sterol carrier protein-x gene and effects of sterol carrier protein-2 inhibitors on lipid uptake in manduca sexta甾醇载体蛋白质x基因的影响甾醇载波protein-2抑制剂在manduca sexta脂质吸收.pdf

Kim and Lan BMC Physiology 2010, 10:9 /1472-6793/10/9 R E S E A R C H A R T I C L E Open Access Research article Sterol carrier protein-x gene and effects of sterol carrier protein-2 inhibitors on lipid uptake in Manduca sexta 1 2 Min-Sik Kim and Que Lan* Abstract Background: Cholesterol uptake and transportation during the feeding larval stages are critical processes in insects because they are auxotrophic for exogenous (dietary) cholesterol. The midgut is the main site for cholesterol uptake in many insects. However, the molecular mechanism by which dietary cholesterol is digested and absorbed within the midgut and then released into the hemolymph for transportation to utilization or storage sites is poorly understood. Sterol carrier proteins (SCP), non-specific lipid transfer proteins, have been spec ulated to be involved in intracellular cholesterol transfer and metabolism in vertebrates. Based on the high degree of homology in the conserved sterol transfer domain to rat and human SCP-2, it is supposed that insect SCP-2 has a parallel function to vertebrate SCP-2. Results: 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. Conclusions: 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. Background