Large self-assembled clathrin lattices spontaneously disassemble without sufficient adaptor proteins
Fig 3
Structure-resolved reaction-diffusion simulations of clathrin assembly kinetics on membranes reproduce in vitro experiment.
(A) Simulations were set up to mimic experimental conditions from published work of Pucadyil et al [25], where fluorescence of clathrin accumulating on membrane tubules was measured with time. A constant (fluctuating) solution concentration of clathrin (at 80nM) was maintained through exchange with a large volume reservoir. (B) Fluorescence of clathrin on membranes is averaged over multiple tubules (black line). The experimental fluorescence data was reported in arbitrary units [25]. This means there is a free scale factor we use to match with our simulations, which measure clathrin accumulation in units of copy numbers per μm2. The model result is shown in blue (averaged from 4 simulation trajectories). Both the simulation data (gray dashed line) and experimental data can be fit to Eq 1A, producing timescales (growth rate k and lag time τ) that can be directly compared to one another. The initial growth is approximately linear, with a steepness given by kE, with E the maximal extent of clathrin on the membrane (Eq 1B). (C) Snapshots of one simulation trajectory at different time points, also see S1 Movie. (D) The macroscopic timescales of the lag time τ (black dots) and initial growth steepness kE (red dots) vary with changes to six model parameters, as shown in each sub-plot D1-D6 and listed in Table 1. We plot the initial growth steepness kE rather than the growth rate k, as it was more amenable to theoretical predictions. The dashed black and red lines are the theoretical fits from our phenomenological models to τ (Eq 2) and kE (Eq 3). For each subplot, the non-varied parameters are otherwise fixed to the optimal values of Table 1.