Mitochondria and sensitivity control in olfactory sensory neurons
 
Fabio Miazzi, Bill Hansson, Dieter Wicher
Department Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knöll-St. 8, D-07745 Jena, Germany
 
A common task for sensory systems is to adjust the sensitivity of the system to the actual requirements. Olfactory receptors, for example, have to detect a broad range of odor concentrations. In insects, odorant receptors (ORs) constitute the most sensitive class of olfactory receptors. Similar to GPCRs, they belong to the class of 7-TM proteins but show an inverted orientation within the plasma membrane. Insect OR are heteromeric constructs composed of an odor-specific OrX protein and an ubiquitary odorant co-receptor, Orco. Both, ORs as well as Orco form non-selective cation channels activated by ligands such as odor molecules or cyclic nucleotides (Wicher et al., Nature 452 (2008) 1007). The sensitivity of ORs is regulated in response to a previous odor contact. The tuning mechanisms form feedback loops and include OR protein phosphorylation and calmodulin binding. Mitochondria play a pivotal role in sensitization in certain compartments of olfactory sensory neurons. While inhibition of Na⁺/Ca²⁺ exchange by CGP37157 disrupts the sensitization in these compartments, inhibition of mitochondrial transport changes the dynamic range of odor perception in these sensory neurons. We propose possible mechanisms by which mitochondrial Ca²⁺ signaling may shape the odor response in sensory neurons.
 
Supported by the Max Planck Society and the DFG (SPP 1392).