Isolation and expression of a sterol carrier protein-2 gene from the yellow fever mosquito, Aedes aegypti.

Trafficking of cholesterol in insects is a very important process due to the fact that insects depend on dietary cholesterol to fulfil their physiological needs. We identified a putative mosquito sterol carrier protein-2 (SCP-2) cDNA from fourth instar subtracted cDNA library. The AeSCP-2 protein has high degree homology in the sterol transfer domain to both rat and human SCP-2. Transcripts of AeSCP-2 in fourth instars were detected strongly in the midgut, and weakly in the head and hindgut. In the early pupae, AeSCP-2 transcription was observed in the thorax, head and body wall of abdomen, but not in the gut. The interaction of mosquito sterol carrier protein-2 (AeSCP-2) with cholesterol was examined. The Kd of purified recombinant AeSCP-2 to cholesterol was 5.6 +/- 0.6 x 10-9 m using radiolabelled cholesterol-binding assay. The results suggest that AeSCP-2 has high affinity to cholesterol and may function as a carrier protein in mosquitoes.