1
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Bougaran P, Bautch VL. Life at the crossroads: the nuclear LINC complex and vascular mechanotransduction. Front Physiol 2024; 15:1411995. [PMID: 38831796 PMCID: PMC11144885 DOI: 10.3389/fphys.2024.1411995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Accepted: 05/02/2024] [Indexed: 06/05/2024] Open
Abstract
Vascular endothelial cells line the inner surface of all blood vessels, where they are exposed to polarized mechanical forces throughout their lifespan. Both basal substrate interactions and apical blood flow-induced shear stress regulate blood vessel development, remodeling, and maintenance of vascular homeostasis. Disruption of these interactions leads to dysfunction and vascular pathologies, although how forces are sensed and integrated to affect endothelial cell behaviors is incompletely understood. Recently the endothelial cell nucleus has emerged as a prominent force-transducing organelle that participates in vascular mechanotransduction, via communication to and from cell-cell and cell-matrix junctions. The LINC complex, composed of SUN and nesprin proteins, spans the nuclear membranes and connects the nuclear lamina, the nuclear envelope, and the cytoskeleton. Here we review LINC complex involvement in endothelial cell mechanotransduction, describe unique and overlapping functions of each LINC complex component, and consider emerging evidence that two major SUN proteins, SUN1 and SUN2, orchestrate a complex interplay that extends outward to cell-cell and cell-matrix junctions and inward to interactions within the nucleus and chromatin. We discuss these findings in relation to vascular pathologies such as Hutchinson-Gilford progeria syndrome, a premature aging disorder with cardiovascular impairment. More knowledge of LINC complex regulation and function will help to understand how the nucleus participates in endothelial cell force sensing and how dysfunction leads to cardiovascular disease.
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Affiliation(s)
- Pauline Bougaran
- Department of Biology, The University of North Carolina, Chapel Hill, NC, United States
| | - Victoria L. Bautch
- Department of Biology, The University of North Carolina, Chapel Hill, NC, United States
- McAllister Heart Institute, The University of North Carolina, Chapel Hill, NC, United States
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2
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Zi-Yi Z, Qin Q, Fei Z, Cun-Yu C, Lin T. Nesprin proteins: bridging nuclear envelope dynamics to muscular dysfunction. Cell Commun Signal 2024; 22:208. [PMID: 38566066 PMCID: PMC10986154 DOI: 10.1186/s12964-024-01593-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Accepted: 03/24/2024] [Indexed: 04/04/2024] Open
Abstract
This review presents a comprehensive exploration of the pivotal role played by the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, with a particular focus on Nesprin proteins, in cellular mechanics and the pathogenesis of muscular diseases. Distinguishing itself from prior works, the analysis delves deeply into the intricate interplay of the LINC complex, emphasizing its indispensable contribution to maintaining cellular structural integrity, especially in mechanically sensitive tissues such as cardiac and striated muscles. Additionally, the significant association between mutations in Nesprin proteins and the onset of Dilated Cardiomyopathy (DCM) and Emery-Dreifuss Muscular Dystrophy (EDMD) is highlighted, underscoring their pivotal role in disease pathogenesis. Through a comprehensive examination of DCM and EDMD cases, the review elucidates the disruptions in the LINC complex, nuclear morphology alterations, and muscular developmental disorders, thus emphasizing the essential function of an intact LINC complex in preserving muscle physiological functions. Moreover, the review provides novel insights into the implications of Nesprin mutations for cellular dynamics in the pathogenesis of muscular diseases, particularly in maintaining cardiac structural and functional integrity. Furthermore, advanced therapeutic strategies, including rectifying Nesprin gene mutations, controlling Nesprin protein expression, enhancing LINC complex functionality, and augmenting cardiac muscle cell function are proposed. By shedding light on the intricate molecular mechanisms underlying nuclear-cytoskeletal interactions, the review lays the groundwork for future research and therapeutic interventions aimed at addressing genetic muscle disorders.
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Affiliation(s)
- Zhou Zi-Yi
- Department of Cardiology, Yichang Central People's Hospital, Yichang, 443003, Hubei, People's Republic of China
- School of Basic Medicine, China Three Gorges University, Yichang, 443000, Hubei, People's Republic of China
| | - Qin Qin
- Department of Cardiology, Yichang Central People's Hospital, Yichang, 443003, Hubei, People's Republic of China
- School of Basic Medicine, China Three Gorges University, Yichang, 443000, Hubei, People's Republic of China
| | - Zhou Fei
- Department of Cardiology, Yichang Central People's Hospital, Yichang, 443003, Hubei, People's Republic of China
| | - Cao Cun-Yu
- School of Basic Medicine, China Three Gorges University, Yichang, 443000, Hubei, People's Republic of China
- College of Basic Medical Sciences, Hubei Key Laboratory of Tumor Microencironment and immunotherapy, China Three Gorges University, Yichang, 443000, Hubei, People's Republic of China
| | - Teng Lin
- Department of Cardiology, Yichang Central People's Hospital, Yichang, 443003, Hubei, People's Republic of China.
- King's College London British Heart Foundation Centre of Research Excellence, School of Cardiovascular and Metabolic Medicine & Sciences, London, SE5 9NU, UK.
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3
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Gurusaran M, Erlandsen BS, Davies OR. The crystal structure of SUN1-KASH6 reveals an asymmetric LINC complex architecture compatible with nuclear membrane insertion. Commun Biol 2024; 7:138. [PMID: 38291267 PMCID: PMC10827754 DOI: 10.1038/s42003-024-05794-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 01/08/2024] [Indexed: 02/01/2024] Open
Abstract
The LINC complex transmits cytoskeletal forces into the nucleus to control the structure and movement of nuclear contents. It is formed of nuclear SUN and cytoplasmic KASH proteins, which interact within the nuclear lumen, immediately below the outer nuclear membrane. However, the symmetrical location of KASH molecules within SUN-KASH complexes in previous crystal structures has been difficult to reconcile with the steric requirements for insertion of their immediately upstream transmembrane helices into the outer nuclear membrane. Here, we report the crystal structure of the SUN-KASH complex between SUN1 and JAW1/LRMP (KASH6) in an asymmetric 9:6 configuration. This intertwined assembly involves two distinct KASH conformations such that all six KASH molecules emerge on the same molecular surface. Hence, they are ideally positioned for insertion of upstream sequences into the outer nuclear membrane. Thus, we report a SUN-KASH complex architecture that appears to be directly compatible with its biological role.
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Affiliation(s)
- Manickam Gurusaran
- Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Michael Swann Building, Max Born Crescent, Edinburgh, EH9 3BF, UK
| | - Benedikte S Erlandsen
- Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Michael Swann Building, Max Born Crescent, Edinburgh, EH9 3BF, UK
| | - Owen R Davies
- Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Michael Swann Building, Max Born Crescent, Edinburgh, EH9 3BF, UK.
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4
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Huang Y, Peng Q, Tian X, Chen C, Zhu X, Huang C, Huo Z, Liu Y, Yang C, Liu C, Zhang P. Nuclear membrane protein SUN2 promotes replication of flaviviruses through modulating cytoskeleton reorganization mediated by NS1. Nat Commun 2024; 15:296. [PMID: 38177122 PMCID: PMC10766649 DOI: 10.1038/s41467-023-44580-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 12/18/2023] [Indexed: 01/06/2024] Open
Abstract
Cytoskeleton is extensively recruited by flaviviruses for their infection. In this study, we uncovered an essential role of a nuclear membrane protein, SAD1/UNC84 domain protein 2 (SUN2) linking cytoskeleton and nucleoskeleton in the flavivirus replication. CRISPR/Cas9-mediated knockout of SUN2, but not SUN1, significantly reduces the replication of Zika virus (ZIKV), dengue virus (DENV), and Japanese encephalitis virus (JEV). In contrast, SUN2 does not affect the infection of non-flaviviridae RNA viruses. All three regions of SUN2 are required for its proviral effect. Mechanistically, SUN2 facilitates rearrangement of cytoskeleton and formation of replication organelles induced by viral infection, and hence promotes viral RNA synthesis. SUN2 is required for the interaction between cytoskeleton actin and ZIKV nonstructural protein 1 (NS1). Expression of dominant negative Nesprin-1 and Nesprin-2, which connect SUN2 to cytoskeleton proteins, alleviates the interaction between actin and NS1 and reduces viral replication levels. In a neonatal mouse infection model, SUN2 knockout dramatically alleviates the in vivo ZIKV replication and development of neuropathology. This work elucidates that recruitment of cytoskeleton proteins by flavivirus is coordinated by nuclear membrane proteins SUN2 and Nesprins, providing evidence for a link between nuclear membrane proteins and flavivirus infection.
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Affiliation(s)
- Yanxia Huang
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China
- Department of Immunology and Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
- Department of Neurosurgery, First Affiliated Hospital of Sun Yat-sen University, Guangzhou, 510080, China
| | - Qinyu Peng
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China
- Department of Immunology and Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Xu Tian
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China
- Department of Immunology and Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Cancan Chen
- Department of Pathology, First Affiliated Hospital of Sun Yat-sen University, Guangzhou, 510080, China
| | - Xuanfeng Zhu
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China
- Department of Immunology and Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Changbai Huang
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China
- Department of Immunology and Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Zhiting Huo
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China
- Department of Immunology and Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Yang Liu
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Chao Yang
- Department of Neurosurgery, First Affiliated Hospital of Sun Yat-sen University, Guangzhou, 510080, China.
- Department of Neurosurgery, Guangxi Hospital Division of The First Affiliated Hospital, Sun Yat-sen University, Guangxi, China.
| | - Chao Liu
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China.
- Department of Immunology and Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China.
| | - Ping Zhang
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China.
- Department of Immunology and Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China.
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5
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Yerima G, Domkam N, Ornowski J, Jahed Z, Mofrad MRK. Force transmission and SUN-KASH higher-order assembly in the LINC complex models. Biophys J 2023; 122:4582-4597. [PMID: 37924205 PMCID: PMC10719071 DOI: 10.1016/j.bpj.2023.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 09/14/2023] [Accepted: 11/01/2023] [Indexed: 11/06/2023] Open
Abstract
The linkers of the nucleoskeleton and cytoskeleton (LINC) complex comprises Sad-1 and UNC-84 (SUN) and Klarsicht, ANC-1, SYNE homology (KASH) domain proteins, whose conserved interactions provide a physical coupling between the cytoskeleton and the nucleoskeleton, thereby mediating the transfer of physical forces across the nuclear envelope. The LINC complex can perform distinct cellular functions by pairing various KASH domain proteins with the same SUN domain protein. Recent studies have suggested a higher-order assembly of SUN and KASH instead of a more widely accepted linear trimer model for the LINC complex. In the present study, we use molecular dynamics simulations to investigate the mechanism of force transfer across the two proposed models of LINC complex assembly, namely the 3:3 linear trimer model and the 6:6 higher-order model. Employing steered molecular dynamics simulations with various structures using forces at different rates and directions, we examine the structural stability of the two models under various biologically relevant conditions. Our results suggest that both models can withstand and transfer significant levels of force while retaining their structural integrity. However, the force response of various SUN/KASH assemblies depend on the force direction and pulling rates. Slower pulling rates result in higher mean square fluctuations of the 3:3 assembly compared to the fast pulling. Interestingly, the 6:6 assembly tends to provide an additional range of motion flexibility and might be more advantageous to the structural rigidity and pliability of the nuclear envelope. These findings offer insights into how the SUN and KASH proteins maintain the structural integrity of the nuclear membrane.
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Affiliation(s)
- Ghafar Yerima
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California
| | - Nya Domkam
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California
| | - Jessica Ornowski
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California
| | - Zeinab Jahed
- Department of Nanoengineering, Jacobs School of Engineering, University of California, San Diego, California.
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California; Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Lab, Berkeley, California.
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6
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McGillivary RM, Starr DA, Luxton GWG. Building and breaking mechanical bridges between the nucleus and cytoskeleton: Regulation of LINC complex assembly and disassembly. Curr Opin Cell Biol 2023; 85:102260. [PMID: 37857179 PMCID: PMC10859145 DOI: 10.1016/j.ceb.2023.102260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 09/15/2023] [Accepted: 09/20/2023] [Indexed: 10/21/2023]
Abstract
The nucleus is physically coupled to the cytoskeleton through LINC complexes, macromolecular bridges composed of SUN and KASH proteins that span the nuclear envelope. LINC complexes are involved in a wide variety of critical cellular processes. For these processes to occur, cells regulate the composition, assembly, and disassembly of LINC complexes. Here we discuss recent studies on the regulation of the SUN-KASH interaction that forms the core of the LINC complex. These new findings encompass the stages of LINC complex assembly, from the formation of SUN-KASH heterooligomers to higher-order assemblies of LINC complexes. There is also new work on how components of the LINC complex are selectively dismantled, particularly by proteasomal degradation. It is becoming increasingly clear that LINC complexes are subject to multiple layers of regulation.
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Affiliation(s)
| | - Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, USA.
| | - G W Gant Luxton
- Department of Molecular and Cellular Biology, University of California, Davis, USA.
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7
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Alexander LT, Durairaj J, Kryshtafovych A, Abriata LA, Bayo Y, Bhabha G, Breyton C, Caulton SG, Chen J, Degroux S, Ekiert DC, Erlandsen BS, Freddolino PL, Gilzer D, Greening C, Grimes JM, Grinter R, Gurusaran M, Hartmann MD, Hitchman CJ, Keown JR, Kropp A, Kursula P, Lovering AL, Lemaitre B, Lia A, Liu S, Logotheti M, Lu S, Markússon S, Miller MD, Minasov G, Niemann HH, Opazo F, Phillips GN, Davies OR, Rommelaere S, Rosas‐Lemus M, Roversi P, Satchell K, Smith N, Wilson MA, Wu K, Xia X, Xiao H, Zhang W, Zhou ZH, Fidelis K, Topf M, Moult J, Schwede T. Protein target highlights in CASP15: Analysis of models by structure providers. Proteins 2023; 91:1571-1599. [PMID: 37493353 PMCID: PMC10792529 DOI: 10.1002/prot.26545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 06/15/2023] [Indexed: 07/27/2023]
Abstract
We present an in-depth analysis of selected CASP15 targets, focusing on their biological and functional significance. The authors of the structures identify and discuss key protein features and evaluate how effectively these aspects were captured in the submitted predictions. While the overall ability to predict three-dimensional protein structures continues to impress, reproducing uncommon features not previously observed in experimental structures is still a challenge. Furthermore, instances with conformational flexibility and large multimeric complexes highlight the need for novel scoring strategies to better emphasize biologically relevant structural regions. Looking ahead, closer integration of computational and experimental techniques will play a key role in determining the next challenges to be unraveled in the field of structural molecular biology.
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Affiliation(s)
- Leila T. Alexander
- BiozentrumUniversity of BaselBaselSwitzerland
- Computational Structural BiologySIB Swiss Institute of BioinformaticsBaselSwitzerland
| | - Janani Durairaj
- BiozentrumUniversity of BaselBaselSwitzerland
- Computational Structural BiologySIB Swiss Institute of BioinformaticsBaselSwitzerland
| | | | - Luciano A. Abriata
- School of Life SciencesÉcole Polytechnique Fédérale de LausanneLausanneSwitzerland
| | - Yusupha Bayo
- Department of BiosciencesUniversity of MilanoMilanItaly
- IBBA‐CNR Unit of MilanoInstitute of Agricultural Biology and BiotechnologyMilanItaly
| | - Gira Bhabha
- Department of Cell BiologyNew York University School of MedicineNew YorkNew YorkUSA
| | | | | | - James Chen
- Department of Cell BiologyNew York University School of MedicineNew YorkNew YorkUSA
| | | | - Damian C. Ekiert
- Department of Cell BiologyNew York University School of MedicineNew YorkNew YorkUSA
- Department of MicrobiologyNew York University School of MedicineNew YorkNew YorkUSA
| | - Benedikte S. Erlandsen
- Wellcome Centre for Cell BiologyInstitute of Cell Biology, University of EdinburghEdinburghUK
| | - Peter L. Freddolino
- Department of Biological Chemistry, Computational Medicine and BioinformaticsUniversity of MichiganAnn ArborMichiganUSA
| | - Dominic Gilzer
- Department of ChemistryBielefeld UniversityBielefeldGermany
| | - Chris Greening
- Department of Microbiology, Biomedicine Discovery InstituteMonash UniversityClaytonVictoriaAustralia
- Securing Antarctica's Environmental FutureMonash UniversityClaytonVictoriaAustralia
- Centre to Impact AMRMonash UniversityClaytonVictoriaAustralia
- ARC Research Hub for Carbon Utilisation and RecyclingMonash UniversityClaytonVictoriaAustralia
| | - Jonathan M. Grimes
- Division of Structural Biology, Wellcome Centre for Human GeneticsUniversity of OxfordOxfordUK
| | - Rhys Grinter
- Department of Microbiology, Biomedicine Discovery InstituteMonash UniversityClaytonVictoriaAustralia
- Centre for Electron Microscopy of Membrane ProteinsMonash Institute of Pharmaceutical SciencesParkvilleVictoriaAustralia
| | - Manickam Gurusaran
- Wellcome Centre for Cell BiologyInstitute of Cell Biology, University of EdinburghEdinburghUK
| | - Marcus D. Hartmann
- Max Planck Institute for BiologyTübingenGermany
- Interfaculty Institute of Biochemistry, University of TübingenTübingenGermany
| | - Charlie J. Hitchman
- Department of Molecular and Cell Biology, Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLeicesterUK
| | - Jeremy R. Keown
- Division of Structural Biology, Wellcome Centre for Human GeneticsUniversity of OxfordOxfordUK
| | - Ashleigh Kropp
- Department of Microbiology, Biomedicine Discovery InstituteMonash UniversityClaytonVictoriaAustralia
| | - Petri Kursula
- Department of BiomedicineUniversity of BergenBergenNorway
- Faculty of Biochemistry and Molecular Medicine & Biocenter OuluUniversity of OuluOuluFinland
| | | | - Bruno Lemaitre
- School of Life SciencesÉcole Polytechnique Fédérale de LausanneLausanneSwitzerland
| | - Andrea Lia
- Department of Molecular and Cell Biology, Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLeicesterUK
- ISPA‐CNR Unit of LecceInstitute of Sciences of Food ProductionLecceItaly
| | - Shiheng Liu
- Department of Microbiology, Immunology, and Molecular GeneticsUniversity of CaliforniaLos AngelesCaliforniaUSA
- California NanoSystems InstituteUniversity of CaliforniaLos AngelesCaliforniaUSA
| | - Maria Logotheti
- Max Planck Institute for BiologyTübingenGermany
- Interfaculty Institute of Biochemistry, University of TübingenTübingenGermany
- Present address:
Institute of BiochemistryUniversity of GreifswaldGreifswaldGermany
| | - Shuze Lu
- Lanzhou University School of Life SciencesLanzhouChina
| | | | | | - George Minasov
- Department of Microbiology‐ImmunologyNorthwestern Feinberg School of MedicineChicagoIllinoisUSA
| | | | - Felipe Opazo
- NanoTag Biotechnologies GmbHGöttingenGermany
- Institute of Neuro‐ and Sensory PhysiologyUniversity of Göttingen Medical CenterGöttingenGermany
- Center for Biostructural Imaging of Neurodegeneration (BIN)University of Göttingen Medical CenterGöttingenGermany
| | - George N. Phillips
- Department of BiosciencesRice UniversityHoustonTexasUSA
- Department of ChemistryRice UniversityHoustonTexasUSA
| | - Owen R. Davies
- Wellcome Centre for Cell BiologyInstitute of Cell Biology, University of EdinburghEdinburghUK
| | - Samuel Rommelaere
- School of Life SciencesÉcole Polytechnique Fédérale de LausanneLausanneSwitzerland
| | - Monica Rosas‐Lemus
- Department of Microbiology‐ImmunologyNorthwestern Feinberg School of MedicineChicagoIllinoisUSA
- Present address:
Department of Molecular Genetics and MicrobiologyUniversity of New MexicoAlbuquerqueNew MexicoUSA
| | - Pietro Roversi
- IBBA‐CNR Unit of MilanoInstitute of Agricultural Biology and BiotechnologyMilanItaly
- Department of Molecular and Cell Biology, Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLeicesterUK
| | - Karla Satchell
- Department of Microbiology‐ImmunologyNorthwestern Feinberg School of MedicineChicagoIllinoisUSA
| | - Nathan Smith
- Department of Biochemistry and the Redox Biology CenterUniversity of NebraskaLincolnNebraskaUSA
| | - Mark A. Wilson
- Department of Biochemistry and the Redox Biology CenterUniversity of NebraskaLincolnNebraskaUSA
| | - Kuan‐Lin Wu
- Department of ChemistryRice UniversityHoustonTexasUSA
| | - Xian Xia
- Department of Microbiology, Immunology, and Molecular GeneticsUniversity of CaliforniaLos AngelesCaliforniaUSA
- California NanoSystems InstituteUniversity of CaliforniaLos AngelesCaliforniaUSA
| | - Han Xiao
- Department of BiosciencesRice UniversityHoustonTexasUSA
- Department of ChemistryRice UniversityHoustonTexasUSA
- Department of BioengineeringRice UniversityHoustonTexasUSA
| | - Wenhua Zhang
- Lanzhou University School of Life SciencesLanzhouChina
| | - Z. Hong Zhou
- Department of Microbiology, Immunology, and Molecular GeneticsUniversity of CaliforniaLos AngelesCaliforniaUSA
- California NanoSystems InstituteUniversity of CaliforniaLos AngelesCaliforniaUSA
| | | | - Maya Topf
- University Medical Center Hamburg‐Eppendorf (UKE)HamburgGermany
- Centre for Structural Systems BiologyLeibniz‐Institut für Virologie (LIV)HamburgGermany
| | - John Moult
- Department of Cell Biology and Molecular Genetics, Institute for Bioscience and Biotechnology ResearchUniversity of MarylandRockvilleMarylandUSA
| | - Torsten Schwede
- BiozentrumUniversity of BaselBaselSwitzerland
- Computational Structural BiologySIB Swiss Institute of BioinformaticsBaselSwitzerland
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8
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Lee GE, Byun J, Lee CJ, Cho YY. Molecular Mechanisms for the Regulation of Nuclear Membrane Integrity. Int J Mol Sci 2023; 24:15497. [PMID: 37895175 PMCID: PMC10607757 DOI: 10.3390/ijms242015497] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 10/19/2023] [Accepted: 10/22/2023] [Indexed: 10/29/2023] Open
Abstract
The nuclear membrane serves a critical role in protecting the contents of the nucleus and facilitating material and signal exchange between the nucleus and cytoplasm. While extensive research has been dedicated to topics such as nuclear membrane assembly and disassembly during cell division, as well as interactions between nuclear transmembrane proteins and both nucleoskeletal and cytoskeletal components, there has been comparatively less emphasis on exploring the regulation of nuclear morphology through nuclear membrane integrity. In particular, the role of type II integral proteins, which also function as transcription factors, within the nuclear membrane remains an area of research that is yet to be fully explored. The integrity of the nuclear membrane is pivotal not only during cell division but also in the regulation of gene expression and the communication between the nucleus and cytoplasm. Importantly, it plays a significant role in the development of various diseases. This review paper seeks to illuminate the biomolecules responsible for maintaining the integrity of the nuclear membrane. It will delve into the mechanisms that influence nuclear membrane integrity and provide insights into the role of type II membrane protein transcription factors in this context. Understanding these aspects is of utmost importance, as it can offer valuable insights into the intricate processes governing nuclear membrane integrity. Such insights have broad-reaching implications for cellular function and our understanding of disease pathogenesis.
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Affiliation(s)
- Ga-Eun Lee
- BK21-4th, and BRL, College of Pharmacy, The Catholic University of Korea, 43, Jibong-ro, Wonmi-gu, Bucheon-si 14662, Gyeonggi-do, Republic of Korea; (G.-E.L.); (J.B.)
| | - Jiin Byun
- BK21-4th, and BRL, College of Pharmacy, The Catholic University of Korea, 43, Jibong-ro, Wonmi-gu, Bucheon-si 14662, Gyeonggi-do, Republic of Korea; (G.-E.L.); (J.B.)
| | - Cheol-Jung Lee
- Research Center for Materials Analysis, Korea Basic Science Institute, 169-148, Gwahak-ro, Yuseong-gu, Daejeon 34133, Chungcheongnam-do, Republic of Korea
| | - Yong-Yeon Cho
- BK21-4th, and BRL, College of Pharmacy, The Catholic University of Korea, 43, Jibong-ro, Wonmi-gu, Bucheon-si 14662, Gyeonggi-do, Republic of Korea; (G.-E.L.); (J.B.)
- RCD Control and Material Research Institute, The Catholic University of Korea, 43, Jibong-ro, Wonmi-gu, Bucheon-si 14662, Gyeonggi-do, Republic of Korea
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9
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Jiao S, Li C, Guo F, Zhang J, Zhang H, Cao Z, Wang W, Bu W, Lin M, Lü J, Zhou Z. SUN1/2 controls macrophage polarization via modulating nuclear size and stiffness. Nat Commun 2023; 14:6416. [PMID: 37828059 PMCID: PMC10570371 DOI: 10.1038/s41467-023-42187-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Accepted: 10/03/2023] [Indexed: 10/14/2023] Open
Abstract
Alteration of the size and stiffness of the nucleus triggered by environmental cues are thought to be important for eukaryotic cell fate and function. However, it remains unclear how context-dependent nuclear remodeling occurs and reprograms gene expression. Here we identify the nuclear envelope proteins SUN1/2 as mechano-regulators of the nucleus during M1 polarization of the macrophage. Specifically, we show that LPS treatment decreases the protein levels of SUN1/2 in a CK2-βTrCP-dependent manner to shrink and soften the nucleus, therefore altering the chromatin accessibility for M1-associated gene expression. Notably, the transmembrane helix of SUN1/2 is solely required and sufficient for the nuclear mechano-remodeling. Consistently, SUN1/2 depletion in macrophages facilitates their phagocytosis, tissue infiltration, and proinflammatory cytokine production, thereby boosting the antitumor immunity in mice. Thus, our study demonstrates that, in response to inflammatory cues, SUN1/2 proteins act as mechano-regulators to remodel the nucleus and chromatin for M1 polarization of the macrophage.
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Affiliation(s)
- Shi Jiao
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, 200438, China.
| | - Chuanchuan Li
- CAS Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China
- Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, 417 E 68th St, New York, NY, 10065, USA
| | - Fenghua Guo
- Department of General Surgery, Hua'shan Hospital, Fudan University Shanghai Medical College, Shanghai, 200040, China
| | - Jinjin Zhang
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Hui Zhang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, 200438, China
| | - Zhifa Cao
- Department of Stomatology, Department of Medical Ultrasound, Shanghai Tenth People's Hospital, Department of Biochemistry and Molecular Biology, Tongji University School of Medicine, Shanghai, 200072, China
| | - Wenjia Wang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, 200438, China
| | - Wenbo Bu
- Department of Materials Science and State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai, 200433, China
| | - Mobin Lin
- Department of General Surgery, Yangpu Hospital, Tongji University School of Medicine, Shanghai, 200090, China.
| | - Junhong Lü
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201203, China.
- College of Pharmacy, Binzhou Medical University, Yantai, 264003, China.
| | - Zhaocai Zhou
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, 200438, China.
- Department of Stomatology, Department of Medical Ultrasound, Shanghai Tenth People's Hospital, Department of Biochemistry and Molecular Biology, Tongji University School of Medicine, Shanghai, 200072, China.
- Collaborative Innovation Center for Cancer Personalized Medicine, School of Public Health, Nanjing Medical University, Nanjing, 211166, China.
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10
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Sharma R, Hetzer MW. Disulfide bond in SUN2 regulates dynamic remodeling of LINC complexes at the nuclear envelope. Life Sci Alliance 2023; 6:e202302031. [PMID: 37188462 PMCID: PMC10193101 DOI: 10.26508/lsa.202302031] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 05/02/2023] [Accepted: 05/02/2023] [Indexed: 05/17/2023] Open
Abstract
The LINC complex tethers the cell nucleus to the cytoskeleton to regulate mechanical forces during cell migration, differentiation, and various diseases. The function of LINC complexes relies on the interaction between highly conserved SUN and KASH proteins that form higher-order assemblies capable of load bearing. These structural details have emerged from in vitro assembled LINC complexes; however, the principles of in vivo assembly remain obscure. Here, we report a conformation-specific SUN2 antibody as a tool to visualize LINC complex dynamics in situ. Using imaging, biochemical, and cellular methods, we find that conserved cysteines in SUN2 undergo KASH-dependent inter- and intra-molecular disulfide bond rearrangements. Disruption of the SUN2 terminal disulfide bond compromises SUN2 localization, turnover, LINC complex assembly in addition to cytoskeletal organization and cell migration. Moreover, using pharmacological and genetic perturbations, we identify components of the ER lumen as SUN2 cysteines redox state regulators. Overall, we provide evidence for SUN2 disulfide bond rearrangement as a physiologically relevant structural modification that regulates LINC complex functions.
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Affiliation(s)
- Rahul Sharma
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Martin W Hetzer
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, USA
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11
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Gurusaran M, Biemans JJ, Wood CW, Davies OR. Molecular insights into LINC complex architecture through the crystal structure of a luminal trimeric coiled-coil domain of SUN1. Front Cell Dev Biol 2023; 11:1144277. [PMID: 37416798 PMCID: PMC10320395 DOI: 10.3389/fcell.2023.1144277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Accepted: 06/09/2023] [Indexed: 07/08/2023] Open
Abstract
The LINC complex, consisting of interacting SUN and KASH proteins, mechanically couples nuclear contents to the cytoskeleton. In meiosis, the LINC complex transmits microtubule-generated forces to chromosome ends, driving the rapid chromosome movements that are necessary for synapsis and crossing over. In somatic cells, it defines nuclear shape and positioning, and has a number of specialised roles, including hearing. Here, we report the X-ray crystal structure of a coiled-coiled domain of SUN1's luminal region, providing an architectural foundation for how SUN1 traverses the nuclear lumen, from the inner nuclear membrane to its interaction with KASH proteins at the outer nuclear membrane. In combination with light and X-ray scattering, molecular dynamics and structure-directed modelling, we present a model of SUN1's entire luminal region. This model highlights inherent flexibility between structured domains, and raises the possibility that domain-swap interactions may establish a LINC complex network for the coordinated transmission of cytoskeletal forces.
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Affiliation(s)
- Manickam Gurusaran
- Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Jelle J. Biemans
- Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Christopher W. Wood
- Institute of Quantitative Biology, Biochemistry and Biotechnology, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Owen R. Davies
- Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh, Scotland, United Kingdom
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12
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Prüschenk S, Majer M, Schlossmann J. Novel Functional Features of cGMP Substrate Proteins IRAG1 and IRAG2. Int J Mol Sci 2023; 24:9837. [PMID: 37372987 DOI: 10.3390/ijms24129837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 06/01/2023] [Accepted: 06/05/2023] [Indexed: 06/29/2023] Open
Abstract
The inositol triphosphate-associated proteins IRAG1 and IRAG2 are cGMP kinase substrate proteins that regulate intracellular Ca2+. Previously, IRAG1 was discovered as a 125 kDa membrane protein at the endoplasmic reticulum, which is associated with the intracellular Ca2+ channel IP3R-I and the PKGIβ and inhibits IP3R-I upon PKGIβ-mediated phosphorylation. IRAG2 is a 75 kDa membrane protein homolog of IRAG1 and was recently also determined as a PKGI substrate. Several (patho-)physiological functions of IRAG1 and IRAG2 were meanwhile elucidated in a variety of human and murine tissues, e.g., of IRAG1 in various smooth muscles, heart, platelets, and other blood cells, of IRAG2 in the pancreas, heart, platelets, and taste cells. Hence, lack of IRAG1 or IRAG2 leads to diverse phenotypes in these organs, e.g., smooth muscle and platelet disorders or secretory deficiency, respectively. This review aims to highlight the recent research regarding these two regulatory proteins to envision their molecular and (patho-)physiological tasks and to unravel their functional interplay as possible (patho-)physiological counterparts.
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Affiliation(s)
- Sally Prüschenk
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Regensburg, 93040 Regensburg, Germany
| | - Michael Majer
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Regensburg, 93040 Regensburg, Germany
| | - Jens Schlossmann
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Regensburg, 93040 Regensburg, Germany
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13
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Vidak S, Serebryannyy LA, Pegoraro G, Misteli T. Activation of endoplasmic reticulum stress in premature aging via the inner nuclear membrane protein SUN2. Cell Rep 2023; 42:112534. [PMID: 37210724 DOI: 10.1016/j.celrep.2023.112534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 03/08/2023] [Accepted: 05/03/2023] [Indexed: 05/23/2023] Open
Abstract
One of the major cellular mechanisms to ensure cellular protein homeostasis is the endoplasmic reticulum (ER) stress response. This pathway is triggered by accumulation of misfolded proteins in the ER lumen. The ER stress response is also activated in the premature aging disease Hutchinson-Gilford progeria syndrome (HGPS). Here, we explore the mechanism of activation of the ER stress response in HGPS. We find that aggregation of the diseases-causing progerin protein at the nuclear envelope triggers ER stress. Induction of ER stress is dependent on the inner nuclear membrane protein SUN2 and its ability to cluster in the nuclear membrane. Our observations suggest that the presence of nucleoplasmic protein aggregates can be sensed, and signaled to the ER lumen, via clustering of SUN2. These results identify a mechanism of communication between the nucleus and the ER and provide insight into the molecular disease mechanisms of HGPS.
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Affiliation(s)
- Sandra Vidak
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | | | - Gianluca Pegoraro
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tom Misteli
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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14
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Mytlis A, Levy K, Elkouby YM. The many faces of the bouquet centrosome MTOC in meiosis and germ cell development. Curr Opin Cell Biol 2023; 81:102158. [PMID: 36913831 DOI: 10.1016/j.ceb.2023.102158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 12/28/2022] [Accepted: 02/12/2023] [Indexed: 03/13/2023]
Abstract
Meiotic chromosomal pairing is facilitated by a conserved cytoskeletal organization. Telomeres associate with perinuclear microtubules via Sun/KASH complexes on the nuclear envelope (NE) and dynein. Telomere sliding on perinuclear microtubules contributes to chromosome homology searches and is essential for meiosis. Telomeres ultimately cluster on the NE, facing the centrosome, in a configuration called the chromosomal bouquet. Here, we discuss novel components and functions of the bouquet microtubule organizing center (MTOC) in meiosis, but also broadly in gamete development. The cellular mechanics of chromosome movements and the bouquet MTOC dynamics are striking. The newly identified zygotene cilium mechanically anchors the bouquet centrosome and completes the bouquet MTOC machinery in zebrafish and mice. We hypothesize that various centrosome anchoring strategies evolved in different species. Evidence suggests that the bouquet MTOC machinery is a cellular organizer, linking meiotic mechanisms with gamete development and morphogenesis. We highlight this cytoskeletal organization as a new platform for creating a holistic understanding of early gametogenesis, with direct implications to fertility and reproduction.
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Affiliation(s)
- Avishag Mytlis
- Department of Developmental Biology and Cancer Research, The Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem, 9112102, Israel; Institute for Medical Research - Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Karine Levy
- Department of Developmental Biology and Cancer Research, The Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem, 9112102, Israel; Institute for Medical Research - Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Yaniv M Elkouby
- Department of Developmental Biology and Cancer Research, The Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem, 9112102, Israel; Institute for Medical Research - Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel.
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15
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Zhang B, Powers JD, McCulloch AD, Chi NC. Nuclear mechanosignaling in striated muscle diseases. Front Physiol 2023; 14:1126111. [PMID: 36960155 PMCID: PMC10027932 DOI: 10.3389/fphys.2023.1126111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Accepted: 02/22/2023] [Indexed: 03/09/2023] Open
Abstract
Mechanosignaling describes processes by which biomechanical stimuli are transduced into cellular responses. External biophysical forces can be transmitted via structural protein networks that span from the cellular membrane to the cytoskeleton and the nucleus, where they can regulate gene expression through a series of biomechanical and/or biochemical mechanosensitive mechanisms, including chromatin remodeling, translocation of transcriptional regulators, and epigenetic factors. Striated muscle cells, including cardiac and skeletal muscle myocytes, utilize these nuclear mechanosignaling mechanisms to respond to changes in their intracellular and extracellular mechanical environment and mediate gene expression and cell remodeling. In this brief review, we highlight and discuss recent experimental work focused on the pathway of biomechanical stimulus propagation at the nucleus-cytoskeleton interface of striated muscles, and the mechanisms by which these pathways regulate gene regulation, muscle structure, and function. Furthermore, we discuss nuclear protein mutations that affect mechanosignaling function in human and animal models of cardiomyopathy. Furthermore, current open questions and future challenges in investigating striated muscle nuclear mechanosignaling are further discussed.
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Affiliation(s)
- Bo Zhang
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States
| | - Joseph D. Powers
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States
| | - Andrew D. McCulloch
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States
- Institute for Engineering in Medicine, University of California San Diego, La Jolla, CA, United States
| | - Neil C. Chi
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States
- Institute for Engineering in Medicine, University of California San Diego, La Jolla, CA, United States
- Department of Medicine, Division of Cardiovascular Medicine, University of California San Diego, La Jolla, CA, United States
- Institute of Genomic Medicine, University of California San Diego, La Jolla, CA, United States
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16
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cKMT1 is a new lysine methyltransferase that methylates the ferredoxin-NADP(+) oxidoreductase (FNR) and regulates energy transfer in cyanobacteria. Mol Cell Proteomics 2023; 22:100521. [PMID: 36858286 PMCID: PMC10090440 DOI: 10.1016/j.mcpro.2023.100521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 02/20/2023] [Accepted: 02/24/2023] [Indexed: 03/03/2023] Open
Abstract
Lysine methylation is a conserved and dynamic regulatory post-translational modification performed by lysine methyltransferases (KMTs). KMTs catalyze the transfer of mono-, di-, or tri-methyl groups to substrate proteins and play a critical regulatory role in all domains of life. To date, only one KMT has been identified in cyanobacteria. Here, we tested all of the predicted KMTs in the cyanobacterium Synechocystis sp. PCC 6803 (Synechocystis), and we biochemically characterized sll1526 that we termed cKMT1 (cyanobacterial lysine methyltransferase 1), and determined that it can catalyze lysine methylation both in vivo and in vitro. Loss of cKMT1 alters photosynthetic electron transfer in Synechocystis. We analyzed cKMT1-regulated methylation sites in Synechocystis using a timsTOF Pro instrument. We identified 305 class I lysine methylation sites within 232 proteins, and of these, 80 methylation sites in 58 proteins were hypomethylated in ΔcKMT1 cells. We further demonstrated that cKMT1 could methylate ferredoxin-NADP(+) oxidoreductase (FNR) and its potential sites of action on FNR were identified. Amino acid residues H118 and Y219 were identified as key residues in the putative active site of cKMT1 as indicated by structure simulation, site-directed mutagenesis, and KMT activity measurement. Using mutations that mimic the unmethylated forms of FNR, we demonstrated that the inability to methylate K139 residues results in a decrease in the redox activity of FNR and affects energy transfer in Synechocystis. Together, our study identified a new KMT in Synechocystis and elucidated a methylation-mediated molecular mechanism catalyzed by cKMT1 for the regulation of energy transfer in cyanobacteria.
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17
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Shaw NM, Rios-Monterrosa JL, Fedorchak GR, Ketterer MR, Coombs GS, Lammerding J, Wallrath LL. Effects of mutant lamins on nucleo-cytoskeletal coupling in Drosophila models of LMNA muscular dystrophy. Front Cell Dev Biol 2022; 10:934586. [PMID: 36120560 PMCID: PMC9471154 DOI: 10.3389/fcell.2022.934586] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 07/20/2022] [Indexed: 11/13/2022] Open
Abstract
The nuclei of multinucleated skeletal muscles experience substantial external force during development and muscle contraction. Protection from such forces is partly provided by lamins, intermediate filaments that form a scaffold lining the inner nuclear membrane. Lamins play a myriad of roles, including maintenance of nuclear shape and stability, mediation of nuclear mechanoresponses, and nucleo-cytoskeletal coupling. Herein, we investigate how disease-causing mutant lamins alter myonuclear properties in response to mechanical force. This was accomplished via a novel application of a micropipette harpooning assay applied to larval body wall muscles of Drosophila models of lamin-associated muscular dystrophy. The assay enables the measurement of both nuclear deformability and intracellular force transmission between the cytoskeleton and nuclear interior in intact muscle fibers. Our studies revealed that specific mutant lamins increase nuclear deformability while other mutant lamins cause nucleo-cytoskeletal coupling defects, which were associated with loss of microtubular nuclear caging. We found that microtubule caging of the nucleus depended on Msp300, a KASH domain protein that is a component of the linker of nucleoskeleton and cytoskeleton (LINC) complex. Taken together, these findings identified residues in lamins required for connecting the nucleus to the cytoskeleton and suggest that not all muscle disease-causing mutant lamins produce similar defects in subcellular mechanics.
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Affiliation(s)
- Nicholas M. Shaw
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - Jose L. Rios-Monterrosa
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - Gregory R. Fedorchak
- The Nancy E. and Peter C. Meinig School of Biomedical Engineering, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, United States
| | - Margaret R. Ketterer
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - Gary S. Coombs
- Biology Department, Waldorf University, Forest City, IA, United States
| | - Jan Lammerding
- The Nancy E. and Peter C. Meinig School of Biomedical Engineering, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, United States
| | - Lori L. Wallrath
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- *Correspondence: Lori L. Wallrath,
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18
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Majumder S, Hsu YY, Moghimianavval H, Andreas M, Giessen TW, Luxton GG, Liu AP. In Vitro Synthesis and Reconstitution Using Mammalian Cell-Free Lysates Enables the Systematic Study of the Regulation of LINC Complex Assembly. Biochemistry 2022; 61:1495-1507. [PMID: 35737522 PMCID: PMC9789527 DOI: 10.1021/acs.biochem.2c00118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Understanding the structure and structure-function relationships of membrane proteins is a fundamental problem in biomedical research. Given the difficulties inherent to performing mechanistic biochemical and biophysical studies of membrane proteins in vitro, we previously developed a facile HeLa cell-based cell-free expression (CFE) system that enables the efficient reconstitution of full-length (FL) functional inner nuclear membrane Sad1/UNC-84 (SUN) proteins (i.e., SUN1 and SUN2) in supported lipid bilayers. Here, we provide evidence that suggests that the reconstitution of CFE-synthesized FL membrane proteins in supported lipid bilayers occurs primarily through the fusion of endoplasmic reticulum-derived microsomes present within our CFE reactions with our supported lipid bilayers. In addition, we demonstrate the ease with which our synthetic biology platform can be used to investigate the impact of the chemical environment on the ability of CFE-synthesized FL SUN proteins reconstituted in supported lipid bilayers to interact with the luminal domain of the KASH protein nesprin-2. Moreover, we use our platform to study the molecular requirements for the homo- and heterotypic interactions between SUN1 and SUN2. Finally, we show that our platform can be used to simultaneously reconstitute three different CFE-synthesized FL membrane proteins in a single supported lipid bilayer. Overall, these results establish our HeLa cell-based CFE and supported lipid bilayer reconstitution platform as a powerful tool for performing mechanistic dissections of the oligomerization and function of FL membrane proteins in vitro. While our platform is not a substitute for cell-based studies, it does provide important mechanistic insights into the biology of difficult-to-study membrane proteins.
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Affiliation(s)
- Sagardip Majumder
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA
| | - Yen-Yu Hsu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA
| | - Hossein Moghimianavval
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA
| | - Michael Andreas
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA
| | - Tobias W. Giessen
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, 48109, USA
| | - G.W. Gant Luxton
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, California, 95616, USA
| | - Allen P. Liu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, USA
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, Michigan, 48109, USA
- Department of Biophysics, University of Michigan, Ann Arbor, Michigan, 48109, USA
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19
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Kim HJ, Liu C, Dernburg AF. How and Why Chromosomes Interact with the Cytoskeleton during Meiosis. Genes (Basel) 2022; 13:genes13050901. [PMID: 35627285 PMCID: PMC9140367 DOI: 10.3390/genes13050901] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 05/09/2022] [Accepted: 05/12/2022] [Indexed: 11/28/2022] Open
Abstract
During the early meiotic prophase, connections are established between chromosomes and cytoplasmic motors via a nuclear envelope bridge, known as a LINC (linker of nucleoskeleton and cytoskeleton) complex. These widely conserved links can promote both chromosome and nuclear motions. Studies in diverse organisms have illuminated the molecular architecture of these connections, but important questions remain regarding how they contribute to meiotic processes. Here, we summarize the current knowledge in the field, outline the challenges in studying these chromosome dynamics, and highlight distinctive features that have been characterized in major model systems.
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Affiliation(s)
- Hyung Jun Kim
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA;
| | - Chenshu Liu
- Howard Hughes Medical Institute, 4000 Jones Bridge Road, Chevy Chase, MD 20815-6789, USA;
| | - Abby F. Dernburg
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA;
- Howard Hughes Medical Institute, 4000 Jones Bridge Road, Chevy Chase, MD 20815-6789, USA;
- Correspondence:
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20
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Wang L, Wu B, Ma Y, Ren Z, Li W. The blooming of an old story on the bouquet. Biol Reprod 2022; 107:289-300. [PMID: 35470849 DOI: 10.1093/biolre/ioac075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 03/09/2022] [Accepted: 04/12/2022] [Indexed: 11/13/2022] Open
Abstract
As an evolutionarily conserved process, the bouquet stage during meiosis was discovered over a century ago, and active research on this important stage continues. Since the discovery of the first bouquet-related protein Taz1p in 1998, several bouquet formation-related proteins have been identified in various eukaryotes. These proteins are involved in the interaction between telomeres and the inner nuclear membrane (INM), and once these interactions are disrupted, meiotic progression is arrested, leading to infertility. Recent studies have provided significant insights into the relationships and interactions among bouquet formation-related proteins. In this review, we summarize the components involved in telomere-INM interactions and focus on their roles in bouquet formation and telomere homeostasis maintenance. In addition, we examined bouquet-related proteins in different species from an evolutionary viewpoint, highlighting the potential interactions among them.
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Affiliation(s)
- Lina Wang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.,Department of Respiratory, China National Clinical Research Center of Respiratory Diseases, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing 100045, China.,University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Bingbing Wu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.,University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Yanjie Ma
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.,University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Zhengxing Ren
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.,University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Wei Li
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.,University of the Chinese Academy of Sciences, Beijing 100049, China.,Institute of Reproductive Health and Perinatology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, 510623 Guangzhou, China
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21
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Computational Analysis of the Potential Impact of MTC Complex Missenses SNPs Associated with Male Infertility. BIOMED RESEARCH INTERNATIONAL 2022; 2022:1664825. [PMID: 35342767 PMCID: PMC8956405 DOI: 10.1155/2022/1664825] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 01/13/2022] [Accepted: 02/23/2022] [Indexed: 01/09/2023]
Abstract
Meiotic chromosomes endure rapid prophase movements that ease the formation of interhomologue recombination intermediates that drive synapsis, crossing over, and segregation process. To generate these fast moves, the meiotic telomere complex (MTC) enables telomere-inner nuclear membrane attachment during meiotic prophase I and transfers cytoskeletal signals via another complex: the LINC complex. Furthermore, disruption or mutations of any of the MTC genes (TERB1, TERB2, and MAJIN) alters telomere association with the nuclear envelope leading to impairment of homologous pairing and synapsis, a meiotic arrest, and consequently to male infertility. To decipher the effect of TERB1, TERB2, and MAJIN missense mutations on protein structure, stability, and function, different bioinformatic tools were used in this study including VEP, Mutabind2, Haddock, Prodigy, Ligplot, ConSurf, DUET and MusiteDeep. In total, thirty mutations were predicted to be deleterious using VEP web server: seventeen for TERB1, eleven for TERB2, and two for MAJIN. All these single nucleotide polymorphisms were further analyzed and only 11 SNPs (W8R, G25R, P649A, I624T, C618R, F607V, S604G, C592Y, C592R, G187W, and R53C) were found to be the most damaging by at least six software tools and exert deleterious effect on the TERB1, TERB2, and MAJIN protein structures and likely functions. They revealed high conservation, less stability, and having a role in posttranslational modifications. This in silico approach provides information to gain further insights about variants that might affect stability, change binding affinity, and edit protein-protein interactions to facilitate their identification and functional characterization associated with male infertility.
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22
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Pawar S, Kutay U. The Diverse Cellular Functions of Inner Nuclear Membrane Proteins. Cold Spring Harb Perspect Biol 2021; 13:a040477. [PMID: 33753404 PMCID: PMC8411953 DOI: 10.1101/cshperspect.a040477] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The nuclear compartment is delimited by a specialized expanded sheet of the endoplasmic reticulum (ER) known as the nuclear envelope (NE). Compared to the outer nuclear membrane and the contiguous peripheral ER, the inner nuclear membrane (INM) houses a unique set of transmembrane proteins that serve a staggering range of functions. Many of these functions reflect the exceptional position of INM proteins at the membrane-chromatin interface. Recent research revealed that numerous INM proteins perform crucial roles in chromatin organization, regulation of gene expression, genome stability, and mediation of signaling pathways into the nucleus. Other INM proteins establish mechanical links between chromatin and the cytoskeleton, help NE remodeling, or contribute to the surveillance of NE integrity and homeostasis. As INM proteins continue to gain prominence, we review these advancements and give an overview on the functional versatility of the INM proteome.
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Affiliation(s)
- Sumit Pawar
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Ulrike Kutay
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
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23
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Jahed Z, Domkam N, Ornowski J, Yerima G, Mofrad MRK. Molecular models of LINC complex assembly at the nuclear envelope. J Cell Sci 2021; 134:269219. [PMID: 34152389 DOI: 10.1242/jcs.258194] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Large protein complexes assemble at the nuclear envelope to transmit mechanical signals between the cytoskeleton and nucleoskeleton. These protein complexes are known as the linkers of the nucleoskeleton and cytoskeleton complexes (LINC complexes) and are formed by the interaction of SUN and KASH domain proteins in the nuclear envelope. Ample evidence suggests that SUN-KASH complexes form higher-order assemblies to withstand and transfer forces across the nuclear envelope. Herein, we present a review of recent studies over the past few years that have shed light on the mechanisms of SUN-KASH interactions, their higher order assembly, and the molecular mechanisms of force transfer across these complexes.
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Affiliation(s)
- Zeinab Jahed
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.,Department of Nanoengineering, Jacobs School of Engineering, University of California, San Diego, CA 92039, USA
| | - Nya Domkam
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720, USA
| | - Jessica Ornowski
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720, USA
| | - Ghafar Yerima
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720, USA
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720, USA.,Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
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24
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Lamin A/C Is Dispensable to Mechanical Repression of Adipogenesis. Int J Mol Sci 2021; 22:ijms22126580. [PMID: 34205295 PMCID: PMC8234021 DOI: 10.3390/ijms22126580] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/10/2021] [Accepted: 06/16/2021] [Indexed: 12/15/2022] Open
Abstract
Mesenchymal stem cells (MSCs) maintain the musculoskeletal system by differentiating into multiple lineages, including osteoblasts and adipocytes. Mechanical signals, including strain and low-intensity vibration (LIV), are important regulators of MSC differentiation via control exerted through the cell structure. Lamin A/C is a protein vital to the nuclear architecture that supports chromatin organization and differentiation and contributes to the mechanical integrity of the nucleus. We investigated whether lamin A/C and mechanoresponsiveness are functionally coupled during adipogenesis in MSCs. siRNA depletion of lamin A/C increased the nuclear area, height, and volume and decreased the circularity and stiffness. Lamin A/C depletion significantly decreased markers of adipogenesis (adiponectin, cellular lipid content) as did LIV treatment despite depletion of lamin A/C. Phosphorylation of focal adhesions in response to mechanical challenge was also preserved during loss of lamin A/C. RNA-seq showed no major adipogenic transcriptome changes resulting from LIV treatment, suggesting that LIV regulation of adipogenesis may not occur at the transcriptional level. We observed that during both lamin A/C depletion and LIV, interferon signaling was downregulated, suggesting potentially shared regulatory mechanism elements that could regulate protein translation. We conclude that the mechanoregulation of adipogenesis and the mechanical activation of focal adhesions function independently from those of lamin A/C.
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25
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Bentebbal SA, Meqbel BR, Salter A, Allan V, Burke B, Horn HF. A human infertility-associated KASH5 variant promotes mitochondrial localization. Sci Rep 2021; 11:10133. [PMID: 33980926 PMCID: PMC8115505 DOI: 10.1038/s41598-021-89439-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 04/22/2021] [Indexed: 02/03/2023] Open
Abstract
KASH5 is the most recently identified member of the KASH domain family of tail anchored, outer nuclear membrane (ONM) and endoplasmic reticulum (ER) proteins. During meiosis prophase I, KASH5 and SUN1 form a complex that spans the nuclear envelope and which links the telomeres of meiotic chromosomes to cytoplasmic dynein. This connection is essential for homologous chromosome dynamics and pairing. A recent study identified a variant in human KASH5 (L535Q) that correlated with male infertility associated with azoospermia. However, no molecular mechanism was described. Here, we report that this amino acid substitution, within the KASH5 transmembrane domain (TMD) has no predicted effects on secondary structure. However, the overall hydrophobicity of the L535Q TMD, is calculated to be lower than the wild-type KASH5, based on the GES (Goldman-Engelman-Steitz) amino acid hydrophobicity scale. This change in hydrophobicity profoundly affects the subcellular localization of KASH5. Through a series of amino acid substitution studies, we show that the L535Q substitution perturbs KASH5 localization to the ER and ONM and instead results in mistargeting to the mitochondria membrane. We suggest that this mislocalization accounts for the infertility and azoospermia phenotype in patients.
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Affiliation(s)
- Sana A. Bentebbal
- grid.452146.00000 0004 1789 3191College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar
| | - Bakhita R. Meqbel
- grid.452146.00000 0004 1789 3191College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar
| | - Anna Salter
- grid.5379.80000000121662407Faculty of Life Sciences, University of Manchester, Manchester, M13 9PT UK ,grid.185448.40000 0004 0637 0221Laboratory of Nuclear Dynamics and Architecture, Institute of Medical Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Victoria Allan
- grid.5379.80000000121662407Faculty of Life Sciences, University of Manchester, Manchester, M13 9PT UK
| | - Brian Burke
- grid.185448.40000 0004 0637 0221Laboratory of Nuclear Dynamics and Architecture, Institute of Medical Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Henning F. Horn
- grid.452146.00000 0004 1789 3191College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar
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26
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Kozono T, Sato H, Okumura W, Jogano C, Tamura-Nakano M, Kawamura YI, Rohrer J, Tonozuka T, Nishikawa A. The N-terminal region of Jaw1 has a role to inhibit the formation of organized smooth endoplasmic reticulum as an intrinsically disordered region. Sci Rep 2021; 11:753. [PMID: 33436890 PMCID: PMC7804115 DOI: 10.1038/s41598-020-80258-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Accepted: 12/18/2020] [Indexed: 02/07/2023] Open
Abstract
Jaw1/LRMP is a type II integral membrane protein that is localized at the endoplasmic reticulum (ER) and outer nuclear membrane. We previously reported that a function of Jaw1 is to maintain the nuclear shape as a KASH protein via its carboxyl terminal region, a component of linker of nucleoskeleton and cytoskeleton complex in the oligomeric state. Although the oligomerization of some KASH proteins via the cytosolic regions serves to stabilize protein-protein interactions, the issue of how the oligomerization of Jaw1 is regulated is not completely understood. Therefore, we focused on three distinct regions on the cytosolic face of Jaw1: the N-terminal region, the coiled-coil domain and the stem region, in terms of oligomerization. A co-immunoprecipitation assay showed that its coiled-coil domain is a candidate for the oligomerization site. Furthermore, our data indicated that the N-terminal region prevents the aberrant oligomerization of Jaw1 as an intrinsically disordered region (IDR). Importantly, the ectopic expression of an N-terminal region deleted mutant caused the formation of organized smooth ER (OSER), structures such as nuclear karmellae and whorls, in B16F10 cells. Furthermore, this OSER interfered with the localization of the oligomer and interactors such as the type III inositol 1,4,5-triphosphate receptor (IP3R3) and SUN2. In summary, the N-terminal region of Jaw1 inhibits the formation of OSER as an IDR to maintain the homeostatic localization of interactors on the ER membrane.
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Affiliation(s)
- Takuma Kozono
- Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan.,Department of Gastroenterology, The Research Center for Hepatitis and Immunology, Research Institute, National Center for Global Health and Medicine, Chiba, 272-8516, Japan
| | - Hiroyuki Sato
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan
| | - Wataru Okumura
- Department of Food and Energy Systems Science, Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, 184-8588, Japan
| | - Chifuyu Jogano
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan
| | - Miwa Tamura-Nakano
- Communal Laboratory, Research Institute, National Center for Global Health and Medicine, Tokyo, 162-8655, Japan
| | - Yuki I Kawamura
- Department of Gastroenterology, The Research Center for Hepatitis and Immunology, Research Institute, National Center for Global Health and Medicine, Chiba, 272-8516, Japan
| | - Jack Rohrer
- Institute of Chemistry and Biotechnology, Zurich University of Applied Sciences, CH-8820, Waedenswil, Switzerland
| | - Takashi Tonozuka
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan
| | - Atsushi Nishikawa
- Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan. .,Department of Applied Biological Chemistry, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan. .,Department of Food and Energy Systems Science, Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, 184-8588, Japan.
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27
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Gurusaran M, Davies OR. A molecular mechanism for LINC complex branching by structurally diverse SUN-KASH 6:6 assemblies. eLife 2021; 10:60175. [PMID: 33393904 PMCID: PMC7800377 DOI: 10.7554/elife.60175] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 01/03/2021] [Indexed: 12/11/2022] Open
Abstract
The Linker of Nucleoskeleton and Cytoskeleton (LINC) complex mechanically couples cytoskeletal and nuclear components across the nuclear envelope to fulfil a myriad of cellular functions, including nuclear shape and positioning, hearing, and meiotic chromosome movements. The canonical model is that 3:3 interactions between SUN and KASH proteins underlie the nucleocytoskeletal linkages provided by the LINC complex. Here, we provide crystallographic and biophysical evidence that SUN-KASH is a constitutive 6:6 complex in which two constituent 3:3 complexes interact head-to-head. A common SUN-KASH topology is achieved through structurally diverse 6:6 interaction mechanisms by distinct KASH proteins, including zinc-coordination by Nesprin-4. The SUN-KASH 6:6 interface provides a molecular mechanism for the establishment of integrative and distributive connections between 3:3 structures within a branched LINC complex network. In this model, SUN-KASH 6:6 complexes act as nodes for force distribution and integration between adjacent SUN and KASH molecules, enabling the coordinated transduction of large forces across the nuclear envelope.
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Affiliation(s)
- Manickam Gurusaran
- Institute of Cell Biology, University of Edinburgh, Edinburgh, United Kingdom.,Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle, United Kingdom
| | - Owen Richard Davies
- Institute of Cell Biology, University of Edinburgh, Edinburgh, United Kingdom.,Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle, United Kingdom
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28
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Kmonickova V, Frolikova M, Steger K, Komrskova K. The Role of the LINC Complex in Sperm Development and Function. Int J Mol Sci 2020; 21:E9058. [PMID: 33260574 PMCID: PMC7730847 DOI: 10.3390/ijms21239058] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Revised: 11/24/2020] [Accepted: 11/26/2020] [Indexed: 11/23/2022] Open
Abstract
The LINC (LInker of Nucleoskeleton and Cytoskeleton) complex is localized within the nuclear envelope and consists of SUN (Sad1/UNc84 homology domain-containing) proteins located in the inner nuclear membrane and KASH (Klarsicht/Anc1/Syne1 homology domain-containing) proteins located in the outer nuclear membrane, hence linking nuclear with cytoplasmic structures. While the nucleoplasm-facing side acts as a key player for correct pairing of homolog chromosomes and rapid chromosome movements during meiosis, the cytoplasm-facing side plays a pivotal role for sperm head development and proper acrosome formation during spermiogenesis. A further complex present in spermatozoa is involved in head-to-tail coupling. An intact LINC complex is crucial for the production of fertile sperm, as mutations in genes encoding for complex proteins are known to be associated with male subfertility in both mice and men. The present review provides a comprehensive overview on our current knowledge of LINC complex subtypes present in germ cells and its central role for male reproduction. Future studies on distinct LINC complex components are an absolute requirement to improve the diagnosis of idiopathic male factor infertility and the outcome of assisted reproduction.
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Affiliation(s)
- Vera Kmonickova
- Laboratory of Reproductive Biology, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV, Prumyslova 595, 252 50 Vestec, Czech Republic; (V.K.); (M.F.)
| | - Michaela Frolikova
- Laboratory of Reproductive Biology, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV, Prumyslova 595, 252 50 Vestec, Czech Republic; (V.K.); (M.F.)
| | - Klaus Steger
- Department of Urology, Pediatric Urology and Andrology, Molecular Andrology, Justus-Liebig University, 35392 Giessen, Germany;
| | - Katerina Komrskova
- Laboratory of Reproductive Biology, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV, Prumyslova 595, 252 50 Vestec, Czech Republic; (V.K.); (M.F.)
- Department of Zoology, Faculty of Science, Charles University, Vinicna 7, 128 44 Prague 2, Czech Republic
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29
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Cruz VE, Esra Demircioglu F, Schwartz TU. Structural Analysis of Different LINC Complexes Reveals Distinct Binding Modes. J Mol Biol 2020; 432:6028-6041. [DOI: 10.1016/j.jmb.2020.09.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 09/22/2020] [Accepted: 09/23/2020] [Indexed: 01/17/2023]
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30
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Fan J, Jin H, Koch BA, Yu HG. Mps2 links Csm4 and Mps3 to form a telomere-associated LINC complex in budding yeast. Life Sci Alliance 2020; 3:3/12/e202000824. [PMID: 32967926 PMCID: PMC7536833 DOI: 10.26508/lsa.202000824] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 09/10/2020] [Accepted: 09/11/2020] [Indexed: 11/24/2022] Open
Abstract
The canonical LINC complex is composed of two different transmembrane proteins; this work reveals the heterotrimeric composition of the telomere-associated LINC complex in budding yeast. The linker of the nucleoskeleton and cytoskeleton (LINC) complex is composed of two transmembrane proteins: the KASH domain protein localized to the outer nuclear membrane and the SUN domain protein to the inner nuclear membrane. In budding yeast, the sole SUN domain protein, Mps3, is thought to pair with either Csm4 or Mps2, two KASH-like proteins, to form two separate LINC complexes. Here, we show that Mps2 mediates the interaction between Csm4 and Mps3 to form a heterotrimeric telomere-associated LINC (t-LINC) complex in budding yeast meiosis. Mps2 binds to Csm4 and Mps3, and all three are localized to the telomere. Telomeric localization of Csm4 depends on both Mps2 and Mps3; in contrast, Mps2’s localization depends on Mps3 but not Csm4. Mps2-mediated t-LINC complex regulates telomere movement and meiotic recombination. By ectopically expressing CSM4 in vegetative yeast cells, we reconstitute the heterotrimeric t-LINC complex and demonstrate its ability to tether telomeres. Our findings therefore reveal the heterotrimeric composition of the t-LINC complex in budding yeast and have implications for understanding variant LINC complex formation.
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Affiliation(s)
- Jinbo Fan
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Hui Jin
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Bailey A Koch
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Hong-Guo Yu
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
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31
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Wang G, Wu X, Zhou L, Gao S, Yun D, Liang A, Sun F. Tethering of Telomeres to the Nuclear Envelope Is Mediated by SUN1-MAJIN and Possibly Promoted by SPDYA-CDK2 During Meiosis. Front Cell Dev Biol 2020; 8:845. [PMID: 33015044 PMCID: PMC7509418 DOI: 10.3389/fcell.2020.00845] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 08/06/2020] [Indexed: 12/31/2022] Open
Abstract
During meiosis, telomeres attach to the nuclear envelope (NE) to promote homologous chromosome moving, pairing, synapsis, and recombination. The telomere-NE attachment is mediated by SUN1, TERB1-TERB2-MAJIN (TTM complex), and TRF1. The interaction of the TTM complex with shelterin is mediated by TERB1 and TRF1, but how SUN1 interacts with the TTM complex is not yet fully understood. In this study, we found that SUN1 not only interacted with TERB1 but also interacted with MAJIN, and the interaction of SUN1 with MAJIN is stronger than TERB1. We also found that SUN1 interacted with SPDYA, an activator of CDK2. The binding sites of MAJIN and SPDYA at SUN1 were mapped, and both MAJIN and SPDYA bound to the N-terminal domain of SUN1 and the two binding sites were close to each other. Furthermore, SPDYA bound to SUN1 via the Ringo domain and recruited CDK2 to SUN1. Then, we found that the interaction of SUN1 with MAJIN was decreased by the CDK2 inhibitors. Taken together, our results provide the possible mechanism of SUN1, MAJIN, and SPDYA-CDK2 in promoting the telomere-NE attachment during meiosis.
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Affiliation(s)
- Guishuan Wang
- Medical School, Institute of Reproductive Medicine, Nantong University, Nantong, China
| | - Xiaolong Wu
- Medical School, Institute of Reproductive Medicine, Nantong University, Nantong, China
| | - Liwei Zhou
- Medical School, Institute of Reproductive Medicine, Nantong University, Nantong, China
| | - Sheng Gao
- Medical School, Institute of Reproductive Medicine, Nantong University, Nantong, China
| | - Damin Yun
- Medical School, Institute of Reproductive Medicine, Nantong University, Nantong, China
| | - Ajuan Liang
- Reproductive Medical Center, Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Fei Sun
- Medical School, Institute of Reproductive Medicine, Nantong University, Nantong, China
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32
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Zhao J, Hu J. Self-Association of Purified Reconstituted ER Luminal Spacer Climp63. Front Cell Dev Biol 2020; 8:500. [PMID: 32612999 PMCID: PMC7308479 DOI: 10.3389/fcell.2020.00500] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 05/25/2020] [Indexed: 01/15/2023] Open
Abstract
Membranes of the endoplasmic reticulum (ER) are shaped into cisternal sheets and cylindrical tubules. How ER sheets are generated and maintained is not clear. ER membrane protein Climp63 is enriched in sheets and routinely used as a marker of this structure. The luminal domain (LD) of Climp63 is predicted to be highly helical, and it may form bridges between parallel membranes, regulating the abundance and width of ER sheets. Here, we purified the LD and full-length (FL) Climp63 to analyze their homotypic interactions. The N-terminal tagged LD formed low-order oligomers in solution, but was extremely aggregation-prone when the GST tag was removed. Purified FL Climp63 formed detectable but moderate interactions with both the FL protein and the LD. When Climp63 was reconstituted into proteoliposomes with its LD facing out, the homotypic interactions were retained and could be competed by soluble LD, though vesicle clustering was not observed. These results demonstrate a direct self-association of Climp63, supporting its role as an ER luminal spacer.
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Affiliation(s)
- Jinghua Zhao
- Department of Genetics and Cell Biology, College of Life Sciences, Nankai University, Tianjin, China
| | - Junjie Hu
- Department of Genetics and Cell Biology, College of Life Sciences, Nankai University, Tianjin, China.,National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
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33
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Abstract
LINC complexes (Linker of Nucleoskeleton and Cytoskeleton), consisting of inner nuclear membrane SUN (Sad1, UNC-84) proteins and outer nuclear membrane KASH (Klarsicht, ANC-1, and Syne Homology) proteins, are essential for nuclear positioning, cell migration and chromosome dynamics. To test the in vivo functions of conserved interfaces revealed by crystal structures, Cain et al used a combination of Caenorhabditis elegans genetics, imaging in cultured NIH 3T3 fibroblasts, and Molecular Dynamic simulations, to study SUN-KASH interactions. Conserved aromatic residues at the -7 position of the C-termini of KASH proteins and conserved disulfide bonds in LINC complexes play important roles in force transmission across the nuclear envelope. Other properties of LINC complexes, such as the helices preceding the SUN domain, the longer coiled-coils spanning the perinuclear space and higher-order organization may also function to transmit mechanical forces generated by the cytoskeleton across the nuclear envelope.
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Affiliation(s)
- Hongyan Hao
- a Department of Molecular and Cellular Biology , University of California , Davis , CA USA
| | - Daniel A Starr
- a Department of Molecular and Cellular Biology , University of California , Davis , CA USA
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34
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Gao Q, Khan R, Yu C, Alsheimer M, Jiang X, Ma H, Shi Q. The testis-specific LINC component SUN3 is essential for sperm head shaping during mouse spermiogenesis. J Biol Chem 2020; 295:6289-6298. [PMID: 32156700 DOI: 10.1074/jbc.ra119.012375] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/06/2020] [Indexed: 01/16/2023] Open
Abstract
Sperm head shaping is a key event in spermiogenesis and is tightly controlled via the acrosome-manchette network. Linker of nucleoskeleton and cytoskeleton (LINC) complexes consist of Sad1 and UNC84 domain-containing (SUN) and Klarsicht/ANC-1/Syne-1 homology (KASH) domain proteins and form conserved nuclear envelope bridges implicated in transducing mechanical forces from the manchette to sculpt sperm nuclei into a hook-like shape. However, the role of LINC complexes in sperm head shaping is still poorly understood. Here we assessed the role of SUN3, a testis-specific LINC component harboring a conserved SUN domain, in spermiogenesis. We show that CRISPR/Cas9-generated Sun3 knockout male mice are infertile, displaying drastically reduced sperm counts and a globozoospermia-like phenotype, including a missing, mislocalized, or fragmented acrosome, as well as multiple defects in sperm flagella. Further examination revealed that the sperm head abnormalities are apparent at step 9 and that the sperm nuclei fail to elongate because of the absence of manchette microtubules and perinuclear rings. These observations indicate that Sun3 deletion likely impairs the ability of the LINC complex to transduce the cytoskeletal force to the nuclear envelope, required for sperm head elongation. We also found that SUN3 interacts with SUN4 in mouse testes and that the level of SUN4 proteins is drastically reduced in Sun3-null mice. Altogether, our results indicate that SUN3 is essential for sperm head shaping and male fertility, providing molecular clues regarding the underlying pathology of the globozoospermia-like phenotype.
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Affiliation(s)
- Qian Gao
- First Affiliated Hospital of the University of Science and Technology of China, Hefei National Laboratory for Physical Sciences at Microscale, Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Diseases, School of Life Sciences, Chinese Academy of Sciences Center for Excellence in Molecular Cell Science, Collaborative Innovation Center of Genetics and Development, University of Science and Technology of China, Hefei 230027, China
| | - Ranjha Khan
- First Affiliated Hospital of the University of Science and Technology of China, Hefei National Laboratory for Physical Sciences at Microscale, Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Diseases, School of Life Sciences, Chinese Academy of Sciences Center for Excellence in Molecular Cell Science, Collaborative Innovation Center of Genetics and Development, University of Science and Technology of China, Hefei 230027, China
| | - Changping Yu
- First Affiliated Hospital of the University of Science and Technology of China, Hefei National Laboratory for Physical Sciences at Microscale, Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Diseases, School of Life Sciences, Chinese Academy of Sciences Center for Excellence in Molecular Cell Science, Collaborative Innovation Center of Genetics and Development, University of Science and Technology of China, Hefei 230027, China
| | - Manfred Alsheimer
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, 97074 Würzburg, Germany
| | - Xiaohua Jiang
- First Affiliated Hospital of the University of Science and Technology of China, Hefei National Laboratory for Physical Sciences at Microscale, Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Diseases, School of Life Sciences, Chinese Academy of Sciences Center for Excellence in Molecular Cell Science, Collaborative Innovation Center of Genetics and Development, University of Science and Technology of China, Hefei 230027, China
| | - Hui Ma
- First Affiliated Hospital of the University of Science and Technology of China, Hefei National Laboratory for Physical Sciences at Microscale, Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Diseases, School of Life Sciences, Chinese Academy of Sciences Center for Excellence in Molecular Cell Science, Collaborative Innovation Center of Genetics and Development, University of Science and Technology of China, Hefei 230027, China
| | - Qinghua Shi
- First Affiliated Hospital of the University of Science and Technology of China, Hefei National Laboratory for Physical Sciences at Microscale, Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Diseases, School of Life Sciences, Chinese Academy of Sciences Center for Excellence in Molecular Cell Science, Collaborative Innovation Center of Genetics and Development, University of Science and Technology of China, Hefei 230027, China
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35
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Hennen J, Hur KH, Kohler J, Reddy Karuka S, Angert I, Luxton GWG, Mueller JD. Identifying Heteroprotein Complexes in the Nuclear Envelope. Biophys J 2019; 118:26-35. [PMID: 31839257 DOI: 10.1016/j.bpj.2019.11.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 11/02/2019] [Accepted: 11/18/2019] [Indexed: 12/26/2022] Open
Abstract
The nucleus is delineated by the nuclear envelope (NE), which is a double membrane barrier composed of the inner and outer nuclear membranes as well as a ∼40-nm wide lumen. In addition to its barrier function, the NE acts as a critical signaling node for a variety of cellular processes, which are mediated by protein complexes within this subcellular compartment. Although fluorescence fluctuation spectroscopy is a powerful tool for characterizing protein complexes in living cells, it was recently demonstrated that conventional fluorescence fluctuation spectroscopy methods are not suitable for applications in the NE because of the presence of slow nuclear membrane undulations. We previously addressed this challenge by developing time-shifted mean-segmented Q (tsMSQ) analysis and applied it to successfully characterize protein homo-oligomerization in the NE. However, many NE complexes, such as the linker of the nucleoskeleton and cytoskeleton complex, are formed by heterotypic interactions, which single-color tsMSQ is unable to characterize. Here, we describe the development of dual-color (DC) tsMSQ to analyze NE heteroprotein complexes built from proteins that carry two spectrally distinct fluorescent labels. Experiments performed on model systems demonstrate that DC tsMSQ properly identifies heteroprotein complexes and their stoichiometry in the NE by accounting for spectral cross talk and local volume fluctuations. Finally, we applied DC tsMSQ to study the assembly of the linker of the nucleoskeleton and cytoskeleton complex, a heteroprotein complex composed of Klarsicht/ANC-1/SYNE homology and Sad1/UNC-84 (SUN) proteins, in the NE of living cells. Using DC tsMSQ, we demonstrate the ability of the SUN protein SUN2 and the Klarsicht/ANC-1/SYNE homology protein nesprin-2 to form a heterocomplex in vivo. Our results are consistent with previously published in vitro studies and demonstrate the utility of the DC tsMSQ technique for characterizing NE heteroprotein complexes.
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Affiliation(s)
- Jared Hennen
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota
| | - Kwang-Ho Hur
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota
| | - John Kohler
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota
| | | | - Isaac Angert
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota
| | - G W Gant Luxton
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota
| | - Joachim D Mueller
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota; Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota.
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36
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A Glance at the Nuclear Envelope Spectrin Repeat Protein 3. BIOMED RESEARCH INTERNATIONAL 2019; 2019:1651805. [PMID: 31828088 PMCID: PMC6886330 DOI: 10.1155/2019/1651805] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 08/14/2019] [Indexed: 12/27/2022]
Abstract
Nuclear envelope spectrin repeat protein 3 (nesprin-3) is an evolutionarily-conserved structural protein, widely-expressed in vertebrate cells. Along with other nesprin family members, nesprin-3 acts as an essential component of the linker of nucleoskeleton and cytoskeleton (LINC) complex. Naturally, nesprin-3 shares many functions with LINC, including the localization of various cellular structures and bridging of the nucleoskeleton and cytoskeleton, observed in vitro. When nesprin-3 was knocked down in vivo, using zebrafish and mouse models, however, the animals were minimally affected. This paradoxical observation should not limit the physiological importance of nesprin-3, as recently, nesprin-3 has reignited the interest of the research community in studies on cancer cells migration. Moreover, nesprin-3 also plays an active role in certain developmental conditions such as adipogenesis and spermatogenesis, although more studies are needed. Meanwhile, the various protein binding partners of nesprin-3 should also be emphasized, as they are necessary for maintaining the structure of nesprin-3 and enabling it to carry out its various physiological and pathological functions. Nesprin-3 promises to further our understanding of these complex cellular events. Therefore, this review will focus on nesprin-3, examining it from a genetic, structural, and functional perspective. The final part of the review will in turn address the limitations of existing research and the future perspectives for the study of nesprin-3.
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Starr DA. A network of nuclear envelope proteins and cytoskeletal force generators mediates movements of and within nuclei throughout Caenorhabditis elegans development. Exp Biol Med (Maywood) 2019; 244:1323-1332. [PMID: 31495194 PMCID: PMC6880151 DOI: 10.1177/1535370219871965] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Nuclear migration and anchorage, together referred to as nuclear positioning, are central to many cellular and developmental events. Nuclear positioning is mediated by a conserved network of nuclear envelope proteins that interacts with force generators in the cytoskeleton. At the heart of this network are li nker of n ucleoskeleton and c ytoskeleton (LINC) complexes made of S ad1 and UN C-84 (SUN) proteins at the inner nuclear membrane and K larsicht, A NC-1, and S yne homology (KASH) proteins in the outer nuclear membrane. LINC complexes span the nuclear envelope, maintain nuclear envelope architecture, designate the surface of nuclei distinctly from the contiguous endoplasmic reticulum, and were instrumental in the early evolution of eukaryotes. LINC complexes interact with lamins in the nucleus and with various cytoplasmic KASH effectors from the surface of nuclei. These effectors regulate the cytoskeleton, leading to a variety of cellular outputs including pronuclear migration, nuclear migration through constricted spaces, nuclear anchorage, centrosome attachment to nuclei, meiotic chromosome movements, and DNA damage repair. How LINC complexes are regulated and how they function are reviewed here. The focus is on recent studies elucidating the best-understood network of LINC complexes, those used throughout Caenorhabditis elegans development.
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Affiliation(s)
- Daniel A Starr
- Department of Molecular and Cellular Biology,
University of California, Davis, CA 95616, USA
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38
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Jahed Z, Fadavi D, Vu UT, Asgari E, Luxton GWG, Mofrad MRK. Molecular Insights into the Mechanisms of SUN1 Oligomerization in the Nuclear Envelope. Biophys J 2019. [PMID: 29539404 DOI: 10.1016/j.bpj.2018.01.015] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The LINC complex is found in a wide variety of organisms and is formed by the transluminal interaction between outer- and inner-nuclear-membrane KASH and SUN proteins, respectively. Most extensively studied are SUN1 and SUN2 proteins, which are widely expressed in mammals. Although SUN1 and SUN2 play functionally redundant roles in several cellular processes, more recent studies have revealed diverse and distinct functions for SUN1. While several recent in vitro structural studies have revealed the molecular details of various fragments of SUN2, no such structural information is available for SUN1. Herein, we conduct a systematic analysis of the molecular relationships between SUN1 and SUN2, highlighting key similarities and differences that could lead to clues into their distinct functions. We use a wide range of computational tools, including multiple sequence alignments, homology modeling, molecular docking, and molecular dynamic simulations, to predict structural differences between SUN1 and SUN2, with the goal of understanding the molecular mechanisms underlying SUN1 oligomerization in the nuclear envelope. Our simulations suggest that the structural model of SUN1 is stable in a trimeric state and that SUN1 trimers can associate through their SUN domains to form lateral complexes. We also ask whether SUN1 could adopt an inactive monomeric conformation as seen in SUN2. Our results imply that the KASH binding domain of SUN1 is also inhibited in monomeric SUN1 but through weaker interactions than in monomeric SUN2.
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Affiliation(s)
- Zeinab Jahed
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, California
| | - Darya Fadavi
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, California
| | - Uyen T Vu
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, California
| | - Ehsaneddin Asgari
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, California
| | - G W Gant Luxton
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, California; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California.
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Wang Y, Chen Y, Chen J, Wang L, Nie L, Long J, Chang H, Wu J, Huang C, Lei M. The meiotic TERB1-TERB2-MAJIN complex tethers telomeres to the nuclear envelope. Nat Commun 2019; 10:564. [PMID: 30718482 PMCID: PMC6361898 DOI: 10.1038/s41467-019-08437-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 01/10/2019] [Indexed: 12/11/2022] Open
Abstract
During meiotic prophase I, telomeres attach to and move on the nuclear envelope (NE), regulating chromosome movement to promote homologous pairing. Meiosis-specific proteins TERB1, TERB2 and MAJIN play a key role in this process. Here, we report the crystal structures of human TERB1-TERB2 and TERB2-MAJIN subcomplexes. Specific disruption of the TERB1-TERB2 or the TERB2-MAJIN interaction in the mouse Terb2 gene abolishes the telomere attachment to the NE and causes aberrant homologous pairing and disordered synapsis. In addition, depletion of SUN1 also partially disrupts the telomere-NE connection. We propose that the telomere-TRF1-TERB1-TERB2-MAJIN-NE interaction network and the telomere-LINC complex connection are likely two separate but cooperative pathways to stably recruit telomeres to the NE in meiosis prophase I. Our work provides a molecular model of the connection between telomeres and the NE and reveals the correlation between aberrant synapsis and the defective telomere attachment to the NE.
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Affiliation(s)
- Yan Wang
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, CAS Center for Excellence on Molecular Cell Science, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 200031, Shanghai, China
| | - Yanyan Chen
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, CAS Center for Excellence on Molecular Cell Science, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 200031, Shanghai, China
| | - Juan Chen
- Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 200011, Shanghai, China.,Shanghai Institute of Precision Medicine, 200125, Shanghai, China
| | - Lijun Wang
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, CAS Center for Excellence on Molecular Cell Science, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 200031, Shanghai, China
| | - Leitong Nie
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agriculture University, 430072, Wuhan, China
| | - Juanjuan Long
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, CAS Center for Excellence on Molecular Cell Science, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 200031, Shanghai, China
| | - Haishuang Chang
- Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 200011, Shanghai, China.,Shanghai Institute of Precision Medicine, 200125, Shanghai, China
| | - Jian Wu
- Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 200011, Shanghai, China.,Shanghai Institute of Precision Medicine, 200125, Shanghai, China
| | - Chenhui Huang
- Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 200011, Shanghai, China. .,Shanghai Institute of Precision Medicine, 200125, Shanghai, China.
| | - Ming Lei
- Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 200011, Shanghai, China. .,Shanghai Institute of Precision Medicine, 200125, Shanghai, China. .,Key laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, 200025, Shanghai, China.
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40
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Brull A, Morales Rodriguez B, Bonne G, Muchir A, Bertrand AT. The Pathogenesis and Therapies of Striated Muscle Laminopathies. Front Physiol 2018; 9:1533. [PMID: 30425656 PMCID: PMC6218675 DOI: 10.3389/fphys.2018.01533] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 10/11/2018] [Indexed: 01/04/2023] Open
Abstract
Emery-Dreifuss muscular dystrophy (EDMD) is a genetic condition characterized by early contractures, skeletal muscle weakness, and cardiomyopathy. During the last 20 years, various genetic approaches led to the identification of causal genes of EDMD and related disorders, all encoding nuclear envelope proteins. By their respective localization either at the inner nuclear membrane or the outer nuclear membrane, these proteins interact with each other and establish a connection between the nucleus and the cytoskeleton. Beside this physical link, these proteins are also involved in mechanotransduction, responding to environmental cues, such as increased tension of the cytoskeleton, by the activation or repression of specific sets of genes. This ability of cells to adapt to environmental conditions is altered in EDMD. Increased knowledge on the pathophysiology of EDMD has led to the development of drug or gene therapies that have been tested on mouse models. This review proposed an overview of the functions played by the different proteins involved in EDMD and related disorders and the current therapeutic approaches tested so far.
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Affiliation(s)
- Astrid Brull
- Sorbonne Université, INSERM, Institut de Myologie, Center of Research in Myology, UMRS 974, Paris, France
| | - Blanca Morales Rodriguez
- Sorbonne Université, INSERM, Institut de Myologie, Center of Research in Myology, UMRS 974, Paris, France.,Sanofi R&D, Chilly Mazarin, France
| | - Gisèle Bonne
- Sorbonne Université, INSERM, Institut de Myologie, Center of Research in Myology, UMRS 974, Paris, France
| | - Antoine Muchir
- Sorbonne Université, INSERM, Institut de Myologie, Center of Research in Myology, UMRS 974, Paris, France
| | - Anne T Bertrand
- Sorbonne Université, INSERM, Institut de Myologie, Center of Research in Myology, UMRS 974, Paris, France
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41
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Cain NE, Jahed Z, Schoenhofen A, Valdez VA, Elkin B, Hao H, Harris NJ, Herrera LA, Woolums BM, Mofrad MRK, Luxton GWG, Starr DA. Conserved SUN-KASH Interfaces Mediate LINC Complex-Dependent Nuclear Movement and Positioning. Curr Biol 2018; 28:3086-3097.e4. [PMID: 30245107 DOI: 10.1016/j.cub.2018.08.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 06/18/2018] [Accepted: 08/01/2018] [Indexed: 12/20/2022]
Abstract
Many nuclear positioning events involve linker of nucleoskeleton and cytoskeleton (LINC) complexes, which transmit forces generated by the cytoskeleton across the nuclear envelope. LINC complexes are formed by trans-luminal interactions between inner nuclear membrane SUN proteins and outer nuclear membrane KASH proteins, but how these interactions are regulated is poorly understood. We combine in vivo C. elegans genetics, in vitro wounded fibroblast polarization, and in silico molecular dynamics simulations to elucidate mechanisms of LINC complexes. The extension of the KASH domain by a single alanine residue or the mutation of the conserved tyrosine at -7 completely blocked the nuclear migration function of C. elegans UNC-83. Analogous mutations at -7 of mouse nesprin-2 disrupted rearward nuclear movements in NIH 3T3 cells, but did not disrupt ANC-1 in nuclear anchorage. Furthermore, conserved cysteines predicted to form a disulfide bond between SUN and KASH proteins are important for the function of certain LINC complexes, and might promote a developmental switch between nuclear migration and nuclear anchorage. Mutations of conserved cysteines in SUN or KASH disrupted ANC-1-dependent nuclear anchorage in C. elegans and Nesprin-2G-dependent nuclear movements in polarizing fibroblasts. However, the SUN cysteine mutation did not disrupt nuclear migration. Moreover, molecular dynamics simulations showed that a disulfide bond is necessary for the maximal transmission of cytoskeleton-generated forces by LINC complexes in silico. Thus, we have demonstrated functions for SUN-KASH binding interfaces, including a predicted intermolecular disulfide bond, as mechanistic determinants of nuclear positioning that may represent targets for regulation.
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Affiliation(s)
- Natalie E Cain
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA
| | - Zeinab Jahed
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, 208A Stanley Hall, Berkeley, CA 94720, USA
| | - Amy Schoenhofen
- Department of Genetics, Cell Biology, and Development, University of Minnesota, 420 Washington Avenue SE, Minneapolis, MN 55455, USA
| | - Venecia A Valdez
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA
| | - Baila Elkin
- Department of Genetics, Cell Biology, and Development, University of Minnesota, 420 Washington Avenue SE, Minneapolis, MN 55455, USA
| | - Hongyan Hao
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA
| | - Nathan J Harris
- Department of Genetics, Cell Biology, and Development, University of Minnesota, 420 Washington Avenue SE, Minneapolis, MN 55455, USA
| | - Leslie A Herrera
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA
| | - Brian M Woolums
- Department of Genetics, Cell Biology, and Development, University of Minnesota, 420 Washington Avenue SE, Minneapolis, MN 55455, USA
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, 208A Stanley Hall, Berkeley, CA 94720, USA
| | - G W Gant Luxton
- Department of Genetics, Cell Biology, and Development, University of Minnesota, 420 Washington Avenue SE, Minneapolis, MN 55455, USA
| | - Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA.
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42
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Recombinant Purification of the Periplasmic Portion of the LINC Complex. Methods Mol Biol 2018. [PMID: 30141034 DOI: 10.1007/978-1-4939-8691-0_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Recombinant expression of proteins and their complexes is the routine laboratory procedure to generate pure reagents for biochemical and structural studies. Here we present the standard procedure developed in our lab for the production of milligram quantities of stoichiometric SUN-KASH complexes. The protocol was specifically developed for the purification of the periplasmic portion of LINC complexes.
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43
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Jahed Z, Vu UT, Fadavi D, Ke H, Rathish A, Kim SCJ, Feng W, Mofrad MRK. A molecular model for LINC complex regulation: activation of SUN2 for KASH binding. Mol Biol Cell 2018; 29:2012-2023. [PMID: 29995584 PMCID: PMC6232973 DOI: 10.1091/mbc.e18-04-0266] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Linkers of the nucleoskeleton and cytoskeleton are key molecular complexes that span the nuclear envelope (NE) and provide a direct linkage between the nucleoskeleton and cytoskeleton. Two major components of these complexes are members of the SUN and KASH protein families that interact in the perinuclear space to allow the transmission of mechanochemical signals across the NE. Structural details of the mammalian SUN domain protein SUN2 have established that SUN2 must form a trimer to bind to KASH, and that this trimerization is mediated through two predicted coiled-coil regions of the protein, CC1 and CC2, which precede the SUN domain. Recent crystallographic data suggest that CC2-SUN formed an unexpected autoinhibited monomer unable to bind to KASH. These structural insights raise the question of how full-length SUN2 transitions from a monomer to a trimer inside the NE. In this study we used a computational approach to model a fragment of SUN2 containing CC1, CC2, and the SUN domain. We observed the dynamics of these modeled structures using ∼1 μs molecular dynamics simulations and showed that the interplay between CC1 and CC2 may be sufficient for the release of CC2-SUN2 from its autoinhibited state. Additionally, using our models and gel filtration analysis, we show the involvement of an E452 residue on CC1 in the monomer–trimer transition of SUN2. Intriguingly, mutations in this residue have been seen in muscular dystrophy–associated SUN2 variants. Finally, we propose a Ca2+-dependent monomer–trimer transition of SUN2.
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Affiliation(s)
- Zeinab Jahed
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94720
| | - Uyen T Vu
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94720
| | - Darya Fadavi
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94720
| | - Huimin Ke
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Akshay Rathish
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94720
| | - Samuel C J Kim
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94720
| | - Wei Feng
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94720.,Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
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SUN1 Regulates HIV-1 Nuclear Import in a Manner Dependent on the Interaction between the Viral Capsid and Cellular Cyclophilin A. J Virol 2018; 92:JVI.00229-18. [PMID: 29643244 DOI: 10.1128/jvi.00229-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 04/04/2018] [Indexed: 12/24/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) can infect nondividing cells via passing through the nuclear pore complex. The nuclear membrane-imbedded protein SUN2 was recently reported to be involved in the nuclear import of HIV-1. Whether SUN1, which shares many functional similarities with SUN2, is involved in this process remained to be explored. Here we report that overexpression of SUN1 specifically inhibited infection by HIV-1 but not that by simian immunodeficiency virus (SIV) or murine leukemia virus (MLV). Overexpression of SUN1 did not affect reverse transcription but led to reduced accumulation of the 2-long-terminal-repeat (2-LTR) circular DNA and integrated viral DNA, suggesting a block in the process of nuclear import. HIV-1 CA was mapped as a determinant for viral sensitivity to SUN1. Treatment of SUN1-expressing cells with cyclosporine (CsA) significantly reduced the sensitivity of the virus to SUN1, and an HIV-1 mutant containing CA-G89A, which does not interact with cyclophilin A (CypA), was resistant to SUN1 overexpression. Downregulation of endogenous SUN1 inhibited the nuclear entry of the wild-type virus but not that of the G89A mutant. These results indicate that SUN1 participates in the HIV-1 nuclear entry process in a manner dependent on the interaction of CA with CypA.IMPORTANCE HIV-1 infects both dividing and nondividing cells. The viral preintegration complex (PIC) can enter the nucleus through the nuclear pore complex. It has been well known that the viral protein CA plays an important role in determining the pathways by which the PIC enters the nucleus. In addition, the interaction between CA and the cellular protein CypA has been reported to be important in the selection of nuclear entry pathways, though the underlying mechanisms are not very clear. Here we show that both SUN1 overexpression and downregulation inhibited HIV-1 nuclear entry. CA played an important role in determining the sensitivity of the virus to SUN1: the regulatory activity of SUN1 toward HIV-1 relied on the interaction between CA and CypA. These results help to explain how SUN1 is involved in the HIV-1 nuclear entry process.
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Kozono T, Tadahira K, Okumura W, Itai N, Tamura-Nakano M, Dohi T, Tonozuka T, Nishikawa A. Jaw1/LRMP has a role in maintaining nuclear shape via interaction with SUN proteins. J Biochem 2018; 164:303-311. [DOI: 10.1093/jb/mvy053] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 05/28/2018] [Indexed: 12/31/2022] Open
Affiliation(s)
- Takuma Kozono
- Department of Food and Energy Systems Science, Graduate School of Bio-Applications Systems Engineering, 3-5-8 Saiwai-cho, Fuchu, Tokyo, Japan
| | - Kazuko Tadahira
- Division of Applied Biological Chemistry, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, Japan
| | - Wataru Okumura
- Department of Food and Energy Systems Science, Graduate School of Bio-Applications Systems Engineering, 3-5-8 Saiwai-cho, Fuchu, Tokyo, Japan
| | - Nao Itai
- Division of Applied Biological Chemistry, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, Japan
| | - Miwa Tamura-Nakano
- Communal Laboratory, Research Institute, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku, Tokyo, Japan
| | - Taeko Dohi
- Department of Gastroenterology, Research Center for Hepatitis and Immunology, Research Institute, National Center for Global Health and Medicine, 1-7-1 Kohnodai, Ichikawa, Chiba, Japan
| | - Takashi Tonozuka
- Division of Applied Biological Chemistry, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, Japan
| | - Atsushi Nishikawa
- Department of Food and Energy Systems Science, Graduate School of Bio-Applications Systems Engineering, 3-5-8 Saiwai-cho, Fuchu, Tokyo, Japan
- Division of Applied Biological Chemistry, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, Japan
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Linker of nucleoskeleton and cytoskeleton complex proteins in cardiomyopathy. Biophys Rev 2018; 10:1033-1051. [PMID: 29869195 PMCID: PMC6082319 DOI: 10.1007/s12551-018-0431-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 05/24/2018] [Indexed: 12/21/2022] Open
Abstract
The linker of nucleoskeleton and cytoskeleton (LINC) complex couples the nuclear lamina to the cytoskeleton. The LINC complex and its associated proteins play diverse roles in cells, ranging from genome organization, nuclear morphology, gene expression, to mechanical stability. The importance of a functional LINC complex is highlighted by the large number of mutations in genes encoding LINC complex proteins that lead to skeletal and cardiac myopathies. In this review, the structure, function, and interactions between components of the LINC complex will be described. Mutations that are known to cause cardiomyopathy in patients will be discussed alongside their respective mouse models. Furthermore, future challenges for the field and emerging technologies to investigate LINC complex function will be discussed.
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47
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SUN2 Modulates HIV-1 Infection and Latency through Association with Lamin A/C To Maintain the Repressive Chromatin. mBio 2018; 9:mBio.02408-17. [PMID: 29717016 PMCID: PMC5930302 DOI: 10.1128/mbio.02408-17] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The postintegrational latency of HIV-1 is characterized by reversible silencing of long terminal repeat (LTR)-driven transcription of the HIV genome. It is known that the formation of repressive chromatin at the 5′-LTR of HIV-1 proviral DNA impedes viral transcription by blocking the recruitment of positive transcription factors. How the repressive chromatin is formed and modulated during HIV-1 infection remains elusive. Elucidation of which chromatin reassembly factor mediates the reorganization of chromatin is likely to facilitate the understanding of the host’s modulation of HIV-1 transcription and latency. Here we revealed that “Sad1 and UNC84 domain containing 2” (SUN2), an inner nuclear membrane protein, maintained the repressive chromatin and inhibited HIV LTR-driven transcription of proviral DNA through an association with lamin A/C. Specifically, lamin A/C tethered SUN2 to the nucleosomes 1 and 2 of the HIV-1 5′-LTR to block the initiation and elongation of HIV-1 transcription. SUN2 knockdown converted chromatin to an active form and thus enhanced the phosphorylation of RNA polymerase II and its recruitment to the 5′-LTR HIV-1 proviral DNA, leading to reactivation of HIV-1 from latency. Conversely, the exogenous factors such as tumor necrosis factor alpha (TNF-α) induced reactivation, and the replication of HIV-1 led to the disassociation between SUN2 and lamin A/C, suggesting that disruption of the association between SUN2 and lamin A/C to convert the repressive chromatin to the active form might be a prerequisite for the initiation of HIV-1 transcription and replication. Together, our findings indicate that SUN2 is a novel chromatin reassembly factor that helps to maintain chromatin in a repressive state and consequently inhibits HIV-1 transcription. Despite the successful use of scores of antiretroviral drugs, HIV latency poses a major impediment to virus eradication. Elucidation of the mechanism of latency facilitates the discovery of new therapeutic strategies. It has been known that the formation of repressive chromatin at the 5′-LTR of HIV-1 proviral DNA impedes viral transcription and maintains viral latency, but how the repressive chromatin is formed and modulated during HIV-1 infection remains elusive. In this study, we performed in-depth virological and cell biological studies and discovered that an inner nuclear membrane protein, SUN2, is a novel chromatin reassembly factor that maintains repressive chromatin and thus modulates HIV-1 transcription and latency: therefore, targeting SUN2 may lead to new strategies for HIV cure.
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48
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Xu Y, Li W, Ke H, Feng W. Structural conservation of the autoinhibitory domain in SUN proteins. Biochem Biophys Res Commun 2018; 496:1337-1343. [DOI: 10.1016/j.bbrc.2018.02.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 02/02/2018] [Indexed: 10/18/2022]
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Hennen J, Angert I, Hur KH, Gant Luxton GW, Mueller JD. Investigating LINC Complex Protein Homo-oligomerization in the Nuclear Envelopes of Living Cells Using Fluorescence Fluctuation Spectroscopy. Methods Mol Biol 2018; 1840:121-135. [PMID: 30141043 DOI: 10.1007/978-1-4939-8691-0_11] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Linkers of nucleoskeleton and cytoskeleton (LINC) complexes are conserved nuclear envelope (NE) spanning molecular bridges which mechanically integrate the nucleus with the cytoskeleton and mediate force transmission into the nucleoplasm. Despite their critical roles in fundamental cellular processes such as meiotic chromosome and nuclear positioning, the mechanism of LINC complex assembly in cells remains unclear. To begin to address this deficit, we recently developed z-scan fluorescence fluctuation spectroscopy (FFS) and brightness analysis as a method for quantifying the oligomeric states of fluorescent protein-tagged NE proteins including nesprins and SUN proteins. Since the homo-oligomerization of SUN2 is critical for its ability to interact with nesprins within the perinuclear space, the knowledge obtained through quantitative brightness experiments reveals important insights into the in vivo mechanisms of LINC complex assembly. Here we describe the procedure we use to determine the brightness of proteins in the NE of living cells. In addition to the measurement procedure, we discuss the instrumentation requirements and present the results of applying this procedure to measure the brightness of nesprin-2 and SUN2.
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Affiliation(s)
- Jared Hennen
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA
| | - Isaac Angert
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA
| | - Kwang-Ho Hur
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA
| | - G W Gant Luxton
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, USA.
| | - Joachim D Mueller
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA.
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Majumder S, Willey PT, DeNies MS, Liu AP, Luxton GWG. A synthetic biology platform for the reconstitution and mechanistic dissection of LINC complex assembly. J Cell Sci 2018; 132:jcs.219451. [DOI: 10.1242/jcs.219451] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 09/19/2018] [Indexed: 11/20/2022] Open
Abstract
The linker of nucleoskeleton and cytoskeleton (LINC) is a conserved nuclear envelope-spanning molecular bridge that is responsible for the mechanical integration of the nucleus with the cytoskeleton. LINC complexes are formed by a transluminal interaction between the outer and inner nuclear membrane KASH and SUN proteins, respectively. Despite recent structural insights, our mechanistic understanding of LINC complex assembly remains limited by the lack of an experimental system for its in vitro reconstitution and manipulation. Here, we describe artificial nuclear membranes (ANMs) as a synthetic biology platform based on mammalian cell-free expression for the rapid reconstitution of SUN proteins in supported lipid bilayers. We demonstrate that SUN1 and SUN2 are oriented in ANMs with solvent-exposed C-terminal KASH-binding SUN domains. We also find that SUN2 possesses a single transmembrane domain, while SUN1 possesses three. Finally, SUN protein-containing ANMs bind synthetic KASH peptides, thereby reconstituting the LINC complex core. This work represents the first in vitro reconstitution of KASH-binding SUN proteins in supported lipid bilayers using cell-free expression, which will be invaluable for testing proposed models of LINC complex assembly and its regulation.
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Affiliation(s)
- Sagardip Majumder
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48019, USA
| | - Patrick T. Willey
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Maxwell S. DeNies
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI, 48019, USA
| | - Allen P. Liu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48019, USA
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI, 48019, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48019, USA
- Biophysics Program, University of Michigan, Ann Arbor, MI, 48019, USA
| | - G. W. Gant Luxton
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
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