Remodeling of sugar chain structures of human interferon-gamma

Natural human interferon (IFN)-gamma has mainly biantennary complex-type su gar chains and scarcely has multiantennary structures, We attempted to remo del the sugar chain structures using IFN-gamma as a model glycoprotein, To obtain the branching glycoforms of IFN-gamma, we introduced the genes for G nT-IV (UDP-N-acetylglucosamine:alpha-1,3-D-mannoside beta-1,4-N-acetylgluco saminyltransferase) and/or GnT-V (UDP-N-acetylglucosamine :a-1,6-D-mannosid e beta-1,6-N-acetylglucosaminyltransferase) into Chinese hamster ovary (CHO ) cells producing human IFN-gamma, The parental CHO cells produced IFN-gamm a with biantennary sugar chains mainly. When the GnT-IV activity was increa sed, triantennary sugar chains with a branch produced by GnT-IV increased u p to 66.9% of the total sugar chains. When the GnT-V activity was increased , triantennary sugar chains with a corresponding branch increased up to 55. 7% of the total sugar chains, When the GnT-IV and -V activities were increa sed at a time, tetraantennary sugar chains increased up to 56.2% of the tot al sugar chains. The proportion of these multiantennary sugar chains corres ponded to the intracellular activities of GnT-IV and -V, What is more, lect in blot and flow cytometric analysis indicated that the multi-branch struct ure of the sugar chains was increased not only on IFN-gamma, one of the sec retory glycoproteins, but also on almost CHO cellular proteins by introduci ng either or both of the GnT genes. The results suggest that the branching structure of sugar chains of glycoproteins could be controlled by cellular GnT-IV and GnT-V activities. This technology can produce glycoforms out of natural occurrence, which should enlarge the potency of glycoprotein therap eutics.