NEURAL DIFFERENTIATION OF THE HUMAN NEUROBLASTOMA CELL-LINE IMR32 INDUCES PRODUCTION OF A THYROTROPIN-RELEASING HORMONE-LIKE PEPTIDE

The human neuroblastoma cell line IMR32 produces and secretes substant ial amounts of TRH-immmonoreactivity (TRH-IR) as measured with radioim munoassay (RIA) using the nonspecific antiserum 4319. It was found tha t synthesis of TRH-IR is dependent on neural differentiation: under se rum-free conditions these cells exhibit neural characteristics as defi ned by morphological and biochemical standards. After culture for 2-5 days in serum-free medium cells grew large neural processes and expres sed neuron-specific markers whereas glial-specific markers were absent . TRH-IR became detectable after 4-8 days serum-free conditions. North ern blot and chromatographic analysis, however, failed to detect proTR H mRNA and authentic TRH in these cells. Moreover, TRH-IR was undetect able in the RIA using TRH-specific antiserum 8880. TRH-IR produced by differentiated cells was retained on a QAE Sephadex A-25 anion-exchang e column and thus negatively charged. HPLC analysis showed coelution w ith the synthetic peptide pGlu-Glu-ProNH(2). Study of the mechanisms r egulating production of this novel peptide in these cells should furth er elucidate the role differentiation plays in the synthesis of neurop eptides.