Amino acid-dependent regulation of insulin-like peptide signaling is mediated by TOR and GATA factors in the disease vector mosquito <i>Aedes aegypti</i>.

Abstract

<i>Aedes aegypti</i> female mosquitoes require vertebrate blood for their egg production and consequently they become vectors of devastating human diseases. Amino acids (AAs) and nutrients originating from a blood meal activate vitellogenesis and fuel embryo development of anautogenous mosquitoes. Insulin-like peptides (ILPs) are indispensable in reproducing female mosquitoes, regulating glycogen and lipid metabolism, and other essential functions. However, how ILPs coordinate their action in response to the AA influx in mosquito reproduction was unknown. We report here that the AA/Target of Rapamycin (TOR) signaling pathway regulates ILPs through GATA transcription factors (TFs). AA infusion combined with RNA-interference TOR silencing of revealed their differential action on ILPs, elevating circulating levels of several ILPs but inhibiting others, in the female mosquito. Experiments involving isoform-specific CRISPR-Cas9 genomic editing and chromatin immunoprecipitation assays showed that the expression of <i>ilp4</i>, <i>ilp6</i>, and <i>ilp7</i> genes was inhibited by the GATA repressor (GATAr) isoform in response to low AA-TOR signaling, while the expression of <i>ilp1</i>, <i>ilp2</i>, <i>ilp3</i>, <i>ilp5</i>, and <i>ilp8</i> genes was activated by the GATA activator isoform after a blood meal in response to the increased AA-TOR signaling. FoxO, a downstream TF in the insulin pathway, was involved in the TOR-GATAr-mediated repression of <i>ilp4</i>, <i>ilp6</i>, and <i>ilp7</i> genes. This work uncovered how AA/TOR signaling controls the ILP pathway in modulation of metabolic requirements of reproducing female mosquitoes.