Self assembly of HIV-1 Gag protein on lipid membranes generates PI(4,5)P₂/Cholesterol nanoclusters

Abstract

The self-assembly of HIV-1 Gag polyprotein at the inner leaflet of the cell host plasma membrane is the key orchestrator of virus assembly. The binding between Gag and the plasma membrane is mediated by specific interaction of the Gag matrix domain and the PI(4,5)P 2 lipid (PIP 2 ). It is unknown whether this interaction could lead to local reorganization of the plasma membrane lipids. In this study, using model membranes, we examined the ability of Gag to segregate specific lipids upon self-assembly. We show for the first time that Gag self-assembly is responsible for the formation of PIP 2 lipid nanoclusters, enriched in cholesterol but not in sphingomyelin. We also show that Gag mainly partition into liquid-disordered domains of these lipid membranes. Our work strongly suggests that, instead of targeting pre-existing plasma membrane lipid domains, Gag is more prone to generate PIP 2 /Cholesterol lipid nanodomains at the inner leaflet of the plasma membrane during early events of virus assembly.

Single molecule localisation microscopy reveals how HIV-1 Gag proteins sense membrane virus assembly sites in living host CD4 T cells

“…S2 ). This suggests that in Jurkat T-cells, the plasma membrane can rescue the lack in efficient CA-CA dimerisation in order to produce immature particles, as already observed on model membranes 10 . This is also in good agreement with the labile membrane bound form of WM Gag mutant observed in 293T HEK cells in the Robinson et al .…”

“…These results indicate that upon alteration of Gag multimerisation capacity, Gag is less bound to cell membranes, confirming a role for Gag oligomerisation in stabilising Gag-membrane interactions, in agreement with 29 . Moreover, it was recently shown that in vitro Gag oligomerisation occurs also on PIP 2 -containing lipid membranes and that it is reduced by the same WM mutation in the CA domain of Gag 10 . Transmission electron microscopy was then used to check whether WT Gag(i)mEOS2 and mutants formed particles (Gag VLPs) (Fig.…”

“…MA is myristoylated and contains a highly basic region involved in Gag targeting and anchoring to the inner leaflet of the host cell plasma membrane where viral assembly occurs (reviewed in 6 – 8 ). CA, via CA-CA interacting domains, promote Gag-Gag oligomerisation in vitro 9 , 10 and in cells 11 . NC, sp2 and p6 are required for Gag assembly and particle budding.…”

Oncogenesis, lipids rafts and liquid crystals: A nanoscopic supplementary field for applied researches and a new hope of advances in cancer

“…The PI3K/Akt/mTor pathway [ 11 , 26 , 27 , 32 , 33 , 34 , 35 ] is an intracellular signaling pathway initiated at the membrane, which is frequently activated in case of cancer. It is involved in cell growth and proliferation, angiogenesis, apoptosis and carbohydrate metabolism.…”

Monitoring HIV-1 Assembly in Living Cells: Insight from Dynamic and Single Molecule Microscopy

“…It is also well known that MA governs membrane targeting. Membrane targeting of Gag requires the N-terminal myristate, as well as residues in MA that form a basic patch (the highly basic region, HBR) and interact with acidic head groups of phospholipids in the PM, including phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) found in the inner leaflet of the PM [4][5][6][7][8][9][10][11][12]. CA contains residues that form critical Gag-Gag interactions and NC is required for viral genomic RNA packaging, as well as non-specific interactions with RNA [13], and is essential for particle assembly [14].…”