Antisense expression of the 20-hydroxyecdysone receptor (EcR) in transfected mosquito cells uncovers a new EcR isoform that varies at the C-terminal end

The insect steroid hormone 20-hydroxyecdysone initiates a cascade of regula tory events in a temporal and tissue-specific manner by first binding to a complex of an ecdysone receptor (EcR) protein and a ultraspiracle protein. Using an antisense (As) ribonucleic acid approach, we show that disruption of EcR expression in transfected C7-10 cells from the mosquito Aedes albopi ctus affects survival and growth. From stably transfected cells, we recover ed a new isoform of A. albopictus AalEcRa, which is named AalEcRb. The dedu ced amino acid sequence of AalEcRb was almost identical to that of AalEcRa, with the exception of a seven amino acid sequence near the C-terminus. Usi ng polymerase chain reaction followed by restriction enzyme analysis, we fo und that AalEcRa is the predominant species expressed by wildtype C7-10 cel ls, while cells transfected with As-EcR expressed both isoforms at approxim ately equal levels.