The effects of tunicamycin on the synthesis and export of fat body proteins and glycoproteins in larvae of the greater wax moth Galleria mellonella (L.)

Abstract

Treatment of fat body from the greater wax moth, Galleria mellonella (L.), with tunicamycin in vitro caused complex alterations in protein synthesis. These included a 50% inhibition of protein synthesis and a greater than 90% inhibition of both protein release and glycoproteins biosyntheis. The inhibition of glycoprotein biosynthesis can be accounted for by the well-documented effects of tunicamycin on GlcNAc-pyrophosphoryl dolichol synthesis, while the two additional effects are likely to have a complex basis. Synthesis and export of the four storage proteins was also studied in fat body treated with tunicamycin. Exposure to antibiotic for short periods of time (2.5 hr) resulted in the sysnthesis of lower mol. wt variants of at least two of these polypeptides in treated cultures, both of which normally contain carbohydrate. Treated fat body released only putative fully-glycosylated forms of the storage proteins which suggests that the attachment of carbohydrate is in one way necessary for their secretion. Newly synthesized storage proteins were not detected in fat body treated with tunicamycin for longer time periods (approx. 7 hr), which indicates carbohydrate may also increase the intracellular half life of this class of proteins.