Continued expression of neuronal traits in chromaffin cells of the adult bovine adrenal gland

Abstract

Intermediate filaments (IF) are a major constituent of the cytoskeleton of most eukaryotic cells.While there are five major classes of IF, amino acid sequence and secondary structure homologies suggest that all IFs evolved from a single precursor gene early in the history of life. Characteristically, IF are 10 nm filaments whose distribution, in most cases, is tissue-type specific. For example, the IFs of muscle cells contain the muscle-specific IF protein desmin, and those of epithelial cells contain subunits of the keratin family. Neurofilaments (NF) are a class of IFs expressed in most neuronal cells and are composed of three polypeptide subunits with apparent molecular weights of 68,000 (NF-L), 150,000 (NF-M) and 200,000 (NF-H). Interestingly, NFs are present in chromaffin cells cultured from bovine adrenal medulla. Chromaffin cells are derived from the neural crest, and the presence of NFs confirms their relatedness to neurons. However, the presence of NFs in vivo has been the subject of debate.