The synthesis and processing of the precursor for
neuropeptide Y (NPY) were studied in 16 human and murine neuroendocrine cell lines. Eight of the cell lines, NS-20Y, PC12, LA-N-5, CHP-234, SMS-KCNR, SH-SY5Y, SMS-KCN, and BE(2)-M17, produced sufficient quantities to permit chromatographic characterization of the NPY immunoreactivity. Although the cell lines varied in the amount of NPY they produced, both within and between cell lines, they displayed a relatively constant pattern of posttranslational modifications. In contrast to observations in
tumor extracts (M. M. T. O'Hare and T. W. Schwartz,
Cancer Res., 49: 7010-7014, 1989), all cell lines studied contained a substantial amount of the intracellular NPY in the form of the unprocessed propeptide, 57% (range, 33-72%) as characterized by both gel filtrations (32 experiments in 8 cell lines) and "in vitro conversion" with
endoproteinase Lys-C. In the majority, 4 of 6 cell lines studied, almost all of the NPY, which by size corresponded to the mature 36-amino
acid form, was amidated as assessed by isoelectric focusing and by a radioimmunoassay specific for the COOH-terminal
amide group of the
peptide. Both the propeptide and smaller molecular forms of NPY were secreted from the cell cultures; however, proteolytic degradation in the tissue culture medium prevented a detailed, meaningful characterization of these
peptides. It is concluded that many neuroendocrine cell lines, especially those derived from human
neuroblastomas, express the NPY gene; the cells display a partly impaired dibasic processing capacity but they generally amidate the products efficiently.