Identification of a New Cytochrome P450 Family, CYP45, from the Lobster,Homarus americanus,and Expression Following Hormone and Xenobiotic Exposures

A new cytochrome P450, the first member of the CYP45 family, was identified from the hepatopancreas of the American lobster,Homarus americanus.The lobster CYP45 shares significant sequence homologies to the vertebrate CYP3 and the invertebrate CYP6, CYP9, CYP28, and CYP30 families, perhaps indicating a common ancestor of these P450s. Of seven tissues examined, CYP45 was expressed only in the hepatopancreas, the crustacean equivalent of the vertebrate liver, pancreas, and intestine. Over the course of the lobster molt cycle, CYP45 expression mirrored the hemolymph titer of ecdysteroids, suggesting its potential involvement in molting hormone dynamics. This idea was strengthened further by ecdysteroid treatment of intermolt-stage lobsters during the lowest hemolymph titers and CYP45 expression levels. Significant elevations in hepatopancreas CYP45 mRNA levels were elicited by such injections over a 2- to 4-day interval. Similar experiments were performed by intubating juvenile lobsters with various xenobiotics. Induction of CYP45 expression occurred following phenobarbital and heptachlor administration, but not by β-naphthoflavone. Hormonal and xenobiotic modulation of lobster CYP45 expression provides a potential pathway for endocrine disruption in lobsters.