Nanodomain stabilization dynamics in plasma membranes of biological cells

We discover that a synergistically amplifying role of stabilizing membrane proteins and continuous lipid recycling can explain the physics governing the stability, polydispersity, and dynamics of lipid raft domains in plasma membranes of biological cells. We establish the conjecture using a generalized order parameter based on theoretical formalism, endorsed by detailed scaling arguments and domain mapping. Quantitative agreements with morphological distributions of raft complexes, as obtained from Förster resonance energy transfer based visualization, support the present theoretical conjecture.

Figure 1

(a) Schematic representation of lipid ordered (raft) and disordered domains of cell membrane. (b) Progressive arrest of domain growth by recycling (${\tau }_R={\tau }_R^0$) and surfactant effect of membrane proteins (with ${\rho }_0=0.5{\rho }_s$ and $0.8{\rho }_s$). Average domain perimeter values are normalized by the $\langle r\rangle$value corresponding to a complete phase separation in the free growth case. $\varphi$ and $\rho$ profile image shots are given for $t=200\tau$. Data averaged over at least 20 ensembles.

Figure 2

(a) Variation of steady-state domain size$\langle \Pi \rangle$with recycling parameter (${\tau }_R/{\tau }_R^0$) and normalized initial concentration of membrane protein (${\rho }_0/{\rho }_s$). Both recycling and surfactant effects have been considered (b) Contour map of the parameter $\Gamma$ in the regime where $\Gamma >1$.

Figure 3

Variation of steady-state domain length scale with initial membrane protein density depends on the relative mobility ($M_{\rho }/M_{\varphi }$). (Inset) Dependence of dispersity ($\langle \delta \rangle$) on initial membrane protein density. ${\tau }_R={\tau }_R^0$ for all data points.

Figure 4

Comparison of model prediction with experimental data (see main text). We have obtained ${\tau }_{R,\mathrm{control}}=1.023{\tau }_R^0$ and model fitting has been done with ${\rho }_0=0.657{\rho }_s$. (Inset) $\langle r\rangle$growth with Cytochalasin D (CD) treatment. We have assumed complete disruption of actin fences with 1μM CD. ${\tau }_R={\tau }_{R,\mathrm{control}}$. Number of samples per data point > 5.