High-level expression of biologically active human prolactin from recombinant baculovirus in insect cells

We examined the feasibility of high-level production of recombinant human p rolactin, a multifunctional protein hormone, in insect cells using a baculo virus expression system. The human prolactin cDNA with and without the secr etory signal sequence was cloned into pFastBac1 baculovirus vector under th e control of polyhedrin promoter. Prolactin was produced upon infection of either Sf9 or High-Five cells with the recombinant baculovirus containing t he human prolactin cDNA. The production of recombinant prolactin varied fro m 20 to 40 mg/L of monolayer culture, depending on the cell types. The prol actin polypeptide with its own secretory signal was secreted into the mediu m. N-terminal amino acid sequence analysis of the recombinant polypeptide p urified from the culture medium indicated that the protein was processed si milar to human pituitary prolactin. Carbohydrate analysis of the purified p rotein indicated that a fraction of the recombinant prolactin made in insec t cells appeared to be glycosylated. Also, both secreted and nonsecreted fo rms of the recombinant prolactin in insect cells were biologically equivale nt to the native human prolactin (pituitary derived) in the Nb2 lymphoma ce ll proliferation assay. (C) 2000 Academic Press.