Vesicular Location and Transport of S100A8 and S100A9 Proteins in Monocytoid Cells

PLoS One. 2015 Dec 14;10(12):e0145217. doi: 10.1371/journal.pone.0145217. eCollection 2015.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport
  • Biotinylation
  • Blotting, Western
  • Calgranulin A / chemistry
  • Calgranulin A / genetics
  • Calgranulin A / metabolism*
  • Calgranulin B / chemistry
  • Calgranulin B / genetics
  • Calgranulin B / metabolism*
  • Cells, Cultured
  • Dimerization
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Interleukin-10 / pharmacology
  • Lysosomes / metabolism
  • Microscopy, Confocal
  • Microscopy, Electron
  • Monocytes / cytology
  • Monocytes / metabolism
  • Surface Plasmon Resonance
  • Tumor Necrosis Factor-alpha / pharmacology
  • Ultracentrifugation
  • Up-Regulation / drug effects

Substances

  • Calgranulin A
  • Calgranulin B
  • Tumor Necrosis Factor-alpha
  • Interleukin-10

Grants and funding

This work was supported by the Swedish Cancer Foundation (Grant # 140520), Kocks Foundation and Österlund Foundation. Active Biotech AB provided support in the form of salaries for authors TL, PB, DL, AO and MR, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the “author contributors” section.