Stimulation of tryptophan hydroxylase production in a serotonin‐producing cell line (RBL2H3) by intracellular calcium mobilizing reagents

Abstract

RBL2H3 cells showed a remarkable increase in their level of tryptophan hydroxylase (up to 25-fold), the rate-limiting enzyme in serotonin biosynthesis, by stimulation with intracellular calcium mobilizers A23187, thapsigargin, and tBuBHQ as well as by stimulation with an antigen in the presence of IgE. The increase in the enzyme protein was visualized by Western blot analysis using anti-tryptophan hydroxylase antiserum. The enzyme turnover (Hasegawa et al., FEBS Lett., 368 (1995) 151-154) was not slowed down during the rise in tryptophan hydroxylase. Actinomycin D prevented the stimulation-induced elevation of the enzyme. These findings strongly suggest that this stimulation was achieved by the accelerated biosynthesis of tryptophan hydroxylase.