Nongenomic action of an insect steroid hormone, 20-hy-droxyecdysone (20E), has been implicated in several 20E-dependent events including the programmed cell death of Bombyxanterior silk glands (ASGs), but no information is available for themodeof evidence for a putative membrane receptor located in the plasma mem-brane of the ASGs. Membrane fractions prepared from the ASGs exhibit high binding activity to [ 3 H]ponasterone A (PonA). The membrane fractions did not contain conven-tional ecdysone receptor as revealedbyWesternblot analysis using antibody raised againstBombyxecdysone receptor A (EcR-A)
