%0 Journal Article
%T Sterol carrier protein-x gene and effects of sterol carrier protein-2 inhibitors on lipid uptake in Manduca sexta
%A Min-Sik Kim
%A Que Lan
%J BMC Physiology
%D 2010
%I BioMed Central
%R 10.1186/1472-6793-10-9
%X We identified the Manduca sexta sterol carrier protein-x and the sterol carrier protein-2 (MsSCP-x/SCP-2) gene from the larval fat body and the midgut cDNAs. The MsSCP-x/SCP-2 protein has a high degree of homology in the SCP-2 domain to other insects' SCP-2. Transcripts of MsSCP-2 were detected at high levels in the midgut and the fat body of M. sexta during the larval stages. Recombinant MsSCP-2 bound to NBD-cholesterol with high affinity, which was suppressed by sterol carrier protein-2 inhibitors.The results suggest that MsSCP-2 may function as a lipid carrier protein in vivo, and targeting insect SCP-2 may be a viable approach for the development of new insecticides.In insects, cholesterol is required as a structural component of cellular membranes and as a precursor for the insect molting hormone (ecdysone). However, insects lack several enzymes in the cholesterol biosynthesis pathway [1], which makes them auxotrophic for exogenous (dietary) cholesterol for satisfactory growth, development and reproduction [2-4]. Therefore, cholesterol uptake and transportation are critical for their survival. Uptake of cholesterol involves intracellular transfer and intercellular transportation. Intracellular cholesterol transfer enables the redistribution of cholesterol within a cell, and intercellular transport is needed for the distribution of cholesterol between cells. It is very well documented that lipophorin (Lp) and lipid transport particles (LTPs) are responsible for the intercellular transportation of cholesterol and lipids in insects [5-7].Cholesterol is highly hydrophobic with solubility of ~10 nM in water at room temperature [8], can be easily inserted into the lipid bilayer and has a fast flip-flop rate (t1/2 = 1-2 minutes) within the lipid bilayer [9]. Diffusion of cholesterol into the lipid bilayer can happen readily, and an aqueous diffusion model has been proposed to account for some of the cholesterol uptake by cells [10]. However, the desorption of membrane
%U http://www.biomedcentral.com/1472-6793/10/9