Meeting Abstract

15.9  Monday, Jan. 4  Novel Posttranslational Processing of POMC in the Anterior Pituitary of the Adult Frog Silurana tropicalis CHEN , Quinn; BRANN, Kalvin; PHANPAKTRA, Atchara; DORES, Robert M.*; University of Denver; University of Denver; University of Denver; University of Denver rdores@du.edu

In most adult vertebrates the posttranslational processing of the prohormone precursor, POMC, yields ACTH(1-39) as a major end product. This outcome is due to the action of the prohormone convertase, PC1. However, steady state analyses of acid extracts of the anterior pituitary of the anuran amphibian Silurana tropicalis yield different results. Sephadex G-50 fractionation of an acid extract of 10 pooled anterior pituitaries yielded a column profile in which ACTH-sized immunoactivity was a minor end product, and the major end-product was an MSH-sized immunoactive form. Subsequent reversed-phase HPLC analysis of the MSH-sized material indicated that this immunoreactive form had the same retention time as S. tropicalis ACTH(1-13)amide. This posttranslational processing pattern has been observed in the anterior pituitaries of larval and neotenic urodele amphibians (Ambystoma tirgrinum and Ambystoma mexicanum), but is novel for the anterior pituitary of a sexually mature adult. An analysis of the posttranslational processing of POMC in the anterior pituitary of the frog Xenopus laevis revealed the typical adult processing pattern – ACTH as the major end-product. These observations would suggest that while the reproductive system of S. tropicalis reaches maturity in the adult stage, the corticotropic cells of the anterior pituitary appear to retain larval features. This conclusion may have implications in terms of the activation of the melanocortin receptor on the adrenalcortical cells of S. tropicalis that secrete corticosterone. This research was supported by NSF grant 0516958 (R.M.D.).