BIOSYNTHESIS OF AEDES-AEGYPTI LIPOPHORIN AND GENE-EXPRESSION OF ITS APOLIPOPROTEINS

The biosynthesis of lipophorin of the yellow fever mosquito, Aedes aeg ypti, was investigated. Fat bodies were incubated in vitro with radiol abeled methionine and cysteine, and radiolabeled proteins secreted int o the medium were analyzed by density gradient ultracentrifugation, SD S-PAGE and fluorography. Lipophorin was synthesized in the fat body an d secreted into the medium. Its density was 1.114 g/ml, similar to tha t of lipophorin circulating in hemolymph. Three peptides of a tryptic digest of apolipophorin II were sequenced and degenerate oligonucleoti de primers were designed based on the amino acid sequences. With these primers, a cDNA product of 1.2 kb was amplified by RT-PCR using as te mplate RNA extracted from adult female mosquitoes 24 h after ingestion of a blood meal. This cDNA was cloned, sequenced and used as a probe for Northern blot analysis, which revealed that the apoproteins of lip ophorin were coded for by a single mRNA of approximately 10 kb. The ex pression of the apolipophorins was induced by blood feeding. From the data presented we concluded that Aedes aegypti lipophorin is synthesiz ed in the fat body and that the expression of its apolipophorins is in duced by blood feeding. (C) 1998 Elsevier Science Ltd. All rights rese rved.