Olfactory Responses in Single Cells
Chemical communication is not only critical in mediating macroorganismal interactions, but plays a profound importance in controlling processes that occur at the level of the single cell. In contrast to the neural approach used for insect olfaction, the relatively simple system of the single cell (bateria, sperm, HEK) permits a molecular approach towards understanding the physiological mechanisms controlling chemosensory behavior (Riffell et al., 2004). To establish the physiological mechanisms controlling sperm chemotaxis, we examined the expression of olfactory receptor proteins on non-nasal epithelial tissues, and found incredibly high levels in male testes. Our work identified the olfactory receptor (OR) protein, hOR-17-4, in mediating sperm chemotactic behaviors (Spehr et al., 2003). This OR was de-orphaned, and was found to be activated by the agonist bourgeonal. Moreover, hOR17-4 activation is coupled to a cAMP transduction pathway through particulate adenylate cyclase, which controls flagellar beating and sperm turning behavior (Spehr et al., 2004; Riffell et al., 2011a,b). Thus, sperm cells respond to olfactory stimuli in an equivalent manner to that of olfactory neurons (Spehr et al., 2006).