Characterization of Aedes aegypti SLC-7 family amino acid transporter CAT3

Aedes aegypti is the primary disease vector for both dengue and yellow fever.  Blood meal derived amino acids are essential for yolk protein precursor synthesis which occurs exclusively in the mosquito’s fat body.  Yolk protein precursors are important for vitellogenesis and egg maturation.  The SoLute Carrier 7 (SLC7) transporter family is responsible for amino acid movement across plasma membranes.  This study addresses Cationic Amino acid Transporter 3 (CAT3) and the role it plays during vitellogenesis.

We have knocked down CAT3 using RNAi and determined the effect of this knockdown on fecundity and immunity of adult female Ae. aegypti. We have expressed CAT3 in Xenopus oocytes and performed an electrophysiological characterization of its transport specificity. We have also tested if recombinant expression of CAT3 in amino acid uptake deficient yeast strains rescues the growth phenotype of these strains.

CAT3’s expression increases 3 hours post blood meal in the ovaries, gut, and whole female mosquitos and 48 hours post blood meal in the thorax and fat body.CAT3 knockdown resulted in reduced female fecundity. The functional analysis showed that CAT3 transports the amino acids L-proline, L-arginine, L-lysine, and L-histidine which all have been shown to be critical for vitellogenic gene expression.   

Identifying CAT3 inhibitors could lead to the development of novel insecticides with a new mode of action.