TY - JOUR
T1 - Mechanistic principles underlying regulation of the actin cytoskeleton by phosphoinositides
AU - Senju, Yosuke
AU - Kalimeri, Maria
AU - Koskela, Essi V.
AU - Somerharju, Pentti
AU - Zhao, Hongxia
AU - Vattulainen, Ilpo
AU - Lappalainen, Pekka
N1 - Funding Information:
ACKNOWLEDGMENTS. We thank Patricia Bassereau, Feng-Ching Tsai (Insti-tut Curie, France), Elina Ikonen, and Maarit Neuvonen (Faculty of Medicine, University of Helsinki) for their helpful discussions and technical advice. The authors also thank the Light Microscopy Unit (Institute of Biotechnology, University of Helsinki), Lotta Gustavsson, Aleksi Ainonen, Markus Korpela, and Anna Liisa Nyfors for technical assistance. The Dia2 and N-WASP cDNAs were kind gifts from Tatyana Svitkina (University of Pennsylvania) and Jack Taunton (University of California, San Francisco), respectively. The cDNAs for ezrin and moesin were provided by the Genome Biology Unit (Biocenter Finland, University of Helsinki). This work was supported by the Academy of Finland (Center of Excellence program; Y.S., M.K., I.V., and P.L.), the Japan Society for the Promotion of Science (Y.S.), and European Research Council Advanced Grant CROWDED-PRO-LIPIDS (to I.V.). We acknowledge the Finnish CSC-IT Centre for Science (Espoo, Finland) for computer resources.
PY - 2017/10/24
Y1 - 2017/10/24
N2 - The actin cytoskeleton powers membrane deformation during many cellular processes, such as migration, morphogenesis, and endocytosis. Membrane phosphoinositides, especially phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], regulate the activities of many actinbinding proteins (ABPs), including profilin, cofilin, Dia2, N-WASP, ezrin, and moesin, but the underlying molecular mechanisms have remained elusive. Moreover, because of a lack of available methodology, the dynamics of membrane interactions have not been experimentally determined for any ABP. Here, we applied a combination of biochemical assays, photobleaching/activation approaches, and atomistic molecular dynamics simulations to uncover the molecular principles by which ABPs interact with phosphoinositide-rich membranes. We show that, despite using different domains for lipid binding, these proteins associate with membranes through similar multivalent electrostatic interactions, without specific binding pockets or penetration into the lipid bilayer. Strikingly, our experiments reveal that these proteins display enormous differences in the dynamics of membrane interactions and in the ranges of phosphoinositide densities that they sense. Profilin and cofilin display transient, low-affinity interactions with phosphoinositide-rich membranes, whereas F-actin assembly factors Dia2 and N-WASP reside on phosphoinositide-richmembranes for longer periods to performtheir functions. Ezrin and moesin, which link the actin cytoskeleton to the plasma membrane, bindmembranes with very high affinity and slow dissociation dynamics. Unlike profilin, cofilin, Dia2, and N-WASP, they do not require high "stimulus-responsive" phosphoinositide density for membrane binding. Moreover, ezrin can limit the lateral diffusion of PI(4,5)P2 along the lipid bilayer. Together, these findings demonstrate that membrane-interaction mechanisms of ABPs evolved to precisely fulfill their specific functions in cytoskeletal dynamics.
AB - The actin cytoskeleton powers membrane deformation during many cellular processes, such as migration, morphogenesis, and endocytosis. Membrane phosphoinositides, especially phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], regulate the activities of many actinbinding proteins (ABPs), including profilin, cofilin, Dia2, N-WASP, ezrin, and moesin, but the underlying molecular mechanisms have remained elusive. Moreover, because of a lack of available methodology, the dynamics of membrane interactions have not been experimentally determined for any ABP. Here, we applied a combination of biochemical assays, photobleaching/activation approaches, and atomistic molecular dynamics simulations to uncover the molecular principles by which ABPs interact with phosphoinositide-rich membranes. We show that, despite using different domains for lipid binding, these proteins associate with membranes through similar multivalent electrostatic interactions, without specific binding pockets or penetration into the lipid bilayer. Strikingly, our experiments reveal that these proteins display enormous differences in the dynamics of membrane interactions and in the ranges of phosphoinositide densities that they sense. Profilin and cofilin display transient, low-affinity interactions with phosphoinositide-rich membranes, whereas F-actin assembly factors Dia2 and N-WASP reside on phosphoinositide-richmembranes for longer periods to performtheir functions. Ezrin and moesin, which link the actin cytoskeleton to the plasma membrane, bindmembranes with very high affinity and slow dissociation dynamics. Unlike profilin, cofilin, Dia2, and N-WASP, they do not require high "stimulus-responsive" phosphoinositide density for membrane binding. Moreover, ezrin can limit the lateral diffusion of PI(4,5)P2 along the lipid bilayer. Together, these findings demonstrate that membrane-interaction mechanisms of ABPs evolved to precisely fulfill their specific functions in cytoskeletal dynamics.
KW - Actin cytoskeleton
KW - Molecular dynamics simulations
KW - Phosphoinositides
KW - Protein-lipid interaction
KW - Signal transduction
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U2 - 10.1073/pnas.1705032114
DO - 10.1073/pnas.1705032114
M3 - Article
C2 - 29073094
AN - SCOPUS:85032030690
SN - 0027-8424
VL - 114
SP - E8977-E8986
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 43
ER -