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Sepúlveda-Ramírez SP, Toledo-Jacobo L, Henson JH, Shuster CB. Cdc42 controls primary mesenchyme cell morphogenesis in the sea urchin embryo. Dev Biol 2018; 437:140-151. [PMID: 29555242 PMCID: PMC5973877 DOI: 10.1016/j.ydbio.2018.03.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 03/05/2018] [Accepted: 03/15/2018] [Indexed: 12/15/2022]
Abstract
In the sea urchin embryo, gastrulation is characterized by the ingression and directed cell migration of primary mesenchyme cells (PMCs), as well as the primary invagination and convergent extension of the endomesoderm. Like all cell shape changes, individual and collective cell motility is orchestrated by Rho family GTPases and their modulation of the actomyosin cytoskeleton. And while endomesoderm specification has been intensively studied in echinoids, much less is known about the proximate regulators driving cell motility. Toward these ends, we employed anti-sense morpholinos, mutant alleles and pharmacological inhibitors to assess the role of Cdc42 during sea urchin gastrulation. While inhibition of Cdc42 expression or activity had only mild effects on PMC ingression, PMC migration, alignment and skeletogenesis were disrupted in the absence of Cdc42, as well as elongation of the archenteron. PMC migration and patterning of the larval skeleton relies on the extension of filopodia, and Cdc42 was required for filopodia in vivo as well as in cultured PMCs. Lastly, filopodial extension required both Arp2/3 and formin actin-nucleating factors, supporting models of filopodial nucleation observed in other systems. Together, these results suggest that Cdc42 plays essential roles during PMC cell motility and organogenesis.
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Affiliation(s)
- Silvia P Sepúlveda-Ramírez
- Department of Biology, New Mexico State University, Las Cruces, NM 88003, United States; University of Washington Friday Harbor Laboratories, Friday Harbor, WA 98250, United States
| | - Leslie Toledo-Jacobo
- Department of Biology, New Mexico State University, Las Cruces, NM 88003, United States; University of Washington Friday Harbor Laboratories, Friday Harbor, WA 98250, United States
| | - John H Henson
- University of Washington Friday Harbor Laboratories, Friday Harbor, WA 98250, United States; Department of Biology, Dickinson College, Carlisle, PA 17013, United States
| | - Charles B Shuster
- Department of Biology, New Mexico State University, Las Cruces, NM 88003, United States; University of Washington Friday Harbor Laboratories, Friday Harbor, WA 98250, United States.
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52
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Masedunskas A, Appaduray MA, Lucas CA, Lastra Cagigas M, Heydecker M, Holliday M, Meiring JCM, Hook J, Kee A, White M, Thomas P, Zhang Y, Adelstein RS, Meckel T, Böcking T, Weigert R, Bryce NS, Gunning PW, Hardeman EC. Parallel assembly of actin and tropomyosin, but not myosin II, during de novo actin filament formation in live mice. J Cell Sci 2018; 131:jcs.212654. [PMID: 29487177 DOI: 10.1242/jcs.212654] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 02/12/2018] [Indexed: 01/04/2023] Open
Abstract
Many actin filaments in animal cells are co-polymers of actin and tropomyosin. In many cases, non-muscle myosin II associates with these co-polymers to establish a contractile network. However, the temporal relationship of these three proteins in the de novo assembly of actin filaments is not known. Intravital subcellular microscopy of secretory granule exocytosis allows the visualisation and quantification of the formation of an actin scaffold in real time, with the added advantage that it occurs in a living mammal under physiological conditions. We used this model system to investigate the de novo assembly of actin, tropomyosin Tpm3.1 (a short isoform of TPM3) and myosin IIA (the form of non-muscle myosin II with its heavy chain encoded by Myh9) on secretory granules in mouse salivary glands. Blocking actin polymerization with cytochalasin D revealed that Tpm3.1 assembly is dependent on actin assembly. We used time-lapse imaging to determine the timing of the appearance of the actin filament reporter LifeAct-RFP and of Tpm3.1-mNeonGreen on secretory granules in LifeAct-RFP transgenic, Tpm3.1-mNeonGreen and myosin IIA-GFP (GFP-tagged MYH9) knock-in mice. Our findings are consistent with the addition of tropomyosin to actin filaments shortly after the initiation of actin filament nucleation, followed by myosin IIA recruitment.
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Affiliation(s)
| | | | | | | | - Marco Heydecker
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia.,Membrane Dynamics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Mira Holliday
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | | | - Jeff Hook
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Anthony Kee
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Melissa White
- South Australian Genome Editing, Facility Robinson Research Institute, University of Adelaide, Adelaide, SA 5005, Australia
| | - Paul Thomas
- South Australian Genome Editing, Facility Robinson Research Institute, University of Adelaide, Adelaide, SA 5005, Australia
| | - Yingfan Zhang
- NHLBI, National Institutes of Health, Bethesda, MD 20892, USA
| | | | - Tobias Meckel
- Membrane Dynamics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Till Böcking
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Roberto Weigert
- Laboratory of Cellular and Molecular Biology, CCR, National Cancer Institute, Bethesda, MD 20892, USA
| | - Nicole S Bryce
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Peter W Gunning
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Edna C Hardeman
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
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53
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Segal D, Zaritsky A, Schejter ED, Shilo BZ. Feedback inhibition of actin on Rho mediates content release from large secretory vesicles. J Cell Biol 2018; 217:1815-1826. [PMID: 29496739 PMCID: PMC5940311 DOI: 10.1083/jcb.201711006] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 12/24/2017] [Accepted: 01/30/2018] [Indexed: 12/02/2022] Open
Abstract
This work identified a cycle of actin assembly and disassembly in large secretory vesicles of Drosophila salivary glands. Actin disassembly is triggered by actin-dependent recruitment of a RhoGAP protein and is essential for the contractility of the vesicle, leading to content release to the lumen. Secretion of adhesive glycoproteins to the lumen of Drosophila melanogaster larval salivary glands is performed by contraction of an actomyosin network assembled around large secretory vesicles, after their fusion to the apical membranes. We have identified a cycle of actin coat nucleation and disassembly that is independent of myosin. Recruitment of active Rho1 to the fused vesicle triggers activation of the formin Diaphanous and actin nucleation. This leads to actin-dependent localization of a RhoGAP protein that locally shuts off Rho1, promoting disassembly of the actin coat. When contraction of vesicles is blocked, the strict temporal order of the recruited elements generates repeated oscillations of actin coat formation and disassembly. Interestingly, different blocks to actin coat disassembly arrested vesicle contraction, indicating that actin turnover is an integral part of the actomyosin contraction cycle. The capacity of F-actin to trigger a negative feedback on its own production may be widely used to coordinate a succession of morphogenetic events or maintain homeostasis.
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Affiliation(s)
- Dagan Segal
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Assaf Zaritsky
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel.,Lyda Hill Department of Bioinformatics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Eyal D Schejter
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Ben-Zion Shilo
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
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54
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Carisey AF, Mace EM, Saeed MB, Davis DM, Orange JS. Nanoscale Dynamism of Actin Enables Secretory Function in Cytolytic Cells. Curr Biol 2018; 28:489-502.e9. [PMID: 29398219 PMCID: PMC5835143 DOI: 10.1016/j.cub.2017.12.044] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 11/13/2017] [Accepted: 12/20/2017] [Indexed: 11/21/2022]
Abstract
Natural killer (NK) cells are innate immune effectors that lyse virally infected and tumorigenic cells through the formation of an immunological synapse. Actin remodeling at the lytic immunological synapse is a critical requirement for multiple facets of cytotoxic function. Activating receptor and integrin signaling leads to the regulated turnover and remodeling of actin, which is required for adhesion, sustained receptor signaling, and ultimately exocytosis. NK cells undergo lytic granule exocytosis in hypodense regions of a pervasive actin network. Although these requirements have been well demonstrated, neither the dynamic regulation of synaptic actin nor its specific function, however, has been determined at a nanoscale level. Here, live-cell super-resolution microscopy demonstrates nanoscale filamentous actin dynamism in NK cell lytic granule secretion. Following cell spreading, the overall content of the branched actin network at an immune synapse is stable over time and contains branched actin fibers and discrete actin foci. Similar actin architecture is generated in cytolytic T cells, although the timescale differs from that of NK cells. Individual filament displacement leads to stochastic clearance formation and disappearance, which are independent of lytic granule positioning. Actin dynamism is dependent upon branched network formation mediated by Arp2/3 and contractility generated by myosin IIA. Importantly, the use of small-molecule inhibitors demonstrates that actin dynamism is ultimately needed for granule secretion. Thus, we describe a requirement for nanoscale actin fiber rearrangement in generating the complex actin architecture that enables lytic granule secretion.
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Affiliation(s)
- Alexandre F Carisey
- Center for Human Immunobiology, Baylor College of Medicine and Texas Children's Hospital, Houston, TX 77030, USA; Manchester Collaborative Centre for Inflammation Research, University of Manchester, 46 Grafton Street, Manchester M13 9NT, UK
| | - Emily M Mace
- Center for Human Immunobiology, Baylor College of Medicine and Texas Children's Hospital, Houston, TX 77030, USA
| | - Mezida B Saeed
- Manchester Collaborative Centre for Inflammation Research, University of Manchester, 46 Grafton Street, Manchester M13 9NT, UK
| | - Daniel M Davis
- Manchester Collaborative Centre for Inflammation Research, University of Manchester, 46 Grafton Street, Manchester M13 9NT, UK
| | - Jordan S Orange
- Center for Human Immunobiology, Baylor College of Medicine and Texas Children's Hospital, Houston, TX 77030, USA.
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55
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Identification of Wiskott-Aldrich syndrome protein (WASP) binding sites on the branched actin filament nucleator Arp2/3 complex. Proc Natl Acad Sci U S A 2018; 115:E1409-E1418. [PMID: 29386393 DOI: 10.1073/pnas.1716622115] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Arp2/3 complex nucleates branched actin filaments important for cellular motility and endocytosis. WASP family proteins are Arp2/3 complex activators that play multiple roles in branching nucleation, but little is known about the structural bases of these WASP functions, owing to an incomplete understanding of how WASP binds Arp2/3 complex. Recent data show WASP binds two sites, and biochemical and structural studies led to models in which the WASP C segment engages the barbed ends of the Arp3 and Arp2 subunits while the WASP A segment binds the back side of the complex on Arp3. However, electron microscopy reconstructions showed density for WASP inconsistent with these models on the opposite (front) side of Arp2/3 complex. Here we use chemical cross-linking and mass spectrometry (XL-MS) along with computational docking and structure-based mutational analysis to map the two WASP binding sites on the complex. Our data corroborate the barbed end and back side binding models and show one WASP binding site on Arp3, on the back side of the complex, and a second site on the bottom of the complex, spanning Arp2 and ARPC1. The XL-MS-identified cross-links rule out the front side binding model and show that the A segment of WASP binds along the bottom side of the ARPC1 subunit, instead of at the Arp2/ARPC1 interface, as suggested by FRET experiments. The identified binding sites support the Arp3 tail release model to explain WASP-mediated activating conformational changes in Arp2/3 complex and provide insight into the roles of WASP in branching nucleation.
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56
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Myosin IIa is critical for cAMP-mediated endothelial secretion of von Willebrand factor. Blood 2017; 131:686-698. [PMID: 29208598 DOI: 10.1182/blood-2017-08-802140] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 11/14/2017] [Indexed: 01/10/2023] Open
Abstract
Nonmuscle myosin II has been implicated in regulation of von Willebrand factor (VWF) release from endothelial Weibel-Palade bodies (WPBs), but the specific role of myosin IIa isoform is poorly defined. Here, we report that myosin IIa is expressed both in primary human endothelial cells and intact mouse vessels, essential for cyclic adenosine monophosphate (cAMP)-mediated endothelial VWF secretion. Downregulation of myosin IIa by shRNAs significantly suppressed both forskolin- and epinephrine-induced VWF secretion. Endothelium-specific myosin IIa knockout mice exhibited impaired epinephrine-stimulated VWF release, prolonged bleeding time, and thrombosis. Further study showed that in resting cells, myosin IIa deficiency disrupted the peripheral localization of Rab27-positive WPBs along stress fibers; on stimulation by cAMP agonists, myosin IIa in synergy with zyxin promotes the formation of a functional actin framework, which is derived from preexisting cortical actin filaments, around WPBs, facilitating fusion and subsequent exocytosis. In summary, our findings not only identify new functions of myosin IIa in regulation of WPB positioning and the interaction between preexisting cortical actin filaments and exocytosing vesicles before fusion but also reveal myosin IIa as a physiological regulator of endothelial VWF secretion in stress-induced hemostasis and thrombosis.
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57
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Tango7 regulates cortical activity of caspases during reaper-triggered changes in tissue elasticity. Nat Commun 2017; 8:603. [PMID: 28928435 PMCID: PMC5605750 DOI: 10.1038/s41467-017-00693-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 07/20/2017] [Indexed: 11/08/2022] Open
Abstract
Caspases perform critical functions in both living and dying cells; however, how caspases perform physiological functions without killing the cell remains unclear. Here we identify a novel physiological function of caspases at the cortex of Drosophila salivary glands. In living glands, activation of the initiator caspase dronc triggers cortical F-actin dismantling, enabling the glands to stretch as they accumulate secreted products in the lumen. We demonstrate that tango7, not the canonical Apaf-1-adaptor dark, regulates dronc activity at the cortex; in contrast, dark is required for cytoplasmic activity of dronc during salivary gland death. Therefore, tango7 and dark define distinct subcellular domains of caspase activity. Furthermore, tango7-dependent cortical dronc activity is initiated by a sublethal pulse of the inhibitor of apoptosis protein (IAP) antagonist reaper. Our results support a model in which biological outcomes of caspase activation are regulated by differential amplification of IAP antagonists, unique caspase adaptor proteins, and mutually exclusive subcellular domains of caspase activity. Caspases are known for their role in cell death, but they can also participate in other physiological functions without killing the cells. Here the authors show that unique caspase adaptor proteins can regulate caspase activity within mutually-exclusive and independently regulated subcellular domains.
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58
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Rui M, Qian J, Liu L, Cai Y, Lv H, Han J, Jia Z, Xie W. The neuronal protein Neurexin directly interacts with the Scribble-Pix complex to stimulate F-actin assembly for synaptic vesicle clustering. J Biol Chem 2017; 292:14334-14348. [PMID: 28710284 PMCID: PMC5582829 DOI: 10.1074/jbc.m117.794040] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 06/29/2017] [Indexed: 01/17/2023] Open
Abstract
Synaptic vesicles (SVs) form distinct pools at synaptic terminals, and this well-regulated separation is necessary for normal neurotransmission. However, how the SV cluster, in particular synaptic compartments, maintains normal neurotransmitter release remains a mystery. The presynaptic protein Neurexin (NRX) plays a significant role in synaptic architecture and function, and some evidence suggests that NRX is associated with neurological disorders, including autism spectrum disorders. However, the role of NRX in SV clustering is unclear. Here, using the neuromuscular junction at the 2-3 instar stages of Drosophila larvae as a model and biochemical imaging and electrophysiology techniques, we demonstrate that Drosophila NRX (DNRX) plays critical roles in regulating synaptic terminal clustering and release of SVs. We found that DNRX controls the terminal clustering and release of SVs by stimulating presynaptic F-actin. Furthermore, our results indicate that DNRX functions through the scaffold protein Scribble and the GEF protein DPix to activate the small GTPase Ras-related C3 Botulinum toxin substrate 1 (Rac1). We observed a direct interaction between the C-terminal PDZ-binding motif of DNRX and the PDZ domains of Scribble and that Scribble bridges DNRX to DPix, forming a DNRX-Scribble-DPix complex that activates Rac1 and subsequently stimulates presynaptic F-actin assembly and SV clustering. Taken together, our work provides important insights into the function of DNRX in regulating SV clustering, which could help inform further research into pathological neurexin-mediated mechanisms in neurological disorders such as autism.
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Affiliation(s)
- Menglong Rui
- From Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Jinjun Qian
- From Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Lijuan Liu
- From Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Yihan Cai
- From Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Huihui Lv
- From Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Junhai Han
- From Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing 210096, China.,the Institute of Life Sciences, the Collaborative Innovation Center for Brain Science, Southeast University, Nanjing 210096, China
| | - Zhengping Jia
- the Department of Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada, and.,the Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Wei Xie
- From Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing 210096, China, .,the Institute of Life Sciences, the Collaborative Innovation Center for Brain Science, Southeast University, Nanjing 210096, China
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59
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Hui TH, Kwan KW, Chun Yip TT, Fong HW, Ngan KC, Yu M, Yao S, Wan Ngan AH, Lin Y. Regulating the Membrane Transport Activity and Death of Cells via Electroosmotic Manipulation. Biophys J 2017; 110:2769-2778. [PMID: 27332135 DOI: 10.1016/j.bpj.2016.05.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 05/03/2016] [Accepted: 05/09/2016] [Indexed: 11/26/2022] Open
Abstract
Although the volume of living cells has been known to heavily influence their behavior and fate, a method allowing us to control the cell size in a programmable manner is still lacking. Here, we develop a technique in which precise changes in the cellular volume can be conveniently introduced by varying the voltage applied across a Nafion membrane that separates the culture medium from a reservoir. It is found that, unlike sudden osmotic shocks, active ion transport across the membrane of leukemia K562 cells will not be triggered by a gradual change in the extracellular osmolarity. Furthermore, when subjected to the same applied voltage, different lung and nasopharyngeal epithelial cancer cells will undergo larger volumetric changes and have a 5-10% higher death rate compared to their normal counterparts. We show that such distinct response is largely caused by the overexpression of aquaporin-4 in tumor cells, with knockout of this water channel protein resulting in a markedly reduced change in the cellular volume. Finally, by taking into account the exchange of water/ion molecules across the Nafion film and the cell membrane, a theoretical model is also proposed to describe the voltage-induced size changes of cells, which explain our experimental observations very well.
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Affiliation(s)
- Tsz Hin 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
| | - Kin Wah Kwan
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China
| | | | - Hong Wai Fong
- Department of Clinical Oncology, Queen Elizabeth Hospital, Hong Kong SAR, China
| | - Kai Cheong Ngan
- Department of Clinical Oncology, Queen Elizabeth Hospital, Hong Kong SAR, China
| | - Miao Yu
- Bioengineering Graduate Program, Biomedical Engineering Division, Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Shuhuai Yao
- Bioengineering Graduate Program, Biomedical Engineering Division, Hong Kong University of Science and Technology, Hong Kong SAR, China; Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Alfonso Hin Wan Ngan
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, 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.
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60
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Milberg O, Shitara A, Ebrahim S, Masedunskas A, Tora M, Tran DT, Chen Y, Conti MA, Adelstein RS, Ten Hagen KG, Weigert R. Concerted actions of distinct nonmuscle myosin II isoforms drive intracellular membrane remodeling in live animals. J Cell Biol 2017; 216:1925-1936. [PMID: 28600434 PMCID: PMC5496622 DOI: 10.1083/jcb.201612126] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 04/02/2017] [Accepted: 05/02/2017] [Indexed: 12/11/2022] Open
Abstract
Membrane remodeling plays a fundamental role during a variety of biological events. However, the dynamics and the molecular mechanisms regulating this process within cells in mammalian tissues in situ remain largely unknown. In this study, we use intravital subcellular microscopy in live mice to study the role of the actomyosin cytoskeleton in driving the remodeling of membranes of large secretory granules, which are integrated into the plasma membrane during regulated exocytosis. We show that two isoforms of nonmuscle myosin II, NMIIA and NMIIB, control distinct steps of the integration process. Furthermore, we find that F-actin is not essential for the recruitment of NMII to the secretory granules but plays a key role in the assembly and activation of NMII into contractile filaments. Our data support a dual role for the actomyosin cytoskeleton in providing the mechanical forces required to remodel the lipid bilayer and serving as a scaffold to recruit key regulatory molecules.
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Affiliation(s)
- Oleg Milberg
- Intracellular Membrane Trafficking Section, National Institutes of Health, Bethesda, MD
| | - Akiko Shitara
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD.,Intracellular Membrane Trafficking Section, National Institutes of Health, Bethesda, MD
| | - Seham Ebrahim
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD
| | - Andrius Masedunskas
- Intracellular Membrane Trafficking Section, National Institutes of Health, Bethesda, MD.,School of Medical Sciences, University of New South Wales, Sidney, Australia
| | - Muhibullah Tora
- Intracellular Membrane Trafficking Section, National Institutes of Health, Bethesda, MD
| | - Duy T Tran
- Developmental Glycobiology Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD
| | - Yun Chen
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD
| | - Mary Anne Conti
- Laboratory of Molecular Cardiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD
| | - Robert S Adelstein
- Laboratory of Molecular Cardiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD
| | - Kelly G Ten Hagen
- Developmental Glycobiology Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD
| | - Roberto Weigert
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD .,Intracellular Membrane Trafficking Section, National Institutes of Health, Bethesda, MD
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61
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Carlier MF, Shekhar S. Global treadmilling coordinates actin turnover and controls the size of actin networks. Nat Rev Mol Cell Biol 2017. [PMID: 28248322 DOI: 10.1038/nrm.(2016)172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Various cellular processes (including cell motility) are driven by the regulated, polarized assembly of actin filaments into distinct force-producing arrays of defined size and architecture. Branched, linear, contractile and cytosolic arrays coexist in vivo, and cells intricately control the number, length and assembly rate of filaments in these arrays. Recent in vitro and in vivo studies have revealed novel molecular mechanisms that regulate the number of filament barbed and pointed ends and their respective assembly and disassembly rates, thus defining classes of dynamically different filaments, which coexist in the same cell. We propose that a global treadmilling process, in which a steady-state amount of polymerizable actin monomers is established by the dynamics of each network, is responsible for defining the size and turnover of coexisting actin networks. Furthermore, signal-induced changes in the partitioning of actin to distinct arrays (mediated by RHO GTPases) result in the establishment of various steady-state concentrations of polymerizable monomers, thereby globally influencing the growth rate of actin filaments.
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Affiliation(s)
- Marie-France Carlier
- Institute for Integrative Biology of the Cell (I2BC), CNRS, Gif-sur-Yvette, Paris 91190, France
| | - Shashank Shekhar
- Institute for Integrative Biology of the Cell (I2BC), CNRS, Gif-sur-Yvette, Paris 91190, France
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62
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Papadopulos A. Membrane shaping by actin and myosin during regulated exocytosis. Mol Cell Neurosci 2017; 84:93-99. [PMID: 28536001 DOI: 10.1016/j.mcn.2017.05.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 04/21/2017] [Accepted: 05/19/2017] [Indexed: 12/01/2022] Open
Abstract
The cortical actin network in neurosecretory cells is a dense mesh of actin filaments underlying the plasma membrane. Interaction of actomyosin with vesicular membranes or the plasma membrane is vital for tethering, retention, transport as well as fusion and fission of exo- and endocytic membrane structures. During regulated exocytosis the cortical actin network undergoes dramatic changes in morphology to accommodate vesicle docking, fusion and replenishment. Most of these processes involve plasma membrane Phosphoinositides (PIP) and investigating the interactions between the actin cortex and secretory structures has become a hotbed for research in recent years. Actin remodelling leads to filopodia outgrowth and the creation of new fusion sites in neurosecretory cells and actin, myosin and dynamin actively shape and maintain the fusion pore of secretory vesicles. Changes in viscoelastic properties of the actin cortex can facilitate vesicular transport and lead to docking and priming of vesicle at the plasma membrane. Small GTPase actin mediators control the state of the cortical actin network and influence vesicular access to their docking and fusion sites. These changes potentially affect membrane properties such as tension and fluidity as well as the mobility of embedded proteins and could influence the processes leading to both exo- and endocytosis. Here we discuss the multitudes of actin and membrane interactions that control successive steps underpinning regulated exocytosis.
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Affiliation(s)
- Andreas Papadopulos
- The Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD, 4072, Australia.
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63
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Loss of the Arp2/3 complex component ARPC1B causes platelet abnormalities and predisposes to inflammatory disease. Nat Commun 2017. [PMID: 28368018 DOI: 10.1038/ncomms14816)] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Human actin-related protein 2/3 complex (Arp2/3), required for actin filament branching, has two ARPC1 component isoforms, with ARPC1B prominently expressed in blood cells. Here we show in a child with microthrombocytopenia, eosinophilia and inflammatory disease, a homozygous frameshift mutation in ARPC1B (p.Val91Trpfs*30). Platelet lysates reveal no ARPC1B protein and greatly reduced Arp2/3 complex. Missense ARPC1B mutations are identified in an unrelated patient with similar symptoms and ARPC1B deficiency. ARPC1B-deficient platelets are microthrombocytes similar to those seen in Wiskott-Aldrich syndrome that show aberrant spreading consistent with loss of Arp2/3 function. Knockout of ARPC1B in megakaryocytic cells results in decreased proplatelet formation, and as observed in platelets from patients, increased ARPC1A expression. Thus loss of ARPC1B produces a unique set of platelet abnormalities, and is associated with haematopoietic/immune symptoms affecting cell lineages where this isoform predominates. In agreement with recent experimental studies, our findings suggest that ARPC1 isoforms are not functionally interchangeable.
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64
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Kahr WHA, Pluthero FG, Elkadri A, Warner N, Drobac M, Chen CH, Lo RW, Li L, Li R, Li Q, Thoeni C, Pan J, Leung G, Lara-Corrales I, Murchie R, Cutz E, Laxer RM, Upton J, Roifman CM, Yeung RSM, Brumell JH, Muise AM. Loss of the Arp2/3 complex component ARPC1B causes platelet abnormalities and predisposes to inflammatory disease. Nat Commun 2017; 8:14816. [PMID: 28368018 PMCID: PMC5382316 DOI: 10.1038/ncomms14816] [Citation(s) in RCA: 147] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 01/31/2017] [Indexed: 12/19/2022] Open
Abstract
Human actin-related protein 2/3 complex (Arp2/3), required for actin filament branching, has two ARPC1 component isoforms, with ARPC1B prominently expressed in blood cells. Here we show in a child with microthrombocytopenia, eosinophilia and inflammatory disease, a homozygous frameshift mutation in ARPC1B (p.Val91Trpfs*30). Platelet lysates reveal no ARPC1B protein and greatly reduced Arp2/3 complex. Missense ARPC1B mutations are identified in an unrelated patient with similar symptoms and ARPC1B deficiency. ARPC1B-deficient platelets are microthrombocytes similar to those seen in Wiskott–Aldrich syndrome that show aberrant spreading consistent with loss of Arp2/3 function. Knockout of ARPC1B in megakaryocytic cells results in decreased proplatelet formation, and as observed in platelets from patients, increased ARPC1A expression. Thus loss of ARPC1B produces a unique set of platelet abnormalities, and is associated with haematopoietic/immune symptoms affecting cell lineages where this isoform predominates. In agreement with recent experimental studies, our findings suggest that ARPC1 isoforms are not functionally interchangeable. ARPC1B is a component of the actin-related protein 2/3 complex (Arp2/3), which is required for actin filament branching. Kahr et al. show that ARPC1B deficiency in humans is associated with severe multisystem disease that includes platelet abnormalities, eosinophilia, eczema and other indicators of immune disease.
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Affiliation(s)
- Walter H A Kahr
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Division of Haematology/Oncology, Department of Paediatrics, University of Toronto and The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Fred G Pluthero
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4
| | - Abdul Elkadri
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Neil Warner
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Marko Drobac
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Chang Hua Chen
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Richard W Lo
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Ling Li
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4
| | - Ren Li
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4
| | - Qi Li
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Cornelia Thoeni
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Jie Pan
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Gabriella Leung
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Irene Lara-Corrales
- Division of Pathology, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Ryan Murchie
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Ernest Cutz
- Division of Pathology, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Ronald M Laxer
- Division of Rheumatology, Department of Paediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Department of Medicine, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Julia Upton
- Division of Immunology, Department of Paediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Chaim M Roifman
- Division of Immunology, Department of Paediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Rae S M Yeung
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada M5S 1A8.,Division of Rheumatology, Department of Paediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Department of Immunology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - John H Brumell
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada M5S 1A8.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Aleixo M Muise
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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Abstract
Real-time imaging of regulated exocytosis in secreting organs can provide unprecedented temporal and spatial detail. Here, we highlight recent advances in 3D time-lapse imaging in Drosophila salivary glands at single-granule resolution. Using fluorescently labeled proteins expressed in the fly, it is now possible to image the dynamics of vesicle biogenesis and the cytoskeletal factors involved in secretion. 3D imaging over time allows one to visualize and define the temporal sequence of events, including clearance of cortical actin, fusion pore formation, mixing of the vesicular and plasma membranes and recruitment of components of the cytoskeleton. We will also discuss the genetic tools available in the fly that allow one to interrogate the essential factors involved in secretory vesicle formation, cargo secretion and the ultimate integration of the vesicular and plasma membranes. We argue that the combination of high-resolution real-time imaging and powerful genetics provides a platform to investigate the role of any factor in regulated secretion.
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Affiliation(s)
- Duy T Tran
- Section on Biological Chemistry, NIDCR, National Institutes of Health, 30 Convent Drive, Bethesda, MD 20892, USA
| | - Kelly G Ten Hagen
- Developmental Glycobiology Section, NIDCR, National Institutes of Health, 30 Convent Drive, Bethesda, MD 20892, USA
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66
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Zyxin regulates endothelial von Willebrand factor secretion by reorganizing actin filaments around exocytic granules. Nat Commun 2017; 8:14639. [PMID: 28256511 PMCID: PMC5338022 DOI: 10.1038/ncomms14639] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 01/17/2017] [Indexed: 12/13/2022] Open
Abstract
Endothelial exocytosis of Weibel-Palade body (WPB) is one of the first lines of defence against vascular injury. However, the mechanisms that control WPB exocytosis in the final stages (including the docking, priming and fusion of granules) are poorly understood. Here we show that the focal adhesion protein zyxin is crucial in this process. Zyxin downregulation inhibits the secretion of von Willebrand factor (VWF), the most abundant cargo in WPBs, from human primary endothelial cells (ECs) induced by cAMP agonists. Zyxin-deficient mice exhibit impaired epinephrine-stimulated VWF release, prolonged bleeding time and thrombosis, largely due to defective endothelial secretion of VWF. Using live-cell super-resolution microscopy, we visualize previously unappreciated reorganization of pre-existing actin filaments around WPBs before fusion, dependent on zyxin and an interaction with the actin crosslinker α-actinin. Our findings identify zyxin as a physiological regulator of endothelial exocytosis through reorganizing local actin network in the final stage of exocytosis.
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67
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Carlier MF, Shekhar S. Global treadmilling coordinates actin turnover and controls the size of actin networks. Nat Rev Mol Cell Biol 2017; 18:389-401. [DOI: 10.1038/nrm.2016.172] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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68
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Abstract
BAR domain proteins can regulate ‘membrane reservoirs’ that provide surface area and buffer membrane tension. Syndapin is an F-BAR and SH3 domain containing protein involved in cytoskeletal remodelling and endocytosis. The Syndapin F-BAR domain is uniquely versatile compared to others in the family and can bend phospholipid membranes into tubules of various diameters and directly bind actin. The Syndapin SH3 domain can also interact with actin remodelling proteins and modulate cytoskeletal contractility. Pseudocleavage furrow extension in the syncytial division cycles of Drosophila embryos requires the homeostatic control of conserved processes that control plasma membrane tension and actin contractility. We find that Syndapin plays an important role in promoting pseudocleavage furrow extension. We propose a model involving roles for Syndapin in membrane dynamics and direct or indirect effect on the cytoskeleton to explain how it affects pseudocleavage furrow growth, independent of its role in endocytosis.
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Affiliation(s)
- Aparna Sherlekar
- Biology, Indian Institute of Science Education and Research, Pune, India
| | - Richa Rikhy
- Biology, Indian Institute of Science Education and Research, Pune, India
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69
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Abstract
A number of mechanisms ensure that the intestine is protected from pathogens and also against our own intestinal microbiota. The outermost of these is the secreted mucus, which entraps bacteria and prevents their translocation into the tissue. Mucus contains many immunomodulatory molecules and is largely produced by the goblet cells. These cells are highly responsive to the signals they receive from the immune system and are also able to deliver antigens from the lumen to dendritic cells in the lamina propria. In this Review, we will give a basic overview of mucus, mucins and goblet cells, and explain how each of these contributes to immune regulation in the intestine.
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Affiliation(s)
- Malin E V Johansson
- Department of Medical Biochemistry, University of Gothenburg, 405 30 Gothenburg, Sweden
| | - Gunnar C Hansson
- Department of Medical Biochemistry, University of Gothenburg, 405 30 Gothenburg, Sweden
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70
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Abstract
An actin filament coat promotes cargo expulsion from large exocytosing vesicles, but the mechanisms of coat formation and force generation have been poorly characterized. Elegant imaging studies of the Drosophila melanogaster salivary gland now reveal how actin and myosin are recruited, and show that myosin II forms a contractile 'cage' that facilitates exocytosis.
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Affiliation(s)
- Christien J Merrifield
- Institute for Integrative Biology of the Cell, Bât. 34, Avenue de la Terrasse, 9198 Gif sur Yvette cedex, France
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71
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Shekhar S, Pernier J, Carlier MF. Regulators of actin filament barbed ends at a glance. J Cell Sci 2016; 129:1085-91. [PMID: 26940918 DOI: 10.1242/jcs.179994] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Cells respond to external stimuli by rapidly remodeling their actin cytoskeleton. At the heart of this function lies the intricately controlled regulation of individual filaments. The barbed end of an actin filament is the hotspot for the majority of the biochemical reactions that control filament assembly. Assays performed in bulk solution and with single filaments have enabled characterization of a plethora of barbed-end-regulating proteins. Interestingly, many of these regulators work in tandem with other proteins, which increase or decrease their affinity for the barbed end in a spatially and temporally controlled manner, often through simultaneous binding of two regulators at the barbed ends, in addition to standard mutually exclusive binding schemes. In this Cell Science at a Glance and the accompanying poster, we discuss key barbed-end-interacting proteins and the kinetic mechanisms by which they regulate actin filament assembly. We take F-actin capping protein, gelsolin, profilin and barbed-end-tracking polymerases, including formins and WH2-domain-containing proteins, as examples, and illustrate how their activity and competition for the barbed end regulate filament dynamics.
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Affiliation(s)
- Shashank Shekhar
- Cytoskeleton Dynamics and Cell Motility, I2BC, CNRS, Gif-sur-Yvette 91198, France
| | - Julien Pernier
- Cytoskeleton Dynamics and Cell Motility, I2BC, CNRS, Gif-sur-Yvette 91198, France
| | - Marie-France Carlier
- Cytoskeleton Dynamics and Cell Motility, I2BC, CNRS, Gif-sur-Yvette 91198, France
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