CYTOLOCATION OF PROSOME ANTIGENS ON INTERMEDIATE FILAMENT SUBNETWORKSOF CYTOKERATIN, VIMENTIN AND DESMIN TYPE

Analysis by double-label indirect immunofluorescence of PtK1 and HeLa cells had previously demonstrated that prosome antigens form networks that superimpose on those of the intermediate filaments of the cytoke ratin type. We show here that in PtK1 cells various prosomal antigens also reside to a variable extent on intermediate filaments subnetworks of the vimentin type. In proliferating human fibroblasts the prosome and vimentin networks were found to coincide, while in proliferating m yoblasts of the C2.7 mouse myogenic cell line the prosomal antigens se em to superimpose on the intermediate filaments of the desmin type. Th us, the prosomes, which are RNP particles of variable composition and subcomplexes of untranslated mRNP, and carry a multicatalytic proteina se activity, seem to co-localize with the specific kind of cytoplasmic intermediate filament in relation to the cell type. These results, wh ich generalize the previous data, are discussed in view of possible ro le(s) for prosomes in mRNA metabolism and/or intermediate filaments re modelling.