Abstract
Anautogenous mosquitoes depend on vertebrate blood as nutrient source for their eggs. A highly efficient set of membrane transporters mediates the massive movement of nutrient amino acids between mosquito tissues after a blood meal. Here we report the characterization of the amino-acid transporter Slimfast (Slif) from the yellow-fever mosquito Aedes aegypti using codon-optimized heterologous expression. Slif is a well-known component of the target-of-rapamycin signalling pathway and fat body nutrient sensor, but its substrate specificity and transport mechanism were unknown. We found that Slif transports essential cationic and neutral amino acids with preference for arginine. It has an unusual dual-affinity mechanism with only the high affinity being Na+ dependent. Tissue-specific expression and blood meal-dependent regulation of Slif are consistent with conveyance of essential amino acids from gut to fat body. Slif represents a novel transport system and type of transceptor for sensing and transporting essential amino acids during mosquito reproduction.
Highlights
Anautogenous mosquitoes depend on vertebrate blood as nutrient source for their eggs
We found an additional intron and an exon at the 50-end of the transcript that was absent in the current annotation of the Ae. aegypti genome (VectorBase AAEL012131; see Supplementary Fig. 1)
The AaSlif gene consists of five exons and four introns, which are spliced to an 1,881nucleotide-long open reading frame (ORF) encoding a 626-amino acids (AAs) protein
Summary
Anautogenous mosquitoes depend on vertebrate blood as nutrient source for their eggs. Post blood meal (PBM) females mosquitoes undergo complex changes in tissue-specific gene expression in order to transfer nutrient AAs from the digested meal to the developing oocytes, a process called vitellogenesis[5,6]. The heterologous expression of the original AaSlif transcript (GenBank accession #: KM593906) in Xenopus laevis oocyte resulted in a significant increase of Arg-induced currents compared with water-injected control oocytes (I 1⁄4 10.2±5.8 nA for 10 mM L-Arg; n43, P 1⁄4 0.014; t-test).
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