4th International AIDS Conference Stockholm, Sweden. — June 12-16, 1988

Int Conf AIDS. 1988 Jun 12-16;4:1.115 (abstract no. 1009)

Barry S..Stein¹, K Steimer², EG Engleman^1
1Stanford University Medical School, Stanford, CA, USA; ²Chiron Corporation, Emeryville, CA, USA

OBJECTIVE: To evaluate processing of HIV-1 envelope proteins in an infected human CD4+ T cell line (VB).

METHODS: HIV-1 envelope glycoproteins were immunoprecipitated from [³⁵S] amino acid labeled HIV-1 infected VB cells and analyzed by 2D SDS-PAGE.

RESULTS: gp160 and gp41 both focus over a pH range of 7.0 to 7.5, whereas gp120 focuses across a broad pH range of 5.0 to 7.5. gp160 and gp120 are Endo H sensitive, however, the mannose trimmed digest continues to focus broadly from pH 5.0 to 7.5, indicating gp120 has both N-asparagine linked high mannose and complex oligosaccharides. gp160 is neuraminidase-resistant with unchanged migration, but gp120 is exquisitely neuraminidase-sensitive migrating at 100 Kd and focusing above pH 7.5. gp160 and gp120 are' therefore differentially glycosylated and vary significantly in sialylation. Monensin perturbs Golgi-mediated glycosylation, interfering with gp120 processing such that it migrates at 100 Kd and focuses at pH 7.5, but exerts little effect on gpl6O. These data suggest 113120 is extensively sialylated in the trans Golgi.

CONCLUSIONS: If mature glycosylated gpl60 is the precursor to gp120 and gp4l, cleavage must occur in the Golgi as gp120 independently undergoes extensive sialylation which is unlikely to be facilitated at the plasma membrane. Alternatively, cleavage of immature gp160 could occur as it traverses the RER. These data reveal gp120 is a hybrid N-linked glycoprotein.

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