1
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Madan A, Kelly KP, Bahk P, Sullivan CE, Poling ME, Brent AE, Alassaf M, Dubrulle J, Rajan A. Atg8/LC3 controls systemic nutrient surplus signaling in flies and humans. Curr Biol 2024; 34:3327-3341.e9. [PMID: 38955177 PMCID: PMC11303106 DOI: 10.1016/j.cub.2024.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 04/26/2024] [Accepted: 06/03/2024] [Indexed: 07/04/2024]
Abstract
Organisms experience constant nutritional flux. Mechanisms at the interface of opposing nutritional states-scarcity and surplus-enable organismal energy homeostasis. Contingent on nutritional stores, adipocytes secrete adipokines, such as the fat hormone leptin, to signal nutrient status to the central brain. Increased leptin secretion underlies metabolic dysregulation during common obesity, but the molecular mechanisms regulating leptin secretion from human adipocytes are poorly understood. Here, we report that Atg8/LC3 family proteins, best known for their role in autophagy during nutrient scarcity, play an evolutionarily conserved role during nutrient surplus by promoting adipokine secretion. We show that in a well-fed state, Atg8/LC3 promotes the secretion of the Drosophila functional leptin ortholog unpaired 2 (Upd2) and leptin from human adipocytes. Proteomic analyses reveal that LC3 directs leptin to a secretory pathway in human cells. We identified LC3-dependent extracellular vesicle (EV) loading and secretion (LDELS) as a required step for leptin release, highlighting a unique secretory route adopted by leptin in human adipocytes. In Drosophila, mutations to Upd2's Atg8 interaction motif (AIM) result in constitutive adipokine retention. Atg8-mediated Upd2 retention alters lipid storage and hunger response and rewires the bulk organismal transcriptome in a manner conducive to starvation survival. Thus, Atg8/LC3's bidirectional role in nutrient sensing-conveying nutrient surplus and responding to nutrient deprivation-enables organisms to manage nutrient flux effectively. We posit that decoding how bidirectional molecular switches-such as Atg8/LC3-operate at the nexus of nutritional scarcity and surplus will inform therapeutic strategies to tackle chronic metabolic disorders.
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Affiliation(s)
- Aditi Madan
- Basic Sciences Division, Fred Hutch, Seattle, WA 98109, USA
| | - Kevin P Kelly
- Basic Sciences Division, Fred Hutch, Seattle, WA 98109, USA
| | - Patrick Bahk
- Basic Sciences Division, Fred Hutch, Seattle, WA 98109, USA
| | | | | | - Ava E Brent
- Basic Sciences Division, Fred Hutch, Seattle, WA 98109, USA
| | - Mroj Alassaf
- Basic Sciences Division, Fred Hutch, Seattle, WA 98109, USA
| | - Julien Dubrulle
- Cellular Imaging Core, Shared Resources, Fred Hutch, Seattle, WA 98109, USA
| | - Akhila Rajan
- Basic Sciences Division, Fred Hutch, Seattle, WA 98109, USA.
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2
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Stjepić V, Nakamura M, Hui J, Parkhurst SM. Two Septin complexes mediate actin dynamics during cell wound repair. Cell Rep 2024; 43:114215. [PMID: 38728140 PMCID: PMC11203717 DOI: 10.1016/j.celrep.2024.114215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 03/18/2024] [Accepted: 04/24/2024] [Indexed: 05/12/2024] Open
Abstract
Cells have robust wound repair systems to prevent further damage or infection and to quickly restore cell cortex integrity when exposed to mechanical and chemical stress. Actomyosin ring formation and contraction at the wound edge are major events during closure of the plasma membrane and underlying cytoskeleton during cell wound repair. Here, we show that all five Drosophila Septins are required for efficient cell wound repair. Based on their different recruitment patterns and knockdown/mutant phenotypes, two distinct Septin complexes, Sep1/Sep2/Pnut and Sep4/Sep5/Pnut, are assembled to regulate actin ring assembly, contraction, and remodeling during the repair process. Intriguingly, we find that these two Septin complexes have different F-actin bending activities. In addition, we find that Anillin regulates the recruitment of only one of two Septin complexes upon wounding. Our results demonstrate that two functionally distinct Septin complexes work side by side to discretely regulate actomyosin ring dynamics during cell wound repair.
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Affiliation(s)
- Viktor Stjepić
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Mitsutoshi Nakamura
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Justin Hui
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Susan M Parkhurst
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA.
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3
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Au NPB, Wu T, Chen X, Gao F, Li YTY, Tam WY, Yu KN, Geschwind DH, Coppola G, Wang X, Ma CHE. Genome-wide study reveals novel roles for formin-2 in axon regeneration as a microtubule dynamics regulator and therapeutic target for nerve repair. Neuron 2023; 111:3970-3987.e8. [PMID: 38086376 DOI: 10.1016/j.neuron.2023.11.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 09/02/2023] [Accepted: 11/10/2023] [Indexed: 12/23/2023]
Abstract
Peripheral nerves regenerate successfully; however, clinical outcome after injury is poor. We demonstrated that low-dose ionizing radiation (LDIR) promoted axon regeneration and function recovery after peripheral nerve injury (PNI). Genome-wide CpG methylation profiling identified LDIR-induced hypermethylation of the Fmn2 promoter, exhibiting injury-induced Fmn2 downregulation in dorsal root ganglia (DRGs). Constitutive knockout or neuronal Fmn2 knockdown accelerated nerve repair and function recovery. Mechanistically, increased microtubule dynamics at growth cones was observed in time-lapse imaging of Fmn2-deficient DRG neurons. Increased HDAC5 phosphorylation and rapid tubulin deacetylation were found in regenerating axons of neuronal Fmn2-knockdown mice after injury. Growth-promoting effect of neuronal Fmn2 knockdown was eliminated by pharmaceutical blockade of HDAC5 or neuronal Hdac5 knockdown, suggesting that Fmn2deletion promotes axon regeneration via microtubule post-translational modification. In silico screening of FDA-approved drugs identified metaxalone, administered either immediately or 24-h post-injury, accelerating function recovery. This work uncovers a novel axon regeneration function of Fmn2 and a small-molecule strategy for PNI.
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Affiliation(s)
| | - Tan Wu
- Department of Surgery, The Chinese University of Hong Kong, Hong Kong, China; Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China
| | - Xinyu Chen
- Department of Neuroscience, City University of Hong Kong, Hong Kong, China
| | - Feng Gao
- Department of Surgery, The Chinese University of Hong Kong, Hong Kong, China; Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China
| | | | - Wing Yip Tam
- Department of Neuroscience, City University of Hong Kong, Hong Kong, China
| | - Kwan Ngok Yu
- Department of Physics, City University of Hong Kong, Hong Kong, China
| | - Daniel H Geschwind
- Program in Neurogenetics, Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Giovanni Coppola
- Program in Neurogenetics, Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Xin Wang
- Department of Surgery, The Chinese University of Hong Kong, Hong Kong, China; Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China
| | - Chi Him Eddie Ma
- Department of Neuroscience, City University of Hong Kong, Hong Kong, China.
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4
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Nakamura M, Parkhurst SM. Calcium influx rapidly establishes distinct spatial recruitments of Annexins to cell wounds. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.03.569799. [PMID: 38105960 PMCID: PMC10723296 DOI: 10.1101/2023.12.03.569799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
To survive daily damage, the formation of actomyosin ring at the wound periphery is required to rapidly close cell wounds. Calcium influx is one of the start signals for these cell wound repair events. Here, we find that rapid recruitment of all three Drosophila calcium responding and phospholipid binding Annexin proteins (AnxB9, AnxB10, AnxB11) to distinct regions around the wound are regulated by the quantity of calcium influx rather than their binding to specific phospholipids. The distinct recruitment patterns of these Annexins regulate the subsequent recruitment of RhoGEF2 and RhoGEF3 through actin stabilization to form a robust actomyosin ring. Surprisingly, we find that reduced extracellular calcium and depletion of intracellular calcium affect cell wound repair differently, despite these two conditions exhibiting similar GCaMP signals. Thus, our results suggest that, in addition to initiating repair events, both the quantity and sources of calcium influx are important for precise Annexin spatiotemporal protein recruitment to cell wounds and efficient wound repair.
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Affiliation(s)
- Mitsutoshi Nakamura
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA 98109
| | - Susan M. Parkhurst
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA 98109
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5
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Stjepić V, Nakamura M, Hui J, Parkhurst SM. Two Septin Complexes Mediate Actin Dynamics During Cell Wound Repair. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.14.567084. [PMID: 38014090 PMCID: PMC10680708 DOI: 10.1101/2023.11.14.567084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Cells have robust wound repair systems to prevent further damage or infection and to quickly restore cell cortex integrity when exposed to mechanical and chemical stress. Actomyosin ring formation and contraction at the wound edge are major events during closure of the plasma membrane and underlying cytoskeleton during cell wound repair. Here, we show that all five Drosophila Septins are required for efficient cell wound repair. Based on their different recruitment patterns and knockdown/mutant phenotypes, two distinct Septin complexes, Sep1-Sep2-Pnut and Sep4-Sep5-Pnut, are assembled to regulate actin ring assembly, contraction, and remodeling during the repair process. Intriguingly, we find that these two Septin complexes have different F-actin bending activities. In addition, we find that Anillin regulates the recruitment of only one of two Septin complexes upon wounding. Our results demonstrate that two functionally distinct Septin complexes work side-by-side to discretely regulate actomyosin ring dynamics during cell wound repair.
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Affiliation(s)
- Viktor Stjepić
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA 98109
| | - Mitsutoshi Nakamura
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA 98109
| | - Justin Hui
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA 98109
| | - Susan M. Parkhurst
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA 98109
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6
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Davidson KA, Nakamura M, Verboon JM, Parkhurst SM. Centralspindlin proteins Pavarotti and Tumbleweed along with WASH regulate nuclear envelope budding. J Cell Biol 2023; 222:e202211074. [PMID: 37163553 PMCID: PMC10174194 DOI: 10.1083/jcb.202211074] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 03/14/2023] [Accepted: 04/26/2023] [Indexed: 05/12/2023] Open
Abstract
Nuclear envelope (NE) budding is a nuclear pore-independent nuclear export pathway, analogous to the egress of herpesviruses, and required for protein quality control, synapse development, and mitochondrial integrity. The physical formation of NE buds is dependent on the Wiskott-Aldrich Syndrome protein, Wash, its regulatory complex (SHRC), and Arp2/3, and requires Wash's actin nucleation activity. However, the machinery governing cargo recruitment and organization within the NE bud remains unknown. Here, we identify Pavarotti (Pav) and Tumbleweed (Tum) as new molecular components of NE budding. Pav and Tum interact directly with Wash and define a second nuclear Wash-containing complex required for NE budding. Interestingly, we find that the actin-bundling activity of Pav is required, suggesting a structural role in the physical and/or organizational aspects of NE buds. Thus, Pav and Tum are providing exciting new entry points into the physical machineries of this alternative nuclear export pathway for large cargos during cell differentiation and development.
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Affiliation(s)
- Kerri A. Davidson
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | | | - Jeffrey M. Verboon
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | - Susan M. Parkhurst
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
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7
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Tello JA, Williams HE, Eppler RM, Steinhilb ML, Khanna M. Animal Models of Neurodegenerative Disease: Recent Advances in Fly Highlight Innovative Approaches to Drug Discovery. Front Mol Neurosci 2022; 15:883358. [PMID: 35514431 PMCID: PMC9063566 DOI: 10.3389/fnmol.2022.883358] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 03/21/2022] [Indexed: 12/22/2022] Open
Abstract
Neurodegenerative diseases represent a formidable challenge to global health. As advances in other areas of medicine grant healthy living into later decades of life, aging diseases such as Alzheimer's disease (AD) and other neurodegenerative disorders can diminish the quality of these additional years, owed largely to the lack of efficacious treatments and the absence of durable cures. Alzheimer's disease prevalence is predicted to more than double in the next 30 years, affecting nearly 15 million Americans, with AD-associated costs exceeding $1 billion by 2050. Delaying onset of AD and other neurodegenerative diseases is critical to improving the quality of life for patients and reducing the burden of disease on caregivers and healthcare systems. Significant progress has been made to model disease pathogenesis and identify points of therapeutic intervention. While some researchers have contributed to our understanding of the proteins and pathways that drive biological dysfunction in disease using in vitro and in vivo models, others have provided mathematical, biophysical, and computational technologies to identify potential therapeutic compounds using in silico modeling. The most exciting phase of the drug discovery process is now: by applying a target-directed approach that leverages the strengths of multiple techniques and validates lead hits using Drosophila as an animal model of disease, we are on the fast-track to identifying novel therapeutics to restore health to those impacted by neurodegenerative disease.
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Affiliation(s)
- Judith A. Tello
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
- Center of Innovation in Brain Science, Tucson, AZ, United States
| | - Haley E. Williams
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
- Center of Innovation in Brain Science, Tucson, AZ, United States
| | - Robert M. Eppler
- Department of Biology, Central Michigan University, Mount Pleasant, MI, United States
| | - Michelle L. Steinhilb
- Department of Biology, Central Michigan University, Mount Pleasant, MI, United States
| | - May Khanna
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
- Center of Innovation in Brain Science, Tucson, AZ, United States
- Department of Molecular Pathobiology, New York University, New York, NY, United States
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8
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Hoyer M, Crevenna AH, Kitel R, Willems K, Czub M, Dubin G, Van Dorpe P, Holak TA, Lamb DC. Analysis tools for single-monomer measurements of self-assembly processes. Sci Rep 2022; 12:4682. [PMID: 35304498 PMCID: PMC8933434 DOI: 10.1038/s41598-022-08245-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 02/22/2022] [Indexed: 11/29/2022] Open
Abstract
Protein assembly plays an important role throughout all phyla of life, both physiologically and pathologically. In particular, aggregation and polymerization of proteins are key-strategies that regulate cellular function. In recent years, methods to experimentally study the assembly process on a single-molecule level have been developed. This progress concomitantly has triggered the question of how to analyze this type of single-filament data adequately and what experimental conditions are necessary to allow a meaningful interpretation of the analysis. Here, we developed two analysis methods for single-filament data: the visitation analysis and the average-rate analysis. We benchmarked and compared both approaches with the classic dwell-time-analysis frequently used to study microscopic association and dissociation rates. In particular, we tested the limitations of each analysis method along the lines of the signal-to-noise ratio, the sampling rate, and the labeling efficiency and bleaching rate of the fluorescent dyes used in single-molecule fluorescence experiments. Finally, we applied our newly developed methods to study the monomer assembly of actin at the single-molecule-level in the presence of the class II nucleator Cappuccino and the WH2 repeats of Spire. For Cappuccino, our data indicated fast elongation circumventing a nucleation phase whereas, for Spire, we found that the four WH2 motifs are not sufficient to promote de novo nucleation of actin.
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Affiliation(s)
- Maria Hoyer
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich (NIM) and Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians University Munich, Munich, Germany
| | - Alvaro H Crevenna
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich (NIM) and Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians University Munich, Munich, Germany.,Epigenetics and Neurobiology Unit, EMBL Rome, Monterotondo, Italy
| | - Radoslaw Kitel
- Department of Organic Chemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland.,Malopolska Centre of Biotechnology, Jagiellonian University, Gronostajowa 7a, 30-387, Krakow, Poland
| | | | - Miroslawa Czub
- Department of Organic Chemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
| | - Grzegorz Dubin
- Malopolska Centre of Biotechnology, Jagiellonian University, Gronostajowa 7a, 30-387, Krakow, Poland
| | | | - Tad A Holak
- Department of Organic Chemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
| | - Don C Lamb
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich (NIM) and Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians University Munich, Munich, Germany.
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9
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Hoyer M, Crevenna AH, Correia JRC, Quezada AG, Lamb DC. Zero-mode waveguides visualize the first steps during gelsolin-mediated actin filament formation. Biophys J 2022; 121:327-335. [PMID: 34896371 PMCID: PMC8790234 DOI: 10.1016/j.bpj.2021.12.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 06/29/2021] [Accepted: 12/07/2021] [Indexed: 01/21/2023] Open
Abstract
Actin filament dynamics underlie key cellular processes. Although the elongation of actin filaments has been extensively studied, the mechanism of nucleation remains unclear. The micromolar concentrations needed for filament formation have prevented direct observation of nucleation dynamics on the single molecule level. To overcome this limitation, we have used the attoliter excitation volume of zero-mode waveguides to directly monitor the early steps of filament assembly. Immobilizing single gelsolin molecules as a nucleator at the bottom of the zero-mode waveguide, we could visualize the actin filament nucleation process. The process is surprisingly dynamic, and two distinct populations during gelsolin-mediated nucleation are observed. The two populations are defined by the stability of the actin dimers and determine whether elongation occurs. Furthermore, by using an inhibitor to block flattening, a conformational change in actin associated with filament formation, elongation was prevented. These observations indicate that a conformational transition and pathway competition determine the nucleation of gelsolin-mediated actin filament formation.
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Affiliation(s)
- Maria Hoyer
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich (NIM) and Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians University Munich, Munich, Germany
| | - Alvaro H. Crevenna
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich (NIM) and Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians University Munich, Munich, Germany,Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal,Corresponding author
| | - Jose Rafael Cabral Correia
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Andrea G. Quezada
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Don C. Lamb
- Department of Chemistry, Center for NanoScience, Nanosystems Initiative Munich (NIM) and Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians University Munich, Munich, Germany,Corresponding author
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10
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Kundu T, Dutta P, Nagar D, Maiti S, Ghose A. Coupling of dynamic microtubules to F-actin by Fmn2 regulates chemotaxis of neuronal growth cones. J Cell Sci 2021; 134:jcs252916. [PMID: 34313311 DOI: 10.1242/jcs.252916] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 05/26/2021] [Indexed: 12/20/2022] Open
Abstract
Dynamic co-regulation of the actin and microtubule subsystems enables the highly precise and adaptive remodelling of the cytoskeleton necessary for critical cellular processes, such as axonal pathfinding. The modes and mediators of this interpolymer crosstalk, however, are inadequately understood. We identify Fmn2, a non-diaphanous-related formin associated with cognitive disabilities, as a novel regulator of cooperative actin-microtubule remodelling in growth cones of both chick and zebrafish neurons. We show that Fmn2 stabilizes microtubules in the growth cones of cultured spinal neurons and in vivo. Super-resolution imaging revealed that Fmn2 facilitates guidance of exploratory microtubules along actin bundles into the chemosensory filopodia. Using live imaging, biochemistry and single-molecule assays, we show that a C-terminal domain in Fmn2 is necessary for the dynamic association between microtubules and actin filaments. In the absence of the cross-bridging function of Fmn2, filopodial capture of microtubules is compromised, resulting in destabilized filopodial protrusions and deficits in growth cone chemotaxis. Our results uncover a critical function for Fmn2 in actin-microtubule crosstalk in neurons and demonstrate that the modulation of microtubule dynamics via associations with F-actin is central to directional motility.
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Affiliation(s)
- Tanushree Kundu
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
| | - Priyanka Dutta
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
| | - Dhriti Nagar
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
| | - Sankar Maiti
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, Nadia, West Bengal, India
| | - Aurnab Ghose
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
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11
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Nakamura M, Verboon JM, Prentiss CL, Parkhurst SM. The kinesin-like protein Pavarotti functions noncanonically to regulate actin dynamics. J Cell Biol 2021; 219:151940. [PMID: 32673395 PMCID: PMC7480107 DOI: 10.1083/jcb.201912117] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 05/07/2020] [Accepted: 06/09/2020] [Indexed: 01/03/2023] Open
Abstract
Pavarotti, the Drosophila MKLP1 orthologue, is a kinesin-like protein that works with Tumbleweed (MgcRacGAP) as the centralspindlin complex. This complex is essential for cytokinesis, where it helps to organize the contractile actomyosin ring at the equator of dividing cells by activating the RhoGEF Pebble. Actomyosin rings also function as the driving force during cell wound repair. We previously showed that Tumbleweed and Pebble are required for the cell wound repair process. Here, we show that Pavarotti also functions during wound repair and confirm that while Pavarotti, Tumbleweed, and Pebble are all used during this cellular repair, each has a unique localization pattern and knockdown phenotype, demonstrating centralspindlin-independent functions. Surprisingly, we find that the classically microtubule-associated Pavarotti binds directly to actin in vitro and in vivo and has a noncanonical role directly regulating actin dynamics. Finally, we demonstrate that this actin regulation by Pavarotti is not specific to cellular wound repair but is also used in normal development.
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Affiliation(s)
- Mitsutoshi Nakamura
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA
| | - Jeffrey M Verboon
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA
| | - Clara L Prentiss
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA
| | - Susan M Parkhurst
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA
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12
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Scepanovic G, Florea A, Fernandez-Gonzalez R. Multiscale In Vivo Imaging of Collective Cell Migration in Drosophila Embryos. Methods Mol Biol 2021; 2179:199-224. [PMID: 32939723 DOI: 10.1007/978-1-0716-0779-4_17] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Coordinated cell movements drive embryonic development and tissue repair, and can also spread disease. Time-lapse microscopy is an integral part in the study of the cell biology of collective cell movements. Advances in imaging techniques enable monitoring dynamic cellular and molecular events in real time within living animals. Here, we demonstrate the use of spinning disk confocal microscopy to investigate coordinated cell movements and epithelial-to-mesenchymal-like transitions during embryonic wound closure in Drosophila. We describe image-based metrics to quantify the efficiency of collective cell migration. Finally, we show the application of super-resolution radial fluctuation microscopy to obtain multidimensional, super-resolution images of protrusive activity in collectively moving cells in vivo. Together, the methods presented here constitute a toolkit for the modern analysis of collective cell migration in living animals.
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Affiliation(s)
- Gordana Scepanovic
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada.,Ted Rogers Centre for Heart Research, University of Toronto, Toronto, ON, Canada
| | - Alexandru Florea
- Ted Rogers Centre for Heart Research, University of Toronto, Toronto, ON, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | - Rodrigo Fernandez-Gonzalez
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada. .,Ted Rogers Centre for Heart Research, University of Toronto, Toronto, ON, Canada. .,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada. .,Developmental and Stem Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.
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13
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Lian G, Chenn A, Ekuta V, Kanaujia S, Sheen V. Formin 2 Regulates Lysosomal Degradation of Wnt-Associated β-Catenin in Neural Progenitors. Cereb Cortex 2020; 29:1938-1952. [PMID: 29659741 DOI: 10.1093/cercor/bhy073] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 02/14/2018] [Accepted: 03/13/2018] [Indexed: 01/07/2023] Open
Abstract
Although neural progenitor proliferation along the ventricular zone is regulated by β-catenin through Wnt signaling, the cytoskeletal mechanisms that regulate expression and localization of these proteins are not well understood. Our prior studies have shown that loss of the actin-binding Filamin A (FlnA) and actin-nucleating protein Formin 2 (Fmn2) impairs endocytosis of low-density-lipoprotein-receptor-related protein 6 (Lrp6), thereby disrupting β-catenin activation, resulting in decreased brain size. Here, we report that activated RhoA-GTPase disengages Fmn2 N- to C-terminal binding to promote Fmn2 activation and redistribution into lysosomal vesicles. Fmn2 colocalizes with β-catenin in lysosomes and promotes its degradation. Further, Fmn2 binds the E3 ligase Smurf2, enhances Smurf2-dependent ubiquitination, and degradation of Dishevelled-2 (Dvl2), thereby initiates β-catenin degradation. Finally, Fmn2 overexpression disrupts neuroepithelial integrity, neuronal migration, and proliferation-phenotypes in E13 mouse embryos, as seen with loss of Fmn2+FlnA function. Conversely, co-expression of Dvl2 with Fmn2 rescues the proliferation defect due to Fmn2 overexpression in mouse embryos. These findings suggest that there is a homeostatic feedback mechanism in the cytoskeletal-dependent regulation of neural proliferation within the cerebral cortex. Upstream, Fmn2 promotes proliferation by stabilizing the Lrp6 receptor, leading to β-catenin activation. Downstream, RhoA-activated Fmn2 promotes lysosomal degradation of Dvl2, leading to β-catenin degradation.
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Affiliation(s)
- Gewei Lian
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Anjen Chenn
- Department of Pathology, University of Illinois College of Medicine, Chicago, IL, USA
| | - Victor Ekuta
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Sneha Kanaujia
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Volney Sheen
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
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14
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Verboon JM, Nakamura M, Davidson KA, Decker JR, Nandakumar V, Parkhurst SM. Drosophila Wash and the Wash regulatory complex function in nuclear envelope budding. J Cell Sci 2020; 133:jcs243576. [PMID: 32503943 PMCID: PMC7358131 DOI: 10.1242/jcs.243576] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Accepted: 05/28/2020] [Indexed: 12/12/2022] Open
Abstract
Nuclear envelope (NE) budding is a recently described phenomenon wherein large macromolecular complexes are packaged inside the nucleus and extruded through the nuclear membranes. Although a general outline of the cellular events occurring during NE budding is now in place, little is yet known about the molecular machinery and mechanisms underlying the physical aspects of NE bud formation. Using a multidisciplinary approach, we identify Wash, its regulatory complex (SHRC), capping protein and Arp2/3 as new molecular components involved in the physical aspects of NE bud formation in a Drosophila model system. Interestingly, Wash affects NE budding in two ways: indirectly through general nuclear lamina disruption via an SHRC-independent interaction with Lamin B leading to inefficient NE bud formation, and directly by blocking NE bud formation along with its SHRC, capping protein and Arp2/3. In addition to NE budding emerging as an important cellular process, it shares many similarities with herpesvirus nuclear egress mechanisms, suggesting new avenues for exploration in both normal and disease biology.
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Affiliation(s)
- Jeffrey M Verboon
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Mitsutoshi Nakamura
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Kerri A Davidson
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Jacob R Decker
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Vivek Nandakumar
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Susan M Parkhurst
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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15
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Hinnant TD, Merkle JA, Ables ET. Coordinating Proliferation, Polarity, and Cell Fate in the Drosophila Female Germline. Front Cell Dev Biol 2020; 8:19. [PMID: 32117961 PMCID: PMC7010594 DOI: 10.3389/fcell.2020.00019] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 01/10/2020] [Indexed: 01/05/2023] Open
Abstract
Gametes are highly specialized cell types produced by a complex differentiation process. Production of viable oocytes requires a series of precise and coordinated molecular events. Early in their development, germ cells are an interconnected group of mitotically dividing cells. Key regulatory events lead to the specification of mature oocytes and initiate a switch to the meiotic cell cycle program. Though the chromosomal events of meiosis have been extensively studied, it is unclear how other aspects of oocyte specification are temporally coordinated. The fruit fly, Drosophila melanogaster, has long been at the forefront as a model system for genetics and cell biology research. The adult Drosophila ovary continuously produces germ cells throughout the organism’s lifetime, and many of the cellular processes that occur to establish oocyte fate are conserved with mammalian gamete development. Here, we review recent discoveries from Drosophila that advance our understanding of how early germ cells balance mitotic exit with meiotic initiation. We discuss cell cycle control and establishment of cell polarity as major themes in oocyte specification. We also highlight a germline-specific organelle, the fusome, as integral to the coordination of cell division, cell polarity, and cell fate in ovarian germ cells. Finally, we discuss how the molecular controls of the cell cycle might be integrated with cell polarity and cell fate to maintain oocyte production.
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Affiliation(s)
- Taylor D Hinnant
- Department of Biology, East Carolina University, Greenville, NC, United States
| | - Julie A Merkle
- Department of Biology, University of Evansville, Evansville, IN, United States
| | - Elizabeth T Ables
- Department of Biology, East Carolina University, Greenville, NC, United States
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16
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Springer R, Zielinski A, Pleschka C, Hoffmann B, Merkel R. Unbiased pattern analysis reveals highly diverse responses of cytoskeletal systems to cyclic straining. PLoS One 2019; 14:e0210570. [PMID: 30865622 PMCID: PMC6415792 DOI: 10.1371/journal.pone.0210570] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 12/26/2018] [Indexed: 01/09/2023] Open
Abstract
In mammalian cells, actin, microtubules, and various types of cytoplasmic intermediate filaments respond to external stretching. Here, we investigated the underlying processes in endothelial cells plated on soft substrates from silicone elastomer. After cyclic stretch (0.13 Hz, 14% strain amplitude) for periods ranging from 5 min to 8 h, cells were fixed and double-stained for microtubules and either actin or vimentin. Cell images were analyzed by a two-step routine. In the first step, micrographs were segmented for potential fibrous structures. In the second step, the resulting binary masks were auto- or cross-correlated. Autocorrelation of segmented images provided a sensitive and objective measure of orientational and translational order of the different cytoskeletal systems. Aligning of correlograms from individual cells removed the influence of only partial alignment between cells and enabled determination of intrinsic cytoskeletal order. We found that cyclic stretching affected the actin cytoskeleton most, microtubules less, and vimentin mostly only via reorientation of the whole cell. Pharmacological disruption of microtubules had barely any influence on actin ordering. The similarity, i.e., cross-correlation, between vimentin and microtubules was much higher than the one between actin and microtubules. Moreover, prolonged cyclic stretching slightly decoupled the cytoskeletal systems as it reduced the cross-correlations in both cases. Finally, actin and microtubules were more correlated at peripheral regions of cells whereas vimentin and microtubules correlated more in central regions.
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Affiliation(s)
- Ronald Springer
- Institute of Complex Systems 7, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Alexander Zielinski
- Institute of Complex Systems 7, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Catharina Pleschka
- Institute of Complex Systems 7, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Bernd Hoffmann
- Institute of Complex Systems 7, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Rudolf Merkel
- Institute of Complex Systems 7, Forschungszentrum Jülich GmbH, Jülich, Germany
- * E-mail:
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17
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Vorontsova JE, Zavoloka EL, Cherezov RO, Simonova OB. Three Important Discoveries in the Field of the Cytoskeleton’s Proteins Functioning on the Drosophila melanogaster Model. Mol Biol 2019. [DOI: 10.1134/s0026893319010163] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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18
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Uraji J, Scheffler K, Schuh M. Functions of actin in mouse oocytes at a glance. J Cell Sci 2018; 131:131/22/jcs218099. [PMID: 30467138 DOI: 10.1242/jcs.218099] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Gametes undergo a specialized and reductional cell division termed meiosis. Female gametes (oocytes) undergo two rounds of meiosis; the first meiotic division produces the fertilizable egg, while the second meiotic division occurs upon fertilization. Both meiotic divisions are highly asymmetric, producing a large egg and small polar bodies. Actin takes over various essential function during oocyte meiosis, many of which commonly rely on microtubules in mitotic cells. Specifically, the actin network has been linked to long-range vesicle transport, nuclear positioning, spindle migration and anchorage, polar body extrusion and accurate chromosome segregation in mammalian oocytes. In this Cell Science at a Glance article and the accompanying poster, we summarize the many functions of the actin cytoskeleton in oocytes, with a focus on findings from the mouse model system.
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Affiliation(s)
- Julia Uraji
- Department of Meiosis, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Kathleen Scheffler
- Department of Meiosis, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Melina Schuh
- Department of Meiosis, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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19
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Courtemanche N. Mechanisms of formin-mediated actin assembly and dynamics. Biophys Rev 2018; 10:1553-1569. [PMID: 30392063 DOI: 10.1007/s12551-018-0468-6] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 10/18/2018] [Indexed: 12/14/2022] Open
Abstract
Cellular viability requires tight regulation of actin cytoskeletal dynamics. Distinct families of nucleation-promoting factors enable the rapid assembly of filament nuclei that elongate and are incorporated into diverse and specialized actin-based structures. In addition to promoting filament nucleation, the formin family of proteins directs the elongation of unbranched actin filaments. Processive association of formins with growing filament ends is achieved through continuous barbed end binding of the highly conserved, dimeric formin homology (FH) 2 domain. In cooperation with the FH1 domain and C-terminal tail region, FH2 dimers mediate actin subunit addition at speeds that can dramatically exceed the rate of spontaneous assembly. Here, I review recent biophysical, structural, and computational studies that have provided insight into the mechanisms of formin-mediated actin assembly and dynamics.
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Affiliation(s)
- Naomi Courtemanche
- Department of Genetics, Cell and Developmental Biology, University of Minnesota, 420 Washington Ave SE, 6-130 MCB, Minneapolis, MN, 55455, USA.
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20
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Almonacid M, Terret ME, Verlhac MH. Control of nucleus positioning in mouse oocytes. Semin Cell Dev Biol 2018; 82:34-40. [DOI: 10.1016/j.semcdb.2017.08.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 08/03/2017] [Indexed: 12/15/2022]
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21
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Migh E, Götz T, Földi I, Szikora S, Gombos R, Darula Z, Medzihradszky KF, Maléth J, Hegyi P, Sigrist S, Mihály J. Microtubule organization in presynaptic boutons relies on the formin DAAM. Development 2018; 145:dev.158519. [PMID: 29487108 DOI: 10.1242/dev.158519] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 02/14/2018] [Indexed: 02/02/2023]
Abstract
Regulation of the cytoskeleton is fundamental to the development and function of synaptic terminals, such as neuromuscular junctions. Despite the identification of numerous proteins that regulate synaptic actin and microtubule dynamics, the mechanisms of cytoskeletal control during terminal arbor formation have remained largely elusive. Here, we show that DAAM, a member of the formin family of cytoskeleton organizing factors, is an important presynaptic regulator of neuromuscular junction development in Drosophila We demonstrate that the actin filament assembly activity of DAAM plays a negligible role in terminal formation; rather, DAAM is necessary for synaptic microtubule organization. Genetic interaction studies consistently link DAAM with the Wg/Ank2/Futsch module of microtubule regulation and bouton formation. Finally, we provide evidence that DAAM is tightly associated with the synaptic active zone scaffold, and electrophysiological data point to a role in the modulation of synaptic vesicle release. Based on these results, we propose that DAAM is an important cytoskeletal effector element of the Wg/Ank2 pathway involved in the determination of basic synaptic structures, and, additionally, that DAAM may couple the active zone scaffold to the presynaptic cytoskeleton.
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Affiliation(s)
- Ede Migh
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Torsten Götz
- Institut für Biologie/Genetik and NeuroCure, Freie Universitat Berlin, Takustrasse 6, D-14195 Berlin, Germany
| | - István Földi
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Szilárd Szikora
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Rita Gombos
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Zsuzsanna Darula
- Laboratory of Proteomics Research, Biological Research Centre, Hungarian Academy of Sciences, Szeged H-6726, Hungary
| | - Katalin F Medzihradszky
- Laboratory of Proteomics Research, Biological Research Centre, Hungarian Academy of Sciences, Szeged H-6726, Hungary
| | - József Maléth
- MTA-SZTE Translational Gastroenterology Research Group, Szeged H-6725, Hungary
| | - Péter Hegyi
- MTA-SZTE Translational Gastroenterology Research Group, Szeged H-6725, Hungary.,Institute for Translational Medicine, University of Pecs, Pécs H-7624, Hungary
| | - Stephan Sigrist
- Institut für Biologie/Genetik and NeuroCure, Freie Universitat Berlin, Takustrasse 6, D-14195 Berlin, Germany
| | - József Mihály
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
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22
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BIG2-ARF1-RhoA-mDia1 Signaling Regulates Dendritic Golgi Polarization in Hippocampal Neurons. Mol Neurobiol 2018; 55:7701-7716. [PMID: 29455446 DOI: 10.1007/s12035-018-0954-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 02/05/2018] [Indexed: 01/08/2023]
Abstract
Proper dendrite development is essential for establishing neural circuitry, and Rho GTPases play key regulatory roles in this process. From mouse brain lysates, we identified Brefeldin A-inhibited guanine exchange factor 2 (BIG2) as a novel Rho GTPase regulatory protein involved in dendrite growth and maintenance. BIG2 was highly expressed during early development, and knockdown of the ARFGEF2 gene encoding BIG2 significantly reduced total dendrite length and the number of branches. Expression of the constitutively active ADP-ribosylation factor 1 ARF1 Q71L rescued the defective dendrite morphogenesis of ARFGEF2-null neurons, indicating that BIG2 controls dendrite growth and maintenance by activating ARF1. Moreover, BIG2 co-localizes with the Golgi apparatus and is required for Golgi deployment into major dendrites in cultured hippocampal neurons. Simultaneous overexpression of BIG2 and ARF1 activated RhoA, and treatment with the RhoA activator lysophosphatidic acid in neurons lacking BIG2 or ARF1 increased the number of cells with dendritic Golgi, suggesting that BIG2 and ARF1 activate RhoA to promote dendritic Golgi polarization. mDia1 was identified as a downstream effector of BIG2-ARF1-RhoA axis, mediating Golgi polarization and dendritic morphogenesis. Furthermore, in utero electroporation of ARFGEF2 shRNA into the embryonic mouse brain confirmed an in vivo role of BIG2 for Golgi deployment into the apical dendrite. Taken together, our results suggest that BIG2-ARF1-RhoA-mDia1 signaling regulates dendritic Golgi polarization and dendrite growth and maintenance in hippocampal neurons.
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23
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Silkworth WT, Kunes KL, Nickel GC, Phillips ML, Quinlan ME, Vizcarra CL. The neuron-specific formin Delphilin nucleates nonmuscle actin but does not enhance elongation. Mol Biol Cell 2017; 29:610-621. [PMID: 29282276 PMCID: PMC6004577 DOI: 10.1091/mbc.e17-06-0363] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 12/06/2017] [Accepted: 12/22/2017] [Indexed: 12/11/2022] Open
Abstract
The formin Delphilin binds the glutamate receptor, GluRδ2, in dendritic spines of Purkinje cells. Both proteins play a role in learning. To understand how Delphilin functions in neurons, we studied the actin assembly properties of this formin. Formins have a conserved formin homology 2 domain, which nucleates and associates with the fast-growing end of actin filaments, influencing filament growth together with the formin homology 1 (FH1) domain. The strength of nucleation and elongation varies widely across formins. Additionally, most formins have conserved domains that regulate actin assembly through an intramolecular interaction. Delphilin is distinct from other formins in several ways: its expression is limited to Purkinje cells, it lacks classical autoinhibitory domains, and its FH1 domain has minimal proline-rich sequence. We found that Delphilin is an actin nucleator that does not accelerate elongation, although it binds to the barbed end of filaments. In addition, Delphilin exhibits a preference for actin isoforms, nucleating nonmuscle actin but not muscle actin, which has not been described or systematically studied in other formins. Finally, Delphilin is the first formin studied that is not regulated by intramolecular interactions. We speculate how the activity we observe is consistent with its localization in the small dendritic spines.
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Affiliation(s)
- William T Silkworth
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Kristina L Kunes
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Grace C Nickel
- Department of Chemistry, Barnard College, New York, NY 10027
| | - Martin L Phillips
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Margot E Quinlan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095 .,Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
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24
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Bernard F, Lepesant JA, Guichet A. Nucleus positioning within Drosophila egg chamber. Semin Cell Dev Biol 2017; 82:25-33. [PMID: 29056490 DOI: 10.1016/j.semcdb.2017.10.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 10/09/2017] [Accepted: 10/12/2017] [Indexed: 12/12/2022]
Abstract
Both types of Drosophila egg chamber germ cells, i.e. oocyte and nurse cells, have to control their nucleus positions in order to produce a viable gamete. Interestingly, while actin microfilaments are crucial to position the nuclei in nurse cells, these are the microtubules that are important for oocyte nucleus to migrate and adopt the correct position. In this review, we discuss the mechanisms underlying these positioning processes in the two cell types with respect to the organization and dynamics of the actin and microtubule skeleton. In the nurse cells it is essential to keep firmly the nuclei in a central position to prevent them from obstructing the ring canals when the cytoplasmic content of the cells is dumped into the oocyte cells toward the end of oogenesis. This is achieved by the assembly of thick filopodia-like actin cables anchored to the plasma membrane, which grow inwardly and eventually encase tightly the nuclei in a cage-like structure. In the oocyte, the migration at an early stage of oogenesis of the nucleus from a posterior location to an anchorage site at an asymmetric anterior position, is an essential step in the setting up of the dorsoventral polarity axis of the future embryo. This process is controlled by an interplay between MT networks that just start to be untangled. Although both mechanisms have evolved to fulfill cell-type specific cell processes in the context of fly oogenesis, interesting parallels can be drawn with other nuclear positioning mechanisms in the mouse oocyte and the developing muscle respectively.
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Affiliation(s)
- Fred Bernard
- Institut Jacques Monod, CNRS UMR 7592, Université Paris-Diderot, Sorbonne Paris Cité, 75205, Paris Cedex, France.
| | - Jean-Antoine Lepesant
- Institut Jacques Monod, CNRS UMR 7592, Université Paris-Diderot, Sorbonne Paris Cité, 75205, Paris Cedex, France.
| | - Antoine Guichet
- Institut Jacques Monod, CNRS UMR 7592, Université Paris-Diderot, Sorbonne Paris Cité, 75205, Paris Cedex, France.
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25
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Hegsted A, Yingling CV, Pruyne D. Inverted formins: A subfamily of atypical formins. Cytoskeleton (Hoboken) 2017; 74:405-419. [PMID: 28921928 DOI: 10.1002/cm.21409] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 08/22/2017] [Accepted: 08/31/2017] [Indexed: 12/25/2022]
Abstract
Formins are a family of regulators of actin and microtubule dynamics that are present in almost all eukaryotes. These proteins are involved in many cellular processes, including cytokinesis, stress fiber formation, and cell polarization. Here we review one subfamily of formins, the inverted formins. Inverted formins as a group break several formin stereotypes, having atypical biochemical properties and domain organization, and they have been linked to kidney disease and neuropathy in humans. In this review, we will explore recent research on members of the inverted formin sub-family in mammals, zebrafish, fruit flies, and worms.
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Affiliation(s)
- Anna Hegsted
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Curtis V Yingling
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - David Pruyne
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York 13210
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26
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De Conto F, Fazzi A, Razin SV, Arcangeletti MC, Medici MC, Belletti S, Chezzi C, Calderaro A. Mammalian Diaphanous-related formin-1 restricts early phases of influenza A/NWS/33 virus (H1N1) infection in LLC-MK2 cells by affecting cytoskeleton dynamics. Mol Cell Biochem 2017; 437:185-201. [PMID: 28744815 DOI: 10.1007/s11010-017-3107-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 07/01/2017] [Indexed: 12/15/2022]
Abstract
Viruses depend on cellular machinery to efficiently replicate. The host cytoskeleton is one of the first cellular systems hijacked by viruses in order to ensure their intracellular transport and promote the development of infection. Our previous results demonstrated that stable microfilaments and microtubules interfered with human influenza A/NWS/33 virus (H1N1) infection in semi-permissive LLC-MK2 cells. Although formins play a key role in cytoskeletal remodelling, few studies addressed a possible role of these proteins in development of viral infection. Here, we have demonstrated that mammalian Diaphanous-related formin-1 (mDia1) is involved in the control of cytoskeleton dynamics during human influenza A virus infection. First, by employing cytoskeleton-perturbing drugs, we evidenced a cross-talk occurring between microtubules and microfilaments that also has implications on the intracellular localization of mDia1. In influenza A/NWS/33 virus-infected LLC-MK2 cells, mDia1 showed a highly dynamic intracellular localization and partially co-localized with actin and tubulin. A depletion of mDia1 by RNA-mediated RNA interference was found to improve the outcome of influenza A/NWS/33 virus infection and to increase the dynamics of microfilament and microtubule networks in LLC-MK2 cells. Consistent with these findings, observations made in epithelial respiratory cells from paediatric patients with acute respiratory disease assessed that the expression of mDia1 is stimulated by influenza A virus but not by respiratory syncytial virus. Taken together, the obtained results suggest that mDia1 restricts the initiation of influenza A/NWS/33 virus infection in LLC-MK2 cells by counteracting cytoskeletal dynamics.
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Affiliation(s)
- Flora De Conto
- Department of Medicine and Surgery, University of Parma, Parma, Italy.
| | - Alessandra Fazzi
- Department of Medicine and Surgery, University of Parma, Parma, Italy
| | - Sergey V Razin
- Institute of Gene Biology, Russian Academy of Sciences and Lomonosow Moscow State University, Moscow, Russia
| | | | | | - Silvana Belletti
- Department of Medicine and Surgery, University of Parma, Parma, Italy
| | - Carlo Chezzi
- Department of Medicine and Surgery, University of Parma, Parma, Italy
| | - Adriana Calderaro
- Department of Medicine and Surgery, University of Parma, Parma, Italy
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27
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Szikora S, Földi I, Tóth K, Migh E, Vig A, Bugyi B, Maléth J, Hegyi P, Kaltenecker P, Sanchez-Soriano N, Mihály J. The formin DAAM is required for coordination of the actin and microtubule cytoskeleton in axonal growth cones. J Cell Sci 2017; 130:2506-2519. [PMID: 28606990 DOI: 10.1242/jcs.203455] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 06/05/2017] [Indexed: 01/10/2023] Open
Abstract
Directed axonal growth depends on correct coordination of the actin and microtubule cytoskeleton in the growth cone. However, despite the relatively large number of proteins implicated in actin-microtubule crosstalk, the mechanisms whereby actin polymerization is coupled to microtubule stabilization and advancement in the peripheral growth cone remained largely unclear. Here, we identified the formin Dishevelled-associated activator of morphogenesis (DAAM) as a novel factor playing a role in concerted regulation of actin and microtubule remodeling in Drosophilamelanogaster primary neurons. In vitro, DAAM binds to F-actin as well as to microtubules and has the ability to crosslink the two filament systems. Accordingly, DAAM associates with the neuronal cytoskeleton, and a significant fraction of DAAM accumulates at places where the actin filaments overlap with that of microtubules. Loss of DAAM affects growth cone and microtubule morphology, and several aspects of microtubule dynamics; and biochemical and cellular assays revealed a microtubule stabilization activity and binding to the microtubule tip protein EB1. Together, these data suggest that, besides operating as an actin assembly factor, DAAM is involved in linking actin remodeling in filopodia to microtubule stabilization during axonal growth.
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Affiliation(s)
- Szilárd Szikora
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - István Földi
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Krisztina Tóth
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Ede Migh
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Andrea Vig
- University of Pécs, Medical School, Department of Biophysics, Szigeti str. 12, Pécs H-7624, Hungary
| | - Beáta Bugyi
- University of Pécs, Medical School, Department of Biophysics, Szigeti str. 12, Pécs H-7624, Hungary.,Szentágothai Research Center, Ifjúság str. 34, Pécs H-7624, Hungary
| | - József Maléth
- MTA-SZTE Translational Gastroenterology Research Group, First Department of Internal Medicine, Szeged H-6720, Hungary
| | - Péter Hegyi
- MTA-SZTE Translational Gastroenterology Research Group, First Department of Internal Medicine, Szeged H-6720, Hungary.,Institute for Translational Medicine, Department of Pathophysiology, University of Pécs, Pécs H-7624, Hungary
| | - Péter Kaltenecker
- Institute for Translational Medicine, Department of Cellular and Molecular Physiology, University of Liverpool, Liverpool L69 3BX, UK
| | - Natalia Sanchez-Soriano
- Institute for Translational Medicine, Department of Cellular and Molecular Physiology, University of Liverpool, Liverpool L69 3BX, UK
| | - József Mihály
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
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Abstract
Objects are commonly moved within the cell by either passive diffusion or active directed transport. A third possibility is advection, in which objects within the cytoplasm are moved with the flow of the cytoplasm. Bulk movement of the cytoplasm, or streaming, as required for advection, is more common in large cells than in small cells. For example, streaming is observed in elongated plant cells and the oocytes of several species. In the Drosophila oocyte, two stages of streaming are observed: relatively slow streaming during mid-oogenesis and streaming that is approximately ten times faster during late oogenesis. These flows are implicated in two processes: polarity establishment and mixing. In this review, I discuss the underlying mechanism of streaming, how slow and fast streaming are differentiated, and what we know about the physiological roles of the two types of streaming.
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Affiliation(s)
- Margot E Quinlan
- Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles, California 90095;
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29
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Abstract
The growth and migration of neurons require continuous remodelling of the neuronal cytoskeleton, providing a versatile cellular framework for force generation and guided movement, in addition to structural support. Actin filaments and microtubules are central to the dynamic action of the cytoskeleton and rapid advances in imaging technologies are enabling ever more detailed visualisation of the dynamic intracellular networks that they form. However, these filaments do not act individually and an expanding body of evidence emphasises the importance of actin-microtubule crosstalk in orchestrating cytoskeletal dynamics. Here, we summarise our current understanding of the structure and dynamics of actin and microtubules in isolation, before reviewing both the mechanisms and the molecular players involved in mediating actin-microtubule crosstalk in neurons.
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Affiliation(s)
- Charlotte H Coles
- Laboratory for Axon Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany.
| | - Frank Bradke
- Laboratory for Axon Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany.
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30
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The WH2 Domain and Actin Nucleation: Necessary but Insufficient. Trends Biochem Sci 2016; 41:478-490. [PMID: 27068179 DOI: 10.1016/j.tibs.2016.03.004] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 02/18/2016] [Accepted: 03/11/2016] [Indexed: 11/22/2022]
Abstract
Two types of sequences, proline-rich domains (PRDs) and the WASP-homology 2 (WH2) domain, are found in most actin filament nucleation and elongation factors discovered thus far. PRDs serve as a platform for protein-protein interactions, often mediating the binding of profilin-actin. The WH2 domain is an abundant actin monomer-binding motif comprising ∼17 amino acids. It frequently occurs in tandem repeats, and functions in nucleation by recruiting actin subunits to form the polymerization nucleus. It is found in Spire, Cordon Bleu (Cobl), Leiomodin (Lmod), Arp2/3 complex activators (WASP, WHAMM, WAVE, etc.), the bacterial nucleators VopL/VopF and Sca2, and some formins. Yet, it is argued here that the WH2 domain plays only an auxiliary role in nucleation, always synergizing with other domains or proteins for this activity.
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31
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Bartolini F, Andres-Delgado L, Qu X, Nik S, Ramalingam N, Kremer L, Alonso MA, Gundersen GG. An mDia1-INF2 formin activation cascade facilitated by IQGAP1 regulates stable microtubules in migrating cells. Mol Biol Cell 2016; 27:1797-808. [PMID: 27030671 PMCID: PMC4884070 DOI: 10.1091/mbc.e15-07-0489] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 03/25/2016] [Indexed: 01/08/2023] Open
Abstract
The formin INF2 is required for stable Glu microtubule formation and inhibition of microtubule dynamics in NIH3T3 cells downstream of mDia1 and LPA. Evidence also shows that the formation of an mDia1/INF2 complex is necessary for microtubule stabilization stimulated by LPA and is regulated by IQGAP1. Multiple formins regulate microtubule (MT) arrays, but whether they function individually or in a common pathway is unknown. Lysophosphatidic acid (LPA) stimulates the formation of stabilized detyrosinated MTs (Glu MTs) in NIH3T3 fibroblasts through RhoA and the formin mDia1. Here we show that another formin, INF2, is necessary for mDia1-mediated induction of Glu MTs and regulation of MT dynamics and that mDia1 can be bypassed by activating INF2. INF2 localized to MTs after LPA treatment in an mDia1-dependent manner, suggesting that mDia1 regulates INF2. Mutants of either formin that disrupt their interaction failed to rescue MT stability in cells depleted of the respective formin, and the mDia1-interacting protein IQGAP1 regulated INF2’s localization to MTs and the induction of Glu MTs by either formin. The N-terminus of IQGAP1 associated with the C-terminus of INF2 directly, suggesting the possibility of a tripartite complex stimulated by LPA. Supporting this, the interaction of mDia1 and INF2 was induced by LPA and dependent on IQGAP1. Our data highlight a unique mechanism of formin action in which mDia1 and INF2 function in series to stabilize MTs and point to IQGAP1 as a scaffold that facilitates the activation of one formin by another.
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Affiliation(s)
- Francesca Bartolini
- Department of Pathology and Cell Biology, Columbia University, New York, NY 10032
| | - Laura Andres-Delgado
- Centro de Biologia Molecular Severo Ochoa, Consejo Superior de Investigaciones Cientificas and Universidad Autonoma de Madrid, 28049 Madrid, Spain
| | - Xiaoyi Qu
- Department of Pathology and Cell Biology, Columbia University, New York, NY 10032
| | - Sara Nik
- Department of Pathology and Cell Biology, Columbia University, New York, NY 10032
| | - Nagendran Ramalingam
- Department of Pathology and Cell Biology, Columbia University, New York, NY 10032
| | - Leonor Kremer
- Centro de Biologia Molecular Severo Ochoa, Consejo Superior de Investigaciones Cientificas and Universidad Autonoma de Madrid, 28049 Madrid, Spain
| | - Miguel A Alonso
- Centro de Biologia Molecular Severo Ochoa, Consejo Superior de Investigaciones Cientificas and Universidad Autonoma de Madrid, 28049 Madrid, Spain
| | - Gregg G Gundersen
- Department of Pathology and Cell Biology, Columbia University, New York, NY 10032
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32
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Sahasrabudhe A, Ghate K, Mutalik S, Jacob A, Ghose A. Formin 2 regulates the stabilization of filopodial tip adhesions in growth cones and affects neuronal outgrowth and pathfinding in vivo. Development 2015; 143:449-60. [PMID: 26718007 DOI: 10.1242/dev.130104] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 12/23/2015] [Indexed: 12/28/2022]
Abstract
Growth cone filopodia are actin-based mechanosensory structures that are essential for chemoreception and the generation of contractile forces necessary for directional motility. However, little is known about the influence of filopodial actin structures on substrate adhesion and filopodial contractility. Formin 2 (Fmn2) localizes along filopodial actin bundles and its depletion does not affect filopodia initiation or elongation. However, Fmn2 activity is required for filopodial tip adhesion maturation and the ability of filopodia to generate traction forces. Dysregulation of filopodia in Fmn2-depleted neurons leads to compromised growth cone motility. Additionally, in mouse fibroblasts, Fmn2 regulates ventral stress fiber assembly and affects the stability of focal adhesions. In the developing chick spinal cord, Fmn2 activity is required cell-autonomously for the outgrowth and pathfinding of spinal commissural neurons. Our results reveal an unanticipated function for Fmn2 in neural development. Fmn2 regulates structurally diverse bundled actin structures, parallel filopodial bundles in growth cones and anti-parallel stress fibers in fibroblasts, in turn modulating the stability of substrate adhesions. We propose Fmn2 as a mediator of actin bundle integrity, enabling efficient force transmission to the adhesion sites.
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Affiliation(s)
- Abhishek Sahasrabudhe
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Ketakee Ghate
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Sampada Mutalik
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Ajesh Jacob
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Aurnab Ghose
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
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33
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Montaville P, Kühn S, Compper C, Carlier MF. Role of the C-terminal Extension of Formin 2 in Its Activation by Spire Protein and Processive Assembly of Actin Filaments. J Biol Chem 2015; 291:3302-18. [PMID: 26668326 DOI: 10.1074/jbc.m115.681379] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Indexed: 11/06/2022] Open
Abstract
Formin 2 (Fmn2), a member of the FMN family of formins, plays an important role in early development. This formin cooperates with profilin and Spire, a WASP homology domain 2 (WH2) repeat protein, to stimulate assembly of a dynamic cytoplasmic actin meshwork that facilitates translocation of the meiotic spindle in asymmetric division of mouse oocytes. The kinase-like non-catalytic domain (KIND) of Spire directly interacts with the C-terminal extension of the formin homology domain 2 (FH2) domain of Fmn2, called FSI. This direct interaction is required for the synergy between the two proteins in actin assembly. We have recently demonstrated how Spire, which caps barbed ends via its WH2 domains, activates Fmn2. Fmn2 by itself associates very poorly to filament barbed ends but is rapidly recruited to Spire-capped barbed ends via the KIND domain, and it subsequently displaces Spire from the barbed end to elicit rapid processive assembly from profilin·actin. Here, we address the mechanism by which Spire and Fmn2 compete at barbed ends and the role of FSI in orchestrating this competition as well as in the processivity of Fmn2. We have combined microcalorimetric, fluorescence, and hydrodynamic binding assays, as well as bulk solution and single filament measurements of actin assembly, to show that removal of FSI converts Fmn2 into a Capping Protein. This activity is mimicked by association of KIND to Fmn2. In addition, FSI binds actin at filament barbed ends as a weak capper and plays a role in displacing the WH2 domains of Spire from actin, thus allowing the association of actin-binding regions of FH2 to the barbed end.
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Affiliation(s)
- Pierre Montaville
- From the Cytoskeleton Dynamics and Motility, Institut de Biologie Intégrative de la Cellule, CNRS, 91198 Gif-sur-Yvette, France
| | - Sonja Kühn
- From the Cytoskeleton Dynamics and Motility, Institut de Biologie Intégrative de la Cellule, CNRS, 91198 Gif-sur-Yvette, France
| | - Christel Compper
- From the Cytoskeleton Dynamics and Motility, Institut de Biologie Intégrative de la Cellule, CNRS, 91198 Gif-sur-Yvette, France
| | - Marie-France Carlier
- From the Cytoskeleton Dynamics and Motility, Institut de Biologie Intégrative de la Cellule, CNRS, 91198 Gif-sur-Yvette, France
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34
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Shevchenko G. Participation of proteins binding both actin filaments and microtubules in higher plant cell growth. CYTOL GENET+ 2015. [DOI: 10.3103/s009545271504009x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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35
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Rodal AA, Del Signore SJ, Martin AC. Drosophila comes of age as a model system for understanding the function of cytoskeletal proteins in cells, tissues, and organisms. Cytoskeleton (Hoboken) 2015; 72:207-24. [PMID: 26074334 DOI: 10.1002/cm.21228] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Revised: 06/11/2015] [Accepted: 06/11/2015] [Indexed: 01/30/2023]
Abstract
For the last 100 years, Drosophila melanogaster has been a powerhouse genetic system for understanding mechanisms of inheritance, development, and behavior in animals. In recent years, advances in imaging and genetic tools have led to Drosophila becoming one of the most effective systems for unlocking the subcellular functions of proteins (and particularly cytoskeletal proteins) in complex developmental settings. In this review, written for non-Drosophila experts, we will discuss critical technical advances that have enabled these cell biological insights, highlighting three examples of cytoskeletal discoveries that have arisen as a result: (1) regulation of Arp2/3 complex in myoblast fusion, (2) cooperation of the actin filament nucleators Spire and Cappuccino in establishment of oocyte polarity, and (3) coordination of supracellular myosin cables. These specific examples illustrate the unique power of Drosophila both to uncover new cytoskeletal structures and functions, and to place these discoveries in a broader in vivo context, providing insights that would have been impossible in a cell culture model or in vitro. Many of the cellular structures identified in Drosophila have clear counterparts in mammalian cells and tissues, and therefore elucidating cytoskeletal functions in Drosophila will be broadly applicable to other organisms.
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Affiliation(s)
- Avital A Rodal
- Department of Biology, Brandeis University, Waltham, Massachusetts
| | | | - Adam C Martin
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
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36
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SMIFH2 has effects on Formins and p53 that perturb the cell cytoskeleton. Sci Rep 2015; 5:9802. [PMID: 25925024 PMCID: PMC5386218 DOI: 10.1038/srep09802] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 03/19/2015] [Indexed: 01/08/2023] Open
Abstract
Formin proteins are key regulators of the cytoskeleton involved in developmental and homeostatic programs, and human disease. For these reasons, small molecules interfering with Formins' activity have gained increasing attention. Among them, small molecule inhibitor of Formin Homology 2 domains (SMIFH2) is often used as a pharmacological Formin blocker. Although SMIFH2 inhibits actin polymerization by Formins and affects the actin cytoskeleton, its cellular mechanism of action and target specificity remain unclear. Here we show that SMIFH2 induces remodelling of actin filaments, microtubules and the Golgi complex as a result of its effects on Formins and p53. We found that SMIFH2 triggers alternated depolymerization-repolymerization cycles of actin and tubulin, increases cell migration, causes scattering of the Golgi complex, and also cytotoxicity at high dose. Moreover, SMIFH2 reduces expression and activity of p53 through a post-transcriptional, proteasome-independent mechanism that influences remodelling of the cytoskeleton. As the action of SMIFH2 may go beyond Formin inhibition, only short-term and low-dose SMIFH2 treatments minimize confounding effects induced by loss of p53 and cytotoxicity.
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37
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Yoo H, Roth-Johnson EA, Bor B, Quinlan ME. Drosophila Cappuccino alleles provide insight into formin mechanism and role in oogenesis. Mol Biol Cell 2015; 26:1875-86. [PMID: 25788286 PMCID: PMC4436832 DOI: 10.1091/mbc.e14-11-1558] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 03/10/2015] [Indexed: 11/11/2022] Open
Abstract
During Drosophila development, the formin actin nucleator Cappuccino (Capu) helps build a cytoplasmic actin mesh throughout the oocyte. Loss of Capu leads to female sterility, presumably because polarity determinants fail to localize properly in the absence of the mesh. To gain deeper insight into how Capu builds this actin mesh, we systematically characterized seven capu alleles, which have missense mutations in Capu's formin homology 2 (FH2) domain. We report that all seven alleles have deleterious effects on fly fertility and the actin mesh in vivo but have strikingly different effects on Capu's biochemical activity in vitro. Using a combination of bulk and single- filament actin-assembly assays, we find that the alleles differentially affect Capu's ability to nucleate and processively elongate actin filaments. We also identify a unique "loop" in the lasso region of Capu's FH2 domain. Removing this loop enhances Capu's nucleation, elongation, and F-actin-bundling activities in vitro. Together our results on the loop and the seven missense mutations provides mechanistic insight into formin function in general and Capu's role in the Drosophila oocyte in particular.
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Affiliation(s)
- Haneul Yoo
- Department of Chemistry and Biochemistry
| | - Elizabeth A Roth-Johnson
- Molecular Biology Interdepartmental PhD Program, University of California, Los Angeles, Los Angeles, CA 90095
| | - Batbileg Bor
- Molecular Biology Interdepartmental PhD Program, University of California, Los Angeles, Los Angeles, CA 90095
| | - Margot E Quinlan
- Department of Chemistry and Biochemistry Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
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38
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Verboon JM, Rahe TK, Rodriguez-Mesa E, Parkhurst SM. Wash functions downstream of Rho1 GTPase in a subset of Drosophila immune cell developmental migrations. Mol Biol Cell 2015; 26:1665-74. [PMID: 25739458 PMCID: PMC4436778 DOI: 10.1091/mbc.e14-08-1266] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 02/25/2015] [Indexed: 01/12/2023] Open
Abstract
Drosophila immune cells undergo four stereotypical developmental migrations to populate the embryo. Wash is a downstream effector of Rho1 and establishes Rho1>Wash>Arp2/3 as the regulatory pathway controlling the cytoskeleton during one of these developmental hemocyte migrations in a WASH regulatory complex–independent manner. Drosophila immune cells, the hemocytes, undergo four stereotypical developmental migrations to populate the embryo, where they provide immune reconnoitering, as well as a number of non–immune-related functions necessary for proper embryogenesis. Here, we describe a role for Rho1 in one of these developmental migrations in which posteriorly located hemocytes migrate toward the head. This migration requires the interaction of Rho1 with its downstream effector Wash, a Wiskott–Aldrich syndrome family protein. Both Wash knockdown and a Rho1 transgene harboring a mutation that prevents Wash binding exhibit the same developmental migratory defect as Rho1 knockdown. Wash activates the Arp2/3 complex, whose activity is needed for this migration, whereas members of the WASH regulatory complex (SWIP, Strumpellin, and CCDC53) are not. Our results suggest a WASH complex–independent signaling pathway to regulate the cytoskeleton during a subset of hemocyte developmental migrations.
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Affiliation(s)
- Jeffrey M Verboon
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109
| | - Travis K Rahe
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109
| | - Evelyn Rodriguez-Mesa
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109
| | - Susan M Parkhurst
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109
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39
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Huang F, Paulson A, Dutta A, Venkatesh S, Smolle M, Abmayr SM, Workman JL. Histone acetyltransferase Enok regulates oocyte polarization by promoting expression of the actin nucleation factor spire. Genes Dev 2015; 28:2750-63. [PMID: 25512562 PMCID: PMC4265678 DOI: 10.1101/gad.249730.114] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
KAT6 histone acetyltransferases (HATs) are highly conserved in eukaryotes and have been shown to play important roles in transcriptional regulation. Here, we demonstrate that the Drosophila KAT6 Enok acetylates histone H3 Lys 23 (H3K23) in vitro and in vivo. Mutants lacking functional Enok exhibited defects in the localization of Oskar (Osk) to the posterior end of the oocyte, resulting in loss of germline formation and abdominal segments in the embryo. RNA sequencing (RNA-seq) analysis revealed that spire (spir) and maelstrom (mael), both required for the posterior localization of Osk in the oocyte, were down-regulated in enok mutants. Chromatin immunoprecipitation showed that Enok is localized to and acetylates H3K23 at the spir and mael genes. Furthermore, Gal4-driven expression of spir in the germline can largely rescue the defective Osk localization in enok mutant ovaries. Our results suggest that the Enok-mediated H3K23 acetylation (H3K23Ac) promotes the expression of spir, providing a specific mechanism linking oocyte polarization to histone modification.
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Affiliation(s)
- Fu Huang
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA
| | - Ariel Paulson
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA
| | - Arnob Dutta
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA
| | | | - Michaela Smolle
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA
| | - Susan M Abmayr
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA; Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, Kansas 66160, USA
| | - Jerry L Workman
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA;
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40
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Vizcarra CL, Bor B, Quinlan ME. The role of formin tails in actin nucleation, processive elongation, and filament bundling. J Biol Chem 2014; 289:30602-30613. [PMID: 25246531 DOI: 10.1074/jbc.m114.588368] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Formins are multidomain proteins that assemble actin in a wide variety of biological processes. They both nucleate and remain processively associated with growing filaments, in some cases accelerating filament growth. The well conserved formin homology 1 and 2 domains were originally thought to be solely responsible for these activities. Recently a role in nucleation was identified for the Diaphanous autoinhibitory domain (DAD), which is C-terminal to the formin homology 2 domain. The C-terminal tail of the Drosophila formin Cappuccino (Capu) is conserved among FMN formins but distinct from other formins. It does not have a DAD domain. Nevertheless, we find that Capu-tail plays a role in filament nucleation similar to that described for mDia1 and other formins. Building on this, replacement of Capu-tail with DADs from other formins tunes nucleation activity. Capu-tail has low-affinity interactions with both actin monomers and filaments. Removal of the tail reduces actin filament binding and bundling. Furthermore, when the tail is removed, we find that processivity is compromised. Despite decreased processivity, the elongation rate of filaments is unchanged. Again, replacement of Capu-tail with DADs from other formins tunes the processive association with the barbed end, indicating that this is a general role for formin tails. Our data show a role for the Capu-tail domain in assembling the actin cytoskeleton, largely mediated by electrostatic interactions. Because of its multifunctionality, the formin tail is a candidate for regulation by other proteins during cytoskeletal rearrangements.
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Affiliation(s)
- Christina L Vizcarra
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095
| | - Batbileg Bor
- Molecular Biology Interdepartmental Ph.D. Program, and University of California Los Angeles, Los Angeles, California 90095
| | - Margot E Quinlan
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095; Molecular Biology Institute, University of California Los Angeles, Los Angeles, California 90095.
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41
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Abstract
Formin proteins were recognized as effectors of Rho GTPases some 15 years ago. They contribute to different cellular actin cytoskeleton structures by their ability to polymerize straight actin filaments at the barbed end. While not all formins necessarily interact with Rho GTPases, a subgroup of mammalian formins, termed Diaphanous-related formins or DRFs, were shown to be activated by small GTPases of the Rho superfamily. DRFs are autoinhibited in the resting state by an N- to C-terminal interaction that renders the central actin polymerization domain inactive. Upon the interaction with a GTP-bound Rho, Rac, or Cdc42 GTPase, the C-terminal autoregulation domain is displaced from its N-terminal recognition site and the formin becomes active to polymerize actin filaments. In this review we discuss the current knowledge on the structure, activation, and function of formin-GTPase interactions for the mammalian formin families Dia, Daam, FMNL, and FHOD. We describe both direct and indirect interactions of formins with GTPases, which lead to formin activation and cytoskeletal rearrangements. The multifaceted function of formins as effector proteins of Rho GTPases thus reflects the diversity of the actin cytoskeleton in cells.
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Affiliation(s)
- Sonja Kühn
- Center of Advanced European Studies and Research (caesar); Group Physical Biochemistry; Bonn, Germany
| | - Matthias Geyer
- Center of Advanced European Studies and Research (caesar); Group Physical Biochemistry; Bonn, Germany
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42
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Randall TS, Ehler E. A formin-g role during development and disease. Eur J Cell Biol 2014; 93:205-11. [PMID: 24342720 DOI: 10.1016/j.ejcb.2013.11.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 11/15/2013] [Accepted: 11/18/2013] [Indexed: 11/22/2022] Open
Abstract
Several different protein families were shown to be involved in the regulation of actin filament formation and have been studied extensively in processes such as cell migration. Among them are members of the formin family, which tend to promote the formation of linear actin filaments. Studies in recent years, often using loss of function animal models, have indicated that formin family members play roles beyond cell motility in vitro and are involved in processes ranging from tissue morphogenesis and cell differentiation to diseases such as cancer and cardiomyopathy. Therefore the aim of this review is to discuss these findings and to start putting them into a subcellular context.
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Affiliation(s)
- Thomas S Randall
- Randall Division of Cell and Molecular Biophysics, Cardiovascular Division, British Heart Foundation Centre of Research Excellence, King's College London, London SE1 1UL, United Kingdom
| | - Elisabeth Ehler
- Randall Division of Cell and Molecular Biophysics, Cardiovascular Division, British Heart Foundation Centre of Research Excellence, King's College London, London SE1 1UL, United Kingdom.
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Pokrywka NJ, Zhang H, Raley-Susman K. Distinct roles for hu li tai shao and swallow in cytoskeletal organization during Drosophila oogenesis. Dev Dyn 2014; 243:906-16. [PMID: 24677508 DOI: 10.1002/dvdy.24132] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 03/19/2014] [Accepted: 03/24/2014] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Cytoskeletal organization is essential for localization of developmentally significant molecules during Drosophila oogenesis. Swallow (Swa) and an isoform of Hu li tai shao (Ovhts-RC) have been implicated in the organization of actin filaments in developing oocytes but their precise roles have been obscured by the dependence of hts RNA localization on swa function. The functional significance of hts RNA localization in the oocyte has not been established. RESULTS In this study we examine Ovhts-RC distribution and cytoskeletal organization under conditions in which Swa protein and/or hts RNA localization are perturbed. We find Swa is required for overall actin organization and for the maintenance of a distinct subset of microtubules in the oocyte. hts RNA localization modulates the distribution of Ovhts-RC in the oocyte and, in turn, local actin filament proliferation. CONCLUSIONS Our results support separate contributions of Swa and hts RNA localization to actin organization during oogenesis. Swa is crucial for the organization of actin networks that lead to the formation of a specialized microtubule population, while Ovhts-RC acts to modulate spatially restricted actin filament growth at the oocyte cortex. This suggests RNA localization can lead to modifications of both the actin and microtubule cytoskeletons at specific subcellular locales.
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Ferreira T, Ou Y, Li S, Giniger E, van Meyel DJ. Dendrite architecture organized by transcriptional control of the F-actin nucleator Spire. Development 2014; 141:650-60. [PMID: 24449841 DOI: 10.1242/dev.099655] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The architectures of dendritic trees are crucial for the wiring and function of neuronal circuits because they determine coverage of receptive territories, as well as the nature and strength of sensory or synaptic inputs. Here, we describe a cell-intrinsic pathway sculpting dendritic arborization (da) neurons in Drosophila that requires Longitudinals Lacking (Lola), a BTB/POZ transcription factor, and its control of the F-actin cytoskeleton through Spire (Spir), an actin nucleation protein. Loss of Lola from da neurons reduced the overall length of dendritic arbors, increased the expression of Spir, and produced inappropriate F-actin-rich dendrites at positions too near the cell soma. Selective removal of Lola from only class IV da neurons decreased the evasive responses of larvae to nociception. The increased Spir expression contributed to the abnormal F-actin-rich dendrites and the decreased nocifensive responses because both were suppressed by reduced dose of Spir. Thus, an important role of Lola is to limit expression of Spir to appropriate levels within da neurons. We found Spir to be expressed in dendritic arbors and to be important for their development. Removal of Spir from class IV da neurons reduced F-actin levels and total branch number, shifted the position of greatest branch density away from the cell soma, and compromised nocifensive behavior. We conclude that the Lola-Spir pathway is crucial for the spatial arrangement of branches within dendritic trees and for neural circuit function because it provides balanced control of the F-actin cytoskeleton.
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Affiliation(s)
- Tiago Ferreira
- McGill Centre for Research in Neuroscience, McGill University Health Centre, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada
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Sadati M, Nourhani A, Fredberg JJ, Qazvini NT. Glass-like dynamics in the cell and in cellular collectives. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2014; 6:137-49. [PMID: 24431332 PMCID: PMC4000035 DOI: 10.1002/wsbm.1258] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2013] [Revised: 10/21/2013] [Accepted: 12/02/2013] [Indexed: 01/19/2023]
Abstract
Prominent fluctuations, heterogeneity, and cooperativity dominate the dynamics of the cytoskeleton as well as the dynamics of the cellular collective. Such systems are out of equilibrium, disordered, and remain poorly understood. To explain these findings, we consider a unifying mechanistic rubric that imagines these systems as comprising phases of soft condensed matter in proximity to a glass or jamming transition, with associated transitions between solid-like versus liquid-like phases. At the scale of the cytoskeleton, data suggest that intermittent dynamics, kinetic arrest, and dynamic heterogeneity represent mesoscale features of glassy protein-protein interactions that link underlying biochemical events to integrative cellular behaviors such as crawling, contraction, and remodeling. At the scale of the multicellular collective, jamming has the potential to unify diverse biological factors that previously had been considered mostly as acting separately and independently. Although a quantitative relationship between intra- and intercellular dynamics is still lacking, glassy dynamics and jamming offer insights linking the mechanobiology of cell to human physiology and pathophysiology.
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Affiliation(s)
- Monirosadat Sadati
- School of Public Health, Harvard University, Boston, MA 02115, United States
| | - Amir Nourhani
- Department of Physics, The Pennsylvania State University, University Park, PA 16802, United States
| | - Jeffrey J. Fredberg
- School of Public Health, Harvard University, Boston, MA 02115, United States
| | - Nader Taheri Qazvini
- School of Public Health, Harvard University, Boston, MA 02115, United States, School of Chemistry, College of Science, University of Tehran, Tehran, Iran
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Spire and Formin 2 synergize and antagonize in regulating actin assembly in meiosis by a ping-pong mechanism. PLoS Biol 2014; 12:e1001795. [PMID: 24586110 PMCID: PMC3934834 DOI: 10.1371/journal.pbio.1001795] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 01/14/2014] [Indexed: 11/24/2022] Open
Abstract
An in vitro study reveals how the three actin binding proteins profilin, formin 2, and Spire functionally cooperate by a ping-pong mechanism to regulate actin assembly during reproductive cell division. In mammalian oocytes, three actin binding proteins, Formin 2 (Fmn2), Spire, and profilin, synergistically organize a dynamic cytoplasmic actin meshwork that mediates translocation of the spindle toward the cortex and is required for successful fertilization. Here we characterize Fmn2 and elucidate the molecular mechanism for this synergy, using bulk solution and individual filament kinetic measurements of actin assembly dynamics. We show that by capping filament barbed ends, Spire recruits Fmn2 and facilitates its association with barbed ends, followed by rapid processive assembly and release of Spire. In the presence of actin, profilin, Spire, and Fmn2, filaments display alternating phases of rapid processive assembly and arrested growth, driven by a “ping-pong” mechanism, in which Spire and Fmn2 alternately kick off each other from the barbed ends. The results are validated by the effects of injection of Spire, Fmn2, and their interacting moieties in mouse oocytes. This original mechanism of regulation of a Rho-GTPase–independent formin, recruited by Spire at Rab11a-positive vesicles, supports a model for modulation of a dynamic actin-vesicle meshwork in the oocyte at the origin of asymmetric positioning of the meiotic spindle. Mammalian reproduction requires successful meiosis, which consists of two strongly asymmetric cell divisions. In meiosis I, movement of the spindle (the subcellular structure that segregates chromosomes during division) toward the oocyte cortex (the outer layer of the egg) is essential for fertility. This process requires that actin filaments assemble in a dynamic mesh, driven by three actin binding proteins, profilin, formin 2, and Spire. To date the molecular mechanisms by which these three proteins cooperate are not known. We now explore this in vitro by a combination of bulk solution and single actin filament assembly assays in the presence of profilin, Spire, and formin 2. Individually, Spire binds to actin filament ends to block their growth, and by itself, formin 2 associates poorly with filament ends, promoting fast processive assembly from the profilin-actin complex. However, when present together, Spire and formin 2 interact with one another (the formin 2 C-terminal binds to the N terminal Spire KIND domain), forming transient complexes at filament ends from which each binds alternately to the filament ends to regulate actin assembly by a ping-pong mechanism. Our in vitro observations are validated by injection studies in mouse oocytes. In oocytes, the additional interaction of Spire and formin 2 with Rab11a-myosin Vb vesicles couples high actin dynamics to vesicle traffic.
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Abreu-Blanco MT, Verboon JM, Parkhurst SM. Coordination of Rho family GTPase activities to orchestrate cytoskeleton responses during cell wound repair. Curr Biol 2014; 24:144-155. [PMID: 24388847 DOI: 10.1016/j.cub.2013.11.048] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 10/23/2013] [Accepted: 11/25/2013] [Indexed: 11/25/2022]
Abstract
BACKGROUND Cells heal disruptions in their plasma membrane using a sophisticated, efficient, and conserved response involving the formation of a membrane plug and assembly of an actomyosin ring. Here we describe how Rho family GTPases modulate the cytoskeleton machinery during single cell wound repair in the genetically amenable Drosophila embryo model. RESULTS We find that Rho, Rac, and Cdc42 rapidly accumulate around the wound and segregate into dynamic, partially overlapping zones. Genetic and pharmacological assays show that each GTPase makes specific contributions to the repair process. Rho1 is necessary for myosin II activation, leading to its association with actin. Rho1, along with Cdc42, is necessary for actin filament formation and subsequent actomyosin ring stabilization. Rac is necessary for actin mobilization toward the wound. These GTPase contributions are subject to crosstalk among the GTPases themselves and with the cytoskeleton. We find Rho1 GTPase uses several downstream effectors, including Diaphanous, Rok, and Pkn, simultaneously to mediate its functions. CONCLUSIONS Our results reveal that the three Rho GTPases are necessary to control and coordinate actin and myosin dynamics during single-cell wound repair in the Drosophila embryo. Wounding triggers the formation of arrays of Rho GTPases that act as signaling centers that modulate the cytoskeleton. In turn, coordinated crosstalk among the Rho GTPases themselves, as well as with the cytoskeleton, is required for assembly/disassembly and translocation of the actomyosin ring. The cell wound repair response is an example of how specific pathways can be activated locally in response to the cell's needs.
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Affiliation(s)
| | - Jeffrey M Verboon
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Susan M Parkhurst
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
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Roth-Johnson EA, Vizcarra CL, Bois JS, Quinlan ME. Interaction between microtubules and the Drosophila formin Cappuccino and its effect on actin assembly. J Biol Chem 2013; 289:4395-404. [PMID: 24362037 DOI: 10.1074/jbc.m113.499921] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Formin family actin nucleators are potential coordinators of the actin and microtubule cytoskeletons, as they can both nucleate actin filaments and bind microtubules in vitro. To gain a more detailed mechanistic understanding of formin-microtubule interactions and formin-mediated actin-microtubule cross-talk, we studied microtubule binding by Cappuccino (Capu), a formin involved in regulating actin and microtubule organization during Drosophila oogenesis. We found that two distinct domains within Capu, FH2 and tail, work together to promote high-affinity microtubule binding. The tail domain appears to bind microtubules through nonspecific charge-based interactions. In contrast, distinct residues within the FH2 domain are important for microtubule binding. We also report the first visualization of a formin polymerizing actin filaments in the presence of microtubules. Interestingly, microtubules are potent inhibitors of the actin nucleation activity of Capu but appear to have little effect on Capu once it is bound to the barbed end of an elongating filament. Because Capu does not simultaneously bind microtubules and assemble actin filaments in vitro, its actin assembly and microtubule binding activities likely require spatial and/or temporal regulation within the Drosophila oocyte.
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Wang J, Zhang Y, Wu J, Meng L, Ren H. AtFH16, [corrected] an Arabidopsis type II formin, binds and bundles both microfilaments and microtubules, and preferentially binds to microtubules. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2013; 55:1002-15. [PMID: 23802884 DOI: 10.1111/jipb.12089] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 06/13/2013] [Indexed: 05/03/2023]
Abstract
Formins are well-known regulators that participate in the organization of the actin cytoskeleton in organisms. The Arabidopsis thaliana L. genome encodes 21 formins, which can be divided into two distinct subfamilies. However, type II formins have to date been less well characterized. Here, we cloned a type II formin, AtFH16, and characterized its biochemical activities on actin and microtubule dynamics. The results show that the FH1FH2 structure of AtFH16 cannot nucleate actin polymerization efficiently, but can bind and bundle microfilaments. AtFH16 FH1FH2 is also able to bind and bundle microtubules, and preferentially binds microtubules over microfilaments in vitro. In addition, AtFH16 FH1FH2 co-localizes with microtubules in onion epidermal cells, indicating a higher binding affinity of AtFH16 FH1FH2 for microtubules rather than microfilaments in vivo. In conclusion, AtFH16 is able to interact with both microfilaments and microtubules, suggesting that AtFH16 probably functions as a bifunctional protein, and may thus participate in plant cellular processes.
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Affiliation(s)
- Jiaojiao Wang
- The Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Science, Beijing Normal University, Beijing 100875, China
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Bausek N, Zeidler MP. Gα73B is a downstream effector of JAK/STAT signalling and a regulator of Rho1 in Drosophila haematopoiesis. J Cell Sci 2013; 127:101-10. [PMID: 24163435 DOI: 10.1242/jcs.132852] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
JAK/STAT signalling regulates many essential developmental processes including cell proliferation and haematopoiesis, whereas its inappropriate activation is associated with the majority of myeloproliferative neoplasias and numerous cancers. Furthermore, high levels of JAK/STAT pathway signalling have also been associated with enhanced metastatic invasion by cancerous cells. Strikingly, gain-of-function mutations in the single Drosophila JAK homologue, Hopscotch, result in haemocyte neoplasia, inappropriate differentiation and the formation of melanised haemocyte-derived 'tumour' masses; phenotypes that are partly orthologous to human gain-of-function JAK2-associated pathologies. Here we show that Gα73B, a novel JAK/STAT pathway target gene, is necessary for JAK/STAT-mediated tumour formation in flies. In addition, although Gα73B does not affect haemocyte differentiation, it does regulate haemocyte morphology and motility under non-pathological conditions. We show that Gα73B is required for constitutive, but not injury-induced, activation of Rho1 and for the localisation of Rho1 into filopodia upon haemocyte activation. Consistent with these results, we also show that Rho1 interacts genetically with JAK/STAT signalling, and that wild-type levels of Rho1 are necessary for tumour formation. Our findings link JAK/STAT transcriptional outputs, Gα73B activity and Rho1-dependent cytoskeletal rearrangements and cell motility, therefore connecting a pathway associated with cancer with a marker indicative of invasiveness. As such, we suggest a mechanism by which JAK/STAT pathway signalling may promote metastasis.
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Affiliation(s)
- Nina Bausek
- MRC Centre for Development and Biomedical Genetics, and The Department of Biomedical Science, The University of Sheffield, Sheffield S10 2TN, UK
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