Olfaction plays a key role in insects, regulating essential behaviors such as i) host-seeking through the detection of organic compounds released by human, animals and plants ii) detection of species specific chemical signals such as sexual and alarm pheromones.
Mosquitoes are the primary transmitters of multiple parasites and viruses that cause malaria, dengue fever, West Nile encephalitis, microcephaly in newborn infants due to Zika virus and many other serious and often fatal diseases. Furthermore, agricultural and farm livestock insect pests, represent primary factors leading to reduced production of major crops and increased losses of farm animals.
Since 2010, Dr. Zographos’ research focuses on biochemical, molecular, functional and structural characterization of Mosquito and Pest insects Odorant Binding Proteins (OBPs), as molecular targets for the structure-based discovery of novel host-seeking disruptors, repellents or attractants. Since 2020, the research in insect olfaction was expanded to the mosquito 7-transmembrane Odorant Receptor coreceptor (ORco). The goal of this direction is the application of OBP- and ORco-structure-based approaches for the discovery of multiple new and effective agents to be employed in the effort to reduce the spread of insect-transmitted infectious diseases as well as control insects of agricultural importance.
OBP-structure-aided repellent discovery (Tsitsanou K.E., Liggri, P.G.V Stamati, E.C.V, E-Christodoulou, E-A)
Much physiological and behavioral evidence has been provided suggesting that insect Odorant Binding Proteins (OBPs) are indispensable for odorant recognition and thus appealing targets for structure-based discovery and design of novel host-seeking disruptors.
We have proposed OBPs as valuable molecular targets for the structure-based discovery and design of disruptors of normal olfactory and host seeking mosquito behavior (Tsitsanou et al., 2012, Tsitsanou, Drakou, et al., 2013, Drakou et al., 2017, Liggri et al., 2019). Significantly, we have now developed and successfully validated a Ligand- & OBP-structure-aided Discovery Protocol that led to identification of novel bioactive leads, attesting the applicability of the OBP-structure-aided discovery method (Thireou et al., 2018, Zographos et al., 2018). Therefore, the study on OBPs of A. gambiae and the determination of their 3D-structures and binding specificities could help us understand the molecular basis of odorant detection by OBPs, in this and other anthropophilic species, towards the development of new effective agents for the prevention of mosquito-borne diseases.
Advanced Research on the 3D Structure of the Mosquito Odorant Receptor Coreceptor (Tsitsanou K.E., Liggri, P.G.V)
Insect Odorant Receptors (ORs) play the central role in the manifestation of behavioral responses. In insects, including mosquitoes, each Olfactory Receptor Neuron (ORN) expresses a divergent member of the OR family (ORx) and a highly conserved one, Odorant Receptor coreceptor (ORco), which is abundantly expressed in insect ORNs. Formation of ORx-ORco heteromers leads to functional ligand (odor)-gated non-selective cation channels, directly activated by odors or pheromone ligands. Recent findings have shown that ORco acts as a ligand-gated channel in the absence of ORx and that it possesses an allosteric site to which modulators can bind directly and noncompetitively inhibit OR activation by odorants (Antagonists) or act as positive allosteric modulators (Agonists) of heteromeric channel function (Iatrou et al., 2022).
The project aims at the biochemical, molecular, functional and structural characterization of the 7-transmembrane Odorant Receptor coreceptor (ORco) of the mosquito Anopheles gambiae, applying the most up-to-date methodology and cutting-edge technology, including Nanodisk technology, Robotic high-throughput in meso crystallogenesis, Micro- and serial-crystallography using synchrotron radiation and high resolution cryo-Electron Microscopy. The results to be obtained from the successful implementation of this project, in addition to being of great importance to public health, could be further exploited for the development of ecologically-smart methods for the control of agricultural and farm livestock insect pests. Therefore, this project could have a major economic impact on the agricultural and livestock raising sectors.