Fig. 5.

Amino acid sensing by glial cells. Glial cells detect amino acids to control metabolism and growth. Comparison of low- (a) and high-protein diet (b) situations shows that in a high-protein diet, amino acids activate the secretion of an unknown factor by the fat body that induces the release of DILP6 by glial cells. Furthermore, glial cells can directly detect amino acids by TORC1 via the Slif amino acid transporter and secrete DILP6. DILP6 promotes the neuroblast reactivation and the release of Jelly belly (Jeb) by acetylcholinergic neurons. Jeb promotes the FoxO phosphorylation in IPCs to allow the dilp5 gene expression and DILPs release. Glial cells express another amino acid transporter Sobremesa (Sbm). Sobremesa is involved in larval development by regulating PTTH secretion and therefore ecdysone. AA amino acids, Ach neuron acetylcholinergic neurons, Alk anaplastic lymphoma kinase receptor, IPCs insulin producing cells, InR insulin receptor, Jeb Jelly belly, PTTH prothoracicotropic hormone, Sbm Sobremesa, Slif Slimfast, TORC1 target of rapamycin