This work aims to identify the molecular mechanisms of cold detection, using the fruit fly Drosophila melanogaster as a model. Sensory systems play key roles in human health. Not only is human sensory system dysfunction associated with disease, the detection of temperature is important for the survival and host-seeking behavior of insect vectors of human disease. At present, our molecular understanding of temperature detection in insects is limited: insect cold receptors have not been reported. Our preliminary data suggest two Ionotropic Receptor family members, IR21a and IR25a, are involved in cold sensing. Ionotropic receptors (IRs) are a subfamily of iGluRs in invertebrates (Drosophila has 66 IRs) known to act not as mediators of glutamate- dependent synaptic transmission, but as chemoreceptors for acids and amines. We are proposing to test the hypothesis that specific isoforms of IR21a and IR25a drive cold avoidance by acting in the cold sensors of the arista and/or labellum. Using cell-specific rescue experiments, we propose to determine which IR21a and IR25a isoforms mediate cold avoidance, and to test whether expression of these IRs in cold sensors is necessary and/or required for cold avoidance. We will also test if IR21a and IR25a mediate cold sensing. Using a combination of calcium imaging and electrophysiology, we will examine the contribution of IR21a and IR25a to cold sensing by examining how the cold-responsiveness of each set of cold sensors is altered in mutants lacking these proteins. I will also test whether IR21a and IR25a act forming a cold receptor by ectopic expression of these proteins in the fly and by heterologous expression in frog oocytes and in cultured mammalian cells. These studies will contribute for the understanding of cold-reception and the identification of the receptors will be extremely significant to elucidate the molecular mechanisms involved.
Sensing temperature is vital for all animals, both to maintain an optimal body temperature and avoid damage from thermal extremes. Not only is human sensory system dysfunction associated with disease, temperature sensing is important for the survival and host-seeking behavior of insect vectors of human disease 1. Mosquito-borne diseases alone are estimated to affect hundreds of millions of people and to be responsible for several million deaths annually 2. At present, the molecular identity of insect cold receptors is unknown. Knowledge of temperature sensing may be applied to control disease-carrying insects. The basic mechanisms of insect thermo-sensation could be used to identify a way for disrupting the life cycle or host-seeking behavior of disease-carrying insects. Studying thermal detection in the experimentally favorable Drosophila system is thus important for both basic science and human health. This work will study the role of members of the ionotropic Glutamate Receptor (iGluR) family. Within the iGluR family, NMDA and AMPA/Kainate receptors regulate neurotransmission from insects to humans. These receptors are targets for anesthetics/antidepressants (e.g., ketamine, an NMDA antagonist7) and anti- convulsants (e.g., perampanel, an AMPA antagonist8), and insect IRs are important in chemoreception6. Demonstrating a role for IRs in thermal detection would identify a new function for iGluR family receptors and give new insight into how such receptors can be regulated.
| Ni, Lina; Klein, Mason; Svec, Kathryn V et al. (2016) The Ionotropic Receptors IR21a and IR25a mediate cool sensing in Drosophila. Elife 5: |
| Knecht, Zachary A; Silbering, Ana F; Ni, Lina et al. (2016) Distinct combinations of variant ionotropic glutamate receptors mediate thermosensation and hygrosensation in Drosophila. Elife 5: |
