The Effect of Carbonyl Cyanide Trifluoromethoxyphenylhydrazone and Methylamine on the Processing and Secretion of the Glycoprotein Hormone Chorionic Gonadotropin by Human Choriocarcinoma Cells

Carbonyl cyanide trifluoromethoxyphenylhydrazone (FCCP), a protonophore, and methylamine, a weak base, agents that dissipate hydrogen gradients across cellular membranes, were used to probe the coupling of hydrogen gradients to the processing and secretion of the glycoprotein hormone hCG by human choriocarcinoma cells (JAR) in culture. Both drugs disrupted the processing of asparagine-linked oligosaccharides such that the secreted hCG forms contained mostly high mannose rather than complex oligosaccharide chains. As the concentrations of FCCP were increased above 1 μg/ml and those of methylamine above 12.5 mg/ml, the secretion of the labeled hCG dimer and free a-subunit was progressively inhibited. Both FCCP and methylamine also inhibited the incorporation of [35S] methionine and [3H]mannose into hCG subunits. Nevertheless, the inhibition of secretion was clearly apparent as an intracellular accumulation of the hCG subunit precursors in spite of the diminished incorporation of radioactive substrates. The ...