Evidence for expression of EcR and USP components of the 20-hydroxyecdysone receptor by a mosquito cell line

The reverse transcriptase polymerase chain reaction (RT-PCR) was used to ex amine whether the C7-10 cell line from the mosquito, Aedes albopictus, expr esses transcripts encoding 20-hydroxyecdysone receptor (EcR) and ultraspira cle (USP) isoforms known to constitute a functional 20-hydroxyecdysone rece ptor. Here we describe recovery and analysis of products with high similari ty to the EcR and to the USP isoform "a" that have been reported from the r elated mosquito, Aedes aegypti. The C7-10 EcR was 97% identical to Aedes ae gypti EcR in amino acid sequence. Key features of the nuclear/steroid hormo ne receptor superfamily, including the zinc fingers, proximal (P)-box, and distal (D)-box were well conserved. However, the C7-10 EcR contained 5 addi tional amino acids in the C-terminal domain F, which required introduction of gaps to maximize alignment. The 5'-untranslated regions of the two mosqu ito EcRs were 98% identical, but the function of this region remains unknow n. The C7-10 USP was 95% identical in amino acid sequence to the longer Aed es aegypti isoform "a." Although only the C7-10 EcR was detected on Norther n blots using total RNA from the cell line, transcripts for both EcR and US P were detected using the RT-PCR procedure. These transcripts appeared to b e expressed constitutively and expression levels were not affected by treat ment of cells with 20-hydroxyecdysone. (C) 2000 Wiley-Liss, Inc.