You are studying a cloned line of neuronal cells that grow in culture and form synapses with a cloned line of muscle cells. These synapses use serotonin as the neurotransmitter, and you have determined, that, as expected, these neuronal cells synthesize serotonin from tryptophan. Using sophisticated molecular cloning techniques, you have isolated the genes for two serotonin transporters, called TransA and TransB, which are expressed in these neuronal cells. A preliminary immunofluores- cence localization of fixed and permeabilized cells found very bright staining of TransA at the nerve cell plasma membrane and little staining elsewhere. TransB, in contrast, stained only very faintly at the nerve cell plasma membrane, but there was intense staining within the cytosol. Required:
In which subcellular membrane or organelle would you expect most of the TransB to be found?