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Liu H, Yan P, Wu C, Rao M, Zhu J, Lv L, Li W, Liang Y, Qi S, Lu K, Kong E. Palmitoylated Sept8-204 modulates learning and anxiety by regulating filopodia arborization and actin dynamics. Sci Signal 2023; 16:eadi8645. [PMID: 38051778 DOI: 10.1126/scisignal.adi8645] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 11/02/2023] [Indexed: 12/07/2023]
Abstract
Septin proteins are involved in diverse physiological functions, including the formation of specialized cytoskeletal structures. Septin 8 (Sept8) is implicated in spine morphogenesis and dendritic branching through palmitoylation. We explored the role and regulation of a Sept8 variant in human neural-like cells and in the mouse brain. We identified Sept8-204 as a brain-specific variant of Sept8 that was abundant in neurons and modified by palmitoylation, specifically at Cys469, Cys470, and Cys472. Sept8-204 palmitoylation was mediated by the palmitoyltransferase ZDHHC7 and was removed by the depalmitoylase PPT1. Palmitoylation of Sept8-204 bound to F-actin and induced cytoskeletal dynamics to promote the outgrowth of filopodia in N2a cells and the arborization of neurites in hippocampal neurons. In contrast, a Sept8-204 variant that could not be palmitoylated because of mutation of all three Cys residues (Sept8-204-3CA) lost its ability to bind F-actin, and expression of this mutant did not promote morphological changes. Genetic deletion of Sept8, Sept8-204, or Zdhhc7 caused deficits in learning and memory and promoted anxiety-like behaviors in mice. Our findings provide greater insight into the regulation of Sept8-204 by palmitoylation and its role in neuronal morphology and function in relation to cognition.
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Affiliation(s)
- Huicong Liu
- Second Affiliated Hospital of Xinxiang Medical University, Xinxiang 453003, China
- Institute of Psychiatry and Neuroscience, Xinxiang Key Laboratory of Protein Palmitoylation and Major Human Diseases, Xinxiang Medical University, Xinxiang 453003, China
| | - Peipei Yan
- Second Affiliated Hospital of Xinxiang Medical University, Xinxiang 453003, China
- Institute of Psychiatry and Neuroscience, Xinxiang Key Laboratory of Protein Palmitoylation and Major Human Diseases, Xinxiang Medical University, Xinxiang 453003, China
| | - Can Wu
- Institute of Psychiatry and Neuroscience, Xinxiang Key Laboratory of Protein Palmitoylation and Major Human Diseases, Xinxiang Medical University, Xinxiang 453003, China
| | - Muding Rao
- Institute of Psychiatry and Neuroscience, Xinxiang Key Laboratory of Protein Palmitoylation and Major Human Diseases, Xinxiang Medical University, Xinxiang 453003, China
| | - Jiangli Zhu
- Department of Urology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and National Collaborative Innovation Center, Chengdu 610041, China
| | - Luxian Lv
- Second Affiliated Hospital of Xinxiang Medical University, Xinxiang 453003, China
| | - Wenqiang Li
- Second Affiliated Hospital of Xinxiang Medical University, Xinxiang 453003, China
| | - Yinming Liang
- Institute of Psychiatry and Neuroscience, Xinxiang Key Laboratory of Protein Palmitoylation and Major Human Diseases, Xinxiang Medical University, Xinxiang 453003, China
| | - Shiqian Qi
- Department of Urology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and National Collaborative Innovation Center, Chengdu 610041, China
| | - Kefeng Lu
- Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610065, China
| | - Eryan Kong
- Second Affiliated Hospital of Xinxiang Medical University, Xinxiang 453003, China
- Institute of Psychiatry and Neuroscience, Xinxiang Key Laboratory of Protein Palmitoylation and Major Human Diseases, Xinxiang Medical University, Xinxiang 453003, China
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Perry JA, Werner ME, Heck BW, Maddox PS, Maddox AS. Septins throughout phylogeny are predicted to have a transmembrane domain, which in Caenorhabditis elegans is functionally important. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.20.567915. [PMID: 38045322 PMCID: PMC10690161 DOI: 10.1101/2023.11.20.567915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Septins, a conserved family of filament-forming proteins, contribute to eukaryotic cell division, polarity, and membrane trafficking. Septins are thought to act in these processes by scaffolding other proteins to the plasma membrane. The mechanisms by which septins associate with the plasma membrane are not well understood but can involve two polybasic domains and/or an amphipathic helix. We discovered that the genomes of organisms throughout phylogeny, but not most commonly used model organisms, encode one or more septins predicted to have transmembrane domains. The nematode Caenorhabditis elegans, which was thought to express only two septin proteins, UNC-59 and UNC-61, translates multiple isoforms of UNC-61, and one isoform, UNC-61a, is predicted to contain a transmembrane domain. UNC-61a localizes specifically to the apical membrane of the C. elegans vulva and is important for maintaining vulval morphology. UNC-61a partially compensates for the loss of the other two UNC-61 isoforms, UNC-61b and UNC-61c. The UNC-61a transmembrane domain is sufficient to localize a fluorophore to membranes in mammalian cells, and its deletion from UNC-61a recapitulates the phenotypes of unc-61a null animals. The localization and loss-of-function phenotypes of UNC-61a and its transmembrane domain suggest roles in cell polarity and secretion and help explain the cellular and tissue biological underpinnings of C. elegans septin null alleles' enigmatically hypomorphic phenotypes. Together, our findings reveal a novel mechanism of septin-membrane association with profound implications for the dynamics and regulation of this association.
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Affiliation(s)
- Jenna A Perry
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Michael E Werner
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Bryan W Heck
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Paul S Maddox
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Amy Shaub Maddox
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC
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Cannon KS, Vargas-Muniz JM, Billington N, Seim I, Ekena J, Sellers JR, Gladfelter AS. A gene duplication of a septin reveals a developmentally regulated filament length control mechanism. J Cell Biol 2023; 222:e202204063. [PMID: 36786832 PMCID: PMC9960279 DOI: 10.1083/jcb.202204063] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 11/20/2022] [Accepted: 01/19/2023] [Indexed: 02/15/2023] Open
Abstract
Septins are a family of conserved filament-forming proteins that function in multiple cellular processes. The number of septin genes within an organism varies, and higher eukaryotes express many septin isoforms due to alternative splicing. It is unclear if different combinations of septin proteins in complex alter the polymers' biophysical properties. We report that a duplication event within the CDC11 locus in Ashbya gossypii gave rise to two similar but distinct Cdc11 proteins: Cdc11a and Cdc1b. CDC11b transcription is developmentally regulated, producing different amounts of Cdc11a- and Cdc11b-complexes in the lifecycle of Ashbya gossypii. Deletion of either gene results in distinct cell polarity defects, suggesting non-overlapping functions. Cdc11a and Cdc11b complexes have differences in filament length and membrane-binding ability. Thus, septin subunit composition has functional consequences on filament properties and cell morphogenesis. Small sequence differences elicit distinct biophysical properties and cell functions of septins, illuminating how gene duplication could be a driving force for septin gene expansions seen throughout the tree of life.
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Affiliation(s)
- Kevin S. Cannon
- Biology Department, University of North Carolina, Chapel Hill, NC, USA
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC, USA
| | - Jose M. Vargas-Muniz
- Microbiology Program, School of Biological Sciences, Southern Illinois University, Carbondale, IL, USA
| | - Neil Billington
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Ian Seim
- Biology Department, University of North Carolina, Chapel Hill, NC, USA
- Department of Applied Physical Sciences, University of North Carolina, Chapel Hill, NC, USA
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Joanne Ekena
- Biology Department, University of North Carolina, Chapel Hill, NC, USA
| | - James R. Sellers
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Amy. S. Gladfelter
- Biology Department, University of North Carolina, Chapel Hill, NC, USA
- Marine Biological Laboratory, Woods Hole, MA, USA
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Shen B, Gao H, Zhang D, Yu H, Chen J, Huang S, Gu P, Zhong Y. miR-124-3p regulates the proliferation and differentiation of retinal progenitor cells through SEPT10. Cell Tissue Res 2023:10.1007/s00441-023-03750-0. [PMID: 36802303 DOI: 10.1007/s00441-023-03750-0] [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: 01/27/2022] [Accepted: 01/26/2023] [Indexed: 02/23/2023]
Abstract
Retinal degenerative diseases such as glaucoma, retinitis pigmentosa, and age-related macular degeneration pose serious threats to human visual health due to lack of effective therapeutic approaches. In recent years, the transplantation of retinal progenitor cells (RPCs) has shown increasing promise in the treatment of these diseases; however, the application of RPC transplantation is limited by both their poor proliferation and their differentiation capabilities. Previous studies have shown that microRNAs (miRNA) act as essential mediators in the fate determination of stem/progenitor cells. In this study, we hypothesized that miR-124-3p plays a regulatory role in the fate of RPC determination by targeting Septin10 (SEPT10) in vitro. We observed that the overexpression of miR124-3p downregulates SEPT10 expression in RPCs, leading to reduced RPC proliferation and increased differentiation, specifically towards both neurons and ganglion cells. Conversely, antisense knockdown of miR-124-3p was shown to boost SEPT10 expression, enhance RPC proliferation, and attenuate differentiation. Moreover, overexpression of SEPT10 rescued miR-124-3p-caused proliferation deficiency while weakening the enhancement of miR-124-3p-induced-RPC differentiation. Results from this study show that miR-124-3p regulates RPC proliferation and differentiation by targeting SEPT10. Furthermore, our findings enable a more comprehensive understanding into the mechanisms of proliferation and differentiation of RPC fate determination. Ultimately, this study may be useful for helping researchers and clinicians to develop more promising and effective approaches to optimize the use of RPCs in treating retinal degeneration diseases.
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Affiliation(s)
- Bingqiao Shen
- Department of Ophthalmology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Huiqin Gao
- Department of Ophthalmology, Ninth People's Hospital Affiliated Medical School, Shanghai Jiaotong University, 639 Zhizaoju Road, Shanghai, 200011, China
| | - Dandan Zhang
- Department of Ophthalmology, Ninth People's Hospital Affiliated Medical School, Shanghai Jiaotong University, 639 Zhizaoju Road, Shanghai, 200011, China
| | - Huan Yu
- Department of Ophthalmology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Junjue Chen
- Department of Ophthalmology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Shouyue Huang
- Department of Ophthalmology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Ping Gu
- Department of Ophthalmology, Ninth People's Hospital Affiliated Medical School, Shanghai Jiaotong University, 639 Zhizaoju Road, Shanghai, 200011, China.
| | - Yisheng Zhong
- Department of Ophthalmology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China.
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Fischer M, Frank D, Rösler R, Johnsson N, Gronemeyer T. Biochemical Characterization of a Human Septin Octamer. Front Cell Dev Biol 2022; 10:771388. [PMID: 35309913 PMCID: PMC8928218 DOI: 10.3389/fcell.2022.771388] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 02/14/2022] [Indexed: 11/25/2022] Open
Abstract
Septins are part of the cytoskeleton and polymerize into non-polar filaments of heteromeric hexamers or octamers. They belong to the class of P-loop GTPases but the roles of GTP binding and hydrolysis on filament formation and dynamics are not well understood. The basic human septin building block is the septin rod, a hetero-octamer composed of SEPT2, SEPT6, SEPT7, and SEPT9 with a stoichiometry of 2:2:2:2 (2-6-7-9-9-7-6-2). Septin rods polymerize by end-to-end and lateral joining into linear filaments and higher ordered structures such as rings, sheets, and gauzes. We purified a recombinant human septin octamer from E. coli for in vitro experimentation that is able to polymerize into filaments. We could show that the C-terminal region of the central SEPT9 subunit contributes to filament formation and that the human septin rod decreases the rate of in vitro actin polymerization. We provide further first kinetic data on the nucleotide uptake- and exchange properties of human hexameric and octameric septin rods. We could show that nucleotide uptake prior to hydrolysis is a dynamic process and that a bound nucleotide is exchangeable. However, the hydrolyzed γ-phosphate is not released from the native protein complex. We consequently propose that GTP hydrolysis in human septins does not follow the typical mechanism known from other small GTPases.
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Affiliation(s)
- Martin Fischer
- Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Dominik Frank
- Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Reinhild Rösler
- Core Unit Mass Spectrometry and Proteomics, Ulm University, Ulm, Germany
| | - Nils Johnsson
- Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Thomas Gronemeyer
- Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
- *Correspondence: Thomas Gronemeyer,
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Cavini IA, Leonardo DA, Rosa HVD, Castro DKSV, D'Muniz Pereira H, Valadares NF, Araujo APU, Garratt RC. The Structural Biology of Septins and Their Filaments: An Update. Front Cell Dev Biol 2021; 9:765085. [PMID: 34869357 PMCID: PMC8640212 DOI: 10.3389/fcell.2021.765085] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/27/2021] [Indexed: 01/22/2023] Open
Abstract
In order to fully understand any complex biochemical system from a mechanistic point of view, it is necessary to have access to the three-dimensional structures of the molecular components involved. Septins and their oligomers, filaments and higher-order complexes are no exception. Indeed, the spontaneous recruitment of different septin monomers to specific positions along a filament represents a fascinating example of subtle molecular recognition. Over the last few years, the amount of structural information available about these important cytoskeletal proteins has increased dramatically. This has allowed for a more detailed description of their individual domains and the different interfaces formed between them, which are the basis for stabilizing higher-order structures such as hexamers, octamers and fully formed filaments. The flexibility of these structures and the plasticity of the individual interfaces have also begun to be understood. Furthermore, recently, light has been shed on how filaments may bundle into higher-order structures by the formation of antiparallel coiled coils involving the C-terminal domains. Nevertheless, even with these advances, there is still some way to go before we fully understand how the structure and dynamics of septin assemblies are related to their physiological roles, including their interactions with biological membranes and other cytoskeletal components. In this review, we aim to bring together the various strands of structural evidence currently available into a more coherent picture. Although it would be an exaggeration to say that this is complete, recent progress seems to suggest that headway is being made in that direction.
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Affiliation(s)
- Italo A Cavini
- São Carlos Institute of Physics, University of São Paulo, São Carlos, Brazil
| | - Diego A Leonardo
- São Carlos Institute of Physics, University of São Paulo, São Carlos, Brazil
| | - Higor V D Rosa
- São Carlos Institute of Physics, University of São Paulo, São Carlos, Brazil
| | - Danielle K S V Castro
- São Carlos Institute of Physics, University of São Paulo, São Carlos, Brazil.,São Carlos Institute of Chemistry, University of São Paulo, São Carlos, Brazil
| | | | | | - Ana P U Araujo
- São Carlos Institute of Physics, University of São Paulo, São Carlos, Brazil
| | - Richard C Garratt
- São Carlos Institute of Physics, University of São Paulo, São Carlos, Brazil
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Hanbuli HME, Amer SII, Ibrahim HA. Expression of Septin 2 and Her2/neu in Colorectal Cancer. J Microsc Ultrastruct 2021; 10:197-203. [PMID: 36687331 PMCID: PMC9846928 DOI: 10.4103/jmau.jmau_38_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 05/15/2021] [Accepted: 07/05/2021] [Indexed: 01/25/2023] Open
Abstract
Background Colorectal cancer (CRC) is a common and lethal disease. Septin 2 belongs to the same class of GTPases as the RAS oncogenes influence the invasion and metastasis of many types of tumor cells. Furthermore, HER2/neu is involved in the tumor genesis and progression of various types of tumors. The role of both molecules is still questionable in CRC. Aim The aim of the study is to examine the expression of septin 2 and Her2/neu in patients with CRC. Materials and Methods The study was conducted on 2 groups; the first group consisted of 70 paraffin blocks for CRC patients and the second group was formed of 24 blocks from patients diagnosed as colorectal adenoma. For each adenoma and carcinoma case, a section was immunohistochemically stained using antihuman SEPT2 polyclonal antibody. For each carcinoma case, another section was immunostained using monoclonal anti-HER2/neu. The results were statistically analyzed and compared with the collected clinicopathologic data of the cases. Results For the carcinoma patients, there was a significant association between SEPT2 staining intensity and histologic type (P = 0.001) and grade (P < 0.001), tumor T (P = 0.001) and N (P = 0.011) stages and the presence of lymphovascular invasion (P < 0.001) and a significant association between Her2/neu immunoreactivity scores (IRSs) and histologic grade (P = 0.048), tumor T (P < 0.001) and N (P = 0.019) stages and the presence of perineural (P = 0.004) and lymphovascular (P = 0.003) invasion. In colonic adenoma patients, there was a significant relation between septin 2 IRSs and the grade of dysplasia in the adenoma (P < 0.001) and significant relation with its expression in carcinoma group (P < 0.001). Conclusion A potential prognostic role of septin 2 and Her2/neu for patients with CRC is suggested as expression of both markers was associated with many important prognostic clinicopathologic variables in patients of CRC.
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Affiliation(s)
- Hala M. El Hanbuli
- Department of Pathology, Faculty of Medicine, Fayoum University, Faiyum, Egypt,Address for correspondence: Associate Prof. Hala M. El Hanbuli, Department of Pathology, Faculty of Medicine, Fayoum University, Keman Fares, Fayoum Governorate, Faiyum 63514, Egypt. E-mail:
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8
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Devlin L, Okletey J, Perkins G, Bowen JR, Nakos K, Montagna C, Spiliotis ET. Proteomic profiling of the oncogenic septin 9 reveals isoform-specific interactions in breast cancer cells. Proteomics 2021; 21:e2100155. [PMID: 34409731 DOI: 10.1002/pmic.202100155] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/05/2021] [Indexed: 02/06/2023]
Abstract
Septins are a family of multimeric GTP-binding proteins, which are abnormally expressed in cancer. Septin 9 (SEPT9) is an essential and ubiquitously expressed septin with multiple isoforms, which have differential expression patterns and effects in breast cancer cells. It is unknown, however, if SEPT9 isoforms associate with different molecular networks and functions. Here, we performed a proteomic screen in MCF-7 breast cancer cells to identify the interactome of GFP-SEPT9 isoforms 1, 4 and 5, which vary significantly in their N-terminal extensions. While all three isoforms associated with SEPT2 and SEPT7, the truncated SEPT9_i4 and SEPT9_i5 interacted with septins of the SEPT6 group more promiscuously than SEPT9_i1, which bound predominately SEPT8. Spatial mapping and functional clustering of non-septin partners showed isoform-specific differences in interactions with proteins of distinct subcellular organelles (e.g., nuclei, centrosomes, cilia) and functions such as cell signalling and ubiquitination. The interactome of the full length SEPT9_i1 was more enriched in cytoskeletal regulators, while the truncated SEPT9_i4 and SEPT9_i5 exhibited preferential and isoform-specific interactions with nuclear, signalling, and ubiquitinating proteins. These data provide evidence for isoform-specific interactions, which arise from truncations in the N-terminal extensions of SEPT9, and point to novel roles in the pathogenesis of breast cancer.
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Affiliation(s)
- Louis Devlin
- Department of Biology, Drexel University, Philadelphia, Pennsylvania, USA.,Sanofi Pasteur, Swiftwater, Pennsylvania, USA
| | - Joshua Okletey
- Department of Biology, Drexel University, Philadelphia, Pennsylvania, USA
| | | | - Jonathan R Bowen
- Department of Biology, Drexel University, Philadelphia, Pennsylvania, USA
| | - Konstantinos Nakos
- Department of Biology, Drexel University, Philadelphia, Pennsylvania, USA
| | - Cristina Montagna
- Department of Radiology & Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey, USA
| | - Elias T Spiliotis
- Department of Biology, Drexel University, Philadelphia, Pennsylvania, USA
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Novel Functions of the Septin Cytoskeleton: Shaping Up Tissue Inflammation and Fibrosis. THE AMERICAN JOURNAL OF PATHOLOGY 2020; 191:40-51. [PMID: 33039354 DOI: 10.1016/j.ajpath.2020.09.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 08/24/2020] [Accepted: 09/16/2020] [Indexed: 12/19/2022]
Abstract
Chronic inflammatory diseases cause profound alterations in tissue homeostasis, including unchecked activation of immune and nonimmune cells leading to disease complications such as aberrant tissue repair and fibrosis. Current anti-inflammatory therapies are often insufficient in preventing or reversing these complications. Remodeling of the intracellular cytoskeleton is critical for cell activation in inflamed and fibrotic tissues; however, the cytoskeleton has not been adequately explored as a therapeutic target in inflammation. Septins are GTP-binding proteins that self-assemble into higher order cytoskeletal structures. The septin cytoskeleton exhibits a number of critical cellular functions, including regulation of cell shape and polarity, cytokinesis, cell migration, vesicle trafficking, and receptor signaling. Surprisingly, little is known about the role of the septin cytoskeleton in inflammation. This article reviews emerging evidence implicating different septins in the regulation of host-pathogen interactions, immune cell functions, and tissue fibrosis. Targeting of the septin cytoskeleton as a potential future therapeutic intervention in human inflammatory and fibrotic diseases is also discussed.
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Nakos K, Radler MR, Spiliotis ET. Septin 2/6/7 complexes tune microtubule plus-end growth and EB1 binding in a concentration- and filament-dependent manner. Mol Biol Cell 2019; 30:2913-2928. [PMID: 31577529 PMCID: PMC6822581 DOI: 10.1091/mbc.e19-07-0362] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Septins (SEPTs) are filamentous guanosine-5′-triphosphate (GTP)-binding proteins, which affect microtubule (MT)-dependent functions including membrane trafficking and cell division, but their precise role in MT dynamics is poorly understood. Here, in vitro reconstitution of MT dynamics with SEPT2/6/7, the minimal subunits of septin heteromers, shows that SEPT2/6/7 has a biphasic concentration-dependent effect on MT growth. Lower concentrations of SEPT2/6/7 enhance MT plus-end growth and elongation, while higher and intermediate concentrations inhibit and pause plus-end growth, respectively. We show that SEPT2/6/7 has a modest preference for GTP- over guanosine diphosphate (GDP)-bound MT lattice and competes with end-binding protein 1 (EB1) for binding to guanosine 5′-O-[γ-thio]triphosphate (GTPγS)-stabilized MTs, which mimic the EB1-preferred GDP-Pi state of polymerized tubulin. Strikingly, SEPT2/6/7 triggers EB1 dissociation from plus-end tips in cis by binding to the MT lattice and in trans when MT plus ends collide with SEPT2/6/7 filaments. At these intersections, SEPT2/6/7 filaments were more potent barriers than actin filaments in pausing MT growth and dissociating EB1 in vitro and in live cells. These data demonstrate that SEPT2/6/7 complexes and filaments can directly impact MT plus-end growth and the tracking of plus end–binding proteins and thereby may facilitate the capture of MT plus ends at intracellular sites of septin enrichment.
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Affiliation(s)
| | - Megan R Radler
- Department of Biology, Drexel University, Philadelphia, PA 19104
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Shen N, Wang T, Li D, Zhu Y, Xie H, Lu Y. Hypermethylation of the SEPT9 Gene Suggests Significantly Poor Prognosis in Cancer Patients: A Systematic Review and Meta-Analysis. Front Genet 2019; 10:887. [PMID: 31608117 PMCID: PMC6761278 DOI: 10.3389/fgene.2019.00887] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 08/22/2019] [Indexed: 12/27/2022] Open
Abstract
Background: Aberrant hypermethylation of the Septin 9 (SEPT9) is an early event in several human cancers, and increasing studies have reported good performance of methylated SEPT9 (mSEPT9) in cancer diagnosis. Recent studies further focused on its value in cancer prognosis, but results are not clearly elucidated. Methods: A comprehensive search to identify relevant studies about the association between mSEPT9 and cancer prognosis was conducted through the EMBASE, PubMed, and Web of Science databases (up to January 2019). The main outcomes were overall survival (OS) and disease-free survival (DFS). The hazard ratio (HR) and 95% confidence interval (CI) for OS and DFS were extracted from each included study and pooled using a random-effects model. Results: Ten eligible studies comprising 1,266 cancer patients were included. Results demonstrated that mSEPT9 was associated with poor OS (HR = 2.07, 95% CI = 1.40–3.06). Specially, mSEPT9 detected in preoperative plasma predicted worse OS in cancer patients (HR = 3.25, 95% CI = 1.93–5.48). In addition, we also identified a significant association of mSEPT9 with decreased DFS of cancer (HR = 3.24, 95% CI = 1.81–5.79). Conclusion: Our meta-analysis supports that mSEPT9 is associated with reduced OS and DFS in cancer patients. Moreover, detection of mSEPT9 using plasma appears to be a convenient and promising way to predict long-term survival of cancer patients.
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Affiliation(s)
- Na Shen
- Department of Laboratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Ting Wang
- Department of Laboratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Delei Li
- Department of Laboratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yaowu Zhu
- Department of Laboratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Huaping Xie
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yanjun Lu
- Department of Laboratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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12
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D'Amore C, Salizzato V, Borgo C, Cesaro L, Pinna LA, Salvi M. A Journey through the Cytoskeleton with Protein Kinase CK2. Curr Protein Pept Sci 2019; 20:547-562. [PMID: 30659536 DOI: 10.2174/1389203720666190119124846] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 12/21/2018] [Accepted: 01/09/2019] [Indexed: 01/15/2023]
Abstract
Substrate pleiotropicity, a very acidic phosphorylation consensus sequence, and an apparent uncontrolled activity, are the main features of CK2, a Ser/Thr protein kinase that is required for a plethora of cell functions. Not surprisingly, CK2 appears to affect cytoskeletal structures and correlated functions such as cell shape, mechanical integrity, cell movement and division. This review outlines our current knowledge of how CK2 regulates cytoskeletal structures, and discusses involved pathways and molecular mechanisms.
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Affiliation(s)
- Claudio D'Amore
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58/B, Padova, Italy
| | - Valentina Salizzato
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58/B, Padova, Italy.,CNR Institute of Neurosciences, Via U. Bassi 58/B, Padova, Italy
| | - Christian Borgo
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58/B, Padova, Italy
| | - Luca Cesaro
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58/B, Padova, Italy
| | - Lorenzo A Pinna
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58/B, Padova, Italy.,CNR Institute of Neurosciences, Via U. Bassi 58/B, Padova, Italy
| | - Mauro Salvi
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58/B, Padova, Italy
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13
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Kumagai PS, Martins CS, Sales EM, Rosa HV, Mendonça DC, Damalio JCP, Spinozzi F, Itri R, Araujo APU. Correct partner makes the difference: Septin G-interface plays a critical role in amyloid formation. Int J Biol Macromol 2019; 133:428-435. [DOI: 10.1016/j.ijbiomac.2019.04.105] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 04/12/2019] [Accepted: 04/15/2019] [Indexed: 01/04/2023]
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14
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An Interaction Network of the Human SEPT9 Established by Quantitative Mass Spectrometry. G3-GENES GENOMES GENETICS 2019; 9:1869-1880. [PMID: 30975701 PMCID: PMC6553528 DOI: 10.1534/g3.119.400197] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Septins regulate the organization of the actin cytoskeleton, vesicle transport and fusion, chromosome alignment and segregation, and cytokinesis in mammalian cells. SEPT9 is part of the core septin hetero-octamer in human cells which is composed of SEPT2, SEPT6, SEPT7, and SEPT9. SEPT9 has been linked to a variety of intracellular functions as well as to diseases and diverse types of cancer. A targeted high-throughput approach to systematically identify the interaction partners of SEPT9 has not yet been performed. We applied a quantitative proteomics approach to establish an interactome of SEPT9 in human fibroblast cells. Among the newly identified interaction partners were members of the myosin family and LIM domain containing proteins. Fluorescence microscopy of SEPT9 and its interaction partners provides additional evidence that SEPT9 might participate in vesicle transport from and to the plasma membrane as well as in the attachment of actin stress fibers to cellular adhesions.
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15
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Septins are critical regulators of osteoclastic bone resorption. Sci Rep 2018; 8:13016. [PMID: 30158637 PMCID: PMC6115361 DOI: 10.1038/s41598-018-31159-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 08/07/2018] [Indexed: 12/23/2022] Open
Abstract
Septins are known to play key roles in supporting cytoskeletal stability, vesicular transport, endo-/exocytosis, stabilizing cellular membranes and forming diffusion barriers. Their function in mammalian cells is poorly investigated. The osteoclast offers an interesting tool to investigate septins because all cellular activities septins were reported to be involved in are critical for osteoclasts. However, the existence of septins in osteoclasts has not even been reported. Here we show that the SEPT9 gene and Septin 9 (SEPT9) protein are expressed and synthesized during differentiation of human osteoclasts. Pharmacological stabilization of septin filaments dose dependently inhibits bone resorption of human osteoclasts in vitro suggesting a role for septins in bone resorption. Attesting to this, conditional deletion of Sept9 in mice leads to elevated levels of trabecular bone and diminished femoral growth in vivo. Finally, systematic interrogation of the spatial organization of SEPT9 by confocal microscopy reveals that SEPT9 is closely associated to the structures known to be critical for osteoclast activity. We propose that septins in general and SEPT9 in particular play a previously unappreciated role in osteoclastic bone resorption.
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16
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Spiliotis ET. Spatial effects - site-specific regulation of actin and microtubule organization by septin GTPases. J Cell Sci 2018; 131:jcs207555. [PMID: 29326311 PMCID: PMC5818061 DOI: 10.1242/jcs.207555] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The actin and microtubule cytoskeletons comprise a variety of networks with distinct architectures, dynamics and protein composition. A fundamental question in eukaryotic cell biology is how these networks are spatially and temporally controlled, so they are positioned in the right intracellular places at the right time. While significant progress has been made in understanding the self-assembly of actin and microtubule networks, less is known about how they are patterned and regulated in a site-specific manner. In mammalian systems, septins are a large family of GTP-binding proteins that multimerize into higher-order structures, which associate with distinct subsets of actin filaments and microtubules, as well as membranes of specific curvature and lipid composition. Recent studies have shed more light on how septins interact with actin and microtubules, and raised the possibility that the cytoskeletal topology of septins is determined by their membrane specificity. Importantly, new functions have emerged for septins regarding the generation, maintenance and positioning of cytoskeletal networks with distinct organization and biochemical makeup. This Review presents new and past findings, and discusses septins as a unique regulatory module that instructs the local differentiation and positioning of distinct actin and microtubule networks.
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Affiliation(s)
- Elias T Spiliotis
- Drexel University, Department of Biology, Drexel University, Philadelphia, PA 19104, USA
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17
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Interaction of Recombinant Gallus gallus SEPT5 and Brain Proteins of H5N1-Avian Influenza Virus-Infected Chickens. Proteomes 2017; 5:proteomes5030023. [PMID: 28895884 PMCID: PMC5620540 DOI: 10.3390/proteomes5030023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 09/05/2017] [Accepted: 09/07/2017] [Indexed: 11/16/2022] Open
Abstract
Septin forms a conserved family of cytoskeletal guanosine triphosphate (GTP) binding proteins that have diverse roles in protein scaffolding, vesicle trafficking, and cytokinesis. The involvement of septins in infectious viral disease pathogenesis has been demonstrated by the upregulation of SEPT5 protein and its mRNA in brain tissues of H5N1-infected chickens, thus, providing evidence for the potential importance of this protein in the pathogenesis of neurovirulence caused by the avian influenza virus. In this study, cloning, expression, and purification of Gallus gallus SEPT5 protein was performed in Escherichia coli. The SEPT5 gene was inserted into the pRSETB expression vector, transformed in the E. coli BL21 (DE3) strain and the expression of SEPT5 protein was induced by IPTG. The SEPT5 protein was shown to be authentic as it was able to be pulled down by a commercial anti-SEPT5 antibody in a co-immunoprecipitation assay. In vivo aggregation of the recombinant protein was limited by cultivation at a reduced temperature of 16 °C. Using co-immunoprecipitation techniques, the purified recombinant SEPT5 protein was used to pull down host’s interacting or binding proteins, i.e., proteins of brains of chickens infected with the H5N1 influenza virus. Interacting proteins, such as CRMP2, tubulin proteins, heat-shock proteins and other classes of septins were identified using LCMS/MS. Results from this study suggest that the codon-optimized SEPT5 gene can be efficiently expressed in the E. coli bacterial system producing authentic SEPT5 protein, thus, enabling multiple host’s proteins to interact with the SEPT5 protein.
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18
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Häcker G. The role of septins in infections with vacuole-dwelling intracellular bacteria. Int J Med Microbiol 2017; 308:25-31. [PMID: 28784332 DOI: 10.1016/j.ijmm.2017.07.010] [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: 06/07/2017] [Revised: 07/21/2017] [Accepted: 07/26/2017] [Indexed: 10/19/2022] Open
Abstract
Septins are a relatively little understood group of GTPases that form large assemblies in cells from all eukaryotes other than plants. Septins were first identified in cell division but have also been implicated in microbial infections. Septins often associate with cytoskeletal proteins - most often described for filamentous (F-) actin - and are considered cytoskeletal components themselves. Septins have increasingly been found to partake in processes that are linked to intracellular membranes, from mitochondria to phagosomes, and evidence is accumulating that septins specifically bind to membranes. Since a number of microorganisms have specialized to live and grow inside membranous vacuoles in the cytosol of mammalian cells, this membrane-association of septins suggests that septins may also be involved in the membranous, vacuolar structures that develop around these microbes. However, data are limited on this issue: septins have been identified by proteome analysis on some microbe-bearing vacuoles, but more extensive experimental data are only available for infections with the obligate intracellular bacterium Chlamydia trachomatis. In this review article I will discuss the available data and speculate about the mechanisms of recruitment and potential functions of septins for vacuole-dwelling microorganisms, which may be peculiar to Chlamydia or may pertain more generally to this class of microbes.
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Affiliation(s)
- Georg Häcker
- Institute of Medical Microbiology and Hygiene, Medical Center-University of Freiburg, Faculty of Medicine, 79104 Freiburg, Germany.
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19
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Kaltdorf KV, Schulze K, Helmprobst F, Kollmannsberger P, Dandekar T, Stigloher C. FIJI Macro 3D ART VeSElecT: 3D Automated Reconstruction Tool for Vesicle Structures of Electron Tomograms. PLoS Comput Biol 2017; 13:e1005317. [PMID: 28056033 PMCID: PMC5289597 DOI: 10.1371/journal.pcbi.1005317] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 02/02/2017] [Accepted: 12/18/2016] [Indexed: 11/18/2022] Open
Abstract
Automatic image reconstruction is critical to cope with steadily increasing data from advanced microscopy. We describe here the Fiji macro 3D ART VeSElecT which we developed to study synaptic vesicles in electron tomograms. We apply this tool to quantify vesicle properties (i) in embryonic Danio rerio 4 and 8 days past fertilization (dpf) and (ii) to compare Caenorhabditis elegans N2 neuromuscular junctions (NMJ) wild-type and its septin mutant (unc-59(e261)). We demonstrate development-specific and mutant-specific changes in synaptic vesicle pools in both models. We confirm the functionality of our macro by applying our 3D ART VeSElecT on zebrafish NMJ showing smaller vesicles in 8 dpf embryos then 4 dpf, which was validated by manual reconstruction of the vesicle pool. Furthermore, we analyze the impact of C. elegans septin mutant unc-59(e261) on vesicle pool formation and vesicle size. Automated vesicle registration and characterization was implemented in Fiji as two macros (registration and measurement). This flexible arrangement allows in particular reducing false positives by an optional manual revision step. Preprocessing and contrast enhancement work on image-stacks of 1nm/pixel in x and y direction. Semi-automated cell selection was integrated. 3D ART VeSElecT removes interfering components, detects vesicles by 3D segmentation and calculates vesicle volume and diameter (spherical approximation, inner/outer diameter). Results are collected in color using the RoiManager plugin including the possibility of manual removal of non-matching confounder vesicles. Detailed evaluation considered performance (detected vesicles) and specificity (true vesicles) as well as precision and recall. We furthermore show gain in segmentation and morphological filtering compared to learning based methods and a large time gain compared to manual segmentation. 3D ART VeSElecT shows small error rates and its speed gain can be up to 68 times faster in comparison to manual annotation. Both automatic and semi-automatic modes are explained including a tutorial.
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Affiliation(s)
- Kristin Verena Kaltdorf
- Division of Electron Microscopy, Biocenter, University of Wuerzburg, Wuerzburg, Germany
- Department of Bioinformatics, Biocenter, University of Wuerzburg, Wuerzburg, Germany
| | - Katja Schulze
- Molecular Biotechnology and Functional Genomics, Technical University of Applied Sciences Wildau, Wildau, Germany
| | - Frederik Helmprobst
- Division of Electron Microscopy, Biocenter, University of Wuerzburg, Wuerzburg, Germany
| | - Philip Kollmannsberger
- Center for Computational and Theoretical Biology, University of Wuerzburg, Wuerzburg, Germany
| | - Thomas Dandekar
- Department of Bioinformatics, Biocenter, University of Wuerzburg, Wuerzburg, Germany
- * E-mail: (TD); (CS)
| | - Christian Stigloher
- Division of Electron Microscopy, Biocenter, University of Wuerzburg, Wuerzburg, Germany
- * E-mail: (TD); (CS)
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20
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Angelis D, Spiliotis ET. Septin Mutations in Human Cancers. Front Cell Dev Biol 2016; 4:122. [PMID: 27882315 PMCID: PMC5101219 DOI: 10.3389/fcell.2016.00122] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Accepted: 10/17/2016] [Indexed: 12/22/2022] Open
Abstract
Septins are GTP-binding proteins that are evolutionarily and structurally related to the RAS oncogenes. Septin expression levels are altered in many cancers and new advances point to how abnormal septin expression may contribute to the progression of cancer. In contrast to the RAS GTPases, which are frequently mutated and actively promote tumorigenesis, little is known about the occurrence and role of septin mutations in human cancers. Here, we review septin missense mutations that are currently in the Catalog of Somatic Mutations in Cancer (COSMIC) database. The majority of septin mutations occur in tumors of the large intestine, skin, endometrium and stomach. Over 25% of the annotated mutations in SEPT2, SEPT4, and SEPT9 belong to large intestine tumors. From all septins, SEPT9 and SEPT14 exhibit the highest mutation frequencies in skin, stomach and large intestine cancers. While septin mutations occur with frequencies lower than 3%, recurring mutations in several invariant and highly conserved amino acids are found across different septin paralogs and tumor types. Interestingly, a significant number of these mutations occur in the GTP-binding pocket and septin dimerization interfaces. Future studies may determine how these somatic mutations affect septin structure and function, whether they contribute to the progression of specific cancers and if they could serve as tumor-specific biomarkers.
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21
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SEPT14 Is Associated with a Reduced Risk for Parkinson's Disease and Expressed in Human Brain. J Mol Neurosci 2016; 59:343-50. [PMID: 27115672 DOI: 10.1007/s12031-016-0738-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 03/22/2016] [Indexed: 12/25/2022]
Abstract
Genes involved in cytoskeletal stability and trafficking, such as MAPT and SNCA, are important risk factors for Parkinson's disease (PD). Two members of the cytoskeletal Septin family, SEPT4 and SEPT5, were implicated in PD pathobiology. We aimed to determine whether Septin genes are associated with Parkinson's disease. To this end, six SNPs located in four different Septin loci were analyzed in 720 PD patients and 740 controls, all of Ashkenazi-Jewish origin. In addition, SEPT14 was sequenced and its expression was determined in different human tissues. Our results revealed that two SNPs in the SEPT14 locus, rs11981883 and rs10241628, were associated with a reduced risk for PD (p = 0.02 and p = 0.005). A third SNP, rs77231105, was localized in the putative promoter of SEPT14 and was predicted to affect the binding of the transcription factor Nkx2.5. This SNP was also associated with a reduced risk for PD (OR = 0.28, p < 0.0007). The three SEPT14 SNPs defined a protective haplotype which significantly reduced the risk for PD by 4-fold (p = 0.002). SEPT14 was found to be expressed in the brain and in the Substantia Nigra. These results suggest that SEPT14 may have a protective role in Parkinson's disease pathogenesis, yet more studies are necessary to validate these results.
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22
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Smith C, Dolat L, Angelis D, Forgacs E, Spiliotis ET, Galkin VE. Septin 9 Exhibits Polymorphic Binding to F-Actin and Inhibits Myosin and Cofilin Activity. J Mol Biol 2015; 427:3273-3284. [PMID: 26297986 DOI: 10.1016/j.jmb.2015.07.026] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Revised: 07/29/2015] [Accepted: 07/31/2015] [Indexed: 02/06/2023]
Abstract
Septins are a highly conserved family of proteins in eukaryotes that is recognized as a novel component of the cytoskeleton. Septin 9 (SEPT9) interacts directly with actin filaments and functions as an actin stress fiber cross-linking protein that promotes the maturation of nascent focal adhesions and cell migration. However, the molecular details of how SEPT9 interacts with F-actin remain unknown. Here, we use electron microscopy and image analysis to show that SEPT9 binds to F-actin in a highly polymorphic fashion. We demonstrate that the basic domain (B-domain) of the N-terminal tail of SEPT9 is responsible for actin cross-linking, while the GTP-binding domain (G-domain) does not bundle F-actin. We show that the B-domain of SEPT9 binds to three sites on F-actin, and the two of these sites overlap with the binding regions of myosin and cofilin. SEPT9 inhibits actin-dependent ATPase activity of myosin and competes with the weakly bound state of myosin for binding to F-actin. At the same time, SEPT9 significantly reduces the extent of F-actin depolymerization by cofilin. Taken together, these data suggest that SEPT9 protects actin filaments from depolymerization by cofilin and myosin and indicate a mechanism by which SEPT9 could maintain the integrity of growing and contracting actin filaments.
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Affiliation(s)
- Clayton Smith
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507, USA
| | - Lee Dolat
- Department of Biology, Drexel University, Philadelphia, PA 19104, USA
| | - Dimitrios Angelis
- Department of Biology, Drexel University, Philadelphia, PA 19104, USA
| | - Eva Forgacs
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507, USA
| | - Elias T Spiliotis
- Department of Biology, Drexel University, Philadelphia, PA 19104, USA.
| | - Vitold E Galkin
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507, USA.
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Reversible paralysis of Schistosoma mansoni by forchlorfenuron, a phenylurea cytokinin that affects septins. Int J Parasitol 2014; 44:523-31. [PMID: 24768753 DOI: 10.1016/j.ijpara.2014.03.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 03/21/2014] [Accepted: 03/23/2014] [Indexed: 02/06/2023]
Abstract
Septins are guanosine-5'-triphosphate-binding proteins involved in wide-ranging cellular processes including cytokinesis, vesicle trafficking, membrane remodelling and scaffolds, and with diverse binding partners. Precise roles for these structural proteins in most processes often remain elusive. Identification of small molecules that inhibit septins could aid in elucidating the functions of septins and has become increasingly important, including the description of roles for septins in pathogenic phenomena such as tumorigenesis. The plant growth regulator forchlorfenuron, a synthetic cytokinin known to inhibit septin dynamics, likely represents an informative probe for septin function. This report deals with septins of the human blood fluke Schistosoma mansoni and their interactions with forchlorfenuron. Recombinant forms of three schistosome septins, SmSEPT5, SmSEPT7.2 and SmSEPT10, interacted with forchlorfenuron, leading to rapid polymerization of filaments. Culturing developmental stages (miracidia, cercariae, adult males) of schistosomes in FCF at 50-500 μM rapidly led to paralysis, which was reversible upon removal of the cytokinin. The reversible paralysis was concentration-, time- and developmental stage-dependent. Effects of forchlorfenuron on the cultured schistosomes were monitored by video and/or by an xCELLigence-based assay of motility, which quantified the effect of forchlorfenuron on fluke motility. The findings implicated a mechanism targeting a molecular system controlling movement in these developmental stages: a direct effect on muscle contraction due to septin stabilization might be responsible for the reversible paralysis, since enrichment of septins has been described within the muscles of schistosomes. This study revealed the reversible effect of forchlorfenuron on both schistosome motility and its striking impact in hastening polymerization of septins. These novel findings suggested routes to elucidate roles for septins in this pathogen, and exploitation of derivatives of forchlorfenuron for anti-schistosomal drugs.
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Abstract
Septins assemble into filaments and higher-order structures that act as scaffolds for diverse cell functions including cytokinesis, cell polarity, and membrane remodeling. Despite their conserved role in cell organization, little is known about how septin filaments elongate and are knitted together into higher-order assemblies. Using fluorescence correlation spectroscopy, we determined that cytosolic septins are in small complexes, suggesting that septin filaments are not formed in the cytosol. When the plasma membrane of live cells is monitored by total internal reflection fluorescence microscopy, we see that septin complexes of variable size diffuse in two dimensions. Diffusing septin complexes collide and make end-on associations to form elongated filaments and higher-order structures, an assembly process we call annealing. Septin assembly by annealing can be reconstituted in vitro on supported lipid bilayers with purified septin complexes. Using the reconstitution assay, we show that septin filaments are highly flexible, grow only from free filament ends, and do not exchange subunits in the middle of filaments. This work shows that annealing is a previously unidentified intrinsic property of septins in the presence of membranes and demonstrates that cells exploit this mechanism to build large septin assemblies.
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Zeraik AE, Pereira HM, Santos YV, Brandão-Neto J, Spoerner M, Santos MS, Colnago LA, Garratt RC, Araújo APU, DeMarco R. Crystal structure of a Schistosoma mansoni septin reveals the phenomenon of strand slippage in septins dependent on the nature of the bound nucleotide. J Biol Chem 2014; 289:7799-811. [PMID: 24464615 DOI: 10.1074/jbc.m113.525352] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Septins are filament-forming GTP-binding proteins involved in important cellular events, such as cytokinesis, barrier formation, and membrane remodeling. Here, we present two crystal structures of the GTPase domain of a Schistosoma mansoni septin (SmSEPT10), one bound to GDP and the other to GTP. The structures have been solved at an unprecedented resolution for septins (1.93 and 2.1 Å, respectively), which has allowed for unambiguous structural assignment of regions previously poorly defined. Consequently, we provide a reliable model for functional interpretation and a solid foundation for future structural studies. Upon comparing the two complexes, we observe for the first time the phenomenon of a strand slippage in septins. Such slippage generates a front-back communication mechanism between the G and NC interfaces. These data provide a novel mechanistic framework for the influence of nucleotide binding to the GTPase domain, opening new possibilities for the study of the dynamics of septin filaments.
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Affiliation(s)
- Ana E Zeraik
- From the Instituto de Física de São Carlos, Universidade de São Paulo, 13563-120 São Carlos, São Paulo, Brazil
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26
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Zeraik AE, Rinaldi G, Mann VH, Popratiloff A, Araujo APU, DeMarco R, Brindley PJ. Septins of Platyhelminths: identification, phylogeny, expression and localization among developmental stages of Schistosoma mansoni. PLoS Negl Trop Dis 2013; 7:e2602. [PMID: 24367716 PMCID: PMC3868516 DOI: 10.1371/journal.pntd.0002602] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 11/08/2013] [Indexed: 01/19/2023] Open
Abstract
Septins are a family of eukaryotic GTP binding proteins conserved from yeasts to humans. Originally identified in mutants of budding yeast, septins participate in diverse cellular functions including cytokinesis, organization of actin networks, cell polarity, vesicle trafficking and many others. Septins assemble into heteroligomers to form filaments and rings. Here, four septins of Schistosoma mansoni are described, which appear to be conserved within the phylum Platyhelminthes. These orthologues were related to the SEPT5, SEPT10 and SEPT7 septins of humans, and hence we have termed the schistosome septins SmSEPT5, SmSEPT10, SmSEPT7.1 and SmSEPT7.2. Septin transcripts were detected throughout the developmental cycle of the schistosome and a similar expression profile was observed for septins in the stages examined, consistent with concerted production of these proteins to form heterocomplexes. Immunolocalization analyses undertaken with antibodies specific for SmSEPT5 and SmSEPT10 revealed a broad tissue distribution of septins in the schistosomulum and colocalization of septin and actin in the longitudinal and circular muscles of the sporocyst. Ciliated epidermal plates of the miracidium were rich in septins. Expression levels for these septins were elevated in germ cells in the miracidium and sporocyst. Intriguingly, septins colocalize with the protonephridial system of the cercaria, which extends laterally along the length of this larval stage. Together, the findings revealed that schistosomes expressed several septins which likely form filaments within the cells, as in other eukaryotes. Identification and localization demonstrating a broad distribution of septins across organs and tissues of schistosome contributes towards the understanding of septins in schistosomes and other flatworms.
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Affiliation(s)
- Ana E. Zeraik
- Departamento de Física e Informática, Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, São Paulo, Brazil
- Department of Microbiology, Immunology & Tropical Medicine, and Research Center for Neglected Tropical and Infectious Diseases of Poverty, School of Medicine & Health Sciences, The George Washington University, Washington, D.C., United States of America
| | - Gabriel Rinaldi
- Department of Microbiology, Immunology & Tropical Medicine, and Research Center for Neglected Tropical and Infectious Diseases of Poverty, School of Medicine & Health Sciences, The George Washington University, Washington, D.C., United States of America
- Departamento de Genética, Facultad de Medicina, Universidad de la República (UDELAR), Montevideo, Uruguay
| | - Victoria H. Mann
- Department of Microbiology, Immunology & Tropical Medicine, and Research Center for Neglected Tropical and Infectious Diseases of Poverty, School of Medicine & Health Sciences, The George Washington University, Washington, D.C., United States of America
| | - Anastas Popratiloff
- Center for Microscopy and Image Analysis, The George Washington University, Washington, D.C., United States of America
| | - Ana P. U. Araujo
- Departamento de Física e Informática, Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, São Paulo, Brazil
| | - Ricardo DeMarco
- Departamento de Física e Informática, Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, São Paulo, Brazil
- * E-mail: (RDM); (PJB)
| | - Paul J. Brindley
- Department of Microbiology, Immunology & Tropical Medicine, and Research Center for Neglected Tropical and Infectious Diseases of Poverty, School of Medicine & Health Sciences, The George Washington University, Washington, D.C., United States of America
- * E-mail: (RDM); (PJB)
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27
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Lassen LB, Füchtbauer A, Schmitz A, Sørensen AB, Pedersen FS, Füchtbauer EM. Septin9 is involved in T-cell development and CD8+ T-cell homeostasis. Cell Tissue Res 2013; 352:695-705. [DOI: 10.1007/s00441-013-1618-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 03/11/2013] [Indexed: 12/18/2022]
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The structure and properties of septin 3: a possible missing link in septin filament formation. Biochem J 2013; 450:95-105. [PMID: 23163726 DOI: 10.1042/bj20120851] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The human genome codes for 13 members of a family of filament-forming GTP-binding proteins known as septins. These have been divided into four different subgroups on the basis of sequence similarity. The differences between the subgroups are believed to control their correct assembly into heterofilaments which have specific roles in membrane remodelling events. Many different combinations of the 13 proteins are theoretically possible and it is therefore important to understand the structural basis of specific filament assembly. However, three-dimensional structures are currently available for only three of the four subgroups. In the present study we describe the crystal structure of a construct of human SEPT3 which belongs to the outstanding subgroup. This construct (SEPT3-GC), which includes the GTP-binding and C-terminal domains, purifies as a nucleotide-free monomer, allowing for its characterization in terms of GTP-binding and hydrolysis. In the crystal structure, SEPT3-GC forms foreshortened filaments which employ the same NC and G interfaces observed in the heterotrimeric complex of human septins 2, 6 and 7, reinforcing the notion of 'promiscuous' interactions described previously. In the present study we describe these two interfaces and relate the structure to its tendency to form monomers and its efficiency in the hydrolysis of GTP. The relevance of these results is emphasized by the fact that septins from the SEPT3 subgroup may be important determinants of polymerization by occupying the terminal position in octameric units which themselves form the building blocks of at least some heterofilaments.
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Abstract
Septins belong to a family of proteins that is highly conserved in eukaryotes and is increasingly recognized as a novel component of the cytoskeleton. All septins are GTP-binding proteins that form hetero-oligomeric complexes and higher-order structures, including filaments and rings. Recent studies have provided structural information about the different levels of septin organization; however, the crucial structural determinants and factors responsible for septin assembly remain unclear. Investigations on the molecular functions of septins have highlighted their roles as scaffolds for protein recruitment and as diffusion barriers for subcellular compartmentalization in numerous biological processes, including cell division and host-microorganism interactions.
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Stanbery L, Petty EM. Steps solidifying a role for SEPT9 in breast cancer suggest that greater strides are needed. Breast Cancer Res 2012; 14:101. [PMID: 22236777 PMCID: PMC3496112 DOI: 10.1186/bcr3056] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Septins comprise a conserved family of GTPase proteins. Of these, human SEPT9 has been widely implicated in cancers of epithelial origin, including breast cancer, as well as leukemia. In a previous issue of Breast Cancer Research, Connolly and colleagues present compelling data further supporting a role for SEPT9 isoforms in early breast cancer development as well as evidence suggesting that cellular localization patterns of SEPT9 isoforms may contribute to oncogenesis.
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Hall PA, Russell SEH. Mammalian septins: dynamic heteromers with roles in cellular morphogenesis and compartmentalization. J Pathol 2011; 226:287-99. [PMID: 21990096 DOI: 10.1002/path.3024] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 10/03/2011] [Accepted: 10/03/2011] [Indexed: 02/06/2023]
Abstract
The septins are a family of GTP-binding proteins, evolutionarily conserved from yeast through to mammals, with roles in multiple core cellular functions. Here we provide an overview of our current knowledge of septin structure and function and focus mainly on mammalian septins, but gain much insight by drawing on knowledge of septins in other organisms. We describe their genomic and transcriptional complexity: a complexity manifest also in the diversity of scaffold structures that septins can form. Septin complexes can act to localize interacting proteins at specific intracellular locales and can also define membrane compartments by defining diffusion barriers. By such activities, septins can contribute to the definition of spatial asymmetry and cell polarity and we suggest a potential role in stem cell biology. Finally, we review the evidence that septins contribute to various disease states and argue that it is a breakdown in the tight regulation of their expression (particularly of individual isoforms), and also their inherent ability to oligomerize, which is pathogenic. Study of the perturbation of septin complex formation in disease will provide valuable insights into septin biology and will be a fertile ground for study.
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Affiliation(s)
- Peter A Hall
- Department of Molecular Oncology and Pathology and Laboratory Medicine, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
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Wittinghofer A. Highlight on septins. Biol Chem 2011; 392:679-80. [DOI: 10.1515/bc.2011.094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
No abstract available
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