Membrane lipid microdomains differentially regulate intracellular signaling events in human neutrophils.
The integrity of lipid microdomains is disrupted after cell treatment with cholesterol-depleting reagents, such as methyl-beta-cyclodextrin (MCD). We investigated the roles of lipid microdomains in the regulation of intracellular signaling events and functional responses in isolated human neutrophils. Treatment of neutrophils with MCD caused inhibition of intracellular calcium increase evoked by interleukin-8 (IL-8) or low concentrations of formyl-Met-Leu-Phe (fMLP). No significant decrease of the initial peak of the calcium response was measured when neutrophils were stimulated with 100 nM or higher concentrations of fMLP. MCD inhibited the phosphorylation of extracellular signal-regulated kinase (Erk) induced by IL-8 or lower concentrations of fMLP. However, Erk phosphorylation evoked by higher concentrations of fMLP was only slightly affected. MCD treatment increased phosphorylation of p38 MAP kinase and caused strong up-regulation of both CD11b and CD66b in resting neutrophils. Cholesterol depletion greatly inhibited IL-8-induced elastase release but had little effect of fMLP-induced degranulation. Our study brings evidence suggesting that lipid microdomains are critically required for the signaling events triggered by IL-8. Calcium mobilization and elastase release induced by WKYMVM, a selective agonist for formyl peptide receptor-like 1 (FPRL1), were significantly inhibited by MCD, suggesting that the resistance of fMLP-mediated responses to MCD is not related to the partition of receptor subtypes to lipid microdomains. It is more probable that cholesterol depletion interferes with the ability of different G proteins to couple to their corresponding receptors and this might account for the differential effects of MCD treatment on chemoattractant-induced effects in human neutrophils.
Tuluc
Florin
F
Department of Physiology, Temple University Medical School, 3420 N. Broad Street, Philadelphia, PA 19140, USA.
Meshki
John
J
Kunapuli
Satya P
SP
D015703:Antigens, CD; D000954:Antigens, Surface / Q000276:immunology / Q000378:metabolism; D039481:CD11b Antigen / Q000276:immunology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D015815:Cell Adhesion Molecules; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology; D002784:Cholesterol / Q000378:metabolism; D003505:Cyclodextrins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005372:Filipin / Q000494:pharmacology; D058851:GPI-Linked Proteins; D006801:Humans; D016209:Interleukin-8 / Q000037:antagonists & inhibitors / Q000276:immunology; D019272:Leukocyte Elastase / Q000378:metabolism; D008274:Magnesium / Q000037:antagonists & inhibitors / Q000378:metabolism; D008563:Membrane Lipids / Q000502:physiology*; D021962:Membrane Microdomains / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology / Q000502:physiology*; D009842:Oligopeptides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000502:physiology*; D013997:Time Factors; D015854:Up-Regulation; D047392:beta-Cyclodextrins; D048051:p38 Mitogen-Activated Protein Kinases
D015703:Antigens, CD; D000954:Antigens, Surface; D039481:CD11b Antigen; C504120:CEACAM8 protein, human; D015815:Cell Adhesion Molecules; D003505:Cyclodextrins; D058851:GPI-Linked Proteins; D016209:Interleukin-8; D008563:Membrane Lipids; D009842:Oligopeptides; C113617:Trp-Lys-Tyr-Met-Val-Met; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D005372:Filipin; D002784:Cholesterol; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D019272:Leukocyte Elastase; D008274:Magnesium; D002118:Calcium