A novel protein that binds juvenile hormone esterase in fat body tissue and pericardial cells of the tobacco hornworm Manduca sexta L.

Juvenile hormone esterase degrades juvenile hormone, which acts in conjunct ion with ecdysteroids to control gene expression in insects. Circulating ju venile hormone esterase is removed from insect blood by pericardial cells a nd degraded in lysosomes, In experiments designed to characterize proteins involved in the degradation of juvenile hormone esterase, a pericardial cel l cDNA phage display library derived from the tobacco hornworm moth Manduca sexta L. was constructed and screened for proteins that bind juvenile horm one esterase, A 732-base pair cDNA encoding a novel 29-kDa protein (P29) wa s isolated. Western and Northern analyses indicated that P29 is present in both pericardial cell and fat body tissues and is expressed in each larval instar, In immunoprecipitation experiments, P29 bound injected recombinant juvenile hormone esterase taken up by pericardial cells and native M. sexta juvenile hormone esterase in fat body tissue, where the enzyme is synthesi zed. Binding assays showed that P29 bound juvenile hormone esterase more st rongly than it did a mutant form of the enzyme with mutations that perturb lysosomal targeting. Based on these data, we propose that P29 functions in pericardial cells to facilitate lysosomal degradation of juvenile hormone e sterase.