Different models have previously been developed to describe the propulsion of pathogens, but without knowledge of the organization of the filaments involved in pushing. In a new modelling approach we sought to simulate the structure of actin comets driving baculovirus obtained by electron tomography as well as the paths followed by baculovirus in host cell cytoplasm. For details of the mathematical model, see Mueller et al., 2014 (Text S1).
Three scenarios of filament interactions with the surface of the virus were considered: (A), continuous tethering of filaments during pushing; (B), tethering only during the initiation of a branch at the filament-virus interface; and (C), no tethering during pushing.
The video shows mathematical simulations of baculovirus propulsion generated according to two of the scenarios above: Continuously tethered and untethered filaments. The case for filaments tethered only during branching resembled closely the case for untethered filaments (Mueller et al., 2014).
An important feature of the model was the requirement of intermittent nucleation (or capture) of filaments at the virus surface to correct for a stochastic paucity of filament ends engaged in pushing. Without this feature motion was irregular. An additional consequence of this feature was the generation of filament subsets, whose existence was suggested from filament tracking in the tomograms.
- Mueller J, Pfanzelter J, Winkler C, Narita A, Le Clainche C, Nemethova M, Carlier MF, Maeda Y, Welch MD, Ohkawa T, Schmeiser C, Resch GP, Small JV. Electron tomography and simulation of baculovirus actin comet tails support a tethered filament model of pathogen propulsion. PLoS Biol. 2014 Jan;12(1):e1001765.