1
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Toneatti R, Shin JM, Shah UH, Mayer CR, Saunders JM, Fribourg M, Arsenovic PT, Janssen WG, Sealfon SC, López-Giménez JF, Benson DL, Conway DE, González-Maeso J. Interclass GPCR heteromerization affects localization and trafficking. Sci Signal 2020; 13:eaaw3122. [PMID: 33082287 PMCID: PMC7717648 DOI: 10.1126/scisignal.aaw3122] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Membrane trafficking processes regulate G protein-coupled receptor (GPCR) activity. Although class A GPCRs are capable of activating G proteins in a monomeric form, they can also potentially assemble into functional GPCR heteromers. Here, we showed that the class A serotonin 5-HT2A receptors (5-HT2ARs) affected the localization and trafficking of class C metabotropic glutamate receptor 2 (mGluR2) through a mechanism that required their assembly as heteromers in mammalian cells. In the absence of agonists, 5-HT2AR was primarily localized within intracellular compartments, and coexpression of 5-HT2AR with mGluR2 increased the intracellular distribution of the otherwise plasma membrane-localized mGluR2. Agonists for either 5-HT2AR or mGluR2 differentially affected trafficking through Rab5-positive endosomes in cells expressing each component of the 5-HT2AR-mGluR2 heterocomplex alone, or together. In addition, overnight pharmacological 5-HT2AR blockade with clozapine, but not with M100907, decreased mGluR2 density through a mechanism that involved heteromerization between 5-HT2AR and mGluR2. Using TAT-tagged peptides and chimeric constructs that are unable to form the interclass 5-HT2AR-mGluR2 complex, we demonstrated that heteromerization was necessary for the 5-HT2AR-dependent effects on mGluR2 subcellular distribution. The expression of 5-HT2AR also augmented intracellular localization of mGluR2 in mouse frontal cortex pyramidal neurons. Together, our data suggest that GPCR heteromerization may itself represent a mechanism of receptor trafficking and sorting.
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MESH Headings
- Amino Acids/pharmacology
- Animals
- Bridged Bicyclo Compounds, Heterocyclic/pharmacology
- Cell Membrane/metabolism
- Clozapine/pharmacology
- Endosomes/metabolism
- HEK293 Cells
- Humans
- Mice, 129 Strain
- Mice, Knockout
- Microscopy, Confocal
- Multiprotein Complexes/chemistry
- Multiprotein Complexes/metabolism
- Protein Multimerization
- Protein Transport/drug effects
- Receptor, Serotonin, 5-HT2A/chemistry
- Receptor, Serotonin, 5-HT2A/genetics
- Receptor, Serotonin, 5-HT2A/metabolism
- Receptors, Metabotropic Glutamate/chemistry
- Receptors, Metabotropic Glutamate/genetics
- Receptors, Metabotropic Glutamate/metabolism
- Serotonin Antagonists/pharmacology
- Signal Transduction
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Affiliation(s)
- Rudy Toneatti
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Jong M Shin
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Urjita H Shah
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Carl R Mayer
- Department of Biomedical Engineering, College of Engineering, Virginia Commonwealth University, Richmond, VA 23220, USA
| | - Justin M Saunders
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Miguel Fribourg
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Translational Transplant Research Center, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Paul T Arsenovic
- Department of Biomedical Engineering, College of Engineering, Virginia Commonwealth University, Richmond, VA 23220, USA
| | - William G Janssen
- Department Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Stuart C Sealfon
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Juan F López-Giménez
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
- Instituto de Parasitología y Biomedicina "López-Neyra", CSIC, E-18016 Granada, Spain
| | - Deanna L Benson
- Department Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Daniel E Conway
- Department of Biomedical Engineering, College of Engineering, Virginia Commonwealth University, Richmond, VA 23220, USA
| | - Javier González-Maeso
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA.
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2
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Narayanan V, Schappell LE, Mayer CR, Duke AA, Armiger TJ, Arsenovic PT, Mohan A, Dahl KN, Gleghorn JP, Conway DE. Osmotic Gradients in Epithelial Acini Increase Mechanical Tension across E-cadherin, Drive Morphogenesis, and Maintain Homeostasis. Curr Biol 2020; 30:624-633.e4. [PMID: 31983640 DOI: 10.1016/j.cub.2019.12.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 10/04/2019] [Accepted: 12/09/2019] [Indexed: 12/13/2022]
Abstract
Epithelial cells spontaneously form acini (also known as cysts or spheroids) with a single, fluid-filled central lumen when grown in 3D matrices. The size of the lumen is dependent on apical secretion of chloride ions, most notably by the CFTR channel, which has been suggested to establish pressure in the lumen due to water influx. To study the cellular biomechanics of acini morphogenesis and homeostasis, we used MDCK-2 cells. Using FRET-force biosensors for E-cadherin, we observed significant increases in the average tension per molecule for each protein in mature 3D acini as compared to 2D monolayers. Increases in CFTR activity resulted in increased E-cadherin forces, indicating that ionic gradients affect cellular tension. Direct measurements of pressure revealed that mature acini experience significant internal hydrostatic pressure (37 ± 10.9 Pa). Changes in CFTR activity resulted in pressure and/or volume changes, both of which affect E-cadherin tension. Increases in CFTR chloride secretion also induced YAP signaling and cellular proliferation. In order to recapitulate disruption of acinar homeostasis, we induced epithelial-to-mesenchymal transition (EMT). During the initial stages of EMT, there was a gradual decrease in E-cadherin force and lumen pressure that correlated with lumen infilling. Strikingly, increasing CFTR activity was sufficient to block EMT. Our results show that ion secretion is an important regulator of morphogenesis and homeostasis in epithelial acini. Furthermore, this work demonstrates that, for closed 3D cellular systems, ion gradients can generate osmotic pressure or volume changes, both of which result in increased cellular tension.
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Affiliation(s)
- Vani Narayanan
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Laurel E Schappell
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716, USA
| | - Carl R Mayer
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Ashley A Duke
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Travis J Armiger
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Paul T Arsenovic
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Abhinav Mohan
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Kris N Dahl
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Jason P Gleghorn
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716, USA
| | - Daniel E Conway
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
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Mayer CR, Arsenovic PT, Bathula K, Denis KB, Conway DE. Characterization of 3D Printed Stretching Devices for Imaging Force Transmission in Live-Cells. Cell Mol Bioeng 2019; 12:289-300. [PMID: 31719915 DOI: 10.1007/s12195-019-00579-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 06/07/2019] [Indexed: 12/26/2022] Open
Abstract
Introduction Cell stretch is a method which can rapidly apply mechanical force through cell-matrix and cell-cell adhesions and can be utilized to better understand underlying biophysical questions related to intracellular force transmission and mechanotransduction. Methods 3D printable stretching devices suitable for live-cell fluorescent imaging were designed using finite element modeling and validated experimentally. These devices were then used along with FRET based nesprin-2G force sensitive biosensors as well as live cell fluorescent staining to understand how the nucleus responds to externally applied mechanical force in cells with both intact LINC (linker of nucleoskeleton and cytoskeleton) complex and cells with the LINC complex disrupted using expression of dominant negative KASH protein. Results The devices were shown to provide a larger strain ranges (300% uniaxial and 60% biaxial) than currently available commercial or academic designs we are aware of. Under uniaxial deformation, the deformation of the nucleus of NIH 3T3 cells per unit of imposed cell strain was shown to be approximately 50% higher in control cells compared to cells with a disrupted LINC complex. Under biaxial deformation, MDCK II cells showed permanent changes in the nuclear morphology as well as actin organization upon unloading, indicating that failure, plastic deformation, or remodeling of the cytoskeleton is occurring in response to the applied stretch. Conclusion Development and open distribution of low-cost, 3D-printable uniaxial and biaxial cell stretching devices compatible with live-cell fluorescent imaging allows a wider range of researchers to investigate mechanical influences on biological questions with only a minimal investment of resources.
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Affiliation(s)
- Carl R Mayer
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284 USA
| | - Paul T Arsenovic
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284 USA
| | - Kranthidhar Bathula
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284 USA
| | - Kevin B Denis
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284 USA
| | - Daniel E Conway
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284 USA
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Mohan A, Schlue KT, Kniffin AF, Mayer CR, Duke AA, Narayanan V, Arsenovic PT, Bathula K, Danielsson BE, Dumbali SP, Maruthamuthu V, Conway DE. Spatial Proliferation of Epithelial Cells Is Regulated by E-Cadherin Force. Biophys J 2018; 115:853-864. [PMID: 30131170 DOI: 10.1016/j.bpj.2018.07.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 06/24/2018] [Accepted: 07/23/2018] [Indexed: 10/28/2022] Open
Abstract
Cell proliferation and contact inhibition play a major role in maintaining epithelial cell homeostasis. Prior experiments have shown that externally applied forces, such as stretch, result in increased proliferation in an E-cadherin force-dependent manner. In this study, the spatial regulation of cell proliferation in large epithelial colonies was examined. Surprisingly, cells at the center of the colony still had increased proliferation as compared to cells in confluent monolayers. E-cadherin forces were found to be elevated for both cells at the edge and center of these larger colonies when compared to confluent monolayers. To determine if high levels of E-cadherin force were necessary to induce proliferation at the center of the colony, a lower-force mutant of E-cadherin was developed. Cells with lower E-cadherin force had significantly reduced proliferation for cells at the center of the colony but minimal differences for cells at the edges of the colony. Similarly, increasing substrate stiffness was found to increase E-cadherin force and increase the proliferation rate across the colony. Taken together, these results show that forces through cell-cell junctions regulate proliferation across large groups of epithelial cells. In addition, an important finding of this study is that junction forces are dynamic and modulate cellular function even in the absence of externally applied loads.
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Affiliation(s)
- Abhinav Mohan
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Kyle T Schlue
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Alex F Kniffin
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Carl R Mayer
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Ashley A Duke
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Vani Narayanan
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Paul T Arsenovic
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Kranthidhar Bathula
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Brooke E Danielsson
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Sandeep P Dumbali
- Department of Mechanical & Aerospace Engineering, Old Dominion University, Norfolk, Virginia
| | - Venkat Maruthamuthu
- Department of Mechanical & Aerospace Engineering, Old Dominion University, Norfolk, Virginia
| | - Daniel E Conway
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia.
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5
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Baddam SR, Arsenovic PT, Narayanan V, Duggan NR, Mayer CR, Newman ST, Abutaleb DA, Mohan A, Kowalczyk AP, Conway DE. The Desmosomal Cadherin Desmoglein-2 Experiences Mechanical Tension as Demonstrated by a FRET-Based Tension Biosensor Expressed in Living Cells. Cells 2018; 7:cells7070066. [PMID: 29949915 PMCID: PMC6070948 DOI: 10.3390/cells7070066] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Revised: 06/21/2018] [Accepted: 06/22/2018] [Indexed: 11/16/2022] Open
Abstract
Cell-cell junctions are critical structures in a number of tissues for mechanically coupling cells together, cell-to-cell signaling, and establishing a barrier. In many tissues, desmosomes are an important component of cell-cell junctions. Loss or impairment of desmosomes presents with clinical phenotypes in the heart and skin as cardiac arrhythmias and skin blistering, respectively. Because heart and skin are tissues that are subject to large mechanical stresses, we hypothesized that desmosomes, similar to adherens junctions, would also experience significant tensile loading. To directly measure mechanical forces across desmosomes, we developed and validated a desmoglein-2 (DSG-2) force sensor, using the existing TSmod Förster resonance energy transfer (FRET) force biosensor. When expressed in human cardiomyocytes, the force sensor reported high tensile loading of DSG-2 during contraction. Additionally, when expressed in Madin-Darby canine kidney (MDCK) epithelial or epidermal (A431) monolayers, the sensor also reported tensile loading. Finally, we observed higher DSG-2 forces in 3D MDCK acini when compared to 2D monolayers. Taken together, our results show that desmosomes experience low levels of mechanical tension in resting cells, with significantly higher forces during active loading.
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Affiliation(s)
- Sindora R Baddam
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
| | - Paul T Arsenovic
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
| | - Vani Narayanan
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
| | - Nicole R Duggan
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
| | - Carl R Mayer
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
| | - Shaston T Newman
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
| | - Dahlia A Abutaleb
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
| | - Abhinav Mohan
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
| | | | - Daniel E Conway
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
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6
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Conway DE, Coon BG, Budatha M, Arsenovic PT, Orsenigo F, Wessel F, Zhang J, Zhuang Z, Dejana E, Vestweber D, Schwartz MA. VE-Cadherin Phosphorylation Regulates Endothelial Fluid Shear Stress Responses through the Polarity Protein LGN. Curr Biol 2017; 27:2219-2225.e5. [PMID: 28712573 DOI: 10.1016/j.cub.2017.06.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 04/28/2017] [Accepted: 06/08/2017] [Indexed: 11/18/2022]
Abstract
Fluid shear stress due to blood flow on the vascular endothelium regulates blood vessel development, remodeling, physiology, and pathology [1, 2]. A complex consisting of PECAM-1, VE-cadherin, and vascular endothelial growth factor receptors (VEGFRs) that resides at endothelial cell-cell junctions transduces signals important for flow-dependent vasodilation, blood vessel remodeling, and atherosclerosis. PECAM-1 transduces forces to activate src family kinases (SFKs), which phosphorylate and transactivate VEGFRs [3-5]. By contrast, VE-cadherin functions as an adaptor that interacts with VEGFRs through their respective cytoplasmic domains and promotes VEGFR activation in flow [6]. Indeed, shear stress triggers rapid increases in force across PECAM-1 but decreases the force across VE-cadherin, in close association with downstream signaling [5]. Interestingly, VE-cadherin cytoplasmic tyrosine Y658 can be phosphorylated by SFKs [7], which is maximally induced by low shear stress in vitro and in vivo [8]. These considerations prompted us to address the involvement of VE-cadherin cytoplasmic tyrosines in flow sensing. We found that phosphorylation of a small pool of VE-cadherin on Y658 is essential for flow sensing through the junctional complex. Y658 phosphorylation induces dissociation of p120ctn, which allows binding of the polarity protein LGN. LGN is then required for multiple flow responses in vitro and in vivo, including activation of inflammatory signaling at regions of disturbed flow, and flow-dependent vascular remodeling. Thus, endothelial flow mechanotransduction through the junctional complex is mediated by a specific pool of VE-cadherin that is phosphorylated on Y658 and bound to LGN.
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Affiliation(s)
- Daniel E Conway
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Brian G Coon
- Department of Medicine (Cardiology), Yale University School of Medicine, New Haven, CT 06511, USA; Yale Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06511, USA
| | - Madhusudhan Budatha
- Department of Medicine (Cardiology), Yale University School of Medicine, New Haven, CT 06511, USA; Yale Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06511, USA
| | - Paul T Arsenovic
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Fabrizio Orsenigo
- FIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milan, Italy
| | - Florian Wessel
- Max Planck Institute for Molecular Biomedicine, 48149 Münster, Germany
| | - Jiasheng Zhang
- Department of Medicine (Cardiology), Yale University School of Medicine, New Haven, CT 06511, USA
| | - Zhenwu Zhuang
- Department of Medicine (Cardiology), Yale University School of Medicine, New Haven, CT 06511, USA
| | - Elisabetta Dejana
- FIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milan, Italy; Department of Biotechnological and Biomolecular Sciences, School of Sciences, University of Milan, Via Celoria, 26, 20133 Milan, Italy
| | - Dietmar Vestweber
- Max Planck Institute for Molecular Biomedicine, 48149 Münster, Germany
| | - Martin A Schwartz
- Department of Medicine (Cardiology), Yale University School of Medicine, New Haven, CT 06511, USA; Yale Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT 06511, USA; Department of Cell Biology, Yale University, New Haven, CT 06510, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06510, USA.
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7
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Arsenovic PT, Bathula K, Conway DE. A Protocol for Using Förster Resonance Energy Transfer (FRET)-force Biosensors to Measure Mechanical Forces across the Nuclear LINC Complex. J Vis Exp 2017. [PMID: 28448008 DOI: 10.3791/54902] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The LINC complex has been hypothesized to be the critical structure that mediates the transfer of mechanical forces from the cytoskeleton to the nucleus. Nesprin-2G is a key component of the LINC complex that connects the actin cytoskeleton to membrane proteins (SUN domain proteins) in the perinuclear space. These membrane proteins connect to lamins inside the nucleus. Recently, a Förster Resonance Energy Transfer (FRET)-force probe was cloned into mini-Nesprin-2G (Nesprin-TS (tension sensor)) and used to measure tension across Nesprin-2G in live NIH3T3 fibroblasts. This paper describes the process of using Nesprin-TS to measure LINC complex forces in NIH3T3 fibroblasts. To extract FRET information from Nesprin-TS, an outline of how to spectrally unmix raw spectral images into acceptor and donor fluorescent channels is also presented. Using open-source software (ImageJ), images are pre-processed and transformed into ratiometric images. Finally, FRET data of Nesprin-TS is presented, along with strategies for how to compare data across different experimental groups.
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Affiliation(s)
- Paul T Arsenovic
- Department of Biomedical Engineering, Virginia Commonwealth University;
| | | | - Daniel E Conway
- Department of Biomedical Engineering, Virginia Commonwealth University
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8
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Arsenovic PT, Ramachandran I, Bathula K, Zhu R, Narang JD, Noll NA, Lemmon CA, Gundersen GG, Conway DE. Nesprin-2G, a Component of the Nuclear LINC Complex, Is Subject to Myosin-Dependent Tension. Biophys J 2016; 110:34-43. [PMID: 26745407 DOI: 10.1016/j.bpj.2015.11.014] [Citation(s) in RCA: 137] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 11/11/2015] [Accepted: 11/12/2015] [Indexed: 01/14/2023] Open
Abstract
The nucleus of a cell has long been considered to be subject to mechanical force. Despite the observation that mechanical forces affect nuclear geometry and movement, how forces are applied onto the nucleus is not well understood. The nuclear LINC (linker of nucleoskeleton and cytoskeleton) complex has been hypothesized to be the critical structure that mediates the transfer of mechanical forces from the cytoskeleton onto the nucleus. Previously used techniques for studying nuclear forces have been unable to resolve forces across individual proteins, making it difficult to clearly establish if the LINC complex experiences mechanical load. To directly measure forces across the LINC complex, we generated a fluorescence resonance energy transfer-based tension biosensor for nesprin-2G, a key structural protein in the LINC complex, which physically links this complex to the actin cytoskeleton. Using this sensor we show that nesprin-2G is subject to mechanical tension in adherent fibroblasts, with highest levels of force on the apical and equatorial planes of the nucleus. We also show that the forces across nesprin-2G are dependent on actomyosin contractility and cell elongation. Additionally, nesprin-2G tension is reduced in fibroblasts from Hutchinson-Gilford progeria syndrome patients. This report provides the first, to our knowledge, direct evidence that nesprin-2G, and by extension the LINC complex, is subject to mechanical force. We also present evidence that nesprin-2G localization to the nuclear membrane is altered under high-force conditions. Because forces across the LINC complex are altered by a variety of different conditions, mechanical forces across the LINC complex, as well as the nucleus in general, may represent an important mechanism for mediating mechanotransduction.
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Affiliation(s)
- Paul T Arsenovic
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Iswarya Ramachandran
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Kranthidhar Bathula
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Ruijun Zhu
- Department of Pathology and Cell Biology, Columbia University, New York, New York
| | - Jiten D Narang
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Natalie A Noll
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Christopher A Lemmon
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Gregg G Gundersen
- Department of Pathology and Cell Biology, Columbia University, New York, New York
| | - Daniel E Conway
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia.
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9
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Arsenovic PT, Maldonado AT, Colleluori VD, Bloss TA. Depletion of the C. elegans NAC engages the unfolded protein response, resulting in increased chaperone expression and apoptosis. PLoS One 2012; 7:e44038. [PMID: 22957041 PMCID: PMC3434205 DOI: 10.1371/journal.pone.0044038] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Accepted: 08/01/2012] [Indexed: 01/10/2023] Open
Abstract
The nascent polypeptide-associated complex (NAC) is a highly conserved heterodimer important for metazoan development, but its molecular function is not well understood. Recent evidence suggests the NAC is a component of the cytosolic chaperone network that interacts with ribosomal complexes and their emerging nascent peptides, such that the loss of the NAC in chaperone-depleted cells results in an increase in misfolded protein stress. We tested whether the NAC functions similarly in Caeonorhabditis (C.) elegans and found that its homologous NAC subunits, i.e. ICD-1 and -2, have chaperone-like characteristics. Loss of the NAC appears to induce misfolded protein stress in the ER triggering the unfolded protein response (UPR). Depletion of the NAC altered the response to heat stress, and led to an up-regulation of hsp-4, a homologue of the human chaperone and ER stress sensor GRP78/BiP. Worms lacking both ICD-1 and the UPR transcription factor XBP-1 generated a higher proportion of defective embryos, showed increased embryonic apoptosis and had a diminished survival rate relative to ICD-1-depleted animals with an intact UPR. Up-regulation of hsp-4 in NAC-depleted animals was specific to certain regions of the embryo; in embryos lacking ICD-1, the posterior region of the embryo showed strong up-regulation of hsp-4, while the anterior region did not. Furthermore, loss of ICD-1 produced prominent lysosomes in the gut region of adults and embryos putatively containing lipofuscins, lipid/protein aggregates associated with cellular aging. These results are the first set of evidence consistent with a role for C. elegans NAC in protein folding and localization during translation. Further, these findings confirm C. elegans as a valuable model for studying organismal and cell-type specific responses to misfolded protein stress.
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Affiliation(s)
| | | | | | - Tim A. Bloss
- Department of Biology, James Madison University, Harrisonburg, Virginia, United States of America
- * E-mail:
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