Inositol hexakisphosphate (IP6) accelerates immature HIV-1 Gag protein assembly towards kinetically-trapped morphologies

Abstract

During the late stages of the HIV-1 lifecycle, immature virions are produced by the concerted activity of Gag polyproteins, primarily mediated by the capsid (CA) and spacer peptide 1 (SP1) domains, which assemble into a spherical lattice, package viral genomic RNA, and deform the plasma membrane. Recently, inositol, hexakisphosphate (IP6) has been identified as an essential assembly cofactor that efficiently produces both immature virions in vivo and immature virus like particles in vitro. To date, however, several distinct mechanistic roles for IP6 have been proposed on the basis of independent functional, structural, and kinetic studies. In this work, we investigate the molecular influence of IP6 on the structural outcomes and dynamics of CA/SP1 assembly using coarse-grained (CG) molecular dynamics (MD) simulations and free energy calculations. Here, we derive a bottom-up, low-resolution, and implicit-solvent CG model of CA/SP1 and IP6, and simulate their assembly under conditions that emulate both in vitro and in vivo systems. Our analysis identifies IP6 as an assembly accelerant that promotes curvature generation and fissure-like defects throughout the lattice. Our findings suggest that IP6 induces kinetically-trapped immature morphologies, which may be physiologically important for later stages of viral morphogenesis and potentially useful for virus-like particle technologies.

Cooperative Membrane Binding of HIV-1 Matrix Proteins

“…None of the Myr groups at the trimer-trimer interface exhibit Myr insertion although they are in 'Myr-exposed' states. On the other hand, in the random dimer model (Figure 2), 4 Myr groups are at a stable inserted state at the end of the 5 µs trajectory. In both simulations, at least one Myr group remained in the sequestered state.…”

“…The Gag polyprotein consists of the matrix (MA), Capsid (CA), spacer-peptide 1 (SP1), nucleocapsid (NC), spacer-peptide 2 (SP2), and p6 domains. While the CA and NC domains contribute to Gag multimerization and RNA encapsidation during the viral assembly [3][4][5] , the p6 domain plays an important role in viral budding. Membrane targeting to the PM and recruitment of the Envelope(Env) protein is mediated by the MA domain, which is post-translationally acylated with a myristate (Myr) group in its N-terminus [6][7][8][9][10] .…”

A Review on FDA Approved Anti-HIV-1 Drugs, Anti-Gag Compounds and Potential Strategies for HIV-1 Eradication

“…IP6 interacts with the six-helix bundle structure and stabilizes the immature Gag lattice. IP6 is also very crucial for assembly of CA into the mature fullerene-like cone lattice [187][188][189][190][191][192].…”

Conformational transitions of the HIV-1 Gag polyprotein upon multimerization and gRNA binding

“…The polyanion, IP6, binds the rings of basic LYS residues (LYS290, LYS359) and the mutations of either LYS residues have been observed to disrupt immature viral particle production and infectivity (37,38). A recent coarse-grained molecular dynamics (CGMD) study revealed that other than the role of IP6 as an assembly accelerator, it promotes kinetically-trapped fissure-like defects in the immature lattice which might play an important role in the later stages of the viral replication cycle (39). In addition, homo-dimeric and homo-trimeric interactions are mediated by the CANTD and CACTD residues.…”