Ultrastructural localization of the S-100-like proteins MRP8 and MRP14 in monocytes is calcium-dependent.
MRP8 and MRP14 are members of the S-100 family of Ca(2+)-binding proteins and are expressed by granulocytes and monocytes. Members of this family have been described to be involved in membrane and cytoskeleton interactions; we therefore studied the subcellular distribution of MRP8/MRP14 in cultured human monocytes at the ultrastructural level. Monospecific rabbit antisera against MRP8 and MRP14 and a monoclonal antibody (moAb 27E10), which exclusively recognizes the MRP8/MRP14 heterodimer but not the monomers, were used in both immunoperoxidase/preembedding- and immunogold/cryotechniques. Comparing non-stimulated monocytes with Ca2+ ionophore A23187-treated cells, we could demonstrate that MRP8 and MRP14 associate with membrane and cytoskeletal structures in a Ca(2+)-dependent manner. Employing moAb 27E10, MRP8/MRP14 complexes were shown to be translocated to these cellular components. In addition, immunogold double-labelling experiments revealed a clear co-localization of MRP8/MRP14 complexes with the type III intermediate filament vimentin. Analysis of immunogold-labelled cryosections of renal allografts after acute vascular rejection demonstrated that a subpopulation of infiltrating macrophages showed a similar association of MRP8/MRP14 to the cytoskeleton in situ; this finding emphasizes the in vivo relevance of our observations. We conclude that Ca(2+)-dependent translocation of MRP8/MRP14 occurs to distinct subcellular components suggesting a role of these proteins for the modulation of cytoskeletal and membrane interactions.
Burwinkel
F
F
Gerhard-Domagk-Institute of Pathology, University of Münster, Germany.
Roth
J
J
Goebeler
M
M
Bitter
U
U
Wrocklage
V
V
Vollmer
E
E
Roessner
A
A
Sorg
C
C
Böcker
W
W
D000943:Antigens, Differentiation / Q000032:analysis*; D002118:Calcium / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000032:analysis*; D040501:Calgranulin A; D040502:Calgranulin B; D002478:Cells, Cultured; D015925:Cryopreservation; D006801:Humans; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D009000:Monocytes / Q000737:chemistry* / Q000648:ultrastructure; D016610:Tissue Embedding
D000943:Antigens, Differentiation; D002135:Calcium-Binding Proteins; D040501:Calgranulin A; D040502:Calgranulin B; D002118:Calcium