BON CELLS DISPLAY THE INTESTINAL PATTERN OF NEUROTENSIN NEUROMEDIN-N PRECURSOR PROCESSING

Antisera towards the bioactive peptides, neurotensin (NT, 13 residues) and neuromedin N (NMN, 6 residues), as well as towards three regions of their 147-residue canine precursor were used to identify and to qua ntitate precursor-derived peptides in extracts of human BON cells. Thi s cell-line, which was obtained from a human pancreatic carcinoid tumo r, constituitively expresses NT/NMN mRNA and secretes NT. Quantitation of seven precursor-derived peptides led us to conclude that BON cells display the intestinal pattern of NT/NMN precursor processing, which is primarily characterized by the production of a large molecular (125 amino acid) form of NMN. Four large molecular components, identified by immunochemical analyses and Western blotting, displayed physico-che mical properties which, for the most part, were consistent with the st ructures predicted from the partially-known human mRNA sequence. Howev er, as shown previously for these peptides in canine gut, the empirica lly determined M(r) and pI values were slightly higher than those pred icted solely from the amino acid content, perhaps due to the presence of additional substituents. These results suggest that BON cells may p rovide a good in vitro model in which to study the regulation of intes tinal NT/NMN precursor processing and the nature of the enzyme(s) invo lved.