title: Interleukin-4 alters early phagosome phenotype by modulating class I PI3K dependent lipid remodeling and protein recruitment.
abstract: Phagocytosis is a complex process that involves membranelipid remodeling and the attraction and retention of key effector proteins. Phagosome phenotype depends on the type of receptor engaged and can be influenced by extracellular signals. Interleukin 4 (IL-4) is a cytokine that induces the alternative activation of macrophages (MΦs) upon prolonged exposure, triggering a different cell phenotype that has an altered phagocytic capacity. In contrast, the direct effects of IL-4 during phagocytosis remain unknown. Here, we investigate the impact of short-term IL-4 exposure (1 hour) during phagocytosis of IgG-opsonized yeast particles by MΦs. By time-lapse confocal microscopy of GFP-tagged lipid-sensing probes, we show that IL-4 increases the negative charge of the phagosomal membrane by prolonging the presence of the negatively charged second messenger PI(3,4,5)P3. Biochemical assays reveal an enhanced PI3K/Akt activity upon phagocytosis in the presence of IL-4. Blocking the specific class I PI3K after the onset of phagocytosis completely abrogates the IL-4-induced changes in lipid remodeling and concomitant membrane charge. Finally, we show that IL-4 direct signaling leads to a significantly prolonged retention profile of the signaling molecules Rac1 and Rab5 to the phagosomal membrane in a PI3K-dependent manner. This protracted early phagosome phenotype suggests an altered maturation, which is supported by the delayed phagosome acidification measured in the presence of IL-4. Our findings reveal that molecular differences in IL-4 levels, in the extracellular microenvironment, influence the coordination of lipid remodeling and protein recruitment, which determine phagosome phenotype and, eventually, fate. Endosomal and phagosomal membranes provide topological constraints to signaling molecules. Therefore, changes in the phagosome phenotype modulated by extracellular factors may represent an additional mechanism that regulates the outcome of phagocytosis and could have significant impact on the net biochemical output of a cell.
authors.affiliation: Department of Tumor Immunology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Sandra
authors.initials: S
authors.lastname: de Keijzer
authors.forename: Marjolein B M
authors.initials: MB
authors.lastname: Meddens
authors.forename: Dilek
authors.initials: D
authors.lastname: Kilic
authors.forename: Ben
authors.initials: B
authors.lastname: Joosten
authors.forename: Inge
authors.initials: I
authors.lastname: Reinieren-Beeren
authors.forename: Diane S
authors.initials: DS
authors.lastname: Lidke
authors.forename: Alessandra
authors.initials: A
authors.lastname: Cambi
mesh_terms: D000818:Animals; D002460:Cell Line; D006863:Hydrogen-Ion Concentration; D007074:Immunoglobulin G / Q000276:immunology; D015847:Interleukin-4 / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D010587:Phagocytosis / Q000187:drug effects; D010588:Phagosomes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D015054:Zymosan / Q000276:immunology
chemical_list: D007074:Immunoglobulin G; D008563:Membrane Lipids; D010716:Phosphatidylinositols; D015847:Interleukin-4; D015054:Zymosan; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt