Cytoskeletal Components Define Protein Location to Membrane Microdomains*

Witold G Szymanski,Henrik Zauber,Alexander Erban,Michal Gorka,Xu Na Wu,Waltraud X Schulze

doi:10.1074/mcp.m114.046904

Abstract

The plasma membrane is an important compartment that undergoes dynamic changes in composition upon external or internal stimuli. The dynamic subcompartmentation of proteins in ordered low-density (DRM) and disordered high-density (DSM) membrane phases is hypothesized to require interactions with cytoskeletal components. Here, we systematically analyzed the effects of actin or tubulin disruption on the distribution of proteins between membrane density phases. We used a proteomic screen to identify candidate proteins with altered submembrane location, followed by biochemical or cell biological characterization in Arabidopsis thaliana. We found that several proteins, such as plasma membrane ATPases, receptor kinases, or remorins resulted in a differential distribution between membrane density phases upon cytoskeletal disruption. Moreover, in most cases, contrasting effects were observed: Disruption of actin filaments largely led to a redistribution of proteins from DRM to DSM membrane fractions while disruption of tubulins resulted in general depletion of proteins from the membranes. We conclude that actin filaments are necessary for dynamic movement of proteins between different membrane phases and that microtubules are not necessarily important for formation of microdomains as such, but rather they may control the protein amount present in the membrane phases.

Highlights

The plasma membrane is an important compartment that undergoes dynamic changes in composition upon external or internal stimuli
Various proteins found with altered distributions between DRM and density membrane phases (DSM) upon cytoskeletal disruption could be confirmed through resulting differences in activity or location patterns
We suggest that actin filaments are necessary for dynamic movement of proteins between different membrane phases

Summary

Introduction

The plasma membrane is an important compartment that undergoes dynamic changes in composition upon external or internal stimuli. In Singer and Nicolson’s model, the cell membrane is a two-dimensionally oriented viscous solution in which the membrane constituents are orientated in the most thermodynamically favorable manner, hiding hydrophobic hydrocarbon chains inside the lipid bilayer and exposing polar and ionic groups to the aqueous phase. Simons and Ikonen suggested that large ordered phases, enriched with cholesterol and sphingolipids, emerge within the plasma membrane and that they function as platforms for enrichment of certain proteins while excluding others [4] This current membrane model suggests that the mixture of sterols and polar lipids within the plasma membrane can appear in two distinct phases: liquid disordered (Ld) and liquid ordered (Lo) phase [5]. In the plant model, organisms’ plasma membrane microdomains turned out to be important in plant defense [10, 11], cell polarity [12, 13], and general signaling properties of the plasma membrane [14, 15]

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