51
|
Rottner K, Faix J, Bogdan S, Linder S, Kerkhoff E. Actin assembly mechanisms at a glance. J Cell Sci 2018; 130:3427-3435. [PMID: 29032357 DOI: 10.1242/jcs.206433] [Citation(s) in RCA: 185] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The actin cytoskeleton and associated motor proteins provide the driving forces for establishing the astonishing morphological diversity and dynamics of mammalian cells. Aside from functions in protruding and contracting cell membranes for motility, differentiation or cell division, the actin cytoskeleton provides forces to shape and move intracellular membranes of organelles and vesicles. To establish the many different actin assembly functions required in time and space, actin nucleators are targeted to specific subcellular compartments, thereby restricting the generation of specific actin filament structures to those sites. Recent research has revealed that targeting and activation of actin filament nucleators, elongators and myosin motors are tightly coordinated by conserved protein complexes to orchestrate force generation. In this Cell Science at a Glance article and the accompanying poster, we summarize and discuss the current knowledge on the corresponding protein complexes and their modes of action in actin nucleation, elongation and force generation.
Collapse
Affiliation(s)
- Klemens Rottner
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, 38106 Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
| | - Jan Faix
- Institute for Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - Sven Bogdan
- Institute for Physiology and Pathophysiology, Department of Molecular Cell Physiology, Philipps-University of Marburg, 35032 Marburg, Germany
| | - Stefan Linder
- Institute for Medical Microbiology, Virology and Hygiene, University Medical Center Eppendorf, 20246 Hamburg, Germany
| | - Eugen Kerkhoff
- Department of Neurology, University Hospital Regensburg, 93053 Regensburg, Germany
| |
Collapse
|
52
|
Blanquie O, Bradke F. Cytoskeleton dynamics in axon regeneration. Curr Opin Neurobiol 2018; 51:60-69. [PMID: 29544200 DOI: 10.1016/j.conb.2018.02.024] [Citation(s) in RCA: 108] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 02/22/2018] [Accepted: 02/26/2018] [Indexed: 11/19/2022]
Abstract
Recent years have seen cytoskeleton dynamics emerging as a key player in axon regeneration. The cytoskeleton, in particular microtubules and actin, ensures the growth of neuronal processes and maintains the singular, highly polarized shape of neurons. Following injury, adult central axons are tipped by a dystrophic structure, the retraction bulb, which prevents their regeneration. Abnormal cytoskeleton dynamics are responsible for the formation of this growth-incompetent structure but pharmacologically modulating cytoskeleton dynamics of injured axons can transform this structure into a growth-competent growth cone. The cytoskeleton also drives the migration of scar-forming cells after an injury. Targeting its dynamics modifies the composition of the inhibitory environment formed by scar tissue and renders it more permissive for regenerating axons. Hence, cytoskeleton dynamics represent an appealing target to promote axon regeneration. As some of cytoskeleton-targeting drugs are used in the clinics for other purposes, they hold the promise to be used as a basis for a regenerative therapy after a spinal cord injury.
Collapse
Affiliation(s)
- Oriane Blanquie
- Laboratory for Axon Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Sigmund-Freud-Strasse 27, 53127 Bonn, Germany.
| | - Frank Bradke
- Laboratory for Axon Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Sigmund-Freud-Strasse 27, 53127 Bonn, Germany.
| |
Collapse
|
53
|
Infection and Transport of Herpes Simplex Virus Type 1 in Neurons: Role of the Cytoskeleton. Viruses 2018; 10:v10020092. [PMID: 29473915 PMCID: PMC5850399 DOI: 10.3390/v10020092] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 02/16/2018] [Accepted: 02/20/2018] [Indexed: 12/22/2022] Open
Abstract
Herpes simplex virus type 1 (HSV-1) is a neuroinvasive human pathogen that has the ability to infect and replicate within epithelial cells and neurons and establish a life-long latent infection in sensory neurons. HSV-1 depends on the host cellular cytoskeleton for entry, replication, and exit. Therefore, HSV-1 has adapted mechanisms to promote its survival by exploiting the microtubule and actin cytoskeletons to direct its active transport, infection, and spread between neurons and epithelial cells during primary and recurrent infections. This review will focus on the currently known mechanisms utilized by HSV-1 to harness the neuronal cytoskeleton, molecular motors, and the secretory and exocytic pathways for efficient virus entry, axonal transport, replication, assembly, and exit from the distinct functional compartments (cell body and axon) of the highly polarized sensory neurons.
Collapse
|
54
|
Freudenblum J, Iglesias JA, Hermann M, Walsen T, Wilfinger A, Meyer D, Kimmel RA. In vivo imaging of emerging endocrine cells reveals a requirement for PI3K-regulated motility in pancreatic islet morphogenesis. Development 2018; 145:dev.158477. [PMID: 29386244 PMCID: PMC5818004 DOI: 10.1242/dev.158477] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 01/10/2018] [Indexed: 01/03/2023]
Abstract
The three-dimensional architecture of the pancreatic islet is integral to beta cell function, but the process of islet formation remains poorly understood due to the difficulties of imaging internal organs with cellular resolution. Within transparent zebrafish larvae, the developing pancreas is relatively superficial and thus amenable to live imaging approaches. We performed in vivo time-lapse and longitudinal imaging studies to follow islet development, visualizing both naturally occurring islet cells and cells arising with an accelerated timecourse following an induction approach. These studies revealed previously unappreciated fine dynamic protrusions projecting between neighboring and distant endocrine cells. Using pharmacological compound and toxin interference approaches, and single-cell analysis of morphology and cell dynamics, we determined that endocrine cell motility is regulated by phosphoinositide 3-kinase (PI3K) and G-protein-coupled receptor (GPCR) signaling. Linking cell dynamics to islet formation, perturbation of protrusion formation disrupted endocrine cell coalescence, and correlated with decreased islet cell differentiation. These studies identified novel cell behaviors contributing to islet morphogenesis, and suggest a model in which dynamic exploratory filopodia establish cell-cell contacts that subsequently promote cell clustering. Summary: Pancreatic endocrine cells extend previously unrecognized dynamic, flexible, fine projections to guide clustering into a compacted islet in a process regulated by PI3K and GPCR.
Collapse
Affiliation(s)
- Julia Freudenblum
- Institute of Molecular Biology/CMBI, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - José A Iglesias
- Johann Radon Institute for Computational and Applied Mathematics (RICAM), Austrian Academy of Sciences, Altenbergerstrasse 69, A-4040 Linz, Austria
| | - Martin Hermann
- Department of Anaesthesiology and Critical Care Medicine, Innsbruck Medical University, Innrain 66, 6020 Innsbruck, Austria
| | - Tanja Walsen
- Department of Neurosurgery, Medical University of Innsbruck, 6020 Innsbruck Austria
| | - Armin Wilfinger
- Institute of Molecular Biology/CMBI, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Dirk Meyer
- Institute of Molecular Biology/CMBI, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Robin A Kimmel
- Institute of Molecular Biology/CMBI, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| |
Collapse
|
55
|
Abstract
The actin cytoskeleton-a collection of actin filaments with their accessory and regulatory proteins-is the primary force-generating machinery in the cell. It can produce pushing (protrusive) forces through coordinated polymerization of multiple actin filaments or pulling (contractile) forces through sliding actin filaments along bipolar filaments of myosin II. Both force types are particularly important for whole-cell migration, but they also define and change the cell shape and mechanical properties of the cell surface, drive the intracellular motility and morphogenesis of membrane organelles, and allow cells to form adhesions with each other and with the extracellular matrix.
Collapse
Affiliation(s)
- Tatyana Svitkina
- Department of Biology, University of Pennsylvania, 221 Leidy Labs, Philadelphia, Pennsylvania 19104
| |
Collapse
|
56
|
Spurlin JW, Nelson CM. Building branched tissue structures: from single cell guidance to coordinated construction. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2015.0527. [PMID: 28348257 DOI: 10.1098/rstb.2015.0527] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/01/2016] [Indexed: 12/15/2022] Open
Abstract
Branched networks are ubiquitous throughout nature, particularly found in tissues that require large surface area within a restricted volume. Many tissues with a branched architecture, such as the vasculature, kidney, mammary gland, lung and nervous system, function to exchange fluids, gases and information throughout the body of an organism. The generation of branched tissues requires regulation of branch site specification, initiation and elongation. Branching events often require the coordination of many cells to build a tissue network for material exchange. Recent evidence has emerged suggesting that cell cooperativity scales with the number of cells actively contributing to branching events. Here, we compare mechanisms that regulate branching, focusing on how cell cohorts behave in a coordinated manner to build branched tissues.This article is part of the themed issue 'Systems morphodynamics: understanding the development of tissue hardware'.
Collapse
Affiliation(s)
- James W Spurlin
- Departments of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544, USA
| | - Celeste M Nelson
- Departments of Chemical and Biological Engineering, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544, USA .,Molecular Biology, Princeton University, 303 Hoyt Laboratory, William Street, Princeton, NJ 08544, USA
| |
Collapse
|
57
|
Fang C, Hui TH, Wei X, Shao X, Lin Y. A combined experimental and theoretical investigation on cellular blebbing. Sci Rep 2017; 7:16666. [PMID: 29192221 PMCID: PMC5709380 DOI: 10.1038/s41598-017-16825-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 11/17/2017] [Indexed: 02/05/2023] Open
Abstract
Although accumulating evidence has demonstrated the important role of membrane blebbing in various cellular processes, the fundamental question of how the initiation/evolution of blebs are influenced by physical factors like membrane-cortex interactions and intracellular pressure remains unclear. Here, we report a combined modeling and experimental study to address this outstanding issue. Specifically, boundary integral method was used to track the motion of membrane (in 3D) during blebbing while possible rupture of the bilayer-cortex adhesion has also been taken into account. We showed that, for a given differential pressure across the cell membrane, the size of the weakened cortex must be over a critical value for blebbing to occur and the steady-state volume of a bleb is proportional to its initial growth rate, all in good agreement with recent experiments. The predicted shape evolution of blebs also matches well with our observations. Finally, a blebbing map, summarizing the essential physics involved, was obtained which exhibits three distinct regimes: no bleb formation corresponding to a low intracellular pressure or a small weakened cortex region; bleb formed with a fixed width when the disrupted cortex zone is very large; and a growing bleb resulted from progressive membrane-cortex detachment under intermediate weakened cortex size.
Collapse
Affiliation(s)
- Chao Fang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.,HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen, Guangdong, China
| | - T H Hui
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.,HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen, Guangdong, China
| | - X Wei
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.,HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen, Guangdong, China
| | - X Shao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.,HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen, Guangdong, China
| | - Yuan Lin
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China. .,HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen, Guangdong, China.
| |
Collapse
|
58
|
Urbančič V, Butler R, Richier B, Peter M, Mason J, Livesey FJ, Holt CE, Gallop JL. Filopodyan: An open-source pipeline for the analysis of filopodia. J Cell Biol 2017; 216:3405-3422. [PMID: 28760769 PMCID: PMC5626553 DOI: 10.1083/jcb.201705113] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 06/28/2017] [Accepted: 07/06/2017] [Indexed: 02/07/2023] Open
Abstract
Filopodia have important sensory and mechanical roles in motile cells. The recruitment of actin regulators, such as ENA/VASP proteins, to sites of protrusion underlies diverse molecular mechanisms of filopodia formation and extension. We developed Filopodyan (filopodia dynamics analysis) in Fiji and R to measure fluorescence in filopodia and at their tips and bases concurrently with their morphological and dynamic properties. Filopodyan supports high-throughput phenotype characterization as well as detailed interactive editing of filopodia reconstructions through an intuitive graphical user interface. Our highly customizable pipeline is widely applicable, capable of detecting filopodia in four different cell types in vitro and in vivo. We use Filopodyan to quantify the recruitment of ENA and VASP preceding filopodia formation in neuronal growth cones, and uncover a molecular heterogeneity whereby different filopodia display markedly different responses to changes in the accumulation of ENA and VASP fluorescence in their tips over time.
Collapse
Affiliation(s)
- Vasja Urbančič
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| | - Richard Butler
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
| | - Benjamin Richier
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| | - Manuel Peter
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| | - Julia Mason
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| | - Frederick J Livesey
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| | - Christine E Holt
- Department of Physiology, Development, and Neuroscience, University of Cambridge, Cambridge, England, UK
| | - Jennifer L Gallop
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| |
Collapse
|
59
|
Zhang Q, Deng S, Sun K, Lin S, Lin Y, Zhu B, Cai X. MMP-2 and Notch signal pathway regulate migration of adipose-derived stem cells and chondrocytes in co-culture systems. Cell Prolif 2017; 50. [PMID: 28925018 DOI: 10.1111/cpr.12385] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2017] [Accepted: 08/15/2017] [Indexed: 02/05/2023] Open
Abstract
OBJECTIVES The crosstalk between chondrocytes and adipose-derived stem cells (ADSCs) could regulate the secretion of multiple growth factors. However, it is not clear how the paracrine action in co-culture systems affect cell migration. This study focused on the changes of cell migration of ADSCs and chondrocytes in co-culture conditions. MATERIALS AND METHODS Primary ADSCs and chondrocytes were isolated from Sprague-Dawley rat. Transwell co-culture systems, inoculated with ADSCs and chondrocytes, were established in vitro. The morphology of the cells was observed 7 days post-seeding by inverted phase-contrast microscope. Additionally, the cytoskeleton changes were investigated by immunofluorescence staining. To detect the abundance of Vinculin, we used immunofluorescence and Western blotting. Additionally, the expression level of MMP-2, Hey1 and Hes1 was examined to determine the mechanisms of co-culture-induced cell migration changes. RESULTS The migration of ADSCs and chondrocytes in co-culture conditions significantly decreased compared with that in mono-culture groups, accompanied by the decrease of filopodia and the expression level of MMP-2. CONCLUSIONS The overall study showed that the migration of ADSCs and chondrocytes differs significantly depending on culture conditions. Moreover, the Notch signalling pathway may be involved in this process. Accordingly, by studying changes in migration caused by co-culture, we obtained new insight into the crosstalk between ADSCs and chondrocytes.
Collapse
Affiliation(s)
- Qi Zhang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Shuwen Deng
- Department of Stomatology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Ke Sun
- Department of Stomatology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Shiyu Lin
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Yunfeng Lin
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Bofeng Zhu
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, College of Stomatology, Xi'an Jiaotong University, Shanxi, China.,Clinical Research Center of Shaanxi Province for Dental and Maxillofacial Diseases, College of Stomatology, Xi'an Jiaotong University, Shanxi, China
| | - Xiaoxiao Cai
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| |
Collapse
|
60
|
Heckman CA, Pandey P, Cayer ML, Biswas T, Zhang Z, Boudreau NS. The tumor promoter-activated protein kinase Cs are a system for regulating filopodia. Cytoskeleton (Hoboken) 2017; 74:297-314. [PMID: 28481056 PMCID: PMC5575509 DOI: 10.1002/cm.21373] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Revised: 04/28/2017] [Accepted: 05/01/2017] [Indexed: 01/02/2023]
Abstract
Different protein kinase C (PKC) isoforms have distinct roles in regulating cell functions. The conventional (α, β, γ) and novel (δ, ɛ, η, θ) classes are targets of phorbol ester tumor promoters, which are surrogates of endogenous second messenger, diacylglycerol. The promoter-stimulated disappearance of filopodia was investigated by use of blocking peptides (BPs) that inhibit PKC maturation and/or docking. Filopodia were partially rescued by a peptide representing PKC ɛ hydrophobic sequence, but also by a myristoylated PKC α/β pseudosubstrate sequence, and an inhibitor of T-cell protein tyrosine phosphatase (TC-PTP). The ability to turn over filopodia was widely distributed among PKC isoforms. PKC α and η hydrophobic sequences enhanced filopodia in cells in the absence of tumor promoter treatment. With transcriptional knockdown of PKC α, the content of PKC ɛ predominated over other isoforms. PKC ɛ could decrease filopodia significantly in promoter-treated cells, and this was attributed to ruffling. The presence of PKC α counteracted the PKC ɛ-mediated enhancement of ruffling. The results showed that there were two mechanisms of filopodia downregulation. One operated in the steady-state and relied on PKC α and η. The other was stimulated by tumor promoters and relied on PKC ɛ. Cycles of protrusion and retraction are characteristic of filopodia and are essential for the cell to orient itself during chemotaxis and haptotaxis. By suppressing filopodia, PKC ɛ can create a long-term "memory" of an environmental signal that may act in nature as a mnemonic device to mark the direction of a repulsive signal.
Collapse
Affiliation(s)
- Carol A. Heckman
- Department of Biological SciencesBowling Green State UniversityLife Sciences Building Room 217Bowling GreenOhio43403
| | - Pratima Pandey
- Department of Biological SciencesBowling Green State UniversityLife Sciences Building Room 217Bowling GreenOhio43403
| | - Marilyn L. Cayer
- Center for Microscopy and MicroanalysisBowling Green State UniversityLife Sciences Building Room 217Bowling GreenOhio43403
| | - Tania Biswas
- Department of Biological SciencesBowling Green State UniversityLife Sciences Building Room 217Bowling GreenOhio43403
| | - Zhong‐Yin Zhang
- Department of Medicinal Chemistry and Molecular PharmacologyPurdue UniversityRobert E. Heine Pharmacy Building, Room 202A, 575 Stadium Mall DriveWest LafayetteIndiana47907
| | - Nancy S. Boudreau
- Department of Applied Statistics and Operations ResearchBowling Green State University344 Business Administration BuildingBowling GreenOhio43403
| |
Collapse
|
61
|
Cheng B, Lin M, Li Y, Huang G, Yang H, Genin GM, Deshpande VS, Lu TJ, Xu F. An Integrated Stochastic Model of Matrix-Stiffness-Dependent Filopodial Dynamics. Biophys J 2017; 111:2051-2061. [PMID: 27806285 DOI: 10.1016/j.bpj.2016.09.026] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 09/18/2016] [Accepted: 09/19/2016] [Indexed: 11/25/2022] Open
Abstract
The ways that living cells regulate their behavior in response to their local mechanical environment underlie growth, development, and healing and are important to critical pathologies such as metastasis and fibrosis. Although extensive experimental evidence supports the hypothesis that this regulation is governed by the dependence of filopodial dynamics upon extracellular matrix stiffness, the pathways for this dependence are unclear. We therefore developed a model to relate filopodial focal adhesion dynamics to integrin-mediated Rho signaling kinetics. Results showed that focal adhesion maturation, i.e., focal adhesion links reinforcement and integrin clustering, dominates over filopodial dynamics. Downregulated focal adhesion maturation leads to the biphasic relationship between extracellular matrix stiffness and retrograde flow that has been observed in embryonic chick forebrain neurons, whereas upregulated maturation leads to the monotonically decreasing relationship that has been observed in mouse embryonic fibroblasts. When integrin-mediated Rho activation and stress-dependent focal adhesion maturation are combined, the model shows how filopodial dynamics endows cells with exquisite mechanosensing. Taken together, the results support the hypothesis that mechanical and structural factors combine with signaling kinetics to enable cells to probe their environments via filopodial dynamics.
Collapse
Affiliation(s)
- Bo Cheng
- The Key Laboratory of Biomedical Information Engineering of the Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an, China
| | - Min Lin
- The Key Laboratory of Biomedical Information Engineering of the Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an, China
| | - Yuhui Li
- The Key Laboratory of Biomedical Information Engineering of the Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an, China
| | - Guoyou Huang
- The Key Laboratory of Biomedical Information Engineering of the Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an, China
| | - Hui Yang
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
| | - Guy M Genin
- The Key Laboratory of Biomedical Information Engineering of the Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an, China
| | - Vikram S Deshpande
- Department of Engineering, University of Cambridge, Cambridge, United Kingdom
| | - Tian Jian Lu
- The Key Laboratory of Biomedical Information Engineering of the Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an, China
| | - Feng Xu
- The Key Laboratory of Biomedical Information Engineering of the Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an, China.
| |
Collapse
|
62
|
Steric Effects Induce Geometric Remodeling of Actin Bundles in Filopodia. Biophys J 2017; 110:2066-75. [PMID: 27166814 PMCID: PMC4939473 DOI: 10.1016/j.bpj.2016.03.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 03/08/2016] [Accepted: 03/09/2016] [Indexed: 11/20/2022] Open
Abstract
Filopodia are ubiquitous fingerlike protrusions, spawned by many eukaryotic cells, to probe and interact with their environments. Polymerization dynamics of actin filaments, comprising the structural core of filopodia, largely determine their instantaneous lengths and overall lifetimes. The polymerization reactions at the filopodial tip require transport of G-actin, which enter the filopodial tube from the filopodial base and diffuse toward the filament barbed ends near the tip. Actin filaments are mechanically coupled into a tight bundle by cross-linker proteins. Interestingly, many of these proteins are relatively short, restricting the free diffusion of cytosolic G-actin throughout the bundle and, in particular, its penetration into the bundle core. To investigate the effect of steric restrictions on G-actin diffusion by the porous structure of filopodial actin filament bundle, we used a particle-based stochastic simulation approach. We discovered that excluded volume interactions result in partial and then full collapse of central filaments in the bundle, leading to a hollowed-out structure. The latter may further collapse radially due to the activity of cross-linking proteins, hence producing conical-shaped filament bundles. Interestingly, electron microscopy experiments on mature filopodia indeed frequently reveal actin bundles that are narrow at the tip and wider at the base. Overall, our work demonstrates that excluded volume effects in the context of reaction-diffusion processes in porous networks may lead to unexpected geometric growth patterns and complicated, history-dependent dynamics of intermediate metastable configurations.
Collapse
|
63
|
Abstract
The eukaryotic actin cytoskeleton is a highly dynamic framework that is involved in many biological processes, such as cell growth, division, morphology, and motility. G-actin polymerizes into microfilaments that associate into bundles, patches, and networks, which, in turn, organize into higher order structures that are fundamental for the course of important physiological events. Actin rings are an example for such higher order actin entities, but this term represents an actually diverse set of subcellular structures that are involved in various processes. This review especially sheds light on a crucial type of non-constricting ring-like actin networks, and categorizes them under the term 'actin fringe'. These 'actin fringes' are visualized as highly dynamic and yet steady structures in the tip of various polarized growing cells. The present comprehensive overview compares the actin fringe characteristics of rapidly elongating pollen tubes with several related actin arrays in other cell types of diverse species. The current state of knowledge about various actin fringe functions is summarized, and the key role of this structure in the polar growth process is discussed.
Collapse
Affiliation(s)
- Octavian O H Stephan
- Department of Biology, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Bavaria 91058, Germany
| |
Collapse
|
64
|
Functional Actin Networks under Construction: The Cooperative Action of Actin Nucleation and Elongation Factors. Trends Biochem Sci 2017; 42:414-430. [DOI: 10.1016/j.tibs.2017.03.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 03/04/2017] [Accepted: 03/07/2017] [Indexed: 12/31/2022]
|
65
|
Slater PG, Hayrapetian L, Lowery LA. Xenopus laevis as a model system to study cytoskeletal dynamics during axon pathfinding. Genesis 2017; 55. [PMID: 28095612 DOI: 10.1002/dvg.22994] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 11/02/2016] [Accepted: 11/04/2016] [Indexed: 01/17/2023]
Abstract
The model system, Xenopus laevis, has been used in innumerable research studies and has contributed to the understanding of multiple cytoskeletal components, including actin, microtubules, and neurofilaments, during axon pathfinding. Xenopus developmental stages have been widely characterized, and the Xenopus genome has been sequenced, allowing gene expression modifications through exogenous molecules. Xenopus cell cultures are ideal for long periods of live imaging because they are easily obtained and maintained, and they do not require special culture conditions. In addition, Xenopus have relatively large growth cones, compared to other vertebrates, thus providing a suitable system for imaging cytoskeletal components. Therefore, X. laevis is an ideal model organism in which to study cytoskeletal dynamics during axon pathfinding.
Collapse
Affiliation(s)
- Paula G Slater
- Department of Biology, Boston College, Chestnut Hill, Massachusetts
| | | | | |
Collapse
|
66
|
Defective Gpsm2/Gα i3 signalling disrupts stereocilia development and growth cone actin dynamics in Chudley-McCullough syndrome. Nat Commun 2017; 8:14907. [PMID: 28387217 PMCID: PMC5385604 DOI: 10.1038/ncomms14907] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 02/13/2017] [Indexed: 01/14/2023] Open
Abstract
Mutations in GPSM2 cause Chudley-McCullough syndrome (CMCS), an autosomal recessive neurological disorder characterized by early-onset sensorineural deafness and brain anomalies. Here, we show that mutation of the mouse orthologue of GPSM2 affects actin-rich stereocilia elongation in auditory and vestibular hair cells, causing deafness and balance defects. The G-protein subunit Gαi3, a well-documented partner of Gpsm2, participates in the elongation process, and its absence also causes hearing deficits. We show that Gpsm2 defines an ∼200 nm nanodomain at the tips of stereocilia and this localization requires the presence of Gαi3, myosin 15 and whirlin. Using single-molecule tracking, we report that loss of Gpsm2 leads to decreased outgrowth and a disruption of actin dynamics in neuronal growth cones. Our results elucidate the aetiology of CMCS and highlight a new molecular role for Gpsm2/Gαi3 in the regulation of actin dynamics in epithelial and neuronal tissues. Mutations in GPSM2 cause a rare disease characterized by deafness and brain abnormalities. Here the authors show that Gpsm2 forms a molecular complex with a heterotrimeric G-protein subunit, whirlin and a myosin motor to regulate actin dynamics in neurons and auditory hair cell stereocilia.
Collapse
|
67
|
Münch J, Grivas D, González-Rajal Á, Torregrosa-Carrión R, de la Pompa JL. Notch signalling restricts inflammation and serpine1 expression in the dynamic endocardium of the regenerating zebrafish heart. Development 2017; 144:1425-1440. [PMID: 28242613 DOI: 10.1242/dev.143362] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 02/20/2017] [Indexed: 01/13/2023]
Abstract
The zebrafish heart regenerates after ventricular damage through a process involving inflammation, fibrotic tissue deposition/removal and myocardial regeneration. Using 3D whole-mount imaging, we reveal a highly dynamic endocardium during cardiac regeneration, including changes in cell morphology, behaviour and gene expression. These events lay the foundation for an initial expansion of the endocardium that matures to form a coherent endocardial structure within the injury site. We studied two important endocardial molecules, Serpine1 and Notch, which are implicated in different aspects of endocardial regeneration. Notch signalling regulates developmental gene expression and features of endocardial maturation. Also, Notch manipulation interferes with attenuation of the inflammatory response and cardiomyocyte proliferation and dedifferentiation. serpine1 is strongly expressed very early in the wound endocardium, with decreasing expression at later time points. serpine1 expression persists in Notch-abrogated hearts, via what appears to be a conserved mechanism. Functional inhibition studies show that Serpine1 controls endocardial maturation and proliferation and cardiomyocyte proliferation. Thus, we describe a highly dynamic endocardium in the regenerating zebrafish heart, with two key endocardial players, Serpine1 and Notch signalling, regulating crucial regenerative processes.
Collapse
Affiliation(s)
- Juliane Münch
- Intercellular Signalling in Cardiovascular Development and Disease Laboratory, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Melchor Fernández Almagro 3, Madrid E-28029, Spain.,Institute of Biochemistry and Biology, Potsdam University, Karl-Liebknecht-Straße 24-25, Potsdam D-14476, Germany
| | - Dimitrios Grivas
- Intercellular Signalling in Cardiovascular Development and Disease Laboratory, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Melchor Fernández Almagro 3, Madrid E-28029, Spain.,CIBER CV, 28029 Madrid, Spain
| | - Álvaro González-Rajal
- Intercellular Signalling in Cardiovascular Development and Disease Laboratory, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Melchor Fernández Almagro 3, Madrid E-28029, Spain.,Cancer Division, Garvan Institute of Medical Research, The Kinghorn Cancer Centre, 370 Victoria Street, Darlinghurst NSW 2010, Australia
| | - Rebeca Torregrosa-Carrión
- Intercellular Signalling in Cardiovascular Development and Disease Laboratory, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Melchor Fernández Almagro 3, Madrid E-28029, Spain.,CIBER CV, 28029 Madrid, Spain
| | - José Luis de la Pompa
- Intercellular Signalling in Cardiovascular Development and Disease Laboratory, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Melchor Fernández Almagro 3, Madrid E-28029, Spain .,CIBER CV, 28029 Madrid, Spain
| |
Collapse
|
68
|
Filopodia formation and endosome clustering induced by mutant plus-end-directed myosin VI. Proc Natl Acad Sci U S A 2017; 114:1595-1600. [PMID: 28143933 DOI: 10.1073/pnas.1616941114] [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] [Indexed: 11/18/2022] Open
Abstract
Myosin VI (MYO6) is the only myosin known to move toward the minus end of actin filaments. It has roles in numerous cellular processes, including maintenance of stereocilia structure, endocytosis, and autophagosome maturation. However, the functional necessity of minus-end-directed movement along actin is unclear as the underlying architecture of the local actin network is often unknown. To address this question, we engineered a mutant of MYO6, MYO6+, which undergoes plus-end-directed movement while retaining physiological cargo interactions in the tail. Expression of this mutant motor in HeLa cells led to a dramatic reorganization of cortical actin filaments and the formation of actin-rich filopodia. MYO6 is present on peripheral adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper 1 (APPL1) signaling endosomes and MYO6+ expression causes a dramatic relocalization and clustering of this endocytic compartment in the cell cortex. MYO6+ and its adaptor GAIP interacting protein, C terminus (GIPC) accumulate at the tips of these filopodia, while APPL1 endosomes accumulate at the base. A combination of MYO6+ mutagenesis and siRNA-mediated depletion of MYO6 binding partners demonstrates that motor activity and binding to endosomal membranes mediated by GIPC and PI(4,5)P2 are crucial for filopodia formation. A similar reorganization of actin is induced by a constitutive dimer of MYO6+, indicating that multimerization of MYO6 on endosomes through binding to GIPC is required for this cellular activity and regulation of actin network structure. This unique engineered MYO6+ offers insights into both filopodia formation and MYO6 motor function at endosomes and at the plasma membrane.
Collapse
|
69
|
Weck ML, Grega-Larson NE, Tyska MJ. MyTH4-FERM myosins in the assembly and maintenance of actin-based protrusions. Curr Opin Cell Biol 2016; 44:68-78. [PMID: 27836411 DOI: 10.1016/j.ceb.2016.10.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 10/12/2016] [Indexed: 12/13/2022]
Abstract
Unconventional myosins are actin-based molecular motors that serve a multitude of roles within the cell. One group of myosin motors, the MyTH4-FERM myosins, play an integral part in building and maintaining finger-like protrusions, which allow cells to interact with their external environment. Suggested to act primarily as transporters, these motor proteins enrich adhesion molecules, actin-regulatory proteins and other factors at the tips of filopodia, microvilli, and stereocilia. Below we review data from biophysical, biochemical, and cell biological studies, which implicate these myosins as central players in the assembly, maintenance and function of actin-based protrusions.
Collapse
Affiliation(s)
- Meredith L Weck
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, 3154 MRB III, PMB 407935, 465 21st Avenue South, Nashville, TN 37240-7935, United States
| | - Nathan E Grega-Larson
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, 3154 MRB III, PMB 407935, 465 21st Avenue South, Nashville, TN 37240-7935, United States
| | - Matthew J Tyska
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, 3154 MRB III, PMB 407935, 465 21st Avenue South, Nashville, TN 37240-7935, United States.
| |
Collapse
|
70
|
Raval MH, Quintero OA, Weck ML, Unrath WC, Gallagher JW, Cui R, Kachar B, Tyska MJ, Yengo CM. Impact of the Motor and Tail Domains of Class III Myosins on Regulating the Formation and Elongation of Actin Protrusions. J Biol Chem 2016; 291:22781-22792. [PMID: 27582493 PMCID: PMC5077211 DOI: 10.1074/jbc.m116.733741] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 08/29/2016] [Indexed: 11/06/2022] Open
Abstract
Class III myosins (MYO3A and MYO3B) are proposed to function as transporters as well as length and ultrastructure regulators within stable actin-based protrusions such as stereocilia and calycal processes. MYO3A differs from MYO3B in that it contains an extended tail domain with an additional actin-binding motif. We examined how the properties of the motor and tail domains of human class III myosins impact their ability to enhance the formation and elongation of actin protrusions. Direct examination of the motor and enzymatic properties of human MYO3A and MYO3B revealed that MYO3A is a 2-fold faster motor with enhanced ATPase activity and actin affinity. A chimera in which the MYO3A tail was fused to the MYO3B motor demonstrated that motor activity correlates with formation and elongation of actin protrusions. We demonstrate that removal of individual exons (30-34) in the MYO3A tail does not prevent filopodia tip localization but abolishes the ability to enhance actin protrusion formation and elongation in COS7 cells. Interestingly, our results demonstrate that MYO3A slows filopodia dynamics and enhances filopodia lifetime in COS7 cells. We also demonstrate that MYO3A is more efficient than MYO3B at increasing formation and elongation of stable microvilli on the surface of cultured epithelial cells. We propose that the unique features of MYO3A, enhanced motor activity, and an extended tail with tail actin-binding motif, allow it to play an important role in stable actin protrusion length and ultrastructure maintenance.
Collapse
Affiliation(s)
- Manmeet H Raval
- From the Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania 17033
| | - Omar A Quintero
- the Department of Biology, University of Richmond, Richmond, Virginia 23173
| | - Meredith L Weck
- the Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - William C Unrath
- From the Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania 17033
| | - James W Gallagher
- the Department of Biology, Lincoln University, Philadelphia, Pennsylvania 19104, and
| | - Runjia Cui
- the Laboratory of Cell Structure and Dynamics, NIDCD, National Institutes of Health, Bethesda, Maryland 20892
| | - Bechara Kachar
- the Laboratory of Cell Structure and Dynamics, NIDCD, National Institutes of Health, Bethesda, Maryland 20892
| | - Matthew J Tyska
- the Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Christopher M Yengo
- From the Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania 17033,
| |
Collapse
|
71
|
Chazeau A, Giannone G. Organization and dynamics of the actin cytoskeleton during dendritic spine morphological remodeling. Cell Mol Life Sci 2016; 73:3053-73. [PMID: 27105623 PMCID: PMC11108290 DOI: 10.1007/s00018-016-2214-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/31/2016] [Accepted: 03/31/2016] [Indexed: 12/18/2022]
Abstract
In the central nervous system, most excitatory post-synapses are small subcellular structures called dendritic spines. Their structure and morphological remodeling are tightly coupled to changes in synaptic transmission. The F-actin cytoskeleton is the main driving force of dendritic spine remodeling and sustains synaptic plasticity. It is therefore essential to understand how changes in synaptic transmission can regulate the organization and dynamics of actin binding proteins (ABPs). In this review, we will provide a detailed description of the organization and dynamics of F-actin and ABPs in dendritic spines and will discuss the current models explaining how the actin cytoskeleton sustains both structural and functional synaptic plasticity.
Collapse
Affiliation(s)
- Anaël Chazeau
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, UMR 5297, 33000, Bordeaux, France
- Interdisciplinary Institute for Neuroscience, CNRS, UMR 5297, 33000, Bordeaux, France
- Cell Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Grégory Giannone
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, UMR 5297, 33000, Bordeaux, France.
- Interdisciplinary Institute for Neuroscience, CNRS, UMR 5297, 33000, Bordeaux, France.
| |
Collapse
|
72
|
Petit V, Larue L. Any route for melanoblasts to colonize the skin! Exp Dermatol 2016; 25:669-73. [DOI: 10.1111/exd.13061] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/20/2016] [Indexed: 12/30/2022]
Affiliation(s)
- Valérie Petit
- Institut Curie; INSERM U1021; Normal and Pathological Development of Melanocytes; PSL Research University; Orsay France
- CNRS UMR 3347; University of Paris-Sud; University of Paris-Saclay; Orsay France
- Equipe Labellisée Ligue Contre le Cancer; Orsay France
| | - Lionel Larue
- Institut Curie; INSERM U1021; Normal and Pathological Development of Melanocytes; PSL Research University; Orsay France
- CNRS UMR 3347; University of Paris-Sud; University of Paris-Saclay; Orsay France
- Equipe Labellisée Ligue Contre le Cancer; Orsay France
| |
Collapse
|
73
|
Abstract
UNLABELLED Growth cones interact with the extracellular matrix (ECM) through integrin receptors at adhesion sites termed point contacts. Point contact adhesions link ECM proteins to the actin cytoskeleton through numerous adaptor and signaling proteins. One presumed function of growth cone point contacts is to restrain or "clutch" myosin-II-based filamentous actin (F-actin) retrograde flow (RF) to promote leading edge membrane protrusion. In motile non-neuronal cells, myosin-II binds and exerts force upon actin filaments at the leading edge, where clutching forces occur. However, in growth cones, it is unclear whether similar F-actin-clutching forces affect axon outgrowth and guidance. Here, we show in Xenopus spinal neurons that RF is reduced in rapidly migrating growth cones on laminin (LN) compared with non-integrin-binding poly-d-lysine (PDL). Moreover, acute stimulation with LN accelerates axon outgrowth over a time course that correlates with point contact formation and reduced RF. These results suggest that RF is restricted by the assembly of point contacts, which we show occurs locally by two-channel imaging of RF and paxillin. Further, using micropatterns of PDL and LN, we demonstrate that individual growth cones have differential RF rates while interacting with two distinct substrata. Opposing effects on RF rates were also observed in growth cones treated with chemoattractive and chemorepulsive axon guidance cues that influence point contact adhesions. Finally, we show that RF is significantly attenuated in vivo, suggesting that it is restrained by molecular clutching forces within the spinal cord. Together, our results suggest that local clutching of RF can control axon guidance on ECM proteins downstream of axon guidance cues. SIGNIFICANCE STATEMENT Here, we correlate point contact adhesions directly with clutching of filamentous actin retrograde flow (RF), which our findings strongly suggest guides developing axons. Acute assembly of new point contact adhesions is temporally and spatially linked to attenuation of RF at sites of forward membrane protrusion. Importantly, clutching of RF is modulated by extracellular matrix (ECM) proteins and soluble axon guidance cues, suggesting that it may regulate axon guidance in vivo. Consistent with this notion, we found that RF rates of spinal neuron growth cones were slower in vivo than what was observed in vitro. Together, our study provides the best evidence that growth cone-ECM adhesions clutch RF locally to guide axons in vivo.
Collapse
|
74
|
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.
Collapse
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.
| |
Collapse
|
75
|
Identification of a shootin1 isoform expressed in peripheral tissues. Cell Tissue Res 2016; 366:75-87. [PMID: 27177867 DOI: 10.1007/s00441-016-2415-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 04/20/2016] [Indexed: 10/24/2022]
Abstract
Shootin1 is a brain-specific cytoplasmic protein involved in neuronal polarity formation and axon outgrowth. It accumulates at the leading edge of axonal growth cones, where it mediates the mechanical coupling between F-actin retrograde flow and cell adhesions as a clutch molecule, thereby producing force for axon outgrowth. In this study, we report a novel splicing isoform of shootin1 which is expressed not only in the brain but also in peripheral tissues. We have renamed the brain-specific shootin1 as shootin1a and termed the novel isoform as shootin1b. Immunoblot and immunohistochemical analyses with a shootin1b-specific antibody revealed that shootin1b is distributed in various mouse tissues including the lung, liver, stomach, intestines, spleen, pancreas, kidney and skin. Interestingly, shootin1b immunoreactivity was widely detected in epithelial cells that constitute simple and stratified epithelia; in some cells, it colocalized with E-cadherin and cortactin at cell-cell contact sites. Shootin1b also localized in dendritic cells in the spleen. These results suggest that shootin1b may function in various peripheral tissues including epithelial cells.
Collapse
|
76
|
Pröls F, Sagar, Scaal M. Signaling filopodia in vertebrate embryonic development. Cell Mol Life Sci 2016; 73:961-74. [PMID: 26621670 PMCID: PMC11108401 DOI: 10.1007/s00018-015-2097-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 10/28/2015] [Accepted: 11/16/2015] [Indexed: 12/11/2022]
Abstract
Next to classical diffusion-based models, filopodia-like cellular protrusions have been proposed to mediate long range signaling events and morphogen gradient formation during communication between distant cells. An increasing wealth of data indicates that in spite of variable characteristics of signaling filopodia in different biological contexts, they represent a paradigm of intercellular crosstalk which is presently being unraveled in a growing literature. Here, we summarize recent advances in investigating the morphology, cellular basis and function of signaling filopodia, with focus on their role during embryonic development in vertebrates.
Collapse
Affiliation(s)
- Felicitas Pröls
- Department of Vertebrate Embryology, Institute of Anatomy II, University of Cologne, Joseph-Stelzmann-Str. 9, 50931, Cologne, Germany
| | - Sagar
- Department of Vertebrate Embryology, Institute of Anatomy II, University of Cologne, Joseph-Stelzmann-Str. 9, 50931, Cologne, Germany
- Max-Planck-Institute of Immunobiology and Epigenetics, Stübeweg 51, 79108, Freiburg, Germany
| | - Martin Scaal
- Department of Vertebrate Embryology, Institute of Anatomy II, University of Cologne, Joseph-Stelzmann-Str. 9, 50931, Cologne, Germany.
| |
Collapse
|
77
|
Surfing along Filopodia: A Particle Transport Revealed by Molecular-Scale Fluctuation Analyses. Biophys J 2016; 108:2114-25. [PMID: 25954870 DOI: 10.1016/j.bpj.2015.02.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 02/13/2015] [Accepted: 02/23/2015] [Indexed: 01/08/2023] Open
Abstract
Filopodia perform cellular functions such as environmental sensing or cell motility, but they also grab for particles and withdraw them leading to an increased efficiency of phagocytic uptake. Remarkably, withdrawal of micron-sized particles is also possible without noticeable movements of the filopodia. Here, we demonstrate that polystyrene beads connected by optical tweezers to the ends of adherent filopodia of J774 macrophages, are transported discontinuously toward the cell body. After a typical resting time of 1-2 min, the cargo is moved with alternating velocities, force constants, and friction constants along the surface of the filopodia. This surfing-like behavior along the filopodium is recorded by feedback-controlled interferometric three-dimensional tracking of the bead motions at 10-100 kHz. We measured transport velocities of up to 120 nm/s and transport forces of ∼ 70 pN. Small changes in position, fluctuation width, and temporal correlation, which are invisible in conventional microscopy, indicate molecular reorganization of transport-relevant proteins in different phases of the entire transport process. A detailed analysis implicates a controlled particle transport with fingerprints of a nanoscale unbinding/binding behavior. The manipulation and analysis methods presented in our study may also be helpful in other fields of cellular biophysics.
Collapse
|
78
|
Leijnse N, Oddershede LB, Bendix PM. An updated look at actin dynamics in filopodia. Cytoskeleton (Hoboken) 2016; 72:71-9. [PMID: 25786787 DOI: 10.1002/cm.21216] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 03/06/2015] [Accepted: 03/09/2015] [Indexed: 11/10/2022]
Abstract
Cells dynamically interact with and probe their environment by growing finger-like structures named filopodia. The dynamics of filopodia are mainly caused by the actin rich core or shaft which sits inside the filopodial membrane and continuously undergoes changes like growth, shrinking, bending, and rotation. Recent experiments combining advanced imaging and manipulation tools have provided detailed quantitative data on the correlation between mechanical properties of filopodia, their molecular composition, and the dynamic architecture of the actin structure. These experiments have revealed how retrograde flow and twisting of the actin shaft within filopodia can generate traction on external substrates. Previously, the mechanism behind filopodial pulling was mainly attributed to retrograde flow of actin, but recent experiments have shown that rotational dynamics can also contribute to the traction force. Although force measurements have indicated a step-like behavior in filopodial pulling, no direct evidence has been provided to link this behavior to a molecular motor like myosin. Therefore, the underlying biochemical and mechanical mechanisms behind filopodial force generation still remain to be resolved.
Collapse
Affiliation(s)
- Natascha Leijnse
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark; Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, 2100, Copenhagen, Denmark
| | | | | |
Collapse
|
79
|
Lehtimäki J, Hakala M, Lappalainen P. Actin Filament Structures in Migrating Cells. Handb Exp Pharmacol 2016; 235:123-152. [PMID: 27469496 DOI: 10.1007/164_2016_28] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cell migration is necessary for several developmental processes in multicellular organisms. Furthermore, many physiological processes such as wound healing and immunological events in adult animals are dependent on cell migration. Consequently, defects in cell migration are linked to various diseases including immunological disorders as well as cancer progression and metastasis formation. Cell migration is driven by specific protrusive and contractile actin filament structures, but the types and relative contributions of these actin filament arrays vary depending on the cell type and the environment of the cell. In this chapter, we introduce the most important actin filament structures that contribute to mesenchymal and amoeboid cell migration modes and discuss the mechanisms by which the assembly and turnover of these structures are controlled by various actin-binding proteins.
Collapse
Affiliation(s)
- Jaakko Lehtimäki
- Institute of Biotechnology, University of Helsinki, 56, 00014, Helsinki, Finland
| | - Markku Hakala
- Institute of Biotechnology, University of Helsinki, 56, 00014, Helsinki, Finland
| | - Pekka Lappalainen
- Institute of Biotechnology, University of Helsinki, 56, 00014, Helsinki, Finland.
| |
Collapse
|
80
|
Actin-Dependent Regulation of Borrelia burgdorferi Phagocytosis by Macrophages. Curr Top Microbiol Immunol 2016; 399:133-154. [DOI: 10.1007/82_2016_26] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
81
|
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.
Collapse
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
| |
Collapse
|
82
|
Paul NR, Allen JL, Chapman A, Morlan-Mairal M, Zindy E, Jacquemet G, Fernandez del Ama L, Ferizovic N, Green DM, Howe JD, Ehler E, Hurlstone A, Caswell PT. α5β1 integrin recycling promotes Arp2/3-independent cancer cell invasion via the formin FHOD3. J Cell Biol 2015; 210:1013-31. [PMID: 26370503 PMCID: PMC4576860 DOI: 10.1083/jcb.201502040] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Rab-coupling protein–mediated integrin trafficking promotes filopodia formation via RhoA-ROCK-FHOD3, generating non-lamellipodial actin spike protrusions that drive cancer cell migration in 3D extracellular matrix and in vivo. Invasive migration in 3D extracellular matrix (ECM) is crucial to cancer metastasis, yet little is known of the molecular mechanisms that drive reorganization of the cytoskeleton as cancer cells disseminate in vivo. 2D Rac-driven lamellipodial migration is well understood, but how these features apply to 3D migration is not clear. We find that lamellipodia-like protrusions and retrograde actin flow are indeed observed in cells moving in 3D ECM. However, Rab-coupling protein (RCP)-driven endocytic recycling of α5β1 integrin enhances invasive migration of cancer cells into fibronectin-rich 3D ECM, driven by RhoA and filopodial spike-based protrusions, not lamellipodia. Furthermore, we show that actin spike protrusions are Arp2/3-independent. Dynamic actin spike assembly in cells invading in vitro and in vivo is regulated by Formin homology-2 domain containing 3 (FHOD3), which is activated by RhoA/ROCK, establishing a novel mechanism through which the RCP–α5β1 pathway reprograms the actin cytoskeleton to promote invasive migration and local invasion in vivo.
Collapse
Affiliation(s)
- Nikki R Paul
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - Jennifer L Allen
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - Anna Chapman
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - Maria Morlan-Mairal
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - Egor Zindy
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - Guillaume Jacquemet
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - Laura Fernandez del Ama
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - Nermina Ferizovic
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - David M Green
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - Jonathan D Howe
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, England, UK
| | - Elisabeth Ehler
- Randall Division of Cell and Molecular Biophysics, Cardiovascular Division, BHF Research Excellence Centre, King's College London, London SE1 1UL, England, UK
| | - Adam Hurlstone
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - Patrick T Caswell
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| |
Collapse
|
83
|
Shneyer BI, Ušaj M, Henn A. Myo19 is an outer mitochondrial membrane motor and effector of starvation-induced filopodia. J Cell Sci 2015; 129:543-56. [PMID: 26659663 DOI: 10.1242/jcs.175349] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 12/05/2015] [Indexed: 12/13/2022] Open
Abstract
Mitochondria respond to environmental cues and stress conditions. Additionally, the disruption of the mitochondrial network dynamics and its distribution is implicated in a variety of neurodegenerative diseases. Here, we reveal a new function for Myo19 in mitochondrial dynamics and localization during the cellular response to glucose starvation. Ectopically expressed Myo19 localized with mitochondria to the tips of starvation-induced filopodia. Corollary to this, RNA interference (RNAi)-mediated knockdown of Myo19 diminished filopodia formation without evident effects on the mitochondrial network. We analyzed the Myo19-mitochondria interaction, and demonstrated that Myo19 is uniquely anchored to the outer mitochondrial membrane (OMM) through a 30-45-residue motif, indicating that Myo19 is a stably attached OMM molecular motor. Our work reveals a new function for Myo19 in mitochondrial positioning under stress.
Collapse
Affiliation(s)
- Boris I Shneyer
- Department of Biology, Technion Israel Institute of Technology, Haifa 3200003, Israel
| | - Marko Ušaj
- Department of Biology, Technion Israel Institute of Technology, Haifa 3200003, Israel
| | - Arnon Henn
- Department of Biology, Technion Israel Institute of Technology, Haifa 3200003, Israel
| |
Collapse
|
84
|
Shekhar S, Kerleau M, Kühn S, Pernier J, Romet-Lemonne G, Jégou A, Carlier MF. Formin and capping protein together embrace the actin filament in a ménage à trois. Nat Commun 2015; 6:8730. [PMID: 26564775 PMCID: PMC4660058 DOI: 10.1038/ncomms9730] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 09/24/2015] [Indexed: 11/09/2022] Open
Abstract
Proteins targeting actin filament barbed ends play a pivotal role in motile processes. While formins enhance filament assembly, capping protein (CP) blocks polymerization. On their own, they both bind barbed ends with high affinity and very slow dissociation. Their barbed-end binding is thought to be mutually exclusive. CP has recently been shown to be present in filopodia and controls their morphology and dynamics. Here we explore how CP and formins may functionally coregulate filament barbed-end assembly. We show, using kinetic analysis of individual filaments by microfluidics-assisted fluorescence microscopy, that CP and mDia1 formin are able to simultaneously bind barbed ends. This is further confirmed using single-molecule imaging. Their mutually weakened binding enables rapid displacement of one by the other. We show that formin FMNL2 behaves similarly, thus suggesting that this is a general property of formins. Implications in filopodia regulation and barbed-end structural regulation are discussed.
Collapse
Affiliation(s)
- Shashank Shekhar
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Mikael Kerleau
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Sonja Kühn
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Julien Pernier
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Guillaume Romet-Lemonne
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Antoine Jégou
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Marie-France Carlier
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| |
Collapse
|
85
|
Abstract
Cellular processes, including morphogenesis, polarization, and motility, rely on a variety of actin-based structures. Although the biochemical composition and filament organization of these structures are different, they often emerge from a common origin. This is possible because the actin structures are highly dynamic. Indeed, they assemble, grow, and disassemble in a time scale of a second to a minute. Therefore, the reorganization of a given actin structure can promote the formation of another. Here, we discuss such transitions and illustrate them with computer simulations.
Collapse
Affiliation(s)
- Gaëlle Letort
- Laboratoire de Physiologie Cellulaire et Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, iRTSV, CNRS/CEA/UGA, Grenoble, France
| | - Hajer Ennomani
- Laboratoire de Physiologie Cellulaire et Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, iRTSV, CNRS/CEA/UGA, Grenoble, France
| | - Laurène Gressin
- Laboratoire de Physiologie Cellulaire et Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, iRTSV, CNRS/CEA/UGA, Grenoble, France
| | - Manuel Théry
- Laboratoire de Physiologie Cellulaire et Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, iRTSV, CNRS/CEA/UGA, Grenoble, France.,Unité de Thérapie Cellulaire, Hôpital Saint Louis, Institut Universitaire d'Hematologie, UMRS1160, INSERM/AP-HP/Université Paris Diderot, Paris, France
| | - Laurent Blanchoin
- Laboratoire de Physiologie Cellulaire et Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, iRTSV, CNRS/CEA/UGA, Grenoble, France
| |
Collapse
|
86
|
Orly G, Naoz M, Gov NS. Physical model for the geometry of actin-based cellular protrusions. Biophys J 2015; 107:576-587. [PMID: 25099797 DOI: 10.1016/j.bpj.2014.05.040] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 05/09/2014] [Accepted: 05/28/2014] [Indexed: 11/17/2022] Open
Abstract
Actin-based cellular protrusions are a ubiquitous feature of cell morphology, e.g., filopodia and microvilli, serving a huge variety of functions. Despite this, there is still no comprehensive model for the mechanisms that determine the geometry of these protrusions. We present here a detailed computational model that addresses a combination of multiple biochemical and physical processes involved in the dynamic regulation of the shape of these protrusions. We specifically explore the role of actin polymerization in determining both the height and width of the protrusions. Furthermore, we show that our generalized model can explain multiple morphological features of these systems, and account for the effects of specific proteins and mutations.
Collapse
Affiliation(s)
- G Orly
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - M Naoz
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - N S Gov
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel.
| |
Collapse
|
87
|
Paksa A, Raz E. Zebrafish germ cells: motility and guided migration. Curr Opin Cell Biol 2015; 36:80-5. [PMID: 26232877 DOI: 10.1016/j.ceb.2015.07.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 06/18/2015] [Accepted: 07/15/2015] [Indexed: 10/24/2022]
Abstract
In the course of embryonic development, the process of cell migration is critical for establishment of the embryonic body plan, for morphogenesis and for organ function. Investigating the molecular mechanisms underlying cell migration is thus crucial for understanding developmental processes and clinical conditions resulting from abnormal cell migration such as cancer metastasis. The long-range migration of primordial germ cells toward the region at which the gonad develops occurs in embryos of various species and thus constitutes a useful in vivo model for single-cell migration. Recent studies employing zebrafish embryos have greatly contributed to the understanding of the mechanisms facilitating the migration of these cells en route to their target.
Collapse
Affiliation(s)
- Azadeh Paksa
- Institute of Cell Biology, Center for Molecular Biology of Inflammation, Von-Esmarch-Str. 56, 48149 Muenster, Germany
| | - Erez Raz
- Institute of Cell Biology, Center for Molecular Biology of Inflammation, Von-Esmarch-Str. 56, 48149 Muenster, Germany.
| |
Collapse
|
88
|
Tamariz E, Varela-Echavarría A. The discovery of the growth cone and its influence on the study of axon guidance. Front Neuroanat 2015; 9:51. [PMID: 26029056 PMCID: PMC4432662 DOI: 10.3389/fnana.2015.00051] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 04/13/2015] [Indexed: 11/25/2022] Open
Abstract
For over a century, there has been a great deal of interest in understanding how neural connectivity is established during development and regeneration. Interest in the latter arises from the possibility that knowledge of this process can be used to re-establish lost connections after lesion or neurodegeneration. At the end of the XIX century, Santiago Ramón y Cajal discovered that the distal tip of growing axons contained a structure that he called the growth cone. He proposed that this structure enabled the axon's oriented growth in response to attractants, now known as chemotropic molecules. He further proposed that the physical properties of the surrounding tissues could influence the growth cone and the direction of growth. This seminal discovery afforded a plausible explanation for directed axonal growth and has led to the discovery of axon guidance mechanisms that include diffusible attractants and repellants and guidance cues anchored to cell membranes or extracellular matrix. In this review the major events in the development of this field are discussed.
Collapse
Affiliation(s)
- Elisa Tamariz
- Instituto de Ciencias de la Salud, Universidad VeracruzanaXalapa, Mexico
| | | |
Collapse
|
89
|
Meyen D, Tarbashevich K, Banisch TU, Wittwer C, Reichman-Fried M, Maugis B, Grimaldi C, Messerschmidt EM, Raz E. Dynamic filopodia are required for chemokine-dependent intracellular polarization during guided cell migration in vivo. eLife 2015; 4. [PMID: 25875301 PMCID: PMC4397908 DOI: 10.7554/elife.05279] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 03/23/2015] [Indexed: 01/08/2023] Open
Abstract
Cell migration and polarization is controlled by signals in the environment. Migrating cells typically form filopodia that extend from the cell surface, but the precise function of these structures in cell polarization and guided migration is poorly understood. Using the in vivo model of zebrafish primordial germ cells for studying chemokine-directed single cell migration, we show that filopodia distribution and their dynamics are dictated by the gradient of the chemokine Cxcl12a. By specifically interfering with filopodia formation, we demonstrate for the first time that these protrusions play an important role in cell polarization by Cxcl12a, as manifested by elevation of intracellular pH and Rac1 activity at the cell front. The establishment of this polarity is at the basis of effective cell migration towards the target. Together, we show that filopodia allow the interpretation of the chemotactic gradient in vivo by directing single-cell polarization in response to the guidance cue. DOI:http://dx.doi.org/10.7554/eLife.05279.001 Some of the cells in an animal embryo have to migrate long distances to reach their final positions; that is to say, to reach the locations where they will participate in the formation of tissues and organs. The migration of cells is also important throughout the entire lifespan of an animal. White blood cells, for example, must be able to move within tissues to search for and fight infections as well as to detect and remove abnormal cells. The front end of a migrating cell typically protrudes. The back of the cell is then pulled and detaches, which allows the whole cell to move forward. Migrating cells generate thin finger-like projections known as filopodia that have been suggested to help the cell sense their external environments and follow chemical cues. It is not clear what happens to a migrating cell in a living organism if the formation of its filopodia is impaired, or even how filipodia help the normal migration of cells in animals. To define how filopodia help to guide migrating cells in an animal, Meyen et al. analyzed the migration of cells called ‘primordial germ cells’ (or PGCs) in zebrafish. These cells form very early on in development of a zebrafish embryo at a position that is far away from their final location (in the testes or ovaries where they will go on to form sperm or egg cells respectively). Meyen et al. revealed that cells that are exposed to the guidance cue (a protein called a chemokine) form more filopodia at their front compared to their rear. The filopodia formed at the cell front also extend and retract more frequently. Meyen et al. further observed that the specific chemokine that guides the cells can bind to the filopodia and enter the cell. This leads to a signal inside the cell that tells the cell to move in the direction where more of the chemokine is found. Indeed, altering the distribution and number of filopodia around the cell's edge decreases the ability of the primordial germ cells to reach their targets. Together, this work shows that the filopodia at the front end of cells are required for sensing the chemokines that guide cell movement. Further work is required to understand the mechanism that determines the distribution of filopodia on the surface of migrating cells, and the role of chemokines in the process. Moreover, this work may also be relevant for understanding the migration of cancer cells, because several types of cancer can invade new tissues by following directional cues including chemokines. DOI:http://dx.doi.org/10.7554/eLife.05279.002
Collapse
Affiliation(s)
- Dana Meyen
- Institute for Cell Biology, Center for Molecular Biology of Inflammation, Münster University, Münster, Germany
| | - Katsiaryna Tarbashevich
- Institute for Cell Biology, Center for Molecular Biology of Inflammation, Münster University, Münster, Germany
| | - Torsten U Banisch
- Institute for Cell Biology, Center for Molecular Biology of Inflammation, Münster University, Münster, Germany
| | - Carolina Wittwer
- Institute for Cell Biology, Center for Molecular Biology of Inflammation, Münster University, Münster, Germany
| | - Michal Reichman-Fried
- Institute for Cell Biology, Center for Molecular Biology of Inflammation, Münster University, Münster, Germany
| | - Benoît Maugis
- Institute for Cell Biology, Center for Molecular Biology of Inflammation, Münster University, Münster, Germany
| | - Cecilia Grimaldi
- Institute for Cell Biology, Center for Molecular Biology of Inflammation, Münster University, Münster, Germany
| | - Esther-Maria Messerschmidt
- Institute for Cell Biology, Center for Molecular Biology of Inflammation, Münster University, Münster, Germany
| | - Erez Raz
- Institute for Cell Biology, Center for Molecular Biology of Inflammation, Münster University, Münster, Germany
| |
Collapse
|
90
|
Chazeau A, Garcia M, Czöndör K, Perrais D, Tessier B, Giannone G, Thoumine O. Mechanical coupling between transsynaptic N-cadherin adhesions and actin flow stabilizes dendritic spines. Mol Biol Cell 2015; 26:859-73. [PMID: 25568337 PMCID: PMC4342023 DOI: 10.1091/mbc.e14-06-1086] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
A combination of quantitative live imaging of fluorescently tagged actin, N-cadherin, and myosin in primary neurons and computer modeling of actin dynamics shows that a clutch-like mechanism connecting N-cadherin–based transsynaptic adhesions and the actin/myosin network drives the stabilization of dendritic filopodia into spines. The morphology of neuronal dendritic spines is a critical indicator of synaptic function. It is regulated by several factors, including the intracellular actin/myosin cytoskeleton and transcellular N-cadherin adhesions. To examine the mechanical relationship between these molecular components, we performed quantitative live-imaging experiments in primary hippocampal neurons. We found that actin turnover and structural motility were lower in dendritic spines than in immature filopodia and increased upon expression of a nonadhesive N-cadherin mutant, resulting in an inverse relationship between spine motility and actin enrichment. Furthermore, the pharmacological stimulation of myosin II induced the rearward motion of actin structures in spines, showing that myosin II exerts tension on the actin network. Strikingly, the formation of stable, spine-like structures enriched in actin was induced at contacts between dendritic filopodia and N-cadherin–coated beads or micropatterns. Finally, computer simulations of actin dynamics mimicked various experimental conditions, pointing to the actin flow rate as an important parameter controlling actin enrichment in dendritic spines. Together these data demonstrate that a clutch-like mechanism between N-cadherin adhesions and the actin flow underlies the stabilization of dendritic filopodia into mature spines, a mechanism that may have important implications in synapse initiation, maturation, and plasticity in the developing brain.
Collapse
Affiliation(s)
- Anaël Chazeau
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France Interdisciplinary Institute for Neuroscience, Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France
| | - Mikael Garcia
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France Interdisciplinary Institute for Neuroscience, Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France CYTOO, Minatec, Grenoble, 38054 Grenoble, France
| | - Katalin Czöndör
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France Interdisciplinary Institute for Neuroscience, Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France
| | - David Perrais
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France Interdisciplinary Institute for Neuroscience, Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France
| | - Béatrice Tessier
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France Interdisciplinary Institute for Neuroscience, Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France
| | - Grégory Giannone
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France Interdisciplinary Institute for Neuroscience, Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France
| | - Olivier Thoumine
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France Interdisciplinary Institute for Neuroscience, Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 5297, F-33000 Bordeaux, France
| |
Collapse
|
91
|
Suraneni P, Fogelson B, Rubinstein B, Noguera P, Volkmann N, Hanein D, Mogilner A, Li R. A mechanism of leading-edge protrusion in the absence of Arp2/3 complex. Mol Biol Cell 2015; 26:901-12. [PMID: 25568333 PMCID: PMC4342026 DOI: 10.1091/mbc.e14-07-1250] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Cells employ protrusive leading edges to navigate and promote their migration in diverse physiological environments. Classical models of leading-edge protrusion rely on a treadmilling dendritic actin network that undergoes continuous assembly nucleated by the Arp2/3 complex, forming ruffling lamellipodia. Recent work demonstrated, however, that, in the absence of the Arp2/3 complex, fibroblast cells adopt a leading edge with filopodia-like protrusions (FLPs) and maintain an ability to move, albeit with altered responses to different environmental signals. We show that formin-family actin nucleators are required for the extension of FLPs but are insufficient to produce a continuous leading edge in fibroblasts lacking Arp2/3 complex. Myosin II is concentrated in arc-like regions of the leading edge in between FLPs, and its activity is required for coordinated advancement of these regions with formin-generated FLPs. We propose that actomyosin contraction acting against membrane tension advances the web of arcs between FLPs. Predictions of this model are verified experimentally. The dependence of myosin II in leading-edge advancement helps explain the previously reported defect in directional movement in the Arpc3-null fibroblasts. We provide further evidence that this defect is cell autonomous during chemotaxis.
Collapse
Affiliation(s)
| | - Ben Fogelson
- Courant Institute and Department of Biology, New York University, New York, NY 10012
| | | | | | - Niels Volkmann
- Bioinformatics and Systems Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
| | - Dorit Hanein
- Bioinformatics and Systems Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037
| | - Alex Mogilner
- Courant Institute and Department of Biology, New York University, New York, NY 10012
| | - Rong Li
- Stowers Institute for Medical Research, Kansas City, MO 64110 Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160
| |
Collapse
|
92
|
Abstract
Cells can interact with their surroundings via filopodia, which are membrane protrusions that extend beyond the cell body. Filopodia are essential during dynamic cellular processes like motility, invasion, and cell-cell communication. Filopodia contain cross-linked actin filaments, attached to the surrounding cell membrane via protein linkers such as integrins. These actin filaments are thought to play a pivotal role in force transduction, bending, and rotation. We investigated whether, and how, actin within filopodia is responsible for filopodia dynamics by conducting simultaneous force spectroscopy and confocal imaging of F-actin in membrane protrusions. The actin shaft was observed to periodically undergo helical coiling and rotational motion, which occurred simultaneously with retrograde movement of actin inside the filopodium. The cells were found to retract beads attached to the filopodial tip, and retraction was found to correlate with rotation and coiling of the actin shaft. These results suggest a previously unidentified mechanism by which a cell can use rotation of the filopodial actin shaft to induce coiling and hence axial shortening of the filopodial actin bundle.
Collapse
|
93
|
|
94
|
Kornberg TB. Cytonemes and the dispersion of morphogens. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2014; 3:445-63. [PMID: 25186102 PMCID: PMC4199865 DOI: 10.1002/wdev.151] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 07/10/2014] [Accepted: 07/25/2014] [Indexed: 01/07/2023]
Abstract
Filopodia are cellular protrusions that have been implicated in many types of mechanosensory activities. Morphogens are signaling proteins that regulate the patterned development of embryos and tissues. Both have long histories that date to the beginnings of cell and developmental biology in the early 20th century, but recent findings tie specialized filopodia called cytonemes to morphogen movement and morphogen signaling. This review explores the conceptual and experimental background for a model of paracrine signaling in which the exchange of morphogens between cells is directed to sites where cytonemes directly link cells that produce morphogens to cells that receive and respond to them.
Collapse
Affiliation(s)
- Thomas B Kornberg
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA
| |
Collapse
|
95
|
Chou AM, Sem KP, Wright GD, Sudhaharan T, Ahmed S. Dynamin1 is a novel target for IRSp53 protein and works with mammalian enabled (Mena) protein and Eps8 to regulate filopodial dynamics. J Biol Chem 2014; 289:24383-96. [PMID: 25031323 DOI: 10.1074/jbc.m114.553883] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Filopodia are dynamic actin-based structures that play roles in processes such as cell migration, wound healing, and axonal guidance. Cdc42 induces filopodial formation through IRSp53, an Inverse-Bin-Amphiphysins-Rvs (I-BAR) domain protein. Previous work from a number of laboratories has shown that IRSp53 generates filopodia by coupling membrane protrusion with actin dynamics through its Src homology 3 domain binding partners. Here, we show that dynamin1 (Dyn1), the large guanosine triphosphatase, is an interacting partner of IRSp53 through pulldown and Förster resonance energy transfer analysis, and we explore its role in filopodial formation. In neuroblastoma cells, Dyn1 localizes to filopodia, associated tip complexes, and the leading edge just behind the anti-capping protein mammalian enabled (Mena). Dyn1 knockdown reduces filopodial formation, which can be rescued by overexpressing wild-type Dyn1 but not the GTPase mutant Dyn1-K44A and the loss-of-function actin binding domain mutant Dyn1-K/E. Interestingly, dynasore, an inhibitor of Dyn GTPase, also reduced filopodial number and increased their lifetime. Using rapid time-lapse total internal reflection fluorescence microscopy, we show that Dyn1 and Mena localize to filopodia only during initiation and assembly. Dyn1 actin binding domain mutant inhibits filopodial formation, suggesting a role in actin elongation. In contrast, Eps8, an actin capping protein, is seen most strongly at filopodial tips during disassembly. Taken together, the results suggest IRSp53 partners with Dyn1, Mena, and Eps8 to regulate filopodial dynamics.
Collapse
Affiliation(s)
- Ai Mei Chou
- From the Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648, Singapore
| | - Kai Ping Sem
- From the Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648, Singapore
| | - Graham Daniel Wright
- From the Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648, Singapore
| | - Thankiah Sudhaharan
- From the Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648, Singapore
| | - Sohail Ahmed
- From the Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648, Singapore
| |
Collapse
|
96
|
Barzik M, McClain LM, Gupton SL, Gertler FB. Ena/VASP regulates mDia2-initiated filopodial length, dynamics, and function. Mol Biol Cell 2014; 25:2604-19. [PMID: 24989797 PMCID: PMC4148250 DOI: 10.1091/mbc.e14-02-0712] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Filopodia are long plasma membrane extensions involved in the formation of adhesive, contractile, and protrusive actin-based structures in spreading and migrating cells. Whether filopodia formed by different molecular mechanisms equally support these cellular functions is unresolved. We used Enabled/vasodilator-stimulated phosphoprotein (Ena/VASP)-deficient MV(D7) fibroblasts, which are also devoid of endogenous mDia2, as a model system to investigate how these different actin regulatory proteins affect filopodia morphology and dynamics independently of one another. Filopodia initiated by either Ena/VASP or mDia2 contained similar molecular inventory but differed significantly in parameters such as number, length, F-actin organization, lifetime, and protrusive persistence. Moreover, in the absence of Ena/VASP, filopodia generated by mDia2 did not support initiation of integrin-dependent signaling cascades required for adhesion and subsequent lamellipodial extension, thereby causing a defect in early cell spreading. Coexpression of VASP with constitutively active mDia2(M/A) rescued these early adhesion defects. We conclude that Ena/VASP and mDia2 support the formation of filopodia with significantly distinct properties and that Ena/VASP regulates mDia2-initiated filopodial morphology, dynamics, and function.
Collapse
Affiliation(s)
- Melanie Barzik
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Leslie M McClain
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Stephanie L Gupton
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Frank B Gertler
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
| |
Collapse
|
97
|
Specialized filopodia: at the 'tip' of morphogen transport and vertebrate tissue patterning. Curr Opin Genet Dev 2014; 27:67-73. [PMID: 24907447 DOI: 10.1016/j.gde.2014.03.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2014] [Revised: 03/19/2014] [Accepted: 03/26/2014] [Indexed: 11/24/2022]
Abstract
For over a century, biologists have strived to unravel the mechanisms that establish how cells are informed of their position in the embryo and differentiate to give rise to complex organs and structures. However, the historical idea that one predominant mode of ligand transport, largely accounted for by free diffusion, can explain how all signaling molecules, known as morphogens, control tissue patterning has greatly hindered our ability to fully appreciate the complexities driving the delivery and reception of signaling molecules at a distance. In reality, a cell's shape, morphology, and location change continuously as development progresses. Thus, cellular context poses distinct challenges for morphogen transport in each unique cellular environment. Emerging studies reveal that some cells overcome such obstacles in an unexpected manner: via long, cellular projections, or specialized filopodia, that link distant cells and traffic signaling components. Here, we will review recent findings describing specialized filopodia and discuss the potential mechanisms and implications for filopodia-based long-range cell signaling and communication, particularly within the developing vertebrate embryo.
Collapse
|
98
|
Zhao C, Liu C, Hogue CWV, Low BC. A cooperative jack model of random coil-to-elongation transition of the FH1 domain by profilin binding explains formin motor behavior in actin polymerization. FEBS Lett 2014; 588:2288-93. [PMID: 24861497 DOI: 10.1016/j.febslet.2014.05.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 04/28/2014] [Accepted: 05/06/2014] [Indexed: 11/24/2022]
Abstract
Filopodia are essential for the development of neuronal growth cones, cell polarity and cell migration. Their protrusions are powered by the polymerization of actin filaments linked to the plasma membrane, catalyzed by formin proteins. The acceleration of polymerization depends on the number of profilin-actins binding with the formin-FH1 domain. Biophysical characterization of the disordered formin-FH1 domain remains a challenge. We analyzed the conformational distribution of the diaphanous-related formin mDia1-FH1 bound with one to six profilins. We found a coil-to-elongation transition in the FH1 domain. We propose a cooperative "jack" model for the Formin-Homology-1 (FH1) domain of formins stacked by profilin-actins.
Collapse
Affiliation(s)
- Chen Zhao
- Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore.
| | - Chengcheng Liu
- Bioprocessing Technology Institute, Agency for Science, Technology and Research, Singapore 138668, Singapore
| | - Christopher W V Hogue
- Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore
| | - Boon Chuan Low
- Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore; Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.
| |
Collapse
|
99
|
Chiu CL, Digman MA, Gratton E. Measuring actin flow in 3D cell protrusions. Biophys J 2014; 105:1746-55. [PMID: 24138850 DOI: 10.1016/j.bpj.2013.07.057] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Revised: 07/26/2013] [Accepted: 07/31/2013] [Indexed: 11/17/2022] Open
Abstract
Actin dynamics is important in determining cell shape, tension, and migration. Methods such as fluorescent speckle microscopy and spatial temporal image correlation spectroscopy have been used to capture high-resolution actin turnover dynamics within cells in two dimensions. However, these methods are not directly applicable in 3D due to lower resolution and poor contrast. Here, we propose to capture actin flow in 3D with high spatial-temporal resolution by combining nanoscale precise imaging by rapid beam oscillation and fluctuation spectroscopy techniques. To measure the actin flow along cell protrusions in cell expressing actin-eGFP cultured in a type I collagen matrix, the laser was orbited around the protrusion and its trajectory was modulated in a clover-shaped pattern perpendicularly to the protrusion. Orbits were also alternated at two positions closely spaced along the protrusion axis. The pair cross-correlation function was applied to the fluorescence fluctuation from these two positions to capture the flow of actin. Measurements done on nonmoving cellular protrusion tips showed no pair-correlation at two orbital positions indicating a lack of flow of F-actin bundles. However, in some protrusions, the pair-correlation approach revealed directional flow of F-actin bundles near the protrusion surface with flow rates in the range of ∼1 μm/min, comparable to results in two dimensions using fluorescent speckle microscopy. Furthermore, we found that the actin flow rate is related to the distance to the protrusion tip. We also observed collagen deformation by concomitantly detecting collagen fibers with reflectance detection during these actin motions. The implementation of the nanoscale precise imaging by rapid beam oscillation method with a cloverleaf-shaped trajectory in conjunction with the pair cross-correlation function method provides a quantitative way of capturing dynamic flows and organization of proteins during cell migration in 3D in conditions of poor contrast.
Collapse
Affiliation(s)
- Chi-Li Chiu
- Department of Developmental and Cell Biology, Laboratory for Fluorescence Dynamics, University of California, Irvine, California
| | | | | |
Collapse
|
100
|
Sinnar SA, Antoku S, Saffin JM, Cooper JA, Halpain S. Capping protein is essential for cell migration in vivo and for filopodial morphology and dynamics. Mol Biol Cell 2014; 25:2152-60. [PMID: 24829386 PMCID: PMC4091828 DOI: 10.1091/mbc.e13-12-0749] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
This study shows that capping protein (CP) is essential for mammalian cell migration in vitro and in vivo. The authors also show that CP is present in filopodia of multiple cell types and that it regulates filopodial structure and function. Thus CP function in both lamellipodia and filopodia may contribute to efficient migration. Capping protein (CP) binds to barbed ends of growing actin filaments and inhibits elongation. CP is essential for actin-based motility in cell-free systems and in Dictyostelium. Even though CP is believed to be critical for creating the lamellipodial actin structure necessary for protrusion and migration, CP's role in mammalian cell migration has not been directly tested. Moreover, recent studies have suggested that structures besides lamellipodia, including lamella and filopodia, may have unappreciated roles in cell migration. CP has been postulated to be absent from filopodia, and thus its role in filopodial activity has remained unexplored. We report that silencing CP in both cultured mammalian B16F10 cells and in neurons of developing neocortex impaired cell migration. Moreover, we unexpectedly observed that low levels of CP were detectable in the majority of filopodia. CP depletion decreased filopodial length, altered filopodial shape, and reduced filopodial dynamics. Our results support an expansion of the potential roles that CP plays in cell motility by implicating CP in filopodia as well as in lamellipodia, both of which are important for locomotion in many types of migrating cells.
Collapse
Affiliation(s)
- Shamim A Sinnar
- Division of Biological Sciences, University of California, San Diego, and Sanford Consortium for Regenerative Medicine, La Jolla, CA 92037
| | - Susumu Antoku
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109
| | - Jean-Michel Saffin
- Division of Biological Sciences, University of California, San Diego, and Sanford Consortium for Regenerative Medicine, La Jolla, CA 92037
| | - Jon A Cooper
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109
| | - Shelley Halpain
- Division of Biological Sciences, University of California, San Diego, and Sanford Consortium for Regenerative Medicine, La Jolla, CA 92037
| |
Collapse
|