title: The presence of membrane Proteinase 3 in neutrophil lipid rafts and its colocalization with FcgammaRIIIb and cytochrome b558.
abstract: Proteinase 3 (PR3), the target autoantigen of antineutrophil cytoplasmic antibodies in the autoimmune vasculitis, Wegener's granulomatosis, is a serine proteinase stored in granules of human neutrophils. PR3 is expressed also on the plasma membrane of unactivated neutrophils, and this expression increases in primed or stimulated cells. In the current study, we demonstrate the presence of PR3, FcgammaRIIIb, and cytochrome b558 of the NADPH oxidase in neutrophil lipid rafts. Activation of neutrophils with PMA, fmet-leu-phe, or TNFalpha known to increase the membrane expression of PR3 did not affect the amount of PR3 in rafts. Unexpectedly, the cytosolic subunits of the NADPH oxidase, p67phox and p47phox, the recruitment of which to the membrane requires cell stimulation, were detected in the rafts of unstimulated neutrophils. Treatment of neutrophils with the cholesterol-sequestering agent methyl-beta-cyclodextrin (MbetaCD) reduced raft p22phox and PR3. MbetaCD diminished membrane FcgammaRIIIb upregulating membrane PR3 (mPR3) and CD11b/CD18. In addition, MbetaCD significantly reduced PMA-induced activity of the NADPH oxidase without altering fmet-leu-phe-elicited activity. Antibody-mediated cross-linking of membrane PR3 caused activation of ERK and JNK kinases and their translocation to rafts. Confocal analysis revealed colocalization of mPR3, FcgammaRIIIb, and p22phox in the membrane, confirmed by their coimmunoprecipitation. Cleavage of neutrophil GPI-anchors by PI-PLC reduced mPR3 and FcgammaRIIIb, implicating a GPI-protein, possibly FcgammaRIIIb, in the attachment of PR3 to the membrane.
authors.affiliation: Department of Biochemistry, The Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Alina
authors.initials: A
authors.lastname: David
authors.forename: Ram
authors.initials: R
authors.lastname: Fridlich
authors.forename: Irit
authors.initials: I
authors.lastname: Aviram
mesh_terms: D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D003573:Cytochrome b Group / Q000235:genetics / Q000378:metabolism*; D058851:GPI-Linked Proteins; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008214:Lymphocytes / Q000737:chemistry; D021962:Membrane Microdomains / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D053146:Myeloblastin; D019255:NADPH Oxidases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D009504:Neutrophils / Q000201:enzymology* / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D015703:Antigens, CD; D003573:Cytochrome b Group; C428200:FCGR3B protein, human; D058851:GPI-Linked Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010750:Phosphoproteins; D017452:Receptors, IgG; D047392:beta-Cyclodextrins; C106354:flotillins; C108732:methyl-beta-cyclodextrin; C036888:cytochrome b558; D019255:NADPH Oxidases; C086986:CYBA protein, human; D012697:Serine Endopeptidases; D053146:Myeloblastin; D013755:Tetradecanoylphorbol Acetate