Photon correlation spectroscopic studies of filamentous actin networks

1991 ◽  
Author(s):  
Jay E. Newman ◽  
Pier L. San Biagio ◽  
Kenneth L. Schick
Keyword(s):  
Spectroscopic Studies ◽  
Filamentous Actin ◽  
Photon Correlation ◽  
Actin Networks

scholarly journals Type I myosins anchor actin assembly to the plasma membrane during clathrin-mediated endocytosis

2019 ◽  
Vol 218 (4) ◽  
pp. 1138-1147 ◽  
Author(s):  
Ross T.A. Pedersen ◽  
David G. Drubin
Keyword(s):  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Force Generation ◽  
Type I ◽  
Actin Assembly ◽  
Filamentous Actin ◽  
Actin Networks ◽  
Wide Range ◽  
Assembly Factors ◽  
Myosin Motors

The actin cytoskeleton generates forces on membranes for a wide range of cellular and subcellular morphogenic events, from cell migration to cytokinesis and membrane trafficking. For each of these processes, filamentous actin (F-actin) interacts with membranes and exerts force through its assembly, its associated myosin motors, or both. These two modes of force generation are well studied in isolation, but how they are coordinated in cells is mysterious. During clathrin-mediated endocytosis, F-actin assembly initiated by the Arp2/3 complex and several proteins that compose the WASP/myosin complex generates the force necessary to deform the plasma membrane into a pit. Here we present evidence that type I myosin is the key membrane anchor for endocytic actin assembly factors in budding yeast. By mooring actin assembly factors to the plasma membrane, this myosin organizes endocytic actin networks and couples actin-generated forces to the plasma membrane to drive invagination and scission. Through this unexpected mechanism, myosin facilitates force generation independent of its motor activity.

Scinderin and cortical F-actin are components of the secretory machinery

1999 ◽  
Vol 77 (9) ◽  
pp. 660-671 ◽  
Author(s):  
J -M Trifaró
Keyword(s):  
Chromaffin Cell ◽  
Secretory Vesicle ◽  
Secretory Vesicles ◽  
Actin Network ◽  
Filamentous Actin ◽  
Actin Networks ◽  
Reserve Pool ◽  
Vesicle Exocytosis

Secretory vesicle exocytosis is the mechanism of release of neurotransmitters and neuropeptides. Secretory vesicles are localized in at least two morphologically and functionally distinct compartments: the reserve pool and the release-ready pool. Filamentous actin networks play an important role in this compartmentalization and in the trafficking of vesicles between these compartments. The cortical F-actin network constitutes a barrier (negative clamp) to the movement of secretory vesicles to release sites, and it must be locally disassembled to allow translocation of secretory vesicles in preparation for exocytosis. The disassembly of the cortical F-actin network is controlled by scinderin (a Ca2+-dependent F-actin severing protein) upon activation by Ca2+ entering the cells during stimulation. There are several factors that regulate scinderin activation (i.e., Ca2+ levels, phosphatidylinositol 4,5-bisphosphate (PIP2), etc.). The results suggest that scinderin and the cortical F-actin network are components of the secretory machinery.Key words: F-actin, scinderin, exocytosis, cytoskeleton, chromaffin cell.

scholarly journals Ca2+ and pH determine the interaction of chromaffin cell scinderin with phosphatidylserine and phosphatidylinositol 4,5,-biphosphate and its cellular distribution during nicotinic-receptor stimulation and protein kinase C activation.

1992 ◽  
Vol 119 (4) ◽  
pp. 797-810 ◽  
Author(s):  
A Rodríguez Del Castillo ◽  
M L Vitale ◽  
J M Trifaró
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Intracellular Ph ◽  
Nicotinic Receptor ◽  
Dependent Manner ◽  
Filamentous Actin ◽  
Membrane Phospholipids ◽  
Receptor Stimulation ◽  
Actin Networks ◽  
Kinase C

Nicotinic stimulation and high K(+)-depolarization of chromaffin cells cause disassembly of cortical filamentous actin networks and redistribution of scinderin, a Ca(2+)-dependent actin filament-severing protein. These events which are Ca(2+)-dependent precede exocytosis. Activation of scinderin by Ca2+ may cause disassembly of actin filaments leaving cortical areas of low cytoplasmic viscosity which are the sites of exocytosis (Vitale, M. L., A. Rodríguez Del Castillo, L. Tchakarov, and J.-M. Trifaró. 1991. J. Cell. Biol. 113:1057-1067). It has been suggested that protein kinase C (PKC) regulates secretion. Therefore, the possibility that PKC activation might modulate scinderin redistribution was investigated. Here we report that PMA, a PKC activator, caused scinderin redistribution, although with a slower onset than that induced by nicotine. PMA effects were independent of either extra or intracellular Ca2+ as indicated by measurements of Ca2+ transients, and they were likely to be mediated through direct activation of PKC because inhibitors of the enzyme completely blocked the response to PMA. Scinderin was not phosphorylated by the kinase and further experiments using the Na+/H+ antiport inhibitors and intracellular pH determinations, demonstrated that PKC-mediated scinderin redistribution was a consequence of an increase in intracellular pH. Moreover, it was shown that scinderin binds to phosphatidylserine and phosphatidylinositol 4,5-biphosphate liposomes in a Ca(2+)-dependent manner, an effect which was modulated by the pH. The results suggest that under resting conditions, cortical scinderin is bound to plasma membrane phospholipids. The results also show that during nicotinic receptor stimulation both a rise in intracellular Ca2+ and pH are observed. The rise in intracellular pH might be the result of the translocation and activation of PKC produced by Ca2+ entry. This also would explain why scinderin redistribution induced by nicotine is partially (26-40%) inhibited by inhibitors of either PKC or the Na+/H+ antiport. In view of these findings, a model which can explain how scinderin redistribution and activity may be regulated by pH and Ca2+ in resting and stimulated conditions is proposed.

scholarly journals F-Actin Cytoskeleton Network Self-Organization Through Competition and Cooperation

2020 ◽  
Vol 36 (1) ◽  
pp. 35-60
Author(s):  
Rachel S. Kadzik ◽  
Kaitlin E. Homa ◽  
David R. Kovar
Keyword(s):  
Actin Binding ◽  
Filamentous Actin ◽  
Cellular Functions ◽  
Actin Organization ◽  
Actin Networks ◽  
Cellular Processes ◽  
Competition And Cooperation ◽  
A Cell ◽  
Overlapping Sets

Many fundamental cellular processes such as division, polarization, endocytosis, and motility require the assembly, maintenance, and disassembly of filamentous actin (F-actin) networks at specific locations and times within the cell. The particular function of each network is governed by F-actin organization, size, and density as well as by its dynamics. The distinct characteristics of different F-actin networks are determined through the coordinated actions of specific sets of actin-binding proteins (ABPs). Furthermore, a cell typically assembles and uses multiple F-actin networks simultaneously within a common cytoplasm, so these networks must self-organize from a common pool of shared globular actin (G-actin) monomers and overlapping sets of ABPs. Recent advances in multicolor imaging and analysis of ABPs and their associated F-actin networks in cells, as well as the development of sophisticated in vitro reconstitutions of networks with ensembles of ABPs, have allowed the field to start uncovering the underlying principles by which cells self-organize diverse F-actin networks to execute basic cellular functions.

scholarly journals Initial ciliary assembly in Chlamydomonas requires Arp2/3-dependent recruitment from a ciliary protein reservoir in the plasma membrane

2020 ◽  
Author(s):  
Brae M Bigge ◽  
Nicholas E Rosenthal ◽  
David Sept ◽  
Courtney M Schroeder ◽  
Prachee Avasthi
Keyword(s):  
Plasma Membrane ◽  
Membrane Protein ◽  
Long Range ◽  
Protein Targeting ◽  
Basal Bodies ◽  
Cell Periphery ◽  
Filamentous Actin ◽  
Actin Networks ◽  
Ciliary Protein ◽  
Broad Approach

ABSTRACTCilia are organelles important for signaling and motility. They are composed of microtubules ensheathed in plasma membrane. The mechanisms related to ciliogenesis also require another cytoskeletal element, actin, which has been shown to be important for organizing the basal bodies and transition zone at the base of cilia and for short- and long-range trafficking. However, most studies of actin’s role in ciliogenesis have taken a broad approach by knocking out all filamentous actin until now. Here, we more delicately dissect the interplay between actin and cilia by specifically focusing on actin networks nucleated by the Arp2/3 complex in Chlamydomonas. We find that knocking out Arp2/3-mediated actin networks dramatically impairs ciliary assembly and maintenance in these cells, and these defects are due to a problem with incorporation and gating of existing ciliary proteins, particularly in the early stages of assembly. We also show that cells lacking the Arp2/3 complex have more dramatic defects in ciliary maintenance using material from non-Golgi sources. Finally, we find relocalization of a ciliary membrane protein from the cell periphery to the cilia by internalization is dependent on actin and the Arp2/3 complex. Based on these results, we propose a new model of ciliary protein targeting during early ciliogenesis in which proteins previously targeted from the Golgi to the plasma membrane are reclaimed from this reservoir by Arp2/3-mediated networks.

scholarly journals The Yeast Actin Cytoskeleton: from Cellular Function to Biochemical Mechanism

2006 ◽  
Vol 70 (3) ◽  
pp. 605-645 ◽  
Author(s):  
James B. Moseley ◽  
Bruce L. Goode
Keyword(s):  
Cell Polarity ◽  
Mechanisms Of Action ◽  
Actin Dynamics ◽  
Biochemical Mechanism ◽  
Cell Morphogenesis ◽  
Filamentous Actin ◽  
Actin Networks ◽  
External Cues ◽  
Associated Proteins ◽  
Biochemical Mechanisms

SUMMARY All cells undergo rapid remodeling of their actin networks to regulate such critical processes as endocytosis, cytokinesis, cell polarity, and cell morphogenesis. These events are driven by the coordinated activities of a set of 20 to 30 highly conserved actin-associated proteins, in addition to many cell-specific actin-associated proteins and numerous upstream signaling molecules. The combined activities of these factors control with exquisite precision the spatial and temporal assembly of actin structures and ensure dynamic turnover of actin structures such that cells can rapidly alter their cytoskeletons in response to internal and external cues. One of the most exciting principles to emerge from the last decade of research on actin is that the assembly of architecturally diverse actin structures is governed by highly conserved machinery and mechanisms. With this realization, it has become apparent that pioneering efforts in budding yeast have contributed substantially to defining the universal mechanisms regulating actin dynamics in eukaryotes. In this review, we first describe the filamentous actin structures found in Saccharomyces cerevisiae (patches, cables, and rings) and their physiological functions, and then we discuss in detail the specific roles of actin-associated proteins and their biochemical mechanisms of action.

Reptation of Microtubules in F-Actin Networks : Effects of Filament Stiffness and Network Topology on Reptation Dynamics

1997 ◽  
Vol 489 ◽  
Author(s):  
Jagesh V. Shah ◽  
Lisa A. Flanagan ◽  
David Bahk ◽  
Paul A. Janmey
Keyword(s):  
Network Topology ◽  
Actin Filaments ◽  
Diffusion Constant ◽  
Actin Network ◽  
Filamentous Actin ◽  
Actin Networks ◽  
Apparent Diffusion ◽  
Thermally Driven

AbstractThe thermally driven motions of fluorescently labeled microtubules embedded in a network of filamentous actin polymers are analysed as the diffusion of a rod-like polymer within a virtual tube formed by the surrounding semiflexible actin filaments. The apparent diffusion constant parallel to the tube scales with the inverse of the microtubule length and the magnitude is consistant with diffusion through a medium with a viscosity of approximately 10 centipoise. Introduction of crosslinks between the actin filaments does not alter the diffusion of the microtubules in the actin network.

scholarly journals The contributions of the actin machinery to endocytic membrane bending and vesicle formation

2018 ◽  
Vol 29 (11) ◽  
pp. 1346-1358 ◽  
Author(s):  
Andrea Picco ◽  
Wanda Kukulski ◽  
Hetty E. Manenschijn ◽  
Tanja Specht ◽  
John A. G. Briggs ◽  
...  
Keyword(s):  
Cross Linking ◽  
Actin Network ◽  
Filamentous Actin ◽  
Actin Networks ◽  
Cellular Processes ◽  
Membrane Invagination ◽  
Imaging Approach ◽  
Proportional Increase ◽  
Membrane Bending ◽  
Membrane Changes

Branched and cross-linked actin networks mediate cellular processes that move and shape membranes. To understand how actin contributes during the different stages of endocytic membrane reshaping, we analyzed deletion mutants of yeast actin network components using a hybrid imaging approach that combines live imaging with correlative microscopy. We could thus temporally dissect the effects of different actin network perturbations, revealing distinct stages of actin-based membrane reshaping. Our data show that initiation of membrane bending requires the actin network to be physically linked to the plasma membrane and to be optimally cross-linked. Once initiated, the membrane invagination process is driven by nucleation and polymerization of new actin filaments, independent of the degree of cross-linking and unaffected by a surplus of actin network components. A key transition occurs 2 s before scission, when the filament nucleation rate drops. From that time point on, invagination growth and vesicle scission are driven by an expansion of the actin network without a proportional increase of net actin amounts. The expansion is sensitive to the amount of filamentous actin and its cross-linking. Our results suggest that the mechanism by which actin reshapes the membrane changes during the progress of endocytosis, possibly adapting to varying force requirements.

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