Conformational signalling pathways in HIV-1 Env
The HIV-1 envelope protein comprises a receptor binding subunit gp120 in non-covalent association with the transmembrane fusion protein gp41. gp120 and gp41 associate via the N- and C-terminal regions of gp120 and the conserved disulfide bonded region of gp41. Binding of gp120 to cellular receptors CD4 and CCR5 results in a series of conformational changes that are detected by the disulfide bonded region of gp41 and activate the membrane fusion activity of gp41. How conformational changes are transmitted through gp120 is currently not known. This project seeks to elucidate the structural mechanism whereby conformational signals induced in gp120 by receptor binding are transmitted to gp41 to activate fusion function. Viruses with attenuating DSR mutations will be serially passaged in PBMCs and/or receptor-positive cell lines to select second site mutations that restore replication. 2nd site “suppressor” mutations will locate structural elements that are functionally linked to the DSR and may be involved in the conformational signalling cascade. By evolving a variety of DSR mutants in the context of R5, X4 and R5X4 HIV-1 strains, we aim to build an operational map of structural elements contributing to gp120-gp41 conformational signalling. We will then assess if the structural elements identified play conserved roles in the conformational cascade by site-directed mutagenesis in a variety of HIV-1 strains. These studies will advance our medium-term objective of identifying novel conserved targets for the development of entry inhibitors that block distinct stages of the fusion cascade.
Funding Support: National Health and Medical Research Council (NHMRC)