N-glycosylation and biological activity of recombinant human alpha1-antitrypsin expressed in a novel human neuronal cell line

Abstract

Human alpha-1-antitrypsin (A1AT) is a protease inhibitor that is involved in the protection of lungs from neutrophil elastase enzyme that drastically modifies tissue functioning. The glycoprotein consists of 394 amino acids and is N-glycosylated at Asn-46, Asn-83, and Asn-247. A1AT deficiency is currently treated with A1AT that is purified from human serum. In view of therapeutic applications, rA1AT was produced using a novel human neuronal cell line (AGE1.HN®) and we investigated the N-glycosylation pattern as well as the in vitro anti-inflammatory activity of the recombinant glycoprotein. rA1AT (300 mg/L) was biologically active as analyzed using elastase assay. The N-glycan pool, released by PNGase F digestion, was characterized using 2D-HPLC, MALDI-TOF mass spectrometry, and by exoglycosidase digestions. A total of 28 N-glycan structures were identified, ranging from diantennary to tetraantennary complex-type N-glycans. Most of the N-glycans were found to be (α1-6) core-fucosylated and part of them contain the Lewis X epitope. The two major compounds are a monosialylated diantennary difucosylated glycan and a disialylated diantennary core-fucosylated glycan, representing 25% and 18% of the total N-glycan pool, respectively. Analysis of the site-specificity revealed that Asn-247 was mainly occupied by diantennary N-glycans whereas Asn-46 was occupied by di-, and triantennary N-glycans. Asn-83 was exclusively occupied by sialylated tri- and tetraantennary N-glycans. Next, we evaluated the anti-inflammatory activity of rA1AT using A1AT purified from human serum as a reference. rA1AT was found to inhibit the production of TNF-α in neutrophils and monocytes as commercial A1AT does.