Lipid transport in arthropods is achieved by highly specialized
lipoproteins, which resemble those described in vertebrate blood. Here, we describe purification and characterization of the
lipid-
apolipoprotein complex,
lipophorin (Lp), in the
malaria vector mosquito Anopheles gambiae. We also describe the Lp-mediated
lipid transfer to developing eggs and the distribution of the imported
lipid in developing embryos. The density of the Lp complex was 1.135 g/ml with an apparent molecular weight of 630 kDa. It is composed of two major
polypeptides, apoLp I (260 kDa) and apoLp II (74 kDa) and composed of 50%
protein, 48%
lipid and 2%
carbohydrate (w/w).
Hydrocarbon,
cholesterol,
phosphatidyl choline, phosphatidyl
ethanolamine,
cholesteryl ester and diacylglyceride were the major Lp-associated
lipids. Using fluorescently tagged
lipids, we observed patterns that suggest that in live developing oocytes, the Lp was taken up by a receptor-mediated endocytic process. Such process was blocked at low temperature and in the presence of excess unlabeled Lp, but not by
bovine serum albumin. Imported Lp was segregated in the spherical yolk bodies (mean size 1.8 microm) and distributed evenly in the cortex of the oocyte. In embryonic larvae, before hatching, a portion of the
fatty acid in vesicles was found evenly distributed along the body, whereas portion of
phospholipids was accumulated in the intestine.