Role of the HIV gp120 Conserved Domain 1 in Processing and Viral Entry

Jizhen Wang,Jayita Sen,Lijun Rong,Michael Caffrey

doi:10.1074/jbc.m806099200

Jizhen Wang, Jayita Sen + Show 2 more

Open Access

https://doi.org/10.1074/jbc.m806099200

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Abstract

The importance of the N-terminal region of HIV gp120 conserved domain 1 (gp120-C1) to envelope function has been examined by alanine-scanning mutagenesis and subsequent characterization of the mutagenic effects on viral entry; envelope expression, processing, and incorporation; and gp120 association with gp41. With respect to the wild-type gp120, mutational effects on viral entry fall into two classes: functional, as defined by >20% entry with respect to wild type, and impaired, as defined by <20% entry with respect to wild type. Based on Western blot analyses of cell lysates and virions, the entry impairment of W35A, V38A, Y39A, Y40A, G41A, V42A, and I52A is due primarily to disruption of envelope processing. The entry impairment of P43A and W45A is apparently due to a combination of effects on processing and incorporation into virions. In contrast, the entry impairment of V44A and F53A is primarily due to disruption of the gp120-gp41 interaction, which results in dissociation of gp120 from the virion. We present a model for gp120-C1 interactions with gp120-C5 and the gp41 disulfide loop in unprocessed gp160 and processed gp120/gp41.

Highlights

Mutants E32A, K33A, I34A, V36A, T37A, K46A, E47A, T49A, T50A, and T51A are functional for viral entry, and they exhibit the wild type pattern of gp[160], gp120, and gp[41] in cell extracts and virions
Note that the Y40A substitution is found in some HIV-1 subtype O strains, which suggests that other mutations compensate to allow processing in these strains
Impaired mutants V44A and F53A exhibit a defect in gp120-gp[41] association

Summary

Introduction

In the case of the mutants, the relatively high levels of gp[160] present in cell lysates suggest that envelope expression has not been significantly affected by any of the substitutions. Many of the mutants that display reduced gp[160] processing are impaired for viral entry (i.e. entry levels are Ͻ20% with respect to the wild type).

Results

Conclusion