Ultrastructural localization of calcium homeostasis modulator 1 in mouse taste buds.

This article focuses on the ultrastructural localization of calcium homeostasis modulator 1 (CALHM1) in taste receptor cells, specifically type II cells that form channel synapses in mouse fungiform and circumvallate taste buds. Using a newly developed monoclonal antibody and immunoelectron microscopy, CALHM1 was found predominantly along the presynaptic plasma membrane of channel synapses facing atypical mitochondria, which supply ATP for neurotransmission, as well as along plasma membranes lined by subsurface cisternae at nerve fiber contact sites. In contrast, CALHM1 was not detected in hybrid synapses of type III taste receptor cells, which form conventional chemical synapses, suggesting that CALHM1 is largely confined to type II cell channel synapses. These findings support existing structural models of channel synapses and provide new insights into the potential role of subsurface cisternae in taste signal transduction.