Stepwise deletion of the HIV type 1 glycoprotein 41 N terminus leads to an increasing export of microvesicles containing uncleaved Env glycoprotein.
Deletion of two or more amino acid residues from the N terminus of HIV-1 gp41 leads to an increasing loss of cleavability of the envelope (Env) precursor on introduction of an env-expressing vector into HeLa-T4+ cells. In protein analysis, this is paralleled by the appearance of a second form of uncleaved Env precursor that is terminally sialylated. Cell-derived microvesicles that preferentially incorporate this form of Env precursor were found in the culture medium. The same applies to a mutant with a nonfunctional cleavage site, indicating that a pathway by which uncleaved Env glycoprotein leaves the cell exists. The amount of exported glycoprotein is augmented as compared with wild-type Env. Transfection with a wild-type Env-expressing vector leads to the presence of extracellular microvesicles that contain only the transmembrane domain of HIV-1 Env. Microvesicles derived from wild-type Env and mutant Env contain sialylated glycoproteins that are resistant to exo- and endoglycosidase treatment unless the particles have been previously lysed by detergent. This raises the possibility that the C-terminal domains of the glycoproteins are exposed on the surface of the exported microvesicles.
Adams
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Institut für Medizinische Mikrobiologie und Virologie, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany.
Scheid
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D000595:Amino Acid Sequence; D000596:Amino Acids / Q000502:physiology; D001665:Binding Sites; D002499:Centrifugation, Density Gradient; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D015686:Gene Products, env / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism; D015700:HIV Envelope Protein gp41 / Q000235:genetics / Q000502:physiology*; D015497:HIV-1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008561:Membrane Fusion; D008969:Molecular Sequence Data; D009154:Mutation; D009439:Neuraminidase / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D017384:Sequence Deletion
D000596:Amino Acids; D015686:Gene Products, env; D006023:Glycoproteins; D015700:HIV Envelope Protein gp41; D011498:Protein Precursors; D006026:Glycoside Hydrolases; D009439:Neuraminidase