title: Vesicular Location and Transport of S100A8 and S100A9 Proteins in Monocytoid Cells.
abstract: We show here, by using surface biotinylation, followed by Western blotting or surface plasmon resonance analysis, that very low levels of S100A8 and/or S100A9 can be detected on the surface of THP-1 cells or freshly isolated human monocytes. This was supported by immune-electron microscopy where we observed membrane-associated expression of the proteins restricted to small patches. By using confocal microscopy we could determine that S100A8 and S100A9 protein in THP-1 cells or freshly isolated human monocytes was mostly present in vesicular structures. This finding was confirmed using immune-electron microscopy. Subcellular fractionation and confocal microscopy showed that these vesicular structures are mainly early endosomes and endolysosomes. Our subsequent studies showed that accumulation of S100A8 and S100A9 in the endolysosomal compartment is associated with induction of their release from the cells. Furthermore, an inhibitor of lysosomal activity could modulate the release of S100A8 and S100A9 in the extracellular milieu. Our current results suggest that the S100A8 and S100A9 proteins are primarily associated with certain kinds of cytosolic vesicles and may be secreted via an endolysosomal pathway.
authors.affiliation: Immunology Group, Lund University, Lund, Sweden.
authors.forename: Paramita
authors.initials: P
authors.lastname: Chakraborty
authors.affiliation: Active Biotech AB, Lund, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Bjork
authors.affiliation: Immunology Group, Lund University, Lund, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Källberg
authors.affiliation: Active Biotech AB, Lund, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Olsson
authors.affiliation: Active Biotech AB, Lund, Sweden.
authors.forename: Matteo
authors.initials: M
authors.lastname: Riva
authors.affiliation: Division of Infection Medicine, Lund University, Lund, Sweden.
authors.forename: Matthias
authors.initials: M
authors.lastname: Mörgelin
authors.affiliation: Active Biotech AB, Lund, Sweden.
authors.forename: David
authors.initials: D
authors.lastname: Liberg
authors.affiliation: Immunology Group, Lund University, Lund, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Ivars
authors.affiliation: Immunology Group, Lund University, Lund, Sweden.|Active Biotech AB, Lund, Sweden.
authors.forename: Tomas
authors.initials: T
authors.lastname: Leanderson
mesh_terms: D001692:Biological Transport; D019921:Biotinylation; D015153:Blotting, Western; D040501:Calgranulin A / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D040502:Calgranulin B / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D019281:Dimerization; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D016753:Interleukin-10 / Q000494:pharmacology; D008247:Lysosomes / Q000378:metabolism; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D009000:Monocytes / Q000166:cytology / Q000378:metabolism; D020349:Surface Plasmon Resonance; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014461:Ultracentrifugation; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D040501:Calgranulin A; D040502:Calgranulin B; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10