scholarly journals Decoding natural astrocyte rhythms: dynamic actin waves result from environmental sensing by primary rodent astrocytes

2021 ◽  
Author(s):  
Kate M. O’Neill ◽  
Emanuela Saracino ◽  
Barbara Barile ◽  
Nicholas J. Mennona ◽  
Maria Grazia Mola ◽  
...  
Keyword(s):  
Water Concentration ◽  
Cell Boundary ◽  
Actin Dynamics ◽  
Substrate Topography ◽  
Actin Cortex ◽  
Extraction Algorithm ◽  
Cytoskeletal Dynamics ◽  
Actin Structure ◽  
Actin Waves

AbstractAstrocytes are key regulators of brain homeostasis, which is essential for proper cognitive function. The role of cytoskeletal dynamics in this critical regulatory process is unknown. Here we find that actin is dynamic in certain subcellular regions, especially near the cell boundary. Our results further indicate that actin dynamics concentrates into “hotspot” regions that selectively respond to certain chemophysical stimuli, specifically the homeostatic challenges of ion or water concentration increases. Substrate topography makes actin dynamics more frequent yet weaker, and it also alters actin network structure. Superresolution images analyzed with a filament extraction algorithm demonstrate that surface topography is associated with a predominant perpendicular alignment of actin filaments near the cell boundary whereas flat substrates result in an actin cortex mainly parallel to the cell boundary. Thus, actin structure and dynamics together integrate information from different aspects of the environment that might steer the operation of neural cell networks.TeaserAstrocytes display dynamic actin that is modulated by combinations of chemophysical stimuli and environmental topographies.

scholarly journals Myosin-II activity generates a dynamic steady state with continuous actin turnover in a minimal actin cortex

2018 ◽  
Author(s):  
Sonal ◽  
Kristina A. Ganzinger ◽  
Sven K. Vogel ◽  
Jonas Mücksch ◽  
Philipp Blumhardt ◽  
...  
Keyword(s):  
Steady State ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Fine Tuning ◽  
Cellular Functions ◽  
Actin Cortex ◽  
Actin Turnover ◽  
Cytoskeletal Dynamics

ABSTRACTDynamic reorganization of the actomyosin cytoskeleton allows a fine-tuning of cell shape that is vital to many cellular functions. It is well established that myosin-II motors generate the forces required for remodeling the cell surface by imparting contractility to actin networks. An additional, less understood, role of myosin-II in cytoskeletal dynamics is believed to be in the regulation of actin turnover; it has been proposed that myosin activity increases actin turnover in various cellular contexts, presumably by contributing to disassembly. In vitro reconstitution of actomyosin networks has confirmed the role of myosin in actin network disassembly, but factors such as diffusional constraints and the use of stabilized filaments have thus far limited the observation of myosin-assisted actin turnover in these networks. Here, we present the reconstitution of a minimal dynamic actin cortex where actin polymerization is catalyzed on the membrane in the presence of myosin-II activity. We demonstrate that myosin activity leads to disassembly and redistribution in this simplified cortex. Consequently, a new dynamic steady state emerges in which actin filaments undergo constant turnover. Our findings suggest a multi-faceted role of myosin-II in fast remodeling of the eukaryotic actin cortex.

scholarly journals Knockout of the neonatal Fc receptor in cultured podocytes alters IL-6 signaling and the actin cytoskeleton

2019 ◽  
Vol 317 (5) ◽  
pp. C1048-C1060 ◽  
Author(s):  
Pantipa Tonsawan ◽  
James Dylewski ◽  
Linda Lewis ◽  
Judith Blaine
Keyword(s):  
Immune Complexes ◽  
Fc Receptor ◽  
Actin Dynamics ◽  
Minimal Amount ◽  
Neonatal Fc Receptor ◽  
Scratch Assay ◽  
Immune Mediated ◽  
Actin Structure ◽  
Robust Response

The neonatal Fc receptor (FcRn) has been shown to be required for antigen presentation in dendritic cells, and global knockout of FcRn attenuates immune-mediated kidney disease. Podocytes express interleukin-6 (IL-6) receptor and produce IL-6 under proinflammatory conditions. Here we examined the role of FcRn in the IL-6-mediated inflammatory response in podocytes. We examined IL-6 production by ELISA and expression by qPCR in wild type (WT) and FcRn knockout (KO) podocytes after treatment with proinflammatory stimuli as well as IL-6-mediated signaling via the JAK/STAT pathway. We also examined podocyte motility in cultured WT and KO podocytes after a proinflammatory challenge. We found that FcRn KO podocytes produced minimal amount of IL-6 after treatment with albumin, IgG, or immune complexes whereas WT podocytes had a robust response. FcRn KO podocytes also had minimal expression of IL-6 compared with WT. By Western blotting, there was significantly less phosphorylated STAT3 in KO podocytes after treatment with IFNγ or immune complexes. In a scratch assay, FcRn KO podocytes showed increased motility comparted KO, suggesting a defect in actin dynamics. Cultured FcRn KO podocytes also demonstrated abnormal stress fibers compared with WT and the defect could be rescued by IL-6 treatment. This study shows that in podocytes, FcRn modulates the IL-6 mediated response to proinflammatory stimuli and regulates podocytes actin structure, motility and synaptopodin expression.

scholarly journals Coatomer-bound Cdc42 regulates dynein recruitment to COPI vesicles

2005 ◽  
Vol 169 (3) ◽  
pp. 383-389 ◽  
Author(s):  
Ji-Long Chen ◽  
Raymond V. Fucini ◽  
Lynne Lacomis ◽  
Hediye Erdjument-Bromage ◽  
Paul Tempst ◽  
...  
Keyword(s):  
Protein Composition ◽  
Actin Dynamics ◽  
Vesicle Formation ◽  
Binding Interaction ◽  
Temporal Regulation ◽  
Golgi Transport ◽  
Gtp Binding ◽  
Cytoskeletal Dynamics ◽  
Precise Role

Cytoskeletal dynamics at the Golgi apparatus are regulated in part through a binding interaction between the Golgi-vesicle coat protein, coatomer, and the regulatory GTP-binding protein Cdc42 (Wu, W.J., J.W. Erickson, R. Lin, and R.A. Cerione. 2000. Nature. 405:800–804; Fucini, R.V., J.L. Chen, C. Sharma, M.M. Kessels, and M. Stamnes. 2002. Mol. Biol. Cell. 13:621–631). The precise role of this complex has not been determined. We have analyzed the protein composition of Golgi-derived coat protomer I (COPI)–coated vesicles after activating or inhibiting signaling through coatomer-bound Cdc42. We show that Cdc42 has profound effects on the recruitment of dynein to COPI vesicles. Cdc42, when bound to coatomer, inhibits dynein binding to COPI vesicles whereas preventing the coatomer–Cdc42 interaction stimulates dynein binding. Dynein recruitment was found to involve actin dynamics and dynactin. Reclustering of nocodazole-dispersed Golgi stacks and microtubule/dynein-dependent ER-to-Golgi transport are both sensitive to disrupting Cdc42 mediated signaling. By contrast, dynein-independent transport to the Golgi complex is insensitive to mutant Cdc42. We propose a model for how proper temporal regulation of motor-based vesicle translocation could be coupled to the completion of vesicle formation.

scholarly journals Apatite-mediated Actin Dynamics in Resorbing Osteoclasts

2004 ◽  
Vol 15 (12) ◽  
pp. 5231-5241 ◽  
Author(s):  
Frédéric Saltel ◽  
Olivier Destaing ◽  
Frédéric Bard ◽  
Diane Eichert ◽  
Pierre Jurdic
Keyword(s):  
Bone Resorption ◽  
Actin Dynamics ◽  
Cell Periphery ◽  
Main Function ◽  
Zone Formation ◽  
Actin Structure ◽  
Sealing Zone ◽  
Mineralized Matrix ◽  
And Migration

The actin cytoskeleton is essential for osteoclasts main function, bone resorption. Two different organizations of actin have been described in osteoclasts, the podosomes belt corresponding to numerous F-actin columns arranged at the cell periphery, and the sealing zone defined as a unique large band of actin. To compare the role of these two different actin organizations, we imaged osteoclasts on various substrata: glass, dentin, and apatite. Using primary osteoclasts expressing GFP-actin, we found that podosome belts and sealing zones, both very dynamic actin structures, were present in mature osteoclasts; podosome belts were observed only in spread osteoclasts adhering onto glass, whereas sealing zone were seen in apico-basal polarized osteoclasts adherent on mineralized matrix. Dynamic observations of several resorption cycles of osteoclasts seeded on apatite revealed that 1) podosomes do not fuse together to form the sealing zone; 2) osteoclasts alternate successive stationary polarized resorption phases with a sealing zone and migration, nonresorption phases without any specific actin structure; and 3) apatite itself promotes sealing zone formation though c-src and Rho signaling. Finally, our work suggests that apatite-mediated sealing zone formation is dependent on both c-src and Rho whereas apico-basal polarization requires only Rho.

scholarly journals Spatiotemporal development of coexisting wave domains of Rho activity in the cell cortex

2021 ◽  
Author(s):  
Siarhei Hladyshau ◽  
Mary Kho ◽  
Shuyi Nie ◽  
Denis Tsygankov
Keyword(s):  
Cell Movement ◽  
Intrinsic Noise ◽  
Actin Dynamics ◽  
Cell Cortex ◽  
Wave Dynamics ◽  
Automated Method ◽  
Spatiotemporal Regulation ◽  
Cytoskeletal Dynamics ◽  
Actin Waves ◽  
Patiria Miniata

Abstract The Rho family GTPases are molecular switches that regulate cytoskeletal dynamics and cell movement through a complex spatiotemporal organization of their activity. In Patiria miniata (starfish) oocytes, such activity generates multiple co-existing regions of coherent propagation of actin waves. Here we use computational modeling to investigate the development and properties of such wave domains. The model reveals that the formation of wave domains requires a balance of the autocatalytic activation and the negative feedback in the Rho signaling motif. Intriguingly, the development of the wave domains is preceded by a stage of low-activity quasi-static patterns, which may not be readily observed in experiments. Spatiotemporal patterns of this stage and the different paths of their destabilization define the behavior of the system in the later high-activity (observable) stage. Accounting for a strong intrinsic noise allowed us to reproduce wave dynamics in both Patiria miniata and Xenopus laevis (frog). For quantitative comparison of simulated and experimental results, we developed an automated method of wave domain detection, which revealed a sharp reversal of pattern formation in the middle of anaphase in starfish oocytes. Overall, our findings provide an insight into spatiotemporal regulation of complex and diverse but still computationally reproducible cell-level actin dynamics.

scholarly journals Plasma membrane nano-organization specifies phosphoinositide effects on Rho-GTPases and actin dynamics in tobacco pollen tubes

2020 ◽  
Author(s):  
Marta Fratini ◽  
Praveen Krishnamoorthy ◽  
Irene Stenzel ◽  
Mara Riechmann ◽  
Kirsten Bacia ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Pollen Tubes ◽  
Actin Dynamics ◽  
Tobacco Pollen ◽  
Dual Distribution ◽  
Cytoskeletal Dynamics

AbstractPollen tube growth requires coordination of cytoskeletal dynamics and apical secretion. The regulatory phospholipid, phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) is enriched in the subapical plasma membrane of pollen tubes and can influence both actin dynamics and secretion. How alternative PtdIns(4,5)P2-effects are specified is unclear. Spinning disc microscopy (SD) reveals dual distribution of a fluorescent PtdIns(4,5)P2-reporter in dynamic plasma membrane nanodomains vs. apparent diffuse membrane labelling, consistent with spatially distinct coexisting pools of PtdIns(4,5)P2. Several PI4P 5-kinases (PIP5Ks) can generate PtdIns(4,5)P2 in pollen tubes. Despite localizing to one membrane region, AtPIP5K2 and NtPIP5K6 display distinctive overexpression effects on cell morphologies, respectively related to altered actin dynamics or membrane trafficking. When analyzed by SD, AtPIP5K2-EYFP associated with nanodomains, whereas NtPIP5K6-EYFP localized diffusely. Chimeric AtPIP5K2 and NtPIP5K6 variants with reciprocally swapped membrane-associating domains evoked reciprocally shifted effects on cell morphology upon overexpression. Overall, PI4P 5-kinase variants targeted to nanodomains stabilized actin, suggesting a specific function of PtdIns(4,5)P2-nanodomains. A distinct role of nanodomain-associated AtPIP5K2 in actin regulation is further supported by proximity to and interaction with the Rho-GTPase NtRac5, and by functional interplay with elements of ROP-signalling. Plasma membrane nano-organization may thus aid the specification of PtdIns(4,5)P2-functions to coordinate cytoskeletal dynamics and secretion in pollen tubes.

Effects of neuronal drebrin on actin dynamics

2021 ◽  
Author(s):  
Elena E. Grintsevich
Keyword(s):  
Synaptic Plasticity ◽  
Posttranslational Modifications ◽  
Neurodegenerative Disorders ◽  
Neuronal Migration ◽  
Recent Progress ◽  
Actin Dynamics ◽  
Cytoskeletal Dynamics ◽  
Health And Disease ◽  
Made In

Drebrin is a key regulator of actin cytoskeleton in neuronal cells which is critical for synaptic plasticity, neuritogenesis, and neuronal migration. It is also known to orchestrate a cross-talk between actin and microtubules. Decreased level of drebrin is a hallmark of multiple neurodegenerative disorders such as Alzheimer's disease. Despite its established importance in health and disease, we still have a lot to learn about drebrin's interactome and its effects on cytoskeletal dynamics. This review aims to summarize the recently reported novel effects of drebrin on actin and its regulators. Here I will also reflect on the most recent progress made in understanding of the role of drebrin isoforms and posttranslational modifications on its functionality.

scholarly journals Enhanced Production of the Mical Redox Domain for Enzymology and F-actin Disassembly Assays

2021 ◽  
Vol 22 (4) ◽  
pp. 1991
Author(s):  
Jimok Yoon ◽  
Heng Wu ◽  
Ruei-Jiun Hung ◽  
Jonathan R. Terman
Keyword(s):  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Actin Dynamics ◽  
Specific Substrate ◽  
Actin Assembly ◽  
Redox Enzymes ◽  
Enhanced Production ◽  
Reversible Redox ◽  
Future Work ◽  
Signaling Process

To change their behaviors, cells require actin proteins to assemble together into long polymers/filaments—and so a critical goal is to understand the factors that control this actin filament (F-actin) assembly and stability. We have identified a family of unusual actin regulators, the MICALs, which are flavoprotein monooxygenase/hydroxylase enzymes that associate with flavin adenine dinucleotide (FAD) and use the co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH) in Redox reactions. F-actin is a specific substrate for these MICAL Redox enzymes, which oxidize specific amino acids within actin to destabilize actin filaments. Furthermore, this MICAL-catalyzed reaction is reversed by another family of Redox enzymes (SelR/MsrB enzymes)—thereby revealing a reversible Redox signaling process and biochemical mechanism regulating actin dynamics. Interestingly, in addition to the MICALs’ Redox enzymatic portion through which MICALs covalently modify and affect actin, MICALs have multiple other domains. Less is known about the roles of these other MICAL domains. Here we provide approaches for obtaining high levels of recombinant protein for the Redox only portion of Mical and demonstrate its catalytic and F-actin disassembly activity. These results provide a ground state for future work aimed at defining the role of the other domains of Mical — including characterizing their effects on Mical’s Redox enzymatic and F-actin disassembly activity.

scholarly journals Microtubule–microtubule sliding by kinesin-1 is essential for normal cytoplasmic streaming in Drosophila oocytes

2016 ◽  
Vol 113 (34) ◽  
pp. E4995-E5004 ◽  
Author(s):  
Wen Lu ◽  
Michael Winding ◽  
Margot Lakonishok ◽  
Jill Wildonger ◽  
Vladimir I. Gelfand
Keyword(s):  
Cytoplasmic Streaming ◽  
Cell Types ◽  
Nurse Cells ◽  
Wild Type ◽  
Actin Cortex ◽  
Microtubule Motor ◽  
Multiple Cell ◽  
Cytoplasmic Microtubules ◽  
Two Populations

Cytoplasmic streaming in Drosophila oocytes is a microtubule-based bulk cytoplasmic movement. Streaming efficiently circulates and localizes mRNAs and proteins deposited by the nurse cells across the oocyte. This movement is driven by kinesin-1, a major microtubule motor. Recently, we have shown that kinesin-1 heavy chain (KHC) can transport one microtubule on another microtubule, thus driving microtubule–microtubule sliding in multiple cell types. To study the role of microtubule sliding in oocyte cytoplasmic streaming, we used a Khc mutant that is deficient in microtubule sliding but able to transport a majority of cargoes. We demonstrated that streaming is reduced by genomic replacement of wild-type Khc with this sliding-deficient mutant. Streaming can be fully rescued by wild-type KHC and partially rescued by a chimeric motor that cannot move organelles but is active in microtubule sliding. Consistent with these data, we identified two populations of microtubules in fast-streaming oocytes: a network of stable microtubules anchored to the actin cortex and free cytoplasmic microtubules that moved in the ooplasm. We further demonstrated that the reduced streaming in sliding-deficient oocytes resulted in posterior determination defects. Together, we propose that kinesin-1 slides free cytoplasmic microtubules against cortically immobilized microtubules, generating forces that contribute to cytoplasmic streaming and are essential for the refinement of posterior determinants.

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