ECDYSTEROID-MEDIATED UPTAKE OF ARYLPHORIN BY LARVAL FAT-BODIES OF CALLIPHORA-VICINA - INVOLVEMENT AND DEVELOPMENTAL REGULATION OF ARYLPHORIN BINDING-PROTEINS

In the final larval instar of the blowfly Calliphora vicina the storag e protein arylphorin is stage-specifically and selectively taken up by the fat body cells from the haemolymph, Previously, we have identifie d three arylphorin binding proteins (ABP 130, ABP 96, ABP 65) in the m embrane fraction of late larvae and white puparia, Here we demonstrate that all ABPs derive from a single translation product (ABP 130) that we consider as arylphorin receptor precursor, The appearance of the A BPs is developmentally regulated throughout the last larval instar, Wh ile ABP 130 and ABP 96 appear at day 4, ABP 65 emerges at the end of l ast larval instar, coinciding with the rise in ecdysteroid titre and t he beginning of arylphorin incorporation. We showed that 20HE induces stage-specifically arylphorin uptake and is responsible for the transf ormation of ABP 96 into ABP 65 plus a 30 kDa protein, which does not b ind arylphorin.