Curvature Sensing by a Viral Scission Protein

Abstract

Membrane scission is the final step in all budding processes wherein a membrane neck is sufficiently constricted so as to allow for fission and the release of the budded particle. For influenza viruses, membrane scission is mediated by an amphipathic helix (AH) domain in the viral M2 protein. While it is known that the M2AH alters membrane curvature, it is not known how the protein is localized to the center neck of budding virions where it would be able to cause membrane scission. Here, we use molecular dynamics simulations on buckled lipid bilayers to show that the M2AH senses membrane curvature and preferentially localizes to regions of high membrane curvature, comparable to that seen at the center neck of budding influenza viruses. These results were then validated using in vitro binding assays to show that the M2AH senses membrane curvature by detecting lipid packing defects in the membrane. Our results show that the M2AH senses membrane curvature and suggest that the AH domain may localize the protein at the viral neck where it can then mediate membrane scission and the release of budding viruses.

Coronavirus envelope protein: current knowledge

“…However, the new virion also remains attached to the membrane as well as the previous virion by a small membranous neck. The continuation of this cycle and repeated initiation of budding results in the formation of consecutive scission-defective virions that resemble beads on a string [180,181]. The same morphology has been reported for the Moloney murine leukaemia virus upon deletion and mutation of p12 protein that functions in its assembly and release [182].…”

“…In the absence of scission machinery, the budding process begins but ultimately stops, and render budding virions attached to the membrane by a small membranous neck. This causes virions to have an uncharacteristically elongated morphology sometimes referred to as "beads-on-a-string" and is seen in viruses that lack the necessary machinery to release the budded virion [179][180][181][182][183]. This is clearly and elegantly demonstrated in the mutation of the matrix-2 (M2) protein, a viral protein responsible for the budding and scission of the influenza virus.…”

Biophysics of membrane curvature remodeling at molecular and mesoscopic lengthscales

“…We note that while equation (5) describes a mean-field treatment, figure 4 does not invoke the mean-field approximation and in that sense is an exact (albeit numerically evaluated) result for μ ex ( n P ). Still, the mean-field picture of the membrane protein interactions described above is a good description of the curvature sensing behavior of the CRP, which is demonstrated experimentally by measuring protein localization to predeformed regions on the cell membrane [69, 102, 140–144]. …”

“…Several CRPs including BAR and ENTH domains are sensitive to the curvature of membranes adhered to wavy substrates [100]. The large-scale ENTH domain simulations show that they adjust their local order to match the anisotropy of their substrates [97] while simulations performed on buckled bilayers demonstrate that amphipathic helices can sense curvature and lipid packing defects [101, 102]. …”

Entropic Forces Drive Clustering and Spatial Localization of Influenza A M2 During Viral Budding

“…At the C-terminus of each there is an amphipathic helix (35), and recent work has shown that both M2 and the M2 AH amphipathic peptide can serve to facilitate budding and scission of filamentous virions (36,37). Moreover, the M2 AH peptide construct retains significant function in membrane remodeling (38) and curvature sensing (39). A correspondence between models of the full-length M2 protein, the M2 construct lacking the extended C-terminal cytoplasmic tail (but including the AHs), and the M2 AH peptide is therefore reasonable in the study of M2's role in budding and scission.…”