Identification and characterization of oxysterol-binding protein (OSBP) related proteins (ORPs) in yellow fever mosquitoes, Aedes aegypti

Oxysterol-binding protein related proteins (ORPs) are lipid-binding proteins that conserved from yeast to humans. They may be involved in cellular sterol transportation, sterol metabolism and signal transduction pathways. Four ORP genes were identified via analysis of the genomic sequence and cloned from Aedes aegypti. According to homology to human ORPs, they are AeORP1, AeORP4, AeORP8 and AeORP9. Using quantitative real-time polymerase chain reaction (qPCR), the temporal and spatial expression of AeORP genes were profiled from 4th instar larvae to adults and in female adults after a blood meal. AeORP1 showed highly head-tissue specificity and the mRNA level was low in larvae and pupae but high in adults. AeORP4 transcription was up-regulated in the midgut of pupae; declining 6 hours after pupation but up-regulated in the emerging adults. Of the two isoforms of AeORP8, the longer transcripts AeORP8B, is the main expressed form. The transcription of both AeORP4 and AeORP9 were induced 48 h after a blood meal. Furthermore, overexpression of AeORPs facilitated [3H]-cholesterol uptake in Aedes aegypti cultured Aag-2 cells.