Quantitative Analysis of Cortical Actin-Membrane Microcluster Interactions

Abstract

The spatial organization of receptors on the plasma membrane is crucial for their signaling efficacy. Previous studies have implied that the cortical-actin (CA) meshwork regulates receptor mobility and organization in the plasma membrane. To understand the molecular mechanisms underlying this process, we sought to quantitatively study the role of the CA meshwork in regulating the clustering and mobility of receptors in an in vitro reconstitution system. Specifically, we are studying the mobility, organization and clustering of Linker for Activation of T cells (LAT) complexes in an artificial lipid bilayer with an attached actomyosin meshwork. Our quantitative analyses using light microscopy and computational image analysis have led to the very exciting observation that while LAT complexes exhibit predominantly confined diffusion in the absence of actin, they exhibit nearly equal populations undergoing confined and normal diffusion in the presence of a CA meshwork. Additionally, presence of a CA meshwork influences both the diffusion speed and size distribution of LAT clusters. These results suggest that actin may be playing a larger and more interesting role in influencing cluster dynamics that extends beyond static spatial organization. Future work will focus on determining the proteins that link LAT complexes to the CA meshwork and on extending this work to cells and other receptor systems.