EXPRESSION AND CHARACTERIZATION OF MURINE OSTEOBLAST-SPECIFIC FACTOR-2 (OSF-2) IN A BACULOVIRUS EXPRESSION SYSTEM

Osteoblast-specific factor 2 (OSF-2) is a similar to 90-kDa protein se lectively expressed in bone. OSF-2 cDNA was recently isolated from mou se and human cDNA libraries and shows limited sequence homology with f asciclin I, a cell adhesion protein expressed in insect nerve cells, H ere we describe the expression of recombinant murine OSF-2 (rmOSF-2) i n a baculovirus/insect cell system, Western blotting analysis employin g polyclonal antiserum raised against a C-terminal synthetic OSF-2 pep tide detected a protein of similar to 90-kDa as early as 2 days after infection of Sf9 cells with the recombinant virus, Tunicamycin treatme nt of infected cells resulted in a mobility shift of OSF-2 (similar to 90-kDa band) on Western blots, N-Glycanase digestion resulted in the same mobility shift of OSF-2, indicating that rmOSF-2 expressed in ins ect cells is N-glycosylated, However, OSF-2 was insensitive to endogly cosidase H digestion while a major fraction of this protein had affini ty for concanavalin A. Finally, it was demonstrated that rmOSF-2 was a ble to bind to heparin, This finding suggests that OSF-2 might be asso ciated with the bone extracellular matrix after secretion by osteo bla sts and participate in cell adhesion and/or cell communication. The es tablishment of the baculovirus expression system with a high productiv ity of recombinant OSF-2 (around 40 mu g/ml at maximum) and its hepari n binding properties should allow us to obtain large amounts of rmOSF- 2. (C) 1995 Academic Press, Inc.