MRP8 and MRP14, S-100-like proteins associated with myeloid differentiation, are translocated to plasma membrane and intermediate filaments in a calcium-dependent manner.
MRP8 and MRP14 are two Ca(2+)-binding proteins of the S-100 family expressed by myelomonocytic cells. Both proteins assemble to noncovalently associated complexes in a Ca(2+)-dependent manner. Members of the S-100 family are known to play a role in cytoskeletal-membrane interactions; therefore, we investigated the subcellular distribution of MRP8/MRP14 and their complexes in human monocytes. Using differential centrifugation and subsequent Western blot or enzyme-linked immunosorbent assay analysis, we found that MRP8/MRP14 were almost completely translocated from the cytoplasma to membrane and cytoskeletal structures in a Ca(2+)-dependent manner. Using a cross-linking technique, complexed forms of MRP8/MRP14 were found to be associated with the plasma membrane. Analysis of MRP-transfected L132 cells showed that the MRP8 as well as the MRP14 component of the MRP8/MRP14 complex may independently bind to membrane and cytoskeletal structures. Furthermore, immunogold electron microscopy showed a colocalization of MRP8/MRP14 and the intermediate filament type III protein vimentin in A23187-treated monocytes. Our data indicate that, in analogy to other S-100-like proteins, MRP8 and MRP14 play a role in Ca(2+)-dependent cytoskeletal-membrane interactions. Restriction of MRP8/MRP14 expression to distinct stages of myelomonocytic differentiation suggests that these proteins are involved in highly specific pathways of intracellular signaling in phagocytes.
Institute of Experimental Dermatology, University of Münster, Germany.
J
J
Roth
F
F
Burwinkel
C
C
van den Bos
M
M
Goebeler
E
E
Vollmer
C
C
Sorg
D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*; D015153:Blotting, Western; D002118:Calcium / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*; D040501:Calgranulin A; D040502:Calgranulin B; D002454:Cell Differentiation; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D007382:Intermediate Filaments / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron; D009000:Monocytes / Q000166:cytology* / Q000378:metabolism*; D014162:Transfection; D014746:Vimentin / Q000032:analysis
D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D002135:Calcium-Binding Proteins; D040501:Calgranulin A; D040502:Calgranulin B; D014746:Vimentin; D002118:Calcium