Native versus recombinant high-mobility group B1 proteins: functional activity in vitro

To compare the functional activity of native HMGB1 proteins from eukaryotic sources with HMGB1 from prokaryotic sources the cDNAs of human and murine HMGB1 were cloned and the proteins expressed in bacteria. Tissue-derived HMGB1 from calf thymus and HMGB1 secreted from Chinese hamster ovary (CHO) cells were purified. Human whole blood, THP-1 cells, and NIH/3T3 cells were exposed to HMGB1 proteins and the induction of tumor necrosis factor-alpha (TNF-alpha) release in whole blood and monocytic THP-1 cells and a proliferation assay in NIH/3T3 cells were used to study functional activity of HMGB1s in vitro. Native and recombinant HMGB1s induced TNF-alpha release in human blood and in THP-1 cells dose-dependently, but recombinant HMGB1s were more effective. Cell proliferation was induced by native and recombinant HMGB1s. The native HMGB1 proteins from eukaryotic sources exert the same (though less pronounced) biological activity in vitro as recombinant HMGB1 proteins from prokaryotic sources.