Effect of various glycosidase treatments on the resistance of the HIV-1 envelope to degradation

Using a CD4-binding assay to assess the conformation of the human immunodeficiency virus envelope glycoprotein (CHO+ Env), we studied the effect of treatment with various glycosidases on the stability of Env in denaturing environments and in biological media: cleavage from Env of either high-mannose-type glycans(HMT(-) Env) by endoglycosidase H or sialic acid residues (Sial(-) Env) by sialidase did not alter Env stability whereas its complete deglycosylation (CHO- Env) by N-glycanase had a large effect. The influence of glycan removal on Env sensitivity to proteases was also studied. Thrombin cleavage within V3 was affected by N-glycanase treatment; both HMT(-) Env and CHO- Env displayed an increased sensitivity to other endoproteases. Thus, partial deglycosylation increases Env sensitivity to proteases but only its total deglycosylation alters its stability. (C) 1997 Federation of European Biochemical Societies.