ABSTRACT
Adequate protein intake is crucial for animals. Despite the recent progress in understanding protein hunger and satiety in the fruit fly Drosophila melanogaster, how fruit flies assess prospective dietary protein sources and ensure protein consumption remains elusive. We show here that three specific amino acids, L-glutamate (L-Glu), L-alanine (L-Ala), and L-aspartate (L-Asp), rapidly promote food consumption in fruit flies when present in food. The effect of dietary amino acids to promote food consumption is independent of mating experience and internal nutritional status. Genetic analysis identifies six brain neurons expressing diuretic hormone 44 (DH44) as a sensor of dietary amino acids. DH44+ neurons can be directly activated by these three amino acids, and are both necessary and sufficient for dietary amino acids to promote food consumption. By conducting single cell RNAseq analysis, we also identify an amino acid transporter, CG13248, which is highly expressed in DH44+ neurons and is required for dietary amino acids to promote food consumption. Therefore, these data suggest that dietary amino acids may enter DH44+ neurons via CG13248 and modulate their activity and hence food consumption. Taken together, these data identify an internal amino acid sensor in the fly brain that evaluate food sources post-ingestively and facilitates adequate protein intake.
