Figure 2.

Schematic diagram of the process of long-term desensitization in D. melanogaster. (1) At rest state, S289 is phosphorylated by PKC98E, and the olfactory receptor channel is sensitive to the odorant stimulation. (2) The ligands bind to the receptors and open the channel, leading to the influx of calcium and (3) the generation of strong action potentials. (4) When the presence of stimuli is prolonged, the accumulating intracellular calcium activates unknown phosphatase(s) that dephosphorylate Orco S289. (5) This dephosphorylation gradually desensitizes the odorant receptor channels, which is reflected by the inhibited electrophysiological response to odorant stimuli (6).