CATs in the fat

Anautogenous mosquitoes use amino acids from the digestion of vertebrate blood to synthesize large amounts of yolk protein precursors in their fat bodies. The mosquito fat body has an efficient amino acid uptake system comprised of transport proteins with varying substrate specificities. Cationic amino acid transporters (CATs), a subfamily of the solute carrier 7 family, have been characterized in other model systems and generally transport the three cationic amino acids L-histidine, L-lysine, and L-arginine. Five putative CATs are encoded in the genome of the yellow fever mosquito Aedes aegypti, three of which are expressed in the fat body of the adult female. RNAi-mediated gene knockdown of CATs in adult females resulted in reduced signaling via the target of rapamycin signaling pathway in the fat body and in reduced egg numbers after a blood meal. The transport specificity of two mosquito CATs has been determined using the Xenopus oocyte expression system.