(757j) Modeling Protein-Lipid Sorting at the HIV-1 Viral Assembly Site

We are interested in understanding the effect of protein binding and aggregation on membrane dynamics at the viral assembly site of HIV-1. Combining molecular dynamics and fluorescence microscopy, we show protein binding of the membrane targeting domain of HIV-1 Gag influences local lipid composition in both leaflets of the plasma membrane. We modeled the membrane as an asymmetric patch with five lipid species native to the plasma membrane using all-atom molecular dynamics. We run micro-second trajectories of unbiased simulations of systems with at least three protein units on the membrane surface to mimic the initiation of viral assembly. We compared results from the simulations with experimental observations to provide a molecular explanation for the recruitment of charged lipids to the protein binding site, specially PIP₂ lipids. Similarly, we examined the effect of local lipid relocation on the inner leaflet at protein binding sites on the lipids on the opposite leaflet. In this work we show the lipidated tail of the membrane targeting domain of Gag is involved in lipid sorting upon insertion, but it is not required for stable protein binding. Recruitment of PIP₂ lipids to the protein binding site stabilizes protein-membrane interactions, which occur primarily at the highly-basic-region of the protein located near the lipid tail of the protein. These observations contribute to our understanding of molecular interactions that prepare a region in the plasma membrane for viral assembly and budding.

Our results advance the understanding of key mechanisms in the viral assembly process of HIV-1 and offer potential new perspectives for inhibitor-based antiretroviral treatments. Additionally, it shows the importance of accurate membrane models to study protein dynamics through simulation, and provides insights into relevant interactions between lipidated peripheral proteins on the membrane surface.