Epinemin: a new protein associated with vimentin filaments in non-neural cells.

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Abstract
A new protein defined by a monoclonal antibody is described, which is associated with vimentin filaments in a variety of cultured cells [3T3, BSC-1, PTK] and in skeletal muscle. By immunofluorescence it is absent in smooth muscle, in cells without vimentin, and in neural vimentin containing cells. This protein has a MW of 44,500, a pl [isoelectric point] of 5, a 2-dimensional tryptic peptide fingerprint pattern different from vimentin, is unrelated to actin by Cleveland peptide analysis and by light microscopy and EM, and is not recognized by either a polyclonal antivimentin antibody or a monoclonal antibody against all classes of intermediate filaments. The protein is resistant to nonionic detergent extraction, is soluble in high salt and can thus be removed from vimentin filaments; however, it fragments with vimentin in either low salt or anionic detergent and collapses with vimentin in colchicine-treated cells. By light microscopy, the distribution of the protein is indistinguishable from vimentin filaments and appears uniform along them. Immunoferritin EM reveals that the molecule is distributed in an intermittent pattern on vimentin filaments. Adopting the terminology of Granger and lazarides, the molecule is called epinemin, meaning upon filaments.