@article {59720, title = {Integrin Mechano-chemical Signaling Generates Plasma Membrane Nanodomains that Promote Cell Spreading.}, journal = {Cell}, volume = {177}, year = {2019}, month = {2019 Jun 13}, pages = {1738-1756.e23}, abstract = {

Glycosylphosphatidylinositol-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, talin-mediated 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.

}, issn = {1097-4172}, doi = {10.1016/j.cell.2019.04.037}, author = {Kalappurakkal, Joseph Mathew and Anilkumar, Anupama Ambika and Patra, Chandrima and van Zanten, Thomas S and Sheetz, Michael P and Mayor, Satyajit} } @article {3560, title = {GPI-anchored protein organization and dynamics at the cell surface.}, journal = {J Lipid Res}, volume = {57}, year = {2016}, month = {2016 Feb}, pages = {159-75}, abstract = {

The surface of eukaryotic cells is a multi-component fluid bilayer in which glycosylphosphatidylinositol (GPI)-anchored proteins are an abundant constituent. In this review, we discuss the complex nature of the organization and dynamics of GPI-anchored proteins at multiple spatial and temporal scales. Different biophysical techniques have been utilized for understanding this organization, including fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, single particle tracking, and a number of super resolution methods. Major insights into the organization and dynamics have also come from exploring the short-range interactions of GPI-anchored proteins by fluorescence (or F{\"o}rster) resonance energy transfer microscopy. Based on the nanometer to micron scale organization, at the microsecond to the second time scale dynamics, a picture of the membrane bilayer emerges where the lipid bilayer appears inextricably intertwined with the underlying dynamic cytoskeleton. These observations have prompted a revision of the current models of plasma membrane organization, and suggest an active actin-membrane composite.

}, issn = {1539-7262}, doi = {10.1194/jlr.R062885}, author = {Saha, Suvrajit and Anilkumar, Anupama Ambika and Mayor, Satyajit} } @article {881, title = {Transbilayer lipid interactions mediate nanoclustering of lipid-anchored proteins.}, journal = {Cell}, volume = {161}, year = {2015}, month = {2015 Apr 23}, pages = {581-94}, abstract = {

Understanding how functional lipid domains in live cell membranes are generated has posed a challenge. Here, we show that transbilayer interactions are necessary for the generation of cholesterol-dependent nanoclusters of GPI-anchored proteins mediated by membrane-adjacent dynamic actin filaments. We find that long saturated acyl-chains are required for forming GPI-anchor nanoclusters. Simultaneously, at the inner leaflet, long acyl-chain-containing phosphatidylserine (PS) is necessary for transbilayer coupling. All-atom molecular dynamics simulations of asymmetric multicomponent-membrane bilayers in a mixed phase provide evidence that immobilization of long saturated acyl-chain lipids at either leaflet stabilizes cholesterol-dependent transbilayer interactions forming local domains with characteristics similar to a liquid-ordered (lo) phase. This is verified by experiments wherein immobilization of long acyl-chain lipids at one leaflet effects transbilayer interactions of corresponding lipids at the opposite leaflet. This suggests a general mechanism for the generation and stabilization of nanoscale cholesterol-dependent and actin-mediated lipid clusters in live cell membranes.

}, keywords = {Actins, Animals, Cell Membrane, CHO Cells, Cricetulus, Glycosylphosphatidylinositols, Lipid-Linked Proteins, Molecular Dynamics Simulation, Phosphatidylserines}, issn = {1097-4172}, doi = {10.1016/j.cell.2015.03.048}, author = {Raghupathy, Riya and Anilkumar, Anupama Ambika and Polley, Anirban and Singh, Parvinder Pal and Yadav, Mahipal and Johnson, Charles and Suryawanshi, Sharad and Saikam, Varma and Sawant, Sanghapal D and Panda, Aniruddha and Guo, Zhongwu and Vishwakarma, Ram A and Rao, Madan and Mayor, Satyajit} }