Integrin Mechano-chemical Signaling Generates Plasma Membrane Nanodomains that Promote Cell Spreading

Joseph Mathew Kalappurakkal,Anupama Ambika Anilkumar,Chandrima Patra,Thomas S Van Zanten,Michael P Sheetz,Satyajit Mayor

doi:10.1016/j.cell.2019.04.037

Abstract

SummaryGlycosylphosphatidylinositol-anchored proteins (GPI-APs) are a major class of lipid-anchored plasma membrane proteins. GPI-APs form nanoclusters generated by cortical acto-myosin activity. While our understanding of the physical principles governing this process is emerging, the molecular machinery and functional relevance of GPI-AP nanoclustering are unknown. Here, we first show that a membrane receptor signaling pathway directs nanocluster formation. Arg-Gly-Asp motif-containing ligands bound to the β1-integrin receptor activate src and focal adhesion kinases, resulting in RhoA signaling. This cascade triggers actin-nucleation via specific formins, which, along with myosin activity, drive the nanoclustering of membrane proteins with actin-binding domains. Concurrently, talinmediated activation of the mechano-transducer vinculin is required for the coupling of the acto-myosin machinery to inner-leaflet lipids, thereby generating GPI-AP nanoclusters. Second, we show that these nanoclusters are functional; disruption of their formation either in GPI-anchor remodeling mutants or in vinculin mutants impairs cell spreading and migration, hallmarks of integrin function.

Highlights

Proteins and lipids can laterally segregate along the plasma membrane (PM) into domains that play a pivotal role in the spatio-temporal regulation of many cellular processes
intercellular adhesion molecule 1 (ICAM-1) binding to its integrin receptor lymphocyte functionassociated antigen-1 (LFA-1) in immune cells results in hotspots of glycosylphosphatidylinositol-anchored proteins (GPI-APs) nanoclusters at the site of activation
To see whether activation of other integrins leads to GPI-AP nanoclustering, we used fluorescence emission anisotropy-based microscopy to assess the extent of resonance energy transfer between like fluorophores tagged to GPI-APs

Summary

Introduction

Proteins and lipids can laterally segregate along the plasma membrane (PM) into domains that play a pivotal role in the spatio-temporal regulation of many cellular processes Such functional domains, enriched in cholesterol, sphingolipids, and outer-leaflet lipid-tethered glycosylphosphatidylinositol-anchored proteins (GPI-APs), have often been termed as membrane rafts (Lingwood and Simons, 2010). We had previously proposed that nanoclusters of GPI-APs are driven by transient remodeling contractile platforms at the inner leaflet called ‘‘asters,’’ composed of dynamic actin filaments and myosin motors (Gowrishankar et al, 2012). These asters immobilize long-acyl-chaincontaining phosphatidylserine (PS) at the inner leaflet. PS interacts across the bilayer with long-acyl-chain-containing GPIAPs at the outer leaflet to facilitate GPI-AP nanoclustering (Raghupathy et al, 2015)

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Discussion

Conclusion