Entropic forces drive clustering and spatial localization of influenza A M2 during viral budding

Abstract

The influenza A matrix 2 (M2) transmembrane protein facilitates virion release from the infected host cell. In particular, M2 plays a role in the induction of membrane curvature and/or in the scission process whereby the envelope is cut upon virion release. Here we show using coarse-grained computer simulations that various M2 assembly geometries emerge due to an entropic driving force, resulting in compact clusters or linearly extended aggregates as a direct consequence of the lateral membrane stresses. Conditions under which these protein assemblies will cause the lipid membrane to curve are explored, and we predict that a critical cluster size is required for this to happen. We go on to demonstrate that under the stress conditions taking place in the cellular membrane as it undergoes large-scale membrane remodeling, the M2 protein will, in principle, be able to both contribute to curvature induction and sense curvature to line up in manifolds where local membrane line tension is high. M2 is found to exhibit linactant behavior in liquid-disordered-liquid-ordered phase-separated lipid mixtures and to be excluded from the liquid-ordered phase, in near-quantitative agreement with experimental observations. Our findings support a role for M2 in membrane remodeling during influenza viral budding both as an inducer and a sensor of membrane curvature, and they suggest a mechanism by which localization of M2 can occur as the virion assembles and releases from the host cell, independent of how the membrane curvature is produced.

TRIM5α self-assembly and compartmentalization of the HIV-1 viral capsid

“…To surmount the computational cost associated with simulations at an atomic level of detail, we developed a CG model for TRIM5α self-assembly on viral capsids, using methods established in prior studies [25][26][27][28] . An atomic model for TRIM5α was first constructed from crystallographic fragments available in the Protein Data Bank, and subsequently coarse-grained at a resolution of 1 CG particle per 5 amino acid residues (Fig.…”

“…The coarse-grained (CG) model was constructed by mapping five amino acid residues into one CG particle using methods similar to ones we have previously published [25][26][27] . Secondary structure elements within each distinct protein domain (RING: resid 1-81; SPRY: resid 286-497) were constrained as rigid bodies, and regions within the coiled coil domain dimer were also held as rigid bodies (Coiledcoil: resid 91-161, 166-216, and 221-281).…”

Protein Amphipathic Helix Insertion: A Mechanism to Induce Membrane Fission

“…Class IV: Passive mechanism, reverse topology. Examples: fission mediated by the herpesvirus fission machine (Bigalke and Heldwein, 2015), influenza A virus AH-containing protein M2 (Herneisen et al, 2017;Martyna et al, 2017;Madsen et al, 2018), Ebola virus VP40 (Soni and Stahelin, 2014;Adu-Gyamfi et al, 2015).…”

A Glu-Glu-Tyr sequence in the cytoplasmic tail of the M2 protein renders IAV susceptible to restriction of HA-M2 association in primary human macrophages

“…Previous studies using epithelial cells show that while M2 is required for pinching off of virus bud and its subsequent release, it is not required for induction of membrane curvature during particle formation (11,13,17,23). It has also been proposed that M2 is recruited after induction of membrane curvature (41,42), which is likely mediated by HA, NA or M1. At sites of virus assembly, M2 is enriched at the neck of the virus bud (17)(18)(19) and is thought to induce positive membrane curvature, which may be sufficient for membrane scission (17,21).…”