Localization of human neutrophil interleukin-8 (CXCL-8) to organelle(s) distinct from the classical granules and secretory vesicles.
Mature human neutrophils contain small amounts of interleukin-8 [CXC chemokine ligand 8 (CXCL-8)], which upon proinflammatory activation, increases significantly. It has been suggested that the CXCL-8 content of resting human neutrophils is stored in the secretory vesicles. Here, we have used a fractionation technique, which allows isolation of these vesicles, and we find that CXCL-8 neither colocalizes with the secretory vesicles nor with markers of any of the classical neutrophil granules. To increase resolution in the system, we induced CXCL-8 production by lipopolysaccharide. After 8 h of stimulation, CXCL-8 was visualized within the cell using immunoelectron microscopy. The images revealed CXCL-8-containing stuctures resembling neutrophil granules, and these were distinct from all known neutrophil organelles, as shown by double immunostaining. Further, the CXCL-8 organelle was present in nonstimulated neutrophil cytoplasts, entities lacking all other known granules and secretory vesicles. Upon fractionation of the cytoplasts, CXCL-8 was found to partly cofractionate with calnexin, a marker for endoplasmic reticulum (ER). Thus, part of CXCL-8 may be localized to the ER or ER-like structures in the neutrophil.
Pellmé
Sara
S
University of Göteborg, Guldhedsgatan 10, S 413 46 Göteborg, Sweden. sara.pellme@rheuma.gu.se
Mörgelin
Matthias
M
Tapper
Hans
H
Mellqvist
Ulf-Henrik
UH
Dahlgren
Claes
C
Karlsson
Anna
A
D015415:Biomarkers / Q000378:metabolism; D037281:Calnexin / Q000378:metabolism; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D006651:Histocytochemistry; D006801:Humans; D016209:Interleukin-8 / Q000276:immunology / Q000378:metabolism*; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008070:Lipopolysaccharides; D046529:Microscopy, Electron, Transmission; D016253:Microscopy, Immunoelectron; D009504:Neutrophils / Q000378:metabolism* / Q000648:ultrastructure; D015388:Organelles / Q000378:metabolism* / Q000648:ultrastructure; D022142:Secretory Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D013347:Subcellular Fractions
D015415:Biomarkers; D016209:Interleukin-8; D008070:Lipopolysaccharides; D037281:Calnexin