HELA-CELLS CONTAIN INTERMEDIATE-SIZED FILAMENTS OF THE PREKERATIN TYPE

Immunofluorescence microscopy using antibodies raised against protein constituents of the different types of intermediate-sized filaments has shown that in HeLa cells filaments containing a prekeratin-like protein (cytokeratin) predominate. The wavy filament bundles decorated by antibodies against prekeratin are similar to those described in other cells of epithelial origin. These bundles of intermediate-sized (6-11 nm) filaments are also described by electron microscopy in intact cells and in cytoskeletal preparations obtained by cell lysis and extraction with low and high salt buffers and Triton X-100. The occasional occurrence of desmosome-attached tonofibrillar bundles of intermediate-sized filaments is also shown. When HeLa cells are treated for long times with colcemid to induce perinuclear whorls of intermediate-sized filaments, these aggregates of filaments are strongly stained by antibody to vimentin, the major polypeptide of the intermediate-sized filaments of murine 3T3 cells. However, they are not stained by antibody to prekeratin, and the display of the prekeratin-containing tonofilament-like structures is similar to that seen in untreated cells. SDS-polyacrylamide gel electrophoresis of cytoskeletons prepared under conditions in which intermediate-sized filaments are retained show the presence of a polypeptide which co-migrates with one component of bovine prekeratin, and a second polypeptide which co-migrates with vimentin purified from mouse 3T3 cells. The data show (i) that two different types of intermediate-sized filaments can be present in the same cell and can be distinguished immunologically; and (ii) that the expression of a prominent epithelial structural marker, i.e. prekeratin-containing filaments, can be maintained in malignancy and continuing proliferation in vitro. © 1978.