Lipophorin conversions during flight of the death's-head hawkmoth Acherontia atropos

Abstract

Flight activity or injection of the death's-head hawkmoth Acherontia atropos with locust synthetic adipokinetic hormone (AKH I) results in a dramatic increase in the concentration of hemolymph diacylglycerol which is carried by specific lipophorins. In resting hawkmoths diacylglycerols are associated with a high-density lipophorin (HDLp, density ∼1.13 g/ml) consisting of two major apolipophorins (apoLp-I and -II, mol. wt ∼240,000 and 70,000, respectively). During flight or after AKH injection the formation of a new low-density lipophorin is induced (LDLp, density ∼1.03 g/ml), exhibiting a much higher lipid loading and consisting of HDLp subunits and an additional subunit (apoLp-III, mol. wt approx. 20,000). This subunit is a regular constitutent of hemolymph proteins in resting hawkmoths and consists of two protein components with slightly different molecular weights. The component with the lowest molecular weight seems to be preferentially incorporated into the newly generated LDLp. In the resting situation the HDLp already contains some apoLp-III. In spite of some minor differences, the overall mechanism of lipophorin rearrangements upon flight activity in the hawkmoth appears to be very similar to the known systems established for both Locusta migratoria and Manduca sexta.