CULTURED AEDES-ALBOPICTUS MOSQUITO CELLS SYNTHESIZE HORMONE-INDUCIBLEPROTEINS

To provide a framework for biochemical investigation of ecdysteroid ac tion in Aedes albopictus mosquito cells, we examined the effect of 20- hydroxyecdysone on cell growth and morphology, synthesis of inducible proteins (EIPs), and expression of a transfected gene regulated by a s ynthetic ecdysteroid response element. When cells were cultured in the continuous presence of 10(-6) M 20- hydroxyecdysone, the rate of grow th decreased and subtle changes in cell morphology were observed. In b oth Aedes aegypti and A. albopictus cells, synthesis of a small number of radiolabeled proteins, which appeared as minor bands on sodium dod ecyl sulfate-polyacrylamide gels, was induced by treatment with 20-hyd roxyecdysone. On two-dimensional polyacrylamide gels, 11 EIPs, ranging in size from approximately 22 to 52 kDa, were identified in A, albopi ctus C7-10 cells. Ten inducible proteins were localized in the cytopla smic fraction; EIP28 and EIP31 were detected in both cytoplasmic and n uclear extracts, and EIP29 was detected only in the nucleus, at a very low level. None of these proteins corresponded to small heat shock pr oteins, whose genes are 20-hydroxyecdysone-inducible in some Drosophil a cell lines. The juvenile hormone analog, methoprene, induced express ion of a 25 kDa protein in C7-10 cells. Although 20-hydroxyecdysone su stained the synthesis of this methoprene-inducible protein, synthesis did not occur in the presence of 20-hydroxyecdysone alone. In transfec ted A. albopictus cells, expression of a recombinant DNA construct con taining two tandem synthetic ecdysteroid regulatory elements based on a D. melanogaster small heat shock protein gene was modestly induced b y 20-hydroxyecdysone.