by intracellular pathways (i.e., MCP-1 and IL-8) that are activated by phospholipids (PLs) [21]. To elucidate the potential of PPIs to induce changes on PLs content in HB8902 cells, the total PL content in cells cultures challenged to PPIs was quantified ( Figure 3D).…”

“…The latter, favored a rapid production of energetic and reducing equivalents as well as increased levels of Krebs cycle intermediates, in concordance with the variations in OCR (pmol min −1 ) ( Figure 3A), supporting an increased non-mitochondrial respiration. The variation of key mediators in glycolysis-P04406, P00558, P18669, P14618, O75874 and P40925-indicate an adaptation towards low utilization of carbohydrates together with the accumulation of tricarboxylic acid cycle intermediates (i.e., citrate, malate) favoring a classical and innate (i.e., TLRs)-induced M1 phenotype [21,26]. Otherwise, macrophage activation through the alternative pathway engaged modest metabolic events.…”

Characterization of plasma proteins in children of different Mycobacterium tuberculosis infection status using label-free quantitative proteomics

“…The selected proteins have previously been reported to be associated with immunity and other infectious diseases [24][25][26][27][28][29][30][31][32][33][34][35]. XRCC4 is an important component of non-homologous end-joining [24].…”

“…A previous study demonstrated that lipid flippases are essential to mediate the endotoxin-induced endocytosis of Toll-like receptor 4 in human macrophages. Macrophages play a primary role in TB transmission [35]. MTB usually replicates within macrophages and spreads to pulmonary lymph nodes.…”

Epigenome-wide association study for 28-day survival of acute respiratory distress syndrome

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