scholarly journals Systematic analysis of the molecular architecture of endocytosis reveals a nanoscale actin nucleation template that drives efficient vesicle formation

2017 ◽  
Author(s):  
Markus Mund ◽  
Johannes Albertus van der Beek ◽  
Joran Deschamps ◽  
Serge Dmitrieff ◽  
Jooske Louise Monster ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
Design Principle ◽  
Vesicle Formation ◽  
Molecular Architecture ◽  
Actin Nucleation ◽  
Systematic Analysis ◽  
Superresolution Microscopy ◽  
Membrane Invagination ◽  
Wasp Family Proteins ◽  
Endocytic Vesicles

Clathrin-mediated endocytosis is an essential cellular function in all eukaryotes that is driven by a self-assembled macromolecular machine of over 50 different proteins in tens to hundreds of copies. How these proteins are organized to produce endocytic vesicles with high precision and efficiency is not understood. Here, we developed high-throughput superresolution microscopy to reconstruct the nanoscale structural organization of 23 endocytic proteins from over 100,000 endocytic sites in yeast. We found that proteins assemble by radially-ordered recruitment according to function. WASP family proteins form a circular nano-scale template on the membrane to spatially control actin nucleation during vesicle formation. Mathematical modeling of actin polymerization showed that this WASP nano-template creates sufficient force for membrane invagination and substantially increases the efficiency of endocytosis. Such nanoscale pre-patterning of actin nucleation may represent a general design principle for directional force generation in membrane remodeling processes such as during cell migration and division.

scholarly journals Profilin connects actin assembly with microtubule dynamics

2016 ◽  
Vol 27 (15) ◽  
pp. 2381-2393 ◽  
Author(s):  
Michaela Nejedla ◽  
Sara Sadi ◽  
Vadym Sulimenko ◽  
Francisca Nunes de Almeida ◽  
Hans Blom ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
Actin Dynamics ◽  
Control Element ◽  
Actin Assembly ◽  
Actin Nucleation ◽  
Superresolution Microscopy ◽  
Drug Treatments ◽  
And Migration ◽  
Wasp Family Proteins ◽  
Microscopy Techniques

Profilin controls actin nucleation and assembly processes in eukaryotic cells. Actin nucleation and elongation promoting factors (NEPFs) such as Ena/VASP, formins, and WASP-family proteins recruit profilin:actin for filament formation. Some of these are found to be microtubule associated, making actin polymerization from microtubule-associated platforms possible. Microtubules are implicated in focal adhesion turnover, cell polarity establishment, and migration, illustrating the coupling between actin and microtubule systems. Here we demonstrate that profilin is functionally linked to microtubules with formins and point to formins as major mediators of this association. To reach this conclusion, we combined different fluorescence microscopy techniques, including superresolution microscopy, with siRNA modulation of profilin expression and drug treatments to interfere with actin dynamics. Our studies show that profilin dynamically associates with microtubules and this fraction of profilin contributes to balance actin assembly during homeostatic cell growth and affects micro­tubule dynamics. Hence profilin functions as a regulator of microtubule (+)-end turnover in addition to being an actin control element.

scholarly journals Three Regions within Acta Promote Arp2/3 Complex-Mediated Actin Nucleation and Listeria monocytogenes Motility

2000 ◽  
Vol 150 (3) ◽  
pp. 527-538 ◽  
Author(s):  
Justin Skoble ◽  
Daniel A. Portnoy ◽  
Matthew D. Welch
Keyword(s):  
Listeria Monocytogenes ◽  
Actin Polymerization ◽  
Sequence Similarity ◽  
Binding Region ◽  
Actin Nucleation ◽  
Homology Sequence ◽  
Infected Cells ◽  
Wasp Family Proteins ◽  
In Cells

The Listeria monocytogenes ActA protein induces actin-based motility by enhancing the actin nucleating activity of the host Arp2/3 complex. Using systematic truncation analysis, we identified a 136-residue NH2-terminal fragment that was fully active in stimulating nucleation in vitro. Further deletion analysis demonstrated that this fragment contains three regions, which are important for nucleation and share functional and/or limited sequence similarity with host WASP family proteins: an acidic stretch, an actin monomer–binding region, and a cofilin homology sequence. To determine the contribution of each region to actin-based motility, we compared the biochemical activities of ActA derivatives with the phenotypes of corresponding mutant bacteria in cells. The acidic stretch functions to increase the efficiency of actin nucleation, the rate and frequency of motility, and the effectiveness of cell–cell spread. The monomer-binding region is required for actin nucleation in vitro, but not for actin polymerization or motility in infected cells, suggesting that redundant mechanisms may exist to recruit monomer in host cytosol. The cofilin homology sequence is critical for stimulating actin nucleation with the Arp2/3 complex in vitro, and is essential for actin polymerization and motility in cells. These data demonstrate that each region contributes to actin-based motility, and that the cofilin homology sequence plays a principal role in activation of the Arp2/3 complex, and is an essential determinant of L. monocytogenes pathogenesis.

scholarly journals Evolutionary Perspectives on the Moonlighting Functions of Bacterial Factors That Support Actin-Based Motility

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Volkan K. Köseoğlu ◽  
Hervé Agaisse
Keyword(s):  
Cell Adhesion ◽  
Host Cell ◽  
Biofilm Formation ◽  
Actin Polymerization ◽  
Current Knowledge ◽  
Bacterial Pathogens ◽  
Actin Nucleation ◽  
Bacterial Aggregation ◽  
Moonlighting Functions ◽  
Evolutionary Perspectives

ABSTRACT Various bacterial pathogens display an intracellular lifestyle and spread from cell to cell through actin-based motility (ABM). ABM requires actin polymerization at the bacterial pole and is mediated by the expression of bacterial factors that hijack the host cell actin nucleation machinery or exhibit intrinsic actin nucleation properties. It is increasingly recognized that bacterial ABM factors, in addition to having a crucial task during the intracellular phase of infection, display “moonlighting” adhesin functions, such as bacterial aggregation, biofilm formation, and host cell adhesion/invasion. Here, we review our current knowledge of ABM factors and their additional functions, and we propose that intracellular ABM functions have evolved from ancestral, extracellular adhesin functions.

scholarly journals EGF stimulates an increase in actin nucleation and filament number at the leading edge of the lamellipod in mammary adenocarcinoma cells

1998 ◽  
Vol 111 (2) ◽  
pp. 199-211 ◽  
Author(s):  
A.Y. Chan ◽  
S. Raft ◽  
M. Bailly ◽  
J.B. Wyckoff ◽  
J.E. Segall ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
De Novo ◽  
Leading Edge ◽  
Mammary Adenocarcinoma ◽  
Actin Dynamics ◽  
Actin Nucleation ◽  
Nucleation Sites ◽  
Nucleation Activity ◽  
Pointed End ◽  
Stimulation Of

Stimulation of metastatic MTLn3 cells with EGF causes the rapid extension of lamellipods, which contain a zone of F-actin at the leading edge. In order to establish the mechanism for accumulation of F-actin at the leading edge and its relationship to lamellipod extension in response to EGF, we have studied the kinetics and location of EGF-induced actin nucleation activity in MTLn3 cells and characterized the actin dynamics at the leading edge by measuring the changes at the pointed and barbed ends of actin filaments upon EGF stimulation of MTLn3 cells. The major result of this study is that stimulation of MTLn3 cells with EGF causes a transient increase in actin nucleation activity resulting from the appearance of free barbed ends very close to the leading edge of extending lamellipods. In addition, cytochalasin D causes a significant decrease in the total F-actin content in EGF-stimulated cells, indicating that both actin polymerization and depolymerization are stimulated by EGF. Pointed end incorporation of rhodamine-labeled actin by the EGF stimulated cells is 2.12+/−0.47 times higher than that of control cells. Since EGF stimulation causes an increase in both barbed and pointed end incorporation of rhodamine-labeled actin in the same location, the EGF-stimulated nucleation sites are more likely due either to severing of pre-existing filaments or de novo nucleation of filaments at the leading edge thereby creating new barbed and pointed ends. The timing and location of EGF-induced actin nucleation activity in MTLn3 cells can account for the observed accumulation of F-actin at the leading edge and demonstrate that this F-actin rich zone is the primary actin polymerization zone after stimulation.

scholarly journals Myosin 1E coordinates actin assembly and cargo trafficking during clathrin-mediated endocytosis

2012 ◽  
Vol 23 (15) ◽  
pp. 2891-2904 ◽  
Author(s):  
Jackie Cheng ◽  
Alexandre Grassart ◽  
David G. Drubin
Keyword(s):  
Mammalian Cells ◽  
Actin Polymerization ◽  
Type I ◽  
Actin Assembly ◽  
Significant Delay ◽  
Src Homology 3 ◽  
Integral Role ◽  
Src Homology 3 Domain ◽  
Src Homology ◽  
Endocytic Vesicles

Myosin 1E (Myo1E) is recruited to sites of clathrin-mediated endocytosis coincident with a burst of actin assembly. The recruitment dynamics and lifetime of Myo1E are similar to those of tagged actin polymerization regulatory proteins. Like inhibition of actin assembly, depletion of Myo1E causes reduced transferrin endocytosis and a significant delay in transferrin trafficking to perinuclear compartments, demonstrating an integral role for Myo1E in these actin-mediated steps. Mistargeting of GFP-Myo1E or its src-homology 3 domain to mitochondria results in appearance of WIP, WIRE, N-WASP, and actin filaments at the mitochondria, providing evidence for Myo1E's role in actin assembly regulation. These results suggest for mammalian cells, similar to budding yeast, interdependence in the recruitment of type I myosins, WIP/WIRE, and N-WASP to endocytic sites for Arp2/3 complex activation to assemble F-actin as endocytic vesicles are being formed.

scholarly journals Genetic dissection of active forgetting in labile and consolidated memories in Drosophila

2019 ◽  
Vol 116 (42) ◽  
pp. 21191-21197 ◽  
Author(s):  
Yang Gao ◽  
Yichun Shuai ◽  
Xuchen Zhang ◽  
Yuwei Peng ◽  
Lianzhang Wang ◽  
...  
Keyword(s):  
Rho Gtpases ◽  
Mushroom Body ◽  
Actin Polymerization ◽  
Molecular Mechanisms ◽  
Genetic Dissection ◽  
Actin Depolymerization ◽  
Downstream Effector ◽  
Different Types ◽  
Wasp Family Proteins

Different memory components are forgotten through distinct molecular mechanisms. In Drosophila, the activation of 2 Rho GTPases (Rac1 and Cdc42), respectively, underlies the forgetting of an early labile memory (anesthesia-sensitive memory, ASM) and a form of consolidated memory (anesthesia-resistant memory, ARM). Here, we dissected the molecular mechanisms that tie Rac1 and Cdc42 to the different types of memory forgetting. We found that 2 WASP family proteins, SCAR/WAVE and WASp, act downstream of Rac1 and Cdc42 separately to regulate ASM and ARM forgetting in mushroom body neurons. Arp2/3 complex, which organizes branched actin polymerization, is a canonical downstream effector of WASP family proteins. However, we found that Arp2/3 complex is required in Cdc42/WASp-mediated ARM forgetting but not in Rac1/SCAR-mediated ASM forgetting. Instead, we identified that Rac1/SCAR may function with formin Diaphanous (Dia), a nucleator that facilitates linear actin polymerization, in ASM forgetting. The present study, complementing the previously identified Rac1/cofilin pathway that regulates actin depolymerization, suggests that Rho GTPases regulate forgetting by recruiting both actin polymerization and depolymerization pathways. Moreover, Rac1 and Cdc42 may regulate different types of memory forgetting by tapping into different actin polymerization mechanisms.

scholarly journals Regulation of WASP/WAVE proteins

2004 ◽  
Vol 166 (7) ◽  
pp. 957-962 ◽  
Author(s):  
Guillaume Bompard ◽  
Emmanuelle Caron
Keyword(s):  
Crucial Role ◽  
Actin Polymerization ◽  
Post Translational Modifications ◽  
Wasp Family Proteins

Despite their homology, the regulation of WASP and WAVE, activators of Arp2/3-dependent actin polymerization, has always been thought to be different. Several recent studies have revealed new aspects of their regulation, highlighting its complexity and the crucial role of post-translational modifications. New data also suggest additional functions for WASP family proteins, pushing us to reconsider existing models.

scholarly journals Remodeling the zonula adherens in response to tension and the role of afadin in this response

2016 ◽  
Vol 213 (2) ◽  
pp. 243-260 ◽  
Author(s):  
Wangsun Choi ◽  
Bipul R. Acharya ◽  
Grégoire Peyret ◽  
Marc-Antoine Fardin ◽  
René-Marc Mège ◽  
...  
Keyword(s):  
Mdck Cells ◽  
Coiled Coil ◽  
Epithelial Cell Line ◽  
Molecular Architecture ◽  
Superresolution Microscopy ◽  
Tissue Integrity ◽  
Dynamic Coordination ◽  
Altered Cell ◽  
Actin Cables ◽  
Cell Cell

Morphogenesis requires dynamic coordination between cell–cell adhesion and the cytoskeleton to allow cells to change shape and move without losing tissue integrity. We used genetic tools and superresolution microscopy in a simple model epithelial cell line to define how the molecular architecture of cell–cell zonula adherens (ZA) is modified in response to elevated contractility, and how these cells maintain tissue integrity. We previously found that depleting zonula occludens 1 (ZO-1) family proteins in MDCK cells induces a highly organized contractile actomyosin array at the ZA. We find that ZO knockdown elevates contractility via a Shroom3/Rho-associated, coiled-coil containing protein kinase (ROCK) pathway. Our data suggest that each bicellular border is an independent contractile unit, with actin cables anchored end-on to cadherin complexes at tricellular junctions. Cells respond to elevated contractility by increasing junctional afadin. Although ZO/afadin knockdown did not prevent contractile array assembly, it dramatically altered cell shape and barrier function in response to elevated contractility. We propose that afadin acts as a robust protein scaffold that maintains ZA architecture at tricellular junctions.

scholarly journals Recruitment, Assembly, and Molecular Architecture of the SpoIIIE DNA Pump Revealed by Superresolution Microscopy

PLoS Biology ◽  
2013 ◽  
Vol 11 (5) ◽  
pp. e1001557 ◽  
Author(s):  
Jean-Bernard Fiche ◽  
Diego I. Cattoni ◽  
Nele Diekmann ◽  
Julio Mateos Langerak ◽  
Caroline Clerte ◽  
...  
Keyword(s):  
Molecular Architecture ◽  
Superresolution Microscopy

scholarly journals Dictyostelium discoideum plasma membranes contain an actin-nucleating activity that requires ponticulin, an integral membrane glycoprotein.

1990 ◽  
Vol 110 (3) ◽  
pp. 681-692 ◽  
Author(s):  
A Shariff ◽  
E J Luna
Keyword(s):  
Dictyostelium Discoideum ◽  
Actin Polymerization ◽  
Plasma Membranes ◽  
Actin Binding ◽  
Heat Denaturation ◽  
Actin Assembly ◽  
Binding Studies ◽  
Actin Nucleation ◽  
Equilibrium Binding ◽  
Nucleation Activity

In previous equilibrium binding studies, Dictyostelium discoideum plasma membranes have been shown to bind actin and to recruit actin into filaments at the membrane surface. However, little is known about the kinetic pathway(s) through which actin assembles at these, or other, membranes. We have used actin fluorescently labeled with N-(1-pyrenyl)iodoacetamide to examine the kinetics of actin assembly in the presence of D. discoideum plasma membranes. We find that these membranes increase the rate of actin polymerization. The rate of membrane-mediated actin polymerization is linearly dependent on membrane protein concentrations up to 20 micrograms/ml. Nucleation (the association of activated actin monomers into oligomers) appears to be the primary step of polymerization that is accelerated. A sole effect on the initial salt-induced actin conformational change (activation) is ruled out because membranes accelerate the polymerization of pre-activated actin as well as actin activated in the presence of membranes. Elongation of preexisting filaments also is not the major step of polymerization facilitated by membranes since membranes stripped of all peripheral components, including actin, increase the rate of actin assembly to about the same extent as do membranes containing small amounts of endogenous actin. Acceleration of the nucleation step by membranes also is supported by an analysis of the dependence of polymerization lag time on actin concentration. The barbed ends of membrane-induced actin nuclei are not obstructed by the membranes because the barbed end blocking agent, cytochalasin D, reduces the rate of membrane-mediated actin nucleation. Similarly, the pointed ends of the nuclei are not blocked by membranes since the depolymerization rate of gelsolin-capped actin is unchanged in the presence of membranes. These results are consistent with previous observations of lateral interactions between membranes and actin filaments. These results also are consistent with two predictions from a model based on equilibrium binding studies; i.e., that plasma membranes should nucleate actin assembly and that membrane-bound actin nuclei should have both ends free (Schwartz, M. A., and E. J. Luna. 1988. J. Cell Biol. 107:201-209). Integral membrane proteins mediate the actin nucleation activity because activity is eliminated by heat denaturation, treatment with reducing agents, or proteolysis of membranes. Activity also is abolished by solubilization with octylglucoside but is reconstituted upon removal or dilution of the detergent. Ponticulin, the major actin-binding protein in plasma membranes, appears to be necessary for nucleation activity since activity is not reconstituted from detergent extracts depleted of ponticulin.

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