A major focus of our laboratory is to elucidate the molecular and neural basis of sugar and amino acid sensing. Carbohydrates, proteins and fats are main components of the diet of most animals, including Drosophila. Thus, detecting these food chemicals and discriminating them from components that have no nutritional value or may be harmful and toxic is one of the most critical aspects of taste sensory perception. We specifically seek to understand how the eight gustatory receptors proteins (Gr5a, Gr61a, Gr64a-f) function together to detect different sugars, such as glucose, fructose, trehalsoe, maltose, sucrose etc. In addition, we are interested in how the cellular responses elicited by these interactions are translated into percepts in the brain, by identifying and characterizing the neural networks that propagate this neural activity.
A second interest of our lab is concerned with the regulation of feeding behavior. Food consumption is not only dependent on the sweet or savory quality of the available food source, but also on the nutrient signals that assist in evaluating the satiation status of an animal. For example, hungry flies will eat a sugar based diet even if this diet is of low sweetness or contaminated with bitter tasting chemicals, whereas satiated flies are much more discriminating and eat only sweet and uncontaminated sugar. Thus, we seek to identify the molecular and neural components of such internal nutrient sensors, and to understand how they modulate the activity of taste circuits. A major breakthrough in this project was accomplished with the identification of the brain based nutrient sensor Gr43a. Gr43a is one of the most conserved members of the insect gustatory receptor protein family, and its binding properties appear very narrowly tuned across species to the sugar fructose (and complex sugars containing a fructose moiety, such as sucrose and melezitose). Gr43a is expressed in the brain and other internal sensory neurons (associated with the proventriculus and the uterus). The most remarkable property of the Gr43a-expressing brain neurons is that they regulate food consumption in a satiation dependent manner: they promote feeding in hungry flies, while they suppress feeding in satiated flies.
The laboratory takes advantage of all molecular and genetic tools available in the Drosophila model system, including classic genetic analysis, transgenesis, gene knock out studies using homologous recombination and all types of expression analyses (microarray, qRT-PCR, RNAseq etc). These molecular approaches are complemented by histochemical and protein expression analyses of the chemosensory systems and the CNS. Finally, the functional analysis of genetically modified animals is conducted both at the organismal level using diverse behavioral paradigms and at the cellular level using live Ca2+ imaging assays.