Analysis of an insect neuropeptide, Schistocerca gregaria ion transport peptide (ITP), expressed in insect cell systems

We have produced an active form of Schistocerca gregaria ion transport pept ide (ITP) in an insect cell expression system. Transformed Drosophila Kcl c ells secreted a form of ITP into the cell culture medium that was proteolyt ically cleaved correctly at the amino (N)-terminus. Concentrated culture su pernatant from transformed Kcl and Hi5 cells had high biological activity w hen tested on isolated locust ilea, Conversely, ITP expressed by baculoviru s-infected Sf9 cells was larger in size and had decreased specific activity compared to ITP produced by Kcl cells due to incorrect cleavage of the pep tide at the N-terminus in the baculovirus system. This demonstrates how pro cessing of the secreted foreign protein (ITP) expressed under the late poly hedrin promoter is compromised in a baculovilus-infected cell, Transient tr ansformation of Kcl cells results in supernatants containing two forms of I TP; one form (A) co-elutes with synthetic ITP and the other form (B) has re duced electrophoretic mobility. In contrast, in stably transformed Kcl cell supernatant, ITP is expressed in a single form, which has the same electro phoretic mobility and specific biological activity as form A produced by tr ansiently transformed gel cells. (C) 1999 Wiley-Liss, Inc.