A FAT BODY-DERIVED PROTEIN IS SELECTIVELY SULFATED DURING TRANSIT TO OVARIAN FOLLICLES IN THE STICK INSECT CARAUSIUS-MOROSUS

A monoclonal antibody raised against ovarian follicles of the stick in sect Carausius morosus reacted with two related polypeptides of 157 an d 85 kDa in both the ovary and the hemolymph. In vitro cultured fat bo dy proved capable of releasing the 157-kDa polypeptide into the cultur e medium and processing it to the lower-molecular-weight polypeptide o f 85 kDa. This was further demonstrated by in vitro exposure to [S-35] methionine. Under the same culturing conditions, ovarian follicles pro ved incapable of synthesizing and/or secreting the 85-kDa polypeptide. However, in vivo [S-35]methionine-labeled ovarian follicles released both polypeptides when cultured in vitro for up to 24 hr. Vitellogenin polypeptides were labeled in vivo following exposure to [H-3]glucosam ine, while 157- and 85-kDa polypeptides were labeled only in ovarian f ollicles exposed in vivo to sodium [S-35]sulfate. Under in vitro condi tions, the 157-kDa polypeptide could be labeled with sodium [S-35]sulf ate only if ovarian follicles were cocultured with fat body. No sulfat ion occurred in fat body or ovarian follicles cultured separately. The se experiments suggest that the 157-kDa polypeptide is a fat body-deri ved polypeptide that is sulfated upon transfer to the ovarian follicle . (C) 1995 Academic Press, Inc.