Fig. 7

Requirement of CG13248 for the increase in food consumption by dietary amino acids. a The list of candidate amino acid transporter genes expressed in DH44⁺ neurons. All genes that are expressed in > 50% of individual DH44⁺ neurons (FPKM ≥ 1) are listed here. Genes in red indicate that we obtained or generated genetic reagents to evaluate their behavioral function. b Changes in food consumption by the addition of amino acid mixture compared to 400 mM sucrose alone (dotted line) when the indicated genes are eliminated either by genetic mutation (CG31547) or by RNAi knockdown in DH44⁺ neurons (all other genes) (n = 20–23). See Materials and Methods for details. c Expression of CG13248 in the fly brain. Scale bar, 20 μm. Red: CG13248. The dotted line indicates the fly brain. The arrow indicates the PI region. d Co-localization of CG13248 and DH44 in the PI region of the fly brain. Scale bar, 10 μm. Green: mCD8GFP in DH44⁺ neurons. Red: CG13248. The arrows indicate neurons with CG13248 expression but not DH44 expression. e Volumes of 400 mM sucrose consumed by flies with the indicated genotypes (n = 21–23). f Changes in food consumption by the addition of 5 mM of the indicated amino acid compared to 400 mM sucrose alone (dotted line) (n = 20–26). g Quantification of in vivo calcium response of DH44⁺ neurons to different food in flies with the indicated genotypes (n = 8–10). h A working model of dietary amino acid sensing in fruit flies. (Left) Besides a well-documented peripheral sensing mechanism involving Ir76b, the present study proposes a speculative model of a central sensing mechanism, in which DH44⁺ neurons detect L-Glu, L-Ala and L-Asp via a putative amino acid transporter CG13248 and possibly also CG4991. (Right) Anatomically, the cell bodies of DH44⁺ neurons are located in the PI region of the fly brain (yellow), sending their axonal projections to the GI tract (green). Dietary amino acids (colored blocks) may enter DH44⁺ neurites in the gut and activate these neurons. Virgin females were used for all experiments shown in this figure. Data are shown as means ± SEM. NS, P > 0.05; *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001