1
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Weingarten DJ, Shrestha A, Orlin DJ, Le Moing CL, Borchardt LA, Jackman SL. Synaptotagmins 3 and 7 mediate the majority of asynchronous release from synapses in the cerebellum and hippocampus. Cell Rep 2024; 43:114595. [PMID: 39116209 DOI: 10.1016/j.celrep.2024.114595] [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: 01/03/2024] [Revised: 05/24/2024] [Accepted: 07/22/2024] [Indexed: 08/10/2024] Open
Abstract
Neurotransmitter release consists of rapid synchronous release followed by longer-lasting asynchronous release (AR). Although the presynaptic proteins that trigger synchronous release are well understood, the mechanisms for AR remain unclear. AR is sustained by low concentrations of intracellular Ca2+ and Sr2+, suggesting the involvement of sensors with high affinities for both ions. Synaptotagmin 7 (SYT7) partly mediates AR, but substantial AR persists in the absence of SYT7. The closely related SYT3 binds Ca2+ and Sr2+ with high affinity, making it a promising candidate to mediate AR. Here, we use knockout mice to study the contribution of SYT3 and SYT7 to AR at cerebellar and hippocampal synapses. AR is dramatically reduced when both isoforms are absent, which alters the number and timing of postsynaptic action potentials. Our results confirm the long-standing prediction that SYT3 mediates AR and show that SYT3 and SYT7 act as dominant mechanisms for AR at three central synapses.
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Affiliation(s)
| | - Amita Shrestha
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Daniel J Orlin
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Chloé L Le Moing
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Luke A Borchardt
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Skyler L Jackman
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA.
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2
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Quinn CJ, Cartwright EJ, Trafford AW, Dibb KM. On the role of dysferlin in striated muscle: membrane repair, t-tubules and Ca 2+ handling. J Physiol 2024; 602:1893-1910. [PMID: 38615232 DOI: 10.1113/jp285103] [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: 06/27/2023] [Accepted: 03/05/2024] [Indexed: 04/15/2024] Open
Abstract
Dysferlin is a 237 kDa membrane-associated protein characterised by multiple C2 domains with a diverse role in skeletal and cardiac muscle physiology. Mutations in DYSF are known to cause various types of human muscular dystrophies, known collectively as dysferlinopathies, with some patients developing cardiomyopathy. A myriad of in vitro membrane repair studies suggest that dysferlin plays an integral role in the membrane repair complex in skeletal muscle. In comparison, less is known about dysferlin in the heart, but mounting evidence suggests that dysferlin's role is similar in both muscle types. Recent findings have shown that dysferlin regulates Ca2+ handling in striated muscle via multiple mechanisms and that this becomes more important in conditions of stress. Maintenance of the transverse (t)-tubule network and the tight coordination of excitation-contraction coupling are essential for muscle contractility. Dysferlin regulates the maintenance and repair of t-tubules, and it is suspected that dysferlin regulates t-tubules and sarcolemmal repair through a similar mechanism. This review focuses on the emerging complexity of dysferlin's activity in striated muscle. Such insights will progress our understanding of the proteins and pathways that regulate basic heart and skeletal muscle function and help guide research into striated muscle pathology, especially that which arises due to dysferlin dysfunction.
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Affiliation(s)
- C J Quinn
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, 3.14 Core Technology Facility, Manchester, UK
| | - E J Cartwright
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, 3.14 Core Technology Facility, Manchester, UK
| | - A W Trafford
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, 3.14 Core Technology Facility, Manchester, UK
| | - K M Dibb
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, 3.14 Core Technology Facility, Manchester, UK
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3
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Wu Z, Kusick GF, Berns MMM, Raychaudhuri S, Itoh K, Walter AM, Chapman ER, Watanabe S. Synaptotagmin 7 docks synaptic vesicles to support facilitation and Doc2α-triggered asynchronous release. eLife 2024; 12:RP90632. [PMID: 38536730 PMCID: PMC10972563 DOI: 10.7554/elife.90632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024] Open
Abstract
Despite decades of intense study, the molecular basis of asynchronous neurotransmitter release remains enigmatic. Synaptotagmin (syt) 7 and Doc2 have both been proposed as Ca2+ sensors that trigger this mode of exocytosis, but conflicting findings have led to controversy. Here, we demonstrate that at excitatory mouse hippocampal synapses, Doc2α is the major Ca2+ sensor for asynchronous release, while syt7 supports this process through activity-dependent docking of synaptic vesicles. In synapses lacking Doc2α, asynchronous release after single action potentials is strongly reduced, while deleting syt7 has no effect. However, in the absence of syt7, docked vesicles cannot be replenished on millisecond timescales. Consequently, both synchronous and asynchronous release depress from the second pulse onward during repetitive activity. By contrast, synapses lacking Doc2α have normal activity-dependent docking, but continue to exhibit decreased asynchronous release after multiple stimuli. Moreover, disruption of both Ca2+ sensors is non-additive. These findings result in a new model whereby syt7 drives activity-dependent docking, thus providing synaptic vesicles for synchronous (syt1) and asynchronous (Doc2 and other unidentified sensors) release during ongoing transmission.
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Affiliation(s)
- Zhenyong Wu
- Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
- Howard Hughes Medical InstituteMadisonUnited States
| | - Grant F Kusick
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
- Biochemistry, Cellular and Molecular Biology Graduate Program, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Manon MM Berns
- Department of Neuroscience, University of CopenhagenCopenhagenDenmark
| | - Sumana Raychaudhuri
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
| | - Kie Itoh
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
| | - Alexander M Walter
- Department of Neuroscience, University of CopenhagenCopenhagenDenmark
- Molecular and Theoretical Neuroscience, Leibniz-Institut für Molekulare Pharmakologie, FMP im CharitéCrossOverBerlinGermany
| | - Edwin R Chapman
- Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
- Howard Hughes Medical InstituteMadisonUnited States
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of MedicineBaltimoreUnited States
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4
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Lebowitz JJ, Kissiwaa SA, Engeln KA, Bowman AM, Williams JT, Jackman SL. Synaptotagmin-7 Counteracts Short-Term Depression during Phasic Dopamine Release. eNeuro 2024; 11:ENEURO.0501-23.2024. [PMID: 38365841 PMCID: PMC10932592 DOI: 10.1523/eneuro.0501-23.2024] [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: 11/29/2023] [Revised: 01/02/2024] [Accepted: 01/17/2024] [Indexed: 02/18/2024] Open
Abstract
Dopamine neurons switch from tonic pacemaker activity to high-frequency bursts in response to salient stimuli. These bursts lead to superlinear increases in dopamine release, and the degree of this increase is highly dependent on firing frequency. The superlinearity and frequency dependence of dopamine release implicate short-term plasticity processes. The presynaptic Ca2+-sensor synaptotagmin-7 (SYT7) has suitable properties to mediate such short-term plasticity and has been implicated in regulating dopamine release from somatodendritic compartments. Here, we use a genetically encoded dopamine sensor and whole-cell electrophysiology in Syt7 KO mice to determine how SYT7 contributes to both axonal and somatodendritic dopamine release. We find that SYT7 mediates a hidden component of facilitation of release from dopamine terminals that can be unmasked by lowering initial release probability or by predepressing synapses with low-frequency stimulation. Depletion of SYT7 increased short-term depression and reduced release during stimulations that mimic in vivo firing. Recordings of D2-mediated inhibitory postsynaptic currents in the substantia nigra pars compacta (SNc) confirmed a similar role for SYT7 in somatodendritic release. Our results indicate that SYT7 drives short-term facilitation of dopamine release, which may explain the frequency dependence of dopamine signaling seen in vivo.
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Affiliation(s)
- Joseph J Lebowitz
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
| | - Sarah A Kissiwaa
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
| | - Kim A Engeln
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
| | - Anna M Bowman
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
| | - John T Williams
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
| | - Skyler L Jackman
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
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5
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Yumura S. Wound Repair of the Cell Membrane: Lessons from Dictyostelium Cells. Cells 2024; 13:341. [PMID: 38391954 PMCID: PMC10886852 DOI: 10.3390/cells13040341] [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: 12/20/2023] [Revised: 01/30/2024] [Accepted: 02/08/2024] [Indexed: 02/24/2024] Open
Abstract
The cell membrane is frequently subjected to damage, either through physical or chemical means. The swift restoration of the cell membrane's integrity is crucial to prevent the leakage of intracellular materials and the uncontrolled influx of extracellular ions. Consequently, wound repair plays a vital role in cell survival, akin to the importance of DNA repair. The mechanisms involved in wound repair encompass a series of events, including ion influx, membrane patch formation, endocytosis, exocytosis, recruitment of the actin cytoskeleton, and the elimination of damaged membrane sections. Despite the absence of a universally accepted general model, diverse molecular models have been proposed for wound repair in different organisms. Traditional wound methods not only damage the cell membrane but also impact intracellular structures, including the underlying cortical actin networks, microtubules, and organelles. In contrast, the more recent improved laserporation selectively targets the cell membrane. Studies on Dictyostelium cells utilizing this method have introduced a novel perspective on the wound repair mechanism. This review commences by detailing methods for inducing wounds and subsequently reviews recent developments in the field.
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Affiliation(s)
- Shigehiko Yumura
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8511, Japan
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6
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Whitlock JM. Muscle Progenitor Cell Fusion in the Maintenance of Skeletal Muscle. Results Probl Cell Differ 2024; 71:257-279. [PMID: 37996682 DOI: 10.1007/978-3-031-37936-9_13] [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] [Indexed: 11/25/2023]
Abstract
Skeletal muscle possesses a resident, multipotent stem cell population that is essential for its repair and maintenance throughout life. Here I highlight the role of this stem cell population in muscle repair and regeneration and review the genetic control of the process; the mechanistic steps of activation, migration, recognition, adhesion, and fusion of these cells; and discuss the novel recognition of the membrane signaling that coordinates myogenic cell-cell fusion, as well as the identification of a two-part fusogen system that facilitates it.
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Affiliation(s)
- Jarred M Whitlock
- Section on Membrane Biology, Eunice Kennedy Shrive National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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7
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Shao Q, Wijaya CS, Wang S, Meng X, Yuan C, Ma C, Xu S. The SNARE complex formed by RIC-4/SEC-22/SYX-2 promotes C. elegans epidermal wound healing. Cell Rep 2023; 42:113349. [PMID: 37910502 DOI: 10.1016/j.celrep.2023.113349] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 09/18/2023] [Accepted: 10/10/2023] [Indexed: 11/03/2023] Open
Abstract
Maintaining cellular viability relies on the integrity of the plasma membrane, which must be repaired upon damage. Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-mediated membrane fusion is a crucial mechanism involved in membrane repair. In C. elegans epidermal cell hyp 7, syntaxin-2 (SYX-2) facilitates large membrane wound repair; however, the underlying molecular mechanism remains unclear. Here, we found that SNAP-25 protein RIC-4 and synaptobrevin protein SEC-22 are required for SYX-2 recruitment at the wound site. They interact to form a SNARE complex to promote membrane repair in vivo and fusion in vitro. Moreover, we found that SEC-22 localized in multiple intracellular compartments, including endosomes and the trans-Golgi network, which recruited to the wounds. Furthermore, inhibition of RAB-5 disrupted SEC-22 localization and prevented its interaction with SYX-2. Our findings suggest that RAB-5 facilitates the formation of the RIC-4/SEC-22/SYX-2 SNARE complex and provides valuable insights into the molecular mechanism of how cells repair large membrane wounds.
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Affiliation(s)
- Qingfang Shao
- International Biomedicine-X Research Center of the Second Affiliated Hospital, Zhejiang University School of Medicine and the Zhejiang University-University of Edinburgh Institute, 718 East Haizhou Road, Haining, Zhejiang 314400, China; Center for Stem Cell and Regenerative Medicine and Department of Burn and Wound Repair of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Chandra Sugiarto Wijaya
- International Biomedicine-X Research Center of the Second Affiliated Hospital, Zhejiang University School of Medicine and the Zhejiang University-University of Edinburgh Institute, 718 East Haizhou Road, Haining, Zhejiang 314400, China; School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Shen Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Xinan Meng
- International Biomedicine-X Research Center of the Second Affiliated Hospital, Zhejiang University School of Medicine and the Zhejiang University-University of Edinburgh Institute, 718 East Haizhou Road, Haining, Zhejiang 314400, China; School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Cheng Yuan
- International Biomedicine-X Research Center of the Second Affiliated Hospital, Zhejiang University School of Medicine and the Zhejiang University-University of Edinburgh Institute, 718 East Haizhou Road, Haining, Zhejiang 314400, China
| | - Cong Ma
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
| | - Suhong Xu
- International Biomedicine-X Research Center of the Second Affiliated Hospital, Zhejiang University School of Medicine and the Zhejiang University-University of Edinburgh Institute, 718 East Haizhou Road, Haining, Zhejiang 314400, China; Center for Stem Cell and Regenerative Medicine and Department of Burn and Wound Repair of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China.
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8
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Zha D, Wang S, Monaghan-Nichols P, Qian Y, Sampath V, Fu M. Mechanisms of Endothelial Cell Membrane Repair: Progress and Perspectives. Cells 2023; 12:2648. [PMID: 37998383 PMCID: PMC10670313 DOI: 10.3390/cells12222648] [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: 09/08/2023] [Revised: 11/14/2023] [Accepted: 11/15/2023] [Indexed: 11/25/2023] Open
Abstract
Endothelial cells are the crucial inner lining of blood vessels, which are pivotal in vascular homeostasis and integrity. However, these cells are perpetually subjected to a myriad of mechanical, chemical, and biological stresses that can compromise their plasma membranes. A sophisticated repair system involving key molecules, such as calcium, annexins, dysferlin, and MG53, is essential for maintaining endothelial viability. These components orchestrate complex mechanisms, including exocytosis and endocytosis, to repair membrane disruptions. Dysfunctions in this repair machinery, often exacerbated by aging, are linked to endothelial cell death, subsequently contributing to the onset of atherosclerosis and the progression of cardiovascular diseases (CVD) and stroke, major causes of mortality in the United States. Thus, identifying the core machinery for endothelial cell membrane repair is critically important for understanding the pathogenesis of CVD and stroke and developing novel therapeutic strategies for combating CVD and stroke. This review summarizes the recent advances in understanding the mechanisms of endothelial cell membrane repair. The future directions of this research area are also highlighted.
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Affiliation(s)
- Duoduo Zha
- Department of Biomedical Science, School of Medicine, University of Missouri Kansas City, 2411 Holmes Street, Kansas City, MO 64108, USA; (D.Z.); (P.M.-N.)
- The National Engineering Research Center for Bioengineering Drugs and Technologies, Institute of Translational Medicine, Nanchang University, 1299 Xuefu Rd, Honggu District, Nanchang 330031, China;
| | - Shizhen Wang
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri Kansas City, 5009 Rockhill Road, Kansas City, MO 64110, USA;
| | - Paula Monaghan-Nichols
- Department of Biomedical Science, School of Medicine, University of Missouri Kansas City, 2411 Holmes Street, Kansas City, MO 64108, USA; (D.Z.); (P.M.-N.)
| | - Yisong Qian
- The National Engineering Research Center for Bioengineering Drugs and Technologies, Institute of Translational Medicine, Nanchang University, 1299 Xuefu Rd, Honggu District, Nanchang 330031, China;
| | - Venkatesh Sampath
- Department of Pediatric, Children’s Mercy Hospital, Children’s Mercy Research Institute, Kansas City, MO 64108, USA;
| | - Mingui Fu
- Department of Biomedical Science, School of Medicine, University of Missouri Kansas City, 2411 Holmes Street, Kansas City, MO 64108, USA; (D.Z.); (P.M.-N.)
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9
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Caballero-Florán RN, Bendahmane M, Gupta JP, Chen X, Wu X, Morales A, Anantharam A, Jenkins PM. Synaptotagmin-7 facilitates acetylcholine release in splanchnic nerve-chromaffin cell synapses during nerve activity. Neurosci Lett 2023; 800:137129. [PMID: 36796621 PMCID: PMC10145958 DOI: 10.1016/j.neulet.2023.137129] [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: 10/25/2021] [Revised: 01/23/2023] [Accepted: 02/11/2023] [Indexed: 02/16/2023]
Abstract
Disturbances that threaten homeostasis elicit activation of the sympathetic nervous system (SNS) and the adrenal medulla. The effectors discharge as a unit to drive global and immediate changes in whole-body physiology. Descending sympathetic information is conveyed to the adrenal medulla via preganglionic splanchnic fibers. These fibers pass into the gland and synapse onto chromaffin cells, which synthesize, store, and secrete catecholamines and vasoactive peptides. While the importance of the sympatho-adrenal branch of the autonomic nervous system has been appreciated for many decades, the mechanisms underlying transmission between presynaptic splanchnic neurons and postsynaptic chromaffin cells have remained obscure. In contrast to chromaffin cells, which have enjoyed sustained attention as a model system for exocytosis, even the Ca2+ sensors that are expressed within splanchnic terminals have not yet been identified. This study shows that a ubiquitous Ca2+-binding protein, synaptotagmin-7 (Syt7), is expressed within the fibers that innervate the adrenal medulla, and that its absence can alter synaptic transmission in the preganglionic terminals of chromaffin cells. The prevailing impact in synapses that lack Syt7 is a decrease in synaptic strength and neuronal short-term plasticity. Evoked excitatory postsynaptic currents (EPSCs) in Syt7 KO preganglionic terminals are smaller in amplitude than in wild-type synapses stimulated in an identical manner. Splanchnic inputs also display robust short-term presynaptic facilitation, which is compromised in the absence of Syt7. These data reveal, for the first time, a role for any synaptotagmin at the splanchnic-chromaffin cell synapse. They also suggest that Syt7 has actions at synaptic terminals that are conserved across central and peripheral branches of the nervous system.
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Affiliation(s)
- René N Caballero-Florán
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, United States
| | - Mounir Bendahmane
- Department of Neuroscience, University of Toledo, Toledo, OH 43614, United States
| | - Julie P Gupta
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, United States
| | - Xiaohuan Chen
- Department of Neuroscience, University of Toledo, Toledo, OH 43614, United States
| | - Xiaojun Wu
- Department of Neuroscience, University of Toledo, Toledo, OH 43614, United States
| | - Alina Morales
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, United States; Department of Neuroscience, University of Toledo, Toledo, OH 43614, United States
| | - Arun Anantharam
- Department of Neuroscience, University of Toledo, Toledo, OH 43614, United States.
| | - Paul M Jenkins
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, United States; Department of Psychiatry, University of Michigan Medical School, Ann Arbor, MI 48109, United States.
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10
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Role of calcium-sensor proteins in cell membrane repair. Biosci Rep 2023; 43:232522. [PMID: 36728029 PMCID: PMC9970828 DOI: 10.1042/bsr20220765] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 01/20/2023] [Accepted: 02/01/2023] [Indexed: 02/03/2023] Open
Abstract
Cell membrane repair is a critical process used to maintain cell integrity and survival from potentially lethal chemical, and mechanical membrane injury. Rapid increases in local calcium levels due to a membrane rupture have been widely accepted as a trigger for multiple membrane-resealing models that utilize exocytosis, endocytosis, patching, and shedding mechanisms. Calcium-sensor proteins, such as synaptotagmins (Syt), dysferlin, S100 proteins, and annexins, have all been identified to regulate, or participate in, multiple modes of membrane repair. Dysfunction of membrane repair from inefficiencies or genetic alterations in these proteins contributes to diseases such as muscular dystrophy (MD) and heart disease. The present review covers the role of some of the key calcium-sensor proteins and their involvement in membrane repair.
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11
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Lebowitz JJ, Banerjee A, Qiao C, Bunzow JR, Williams JT, Kaeser PS. Synaptotagmin-1 is a Ca 2+ sensor for somatodendritic dopamine release. Cell Rep 2023; 42:111915. [PMID: 36640316 PMCID: PMC9993464 DOI: 10.1016/j.celrep.2022.111915] [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: 07/10/2022] [Revised: 11/07/2022] [Accepted: 12/13/2022] [Indexed: 12/31/2022] Open
Abstract
Modes of somatodendritic transmission range from rapid synaptic signaling to protracted regulation over distance. Somatodendritic dopamine secretion in the midbrain leads to D2 receptor-induced modulation of dopamine neurons on the timescale of seconds. Temporally imprecise release mechanisms are often presumed to be at play, and previous work indeed suggested roles for slow Ca2+ sensors. We here use mouse genetics and whole-cell electrophysiology to establish that the fast Ca2+ sensor synaptotagmin-1 (Syt-1) is important for somatodendritic dopamine release. Syt-1 ablation from dopamine neurons strongly reduces stimulus-evoked D2 receptor-mediated inhibitory postsynaptic currents (D2-IPSCs) in the midbrain. D2-IPSCs evoked by paired stimuli exhibit less depression, and high-frequency trains restore dopamine release. Spontaneous somatodendritic dopamine secretion is independent of Syt-1, supporting that its exocytotic mechanisms differ from evoked release. We conclude that somatodendritic dopamine transmission relies on the fast Ca2+ sensor Syt-1, leading to synchronous release in response to the initial stimulus.
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Affiliation(s)
- Joseph J Lebowitz
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Aditi Banerjee
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Claire Qiao
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - James R Bunzow
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - John T Williams
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA.
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
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12
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Mesnard CS, Hays CL, Barta CL, Sladek AL, Grassmeyer JJ, Hinz KK, Quadros RM, Gurumurthy CB, Thoreson WB. Synaptotagmins 1 and 7 in vesicle release from rods of mouse retina. Exp Eye Res 2022; 225:109279. [PMID: 36280223 PMCID: PMC9830644 DOI: 10.1016/j.exer.2022.109279] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 09/14/2022] [Accepted: 10/10/2022] [Indexed: 01/13/2023]
Abstract
Synaptotagmins are the primary Ca2+ sensors for synaptic exocytosis. Previous work suggested synaptotagmin-1 (Syt1) mediates evoked vesicle release from cone photoreceptor cells in the vertebrate retina whereas release from rods may involve another sensor in addition to Syt1. We found immunohistochemical evidence for syntaptotagmin-7 (Syt7) in mouse rod terminals and so performed electroretinograms (ERG) and single-cell recordings using mice in which Syt1 and/or Syt7 were conditionally removed from rods and/or cones. Synaptic release was measured in mouse rods by recording presynaptic anion currents activated during glutamate re-uptake and from exocytotic membrane capacitance changes. Deleting Syt1 from rods reduced glutamate release evoked by short depolarizing steps but not long steps whereas deleting Syt7 from rods reduced release evoked by long but not short steps. Deleting both sensors completely abolished depolarization-evoked release from rods. Effects of various intracellular Ca2+ buffers showed that Syt1-mediated release from rods involves vesicles close to ribbon-associated Ca2+ channels whereas Syt7-mediated release evoked by longer steps involves more distant release sites. Spontaneous release from rods was unaffected by eliminating Syt7. While whole animal knockout of Syt7 slightly reduced ERG b-waves and oscillatory potentials, selective elimination of Syt7 from rods had no effect on ERGs. Furthermore, eliminating Syt1 from rods and cones abolished ERG b-waves and additional elimination of Syt7 had no further effect. These results show that while Syt7 contributes to slow non-ribbon release from rods, Syt1 is the principal sensor shaping rod and cone inputs to bipolar cells in response to light flashes.
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Affiliation(s)
- C S Mesnard
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA; Pharmacology and Experimental Neuroscience, USA
| | - C L Hays
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA
| | - C L Barta
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA
| | - A L Sladek
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA
| | - J J Grassmeyer
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA; Pharmacology and Experimental Neuroscience, USA
| | - K K Hinz
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA
| | - R M Quadros
- Pharmacology and Experimental Neuroscience, USA; Mouse Genome Engineering Core Facility, Vice Chancellor for Research Office, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68106, USA
| | - C B Gurumurthy
- Pharmacology and Experimental Neuroscience, USA; Mouse Genome Engineering Core Facility, Vice Chancellor for Research Office, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68106, USA
| | - W B Thoreson
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA; Pharmacology and Experimental Neuroscience, USA.
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13
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Weingarten DJ, Shrestha A, Juda-Nelson K, Kissiwaa SA, Spruston E, Jackman SL. Fast resupply of synaptic vesicles requires synaptotagmin-3. Nature 2022; 611:320-325. [PMID: 36261524 DOI: 10.1038/s41586-022-05337-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 09/12/2022] [Indexed: 01/09/2023]
Abstract
Sustained neuronal activity demands a rapid resupply of synaptic vesicles to maintain reliable synaptic transmission. Such vesicle replenishment is accelerated by submicromolar presynaptic Ca2+ signals by an as-yet unidentified high-affinity Ca2+ sensor1,2. Here we identify synaptotagmin-3 (SYT3)3,4 as that presynaptic high-affinity Ca2+ sensor, which drives vesicle replenishment and short-term synaptic plasticity. Synapses in Syt3 knockout mice exhibited enhanced short-term depression, and recovery from depression was slower and insensitive to presynaptic residual Ca2+. During sustained neuronal firing, SYT3 accelerated vesicle replenishment and increased the size of the readily releasable pool. SYT3 also mediated short-term facilitation under conditions of low release probability and promoted synaptic enhancement together with another high-affinity synaptotagmin, SYT7 (ref. 5). Biophysical modelling predicted that SYT3 mediates both replenishment and facilitation by promoting the transition of loosely docked vesicles to tightly docked, primed states. Our results reveal a crucial role for presynaptic SYT3 in the maintenance of reliable high-frequency synaptic transmission. Moreover, multiple forms of short-term plasticity may converge on a mechanism of reversible, Ca2+-dependent vesicle docking.
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Affiliation(s)
| | - Amita Shrestha
- Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Kessa Juda-Nelson
- Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Sarah A Kissiwaa
- Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Evan Spruston
- Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Skyler L Jackman
- Vollum Institute, Oregon Health and Science University, Portland, OR, USA.
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14
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Recruitment of tetraspanin TSP-15 to epidermal wounds promotes plasma membrane repair in C. elegans. Dev Cell 2022; 57:1630-1642.e4. [PMID: 35777354 DOI: 10.1016/j.devcel.2022.06.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 04/26/2022] [Accepted: 06/07/2022] [Indexed: 01/14/2023]
Abstract
Maintaining the integrity of the plasma membrane after cellular damage is essential for cell survival. However, it is unclear how cells repair large membrane injuries in vivo. Here, we report that the tetraspanin protein, TSP-15, is recruited to large membrane wounds and forms a ring-like structure in C. elegans epidermis and promotes membrane repair after an injury. TSP-15 recruits from the adjacent region underneath the plasma membrane to the wound site in a RAB-5-dependent manner upon membrane damage. Genetic and live-imaging analysis suggested that the endosomal sorting complex required for transport III (ESCRT III) is necessary for recruiting TSP-15 from the early endosome to the damaged membrane. Moreover, TSP-15 interacts with and is required for the accumulation of t-SNARE protein Syntaxin-2, which facilitates membrane repair. These findings provide valuable insights into the role of the conserved tetraspanin TSP-15 in the cellular repair of large wounds resulting from environmental insults.
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15
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Hikima T, Witkovsky P, Khatri L, Chao MV, Rice ME. Synaptotagmins 1 and 7 Play Complementary Roles in Somatodendritic Dopamine Release. J Neurosci 2022; 42:3919-3930. [PMID: 35361702 PMCID: PMC9097777 DOI: 10.1523/jneurosci.2416-21.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 02/18/2022] [Accepted: 03/18/2022] [Indexed: 11/21/2022] Open
Abstract
The molecular mechanisms underlying somatodendritic dopamine (DA) release remain unresolved, despite the passing of decades since its discovery. Our previous work showed robust release of somatodendritic DA in submillimolar extracellular Ca2+ concentration ([Ca2+]o). Here we tested the hypothesis that the high-affinity Ca2+ sensor synaptotagmin 7 (Syt7), is a key determinant of somatodendritic DA release and its Ca2+ dependence. Somatodendritic DA release from SNc DA neurons was assessed using whole-cell recording in midbrain slices from male and female mice to monitor evoked DA-dependent D2 receptor-mediated inhibitory currents (D2ICs). Single-cell application of an antibody to Syt7 (Syt7 Ab) decreased pulse train-evoked D2ICs, revealing a functional role for Syt7. The assessment of the Ca2+ dependence of pulse train-evoked D2ICs confirmed robust DA release in submillimolar [Ca2+]o in wild-type (WT) neurons, but loss of this sensitivity with intracellular Syt7 Ab or in Syt7 knock-out (KO) mice. In millimolar [Ca2+]o, pulse train-evoked D2ICs in Syt7 KOs showed a greater reduction in decreased [Ca2+]o than seen in WT mice; the effect on single pulse-evoked DA release, however, did not differ between genotypes. Single-cell application of a Syt1 Ab had no effect on train-evoked D2ICs in WT SNc DA neurons, but did cause a decrease in D2IC amplitude in Syt7 KOs, indicating a functional substitution of Syt1 for Syt7. In addition, Syt1 Ab decreased single pulse-evoked D2ICs in WT cells, indicating the involvement of Syt1 in tonic DA release. Thus, Syt7 and Syt1 play complementary roles in somatodendritic DA release from SNc DA neurons.SIGNIFICANCE STATEMENT The respective Ca2+ dependence of somatodendritic and axonal dopamine (DA) release differs, resulting in the persistence of somatodendritic DA release in submillimolar Ca2+ concentrations too low to support axonal release. We demonstrate that synaptotagmin7 (Syt7), a high-affinity Ca2+ sensor, underlies phasic somatodendritic DA release and its Ca2+ sensitivity in the substantia nigra pars compacta. In contrast, we found that synaptotagmin 1 (Syt1), the Ca2+ sensor underlying axonal DA release, plays a role in tonic, but not phasic, somatodendritic DA release in wild-type mice. However, Syt1 can facilitate phasic DA release after Syt7 deletion. Thus, we show that both Syt1 and Syt7 act as Ca2+ sensors subserving different aspects of somatodendritic DA release processes.
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Affiliation(s)
- Takuya Hikima
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, New York 10016
| | - Paul Witkovsky
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, New York 10016
| | - Latika Khatri
- Department of Cell Biology, New York University Grossman School of Medicine, New York, New York 10016
| | - Moses V Chao
- Department of Cell Biology, New York University Grossman School of Medicine, New York, New York 10016
- Department of Psychiatry, New York University Grossman School of Medicine, New York, New York 10016
- Department of Neuroscience & Physiology, New York University Grossman School of Medicine, New York, New York 10016
| | - Margaret E Rice
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, New York 10016
- Department of Neuroscience & Physiology, New York University Grossman School of Medicine, New York, New York 10016
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16
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Delignat-Lavaud B, Ducrot C, Kouwenhoven W, Feller N, Trudeau LÉ. Implication of synaptotagmins 4 and 7 in activity-dependent somatodendritic dopamine release in the ventral midbrain. Open Biol 2022; 12:210339. [PMID: 35232250 PMCID: PMC8889187 DOI: 10.1098/rsob.210339] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 01/31/2022] [Indexed: 01/07/2023] Open
Abstract
Dopamine (DA) neurons can release DA not just from axon terminals, but also from their somatodendritic (STD) compartment through a mechanism that is still incompletely understood. Using voltammetry in mouse mesencephalic brain slices, we find that STD DA release has low capacity and shows a calcium sensitivity that is comparable to that of axonal release. We find that the molecular mechanism of STD DA release differs from axonal release with regard to the implication of synaptotagmin (Syt) calcium sensors. While individual constitutive knockout of Syt4 or Syt7 is not sufficient to reduce STD DA release, the removal of both isoforms reduces this release by approximately 50%, leaving axonal release unimpaired. Our work unveils clear differences in the mechanisms of STD and axonal DA release.
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Affiliation(s)
- Benoît Delignat-Lavaud
- Department of Pharmacology and Physiology, Université de Montréal, QC, Canada H3T 1J4
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, QC, Canada H3T 1J4
- Neural Signaling and Circuitry Research Group (SNC), Montréal, QC, Canada H3C 3J7
| | - Charles Ducrot
- Department of Pharmacology and Physiology, Université de Montréal, QC, Canada H3T 1J4
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, QC, Canada H3T 1J4
- Neural Signaling and Circuitry Research Group (SNC), Montréal, QC, Canada H3C 3J7
| | - Willemieke Kouwenhoven
- Department of Pharmacology and Physiology, Université de Montréal, QC, Canada H3T 1J4
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, QC, Canada H3T 1J4
- Neural Signaling and Circuitry Research Group (SNC), Montréal, QC, Canada H3C 3J7
| | - Nina Feller
- Department of Pharmacology and Physiology, Université de Montréal, QC, Canada H3T 1J4
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, QC, Canada H3T 1J4
- Neural Signaling and Circuitry Research Group (SNC), Montréal, QC, Canada H3C 3J7
| | - Louis-Éric Trudeau
- Department of Pharmacology and Physiology, Université de Montréal, QC, Canada H3T 1J4
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, QC, Canada H3T 1J4
- Neural Signaling and Circuitry Research Group (SNC), Montréal, QC, Canada H3C 3J7
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17
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Bhattacharya S, Silkunas M, Gudvangen E, Mangalanathan U, Pakhomova ON, Pakhomov AG. Ca 2+ dependence and kinetics of cell membrane repair after electropermeabilization. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183823. [PMID: 34838875 DOI: 10.1016/j.bbamem.2021.183823] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 11/15/2021] [Accepted: 11/19/2021] [Indexed: 01/24/2023]
Abstract
Electroporation, in particular with nanosecond pulses, is an efficient technique to generate nanometer-size membrane lesions without the use of toxins or other chemicals. The restoration of the membrane integrity takes minutes and is only partially dependent on [Ca2+]. We explored the impact of Ca2+ on the kinetics of membrane resealing by monitoring the entry of a YO-PRO-1 dye (YP) in BPAE and HEK cells. Ca2+ was promptly removed or added after the electric pulse (EP) by a fast-step perfusion. YP entry increased sharply after the EP and gradually slowed down following either a single- or a double-exponential function. In BPAE cells permeabilized by a single 300- or 600-ns EP at 14 kV/cm in a Ca2+-free medium, perfusion with 2 mM of external Ca2+ advanced the 90% resealing and reduced the dye uptake about twofold. Membrane restoration was accomplished by a combination of fast, Ca2+-independent resealing (τ = 13-15 s) and slow, Ca2+-dependent processes (τ ~70 s with Ca2+ and ~ 110 s or more without it). These time constants did not change when the membrane damage was doubled by increasing EP duration from 300 to 600 ns. However, injury by microsecond-range EP (300 and 600 μs) took longer to recover even when the membrane initially was less damaged, presumably because of the larger size of pores made in the membrane. Full membrane recovery was not prevented by blocking both extra- and intracellular Ca2+ (by loading cells with BAPTA or after Ca2+ depletion from the reticulum), suggesting the recruitment of unknown Ca2+-independent repair mechanisms.
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Affiliation(s)
- Sayak Bhattacharya
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA
| | - Mantas Silkunas
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA; Institute for Digestive System Research, Lithuanian University of Health Sciences, 44307 Kaunas, Lithuania
| | - Emily Gudvangen
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA
| | - Uma Mangalanathan
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA
| | - Olga N Pakhomova
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA
| | - Andrei G Pakhomov
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA.
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18
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Mulari S, Eskin A, Lampinen M, Nummi A, Nieminen T, Teittinen K, Ojala T, Kankainen M, Vento A, Laurikka J, Kupari M, Harjula A, Tuncbag N, Kankuri E. Ischemic Heart Disease Selectively Modifies the Right Atrial Appendage Transcriptome. Front Cardiovasc Med 2021; 8:728198. [PMID: 34926599 PMCID: PMC8674465 DOI: 10.3389/fcvm.2021.728198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 11/01/2021] [Indexed: 11/20/2022] Open
Abstract
Background: Although many pathological changes have been associated with ischemic heart disease (IHD), molecular-level alterations specific to the ischemic myocardium and their potential to reflect disease severity or therapeutic outcome remain unclear. Currently, diagnosis occurs relatively late and evaluating disease severity is largely based on clinical symptoms, various imaging modalities, or the determination of risk factors. This study aims to identify IHD-associated signature RNAs from the atrial myocardium and evaluate their ability to reflect disease severity or cardiac surgery outcomes. Methods and Results: We collected right atrial appendage (RAA) biopsies from 40 patients with invasive coronary angiography (ICA)-positive IHD undergoing coronary artery bypass surgery and from 8 patients ICA-negative for IHD (non-IHD) undergoing valvular surgery. Following RNA sequencing, RAA transcriptomes were analyzed against 429 donors from the GTEx project without cardiac disease. The IHD transcriptome was characterized by repressed RNA expression in pathways for cell-cell contacts and mitochondrial dysfunction. Increased expressions of the CSRNP3, FUT10, SHD, NAV2-AS4, and hsa-mir-181 genes resulted in significance with the complexity of coronary artery obstructions or correlated with a functional cardiac benefit from bypass surgery. Conclusions: Our results provide an atrial myocardium-focused insight into IHD signature RNAs. The specific gene expression changes characterized here, pave the way for future disease mechanism-based identification of biomarkers for early detection and treatment of IHD.
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Affiliation(s)
- Severi Mulari
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Heart and Lung Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Arda Eskin
- Department of Health Informatics, Graduate School of Informatics, Middle East Technical University (METU), Ankara, Turkey
| | - Milla Lampinen
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Department of Oral and Maxillofacial Diseases, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Annu Nummi
- Heart and Lung Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Tuomo Nieminen
- Heart and Lung Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Kari Teittinen
- Heart and Lung Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Teija Ojala
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Matti Kankainen
- Research Programs Unit, University of Helsinki, Helsinki, Finland
| | - Antti Vento
- Heart and Lung Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Jari Laurikka
- Department of Cardiothoracic Surgery, Heart Center, Tampere University Hospital, Tampere, Finland
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Markku Kupari
- Heart and Lung Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Ari Harjula
- Heart and Lung Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Nurcan Tuncbag
- Department of Health Informatics, Graduate School of Informatics, Middle East Technical University (METU), Ankara, Turkey
- Department of Chemical and Biological Engineering, College of Engineering, Koc University, Istanbul, Turkey
- School of Medicine, Koc University, Istanbul, Turkey
| | - Esko Kankuri
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
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19
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Vevea JD, Kusick GF, Courtney KC, Chen E, Watanabe S, Chapman ER. Synaptotagmin 7 is targeted to the axonal plasma membrane through γ-secretase processing to promote synaptic vesicle docking in mouse hippocampal neurons. eLife 2021; 10:e67261. [PMID: 34543184 PMCID: PMC8452306 DOI: 10.7554/elife.67261] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 08/27/2021] [Indexed: 12/28/2022] Open
Abstract
Synaptotagmin 7 (SYT7) has emerged as a key regulator of presynaptic function, but its localization and precise role in the synaptic vesicle cycle remain the subject of debate. Here, we used iGluSnFR to optically interrogate glutamate release, at the single-bouton level, in SYT7KO-dissociated mouse hippocampal neurons. We analyzed asynchronous release, paired-pulse facilitation, and synaptic vesicle replenishment and found that SYT7 contributes to each of these processes to different degrees. 'Zap-and-freeze' electron microscopy revealed that a loss of SYT7 diminishes docking of synaptic vesicles after a stimulus and inhibits the recovery of depleted synaptic vesicles after a stimulus train. SYT7 supports these functions from the axonal plasma membrane, where its localization and stability require both γ-secretase-mediated cleavage and palmitoylation. In summary, SYT7 is a peripheral membrane protein that controls multiple modes of synaptic vesicle (SV) exocytosis and plasticity, in part, through enhancing activity-dependent docking of SVs.
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Affiliation(s)
- Jason D Vevea
- Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
- Howard Hughes Medical InstituteMadisonUnited States
| | - Grant F Kusick
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
- Biochemistry, Cellular and Molecular Biology Graduate Program, Johns Hopkins University, School of MedicineBaltimoreUnited States
| | - Kevin C Courtney
- Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
- Howard Hughes Medical InstituteMadisonUnited States
| | - Erin Chen
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of MedicineBaltimoreUnited States
| | - Edwin R Chapman
- Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
- Howard Hughes Medical InstituteMadisonUnited States
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20
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Martinetti LE, Bonekamp KE, Autio DM, Kim HH, Crandall SR. Short-Term Facilitation of Long-Range Corticocortical Synapses Revealed by Selective Optical Stimulation. Cereb Cortex 2021; 32:1932-1949. [PMID: 34519352 PMCID: PMC9070351 DOI: 10.1093/cercor/bhab325] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 08/10/2021] [Accepted: 08/11/2021] [Indexed: 11/14/2022] Open
Abstract
Short-term plasticity regulates the strength of central synapses as a function of previous activity. In the neocortex, direct synaptic interactions between areas play a central role in cognitive function, but the activity-dependent regulation of these long-range corticocortical connections and their impact on a postsynaptic target neuron is unclear. Here, we use an optogenetic strategy to study the connections between mouse primary somatosensory and motor cortex. We found that short-term facilitation was strong in both corticocortical synapses, resulting in far more sustained responses than local intracortical and thalamocortical connections. A major difference between pathways was that the synaptic strength and magnitude of facilitation were distinct for individual excitatory cells located across all cortical layers and specific subtypes of GABAergic neurons. Facilitation was dependent on the presynaptic calcium sensor synaptotagmin-7 and altered by several optogenetic approaches. Current-clamp recordings revealed that during repetitive activation, the short-term dynamics of corticocortical synapses enhanced the excitability of layer 2/3 pyramidal neurons, increasing the probability of spiking with activity. Furthermore, the properties of the connections linking primary with secondary somatosensory cortex resemble those between somatosensory-motor areas. These short-term changes in transmission properties suggest long-range corticocortical synapses are specialized for conveying information over relatively extended periods.
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Affiliation(s)
| | | | - Dawn M Autio
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA
| | - Hye-Hyun Kim
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA
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21
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Ca 2+ roles in electroporation-induced changes of cancer cell physiology: From membrane repair to cell death. Bioelectrochemistry 2021; 142:107927. [PMID: 34425390 DOI: 10.1016/j.bioelechem.2021.107927] [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: 04/15/2021] [Revised: 08/06/2021] [Accepted: 08/10/2021] [Indexed: 12/17/2022]
Abstract
The combination of Ca2+ ions and electroporation has gained attention as potential alternative to electrochemotherapy. Ca2+ is an important component of the cell membrane repair system and its presence directly influences the dynamics of the pore cycle after electroporation which can be exploited for cancer therapies. Here, the influence of Ca2+ concentration is investigated on small molecule electrotransfer and release of Calcein from 4T1, MX-1, B16F10, U87 cancer cells after cell exposure to microsecond electric pulses. Moreover, we investigated simultaneous molecule electrotransfer and intracellular calcium ion influx when media was supplemented with different Ca2+ concentrations. Results show that increased concentrations of calcium ions reduce the electrotransfer of small molecules to different lines of cancer cells as well as the release of Calcein. These effects are related with an enhanced membrane repair mechanism. Overall, we show that the efficiency of molecular electrotransfer can be controlled by regulating Ca2+ concentration in the electroporation medium. For the first time, the cause of cancer cell death in vitro from 1 mM CaCl2 concentrations is related to the irreversible loss of Ca2+ homeostasis after cell electroporation. Our findings provide fundamental insight on the mechanisms of Ca2+ electroporation that might lead to improved therapeutic outcomes.
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22
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Wang QW, Wang YH, Wang B, Chen Y, Lu SY, Yao J. Synaptotagmin-7-mediated activation of spontaneous NMDAR currents is disrupted in bipolar disorder susceptibility variants. PLoS Biol 2021; 19:e3001323. [PMID: 34228711 PMCID: PMC8284830 DOI: 10.1371/journal.pbio.3001323] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 07/16/2021] [Accepted: 06/15/2021] [Indexed: 11/19/2022] Open
Abstract
Synaptotagmin-7 (Syt7) plays direct or redundant Ca2+ sensor roles in multiple forms of vesicle exocytosis in synapses. Here, we show that Syt7 is a redundant Ca2+ sensor with Syt1/Doc2 to drive spontaneous glutamate release, which functions uniquely to activate the postsynaptic GluN2B-containing NMDARs that significantly contribute to mental illness. In mouse hippocampal neurons lacking Syt1/Doc2, Syt7 inactivation largely diminishes spontaneous release. Using 2 approaches, including measuring Ca2+ dose response and substituting extracellular Ca2+ with Sr2+, we detect that Syt7 directly triggers spontaneous release via its Ca2+ binding motif to activate GluN2B-NMDARs. Furthermore, modifying the localization of Syt7 in the active zone still allows Syt7 to drive spontaneous release, but the GluN2B-NMDAR activity is abolished. Finally, Syt7 SNPs identified in bipolar disorder patients destroy the function of Syt7 in spontaneous release in patient iPSC-derived and mouse hippocampal neurons. Therefore, Syt7 could contribute to neuropsychiatric disorders through driving spontaneous glutamate release.
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Affiliation(s)
- Qiu-Wen Wang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
| | - Ying-Han Wang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
| | - Bing Wang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yun Chen
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
| | - Si-Yao Lu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
| | - Jun Yao
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
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23
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Liu H, Xu J, Lan Y, Lim HW, Jiang R. The Scleraxis Transcription Factor Directly Regulates Multiple Distinct Molecular and Cellular Processes During Early Tendon Cell Differentiation. Front Cell Dev Biol 2021; 9:654397. [PMID: 34150754 PMCID: PMC8211106 DOI: 10.3389/fcell.2021.654397] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Accepted: 05/05/2021] [Indexed: 12/13/2022] Open
Abstract
Proper development of tendons is crucial for the integration and function of the musculoskeletal system. Currently little is known about the molecular mechanisms controlling tendon development and tendon cell differentiation. The transcription factor Scleraxis (Scx) is expressed throughout tendon development and plays essential roles in both embryonic tendon development and adult tendon healing, but few direct target genes of Scx in tendon development have been reported and genome-wide identification of Scx direct target genes in vivo has been lacking. In this study, we have generated a ScxFlag knockin mouse strain, which produces fully functional endogenous Scx proteins containing a 2xFLAG epitope tag at the carboxy terminus. We mapped the genome-wide Scx binding sites in the developing limb tendon tissues, identifying 12,097 high quality Scx regulatory cis-elements in-around 7,520 genes. Comparative analysis with previously reported embryonic tendon cell RNA-seq data identified 490 candidate Scx direct target genes in early tendon development. Furthermore, we characterized a new Scx gene-knockout mouse line and performed whole transcriptome RNA sequencing analysis of E15.5 forelimb tendon cells from Scx–/– embryos and control littermates, identifying 68 genes whose expression in the developing tendon tissues significantly depended on Scx function. Combined analysis of the ChIP-seq and RNA-seq data yielded 32 direct target genes that required Scx for activation and an additional 17 target genes whose expression was suppressed by Scx during early tendon development. We further analyzed and validated Scx-dependent tendon-specific expression patterns of a subset of the target genes, including Fmod, Kera, Htra3, Ssc5d, Tnmd, and Zfp185, by in situ hybridization and real-time quantitative polymerase chain reaction assays. These results provide novel insights into the molecular mechanisms mediating Scx function in tendon development and homeostasis. The ChIP-seq and RNA-seq data provide a rich resource for aiding design of further studies of the mechanisms regulating tendon cell differentiation and tendon tissue regeneration. The ScxFlag mice provide a valuable new tool for unraveling the molecular mechanisms involving Scx in the protein interaction and gene-regulatory networks underlying many developmental and disease processes.
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Affiliation(s)
- Han Liu
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Jingyue Xu
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Yu Lan
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States.,Division of Plastic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States.,Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH, United States.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Hee-Woong Lim
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States.,Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Rulang Jiang
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States.,Division of Plastic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States
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24
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Dynamics of Myosin II Filaments during Wound Repair in Dividing Cells. Cells 2021; 10:cells10051229. [PMID: 34067877 PMCID: PMC8156316 DOI: 10.3390/cells10051229] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/14/2021] [Accepted: 05/15/2021] [Indexed: 12/16/2022] Open
Abstract
Wound repair of cell membranes is essential for cell survival. Myosin II contributes to wound pore closure by interacting with actin filaments in larger cells; however, its role in smaller cells is unclear. In this study, we observed wound repair in dividing cells for the first time. The cell membrane in the cleavage furrow, where myosin II localized, was wounded by laserporation. Upon wounding, actin transiently accumulated, and myosin II transiently disappeared from the wound site. Ca2+ influx from the external medium triggered both actin and myosin II dynamics. Inhibition of calmodulin reduced both actin and myosin II dynamics. The wound closure time in myosin II-null cells was the same as that in wild-type cells, suggesting that myosin II is not essential for wound repair. We also found that disassembly of myosin II filaments by phosphorylation did not contribute to their disappearance, indicating a novel mechanism for myosin II delocalization from the cortex. Furthermore, we observed that several furrow-localizing proteins such as GAPA, PakA, myosin heavy chain kinase C, PTEN, and dynamin disappeared upon wounding. Herein, we discuss the possible mechanisms of myosin dynamics during wound repair.
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25
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Ermini L, Farrell A, Alahari S, Ausman J, Park C, Sallais J, Melland-Smith M, Porter T, Edson M, Nevo O, Litvack M, Post M, Caniggia I. Ceramide-Induced Lysosomal Biogenesis and Exocytosis in Early-Onset Preeclampsia Promotes Exosomal Release of SMPD1 Causing Endothelial Dysfunction. Front Cell Dev Biol 2021; 9:652651. [PMID: 34017832 PMCID: PMC8130675 DOI: 10.3389/fcell.2021.652651] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 04/06/2021] [Indexed: 11/13/2022] Open
Abstract
Aberrant ceramide build-up in preeclampsia, a serious disorder of pregnancy, causes exuberant autophagy-mediated trophoblast cell death. The significance of ceramide accumulation for lysosomal biogenesis in preeclampsia is unknown. Here we report that lysosome formation is markedly increased in trophoblast cells of early-onset preeclamptic placentae, in particular in syncytiotrophoblasts. This is accompanied by augmented levels of transcription factor EB (TFEB). In vitro and in vivo experiments demonstrate that ceramide increases TFEB expression and nuclear translocation and induces lysosomal formation and exocytosis. Further, we show that TFEB directly regulates the expression of lysosomal sphingomyelin phosphodiesterase (L-SMPD1) that degrades sphingomyelin to ceramide. In early-onset preeclampsia, ceramide-induced lysosomal exocytosis carries L-SMPD1 to the apical membrane of the syncytial epithelium, resulting in ceramide accumulation in lipid rafts and release of active L-SMPD1 via ceramide-enriched exosomes into the maternal circulation. The SMPD1-containing exosomes promote endothelial activation and impair endothelial tubule formation in vitro. Both exosome-induced processes are attenuated by SMPD1 inhibitors. These findings suggest that ceramide-induced lysosomal biogenesis and exocytosis in preeclamptic placentae contributes to maternal endothelial dysfunction, characteristic of this pathology.
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Affiliation(s)
- Leonardo Ermini
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada
| | - Abby Farrell
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada.,Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada
| | - Sruthi Alahari
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada
| | - Jonathan Ausman
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada.,Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada
| | - Chanho Park
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Julien Sallais
- Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada
| | - Megan Melland-Smith
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada
| | - Tyler Porter
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada
| | - Michael Edson
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada
| | - Ori Nevo
- Sunnybrook Health Sciences Centre, Toronto, ON, Canada
| | - Michael Litvack
- Translational Medicine Program, Peter Gilgan Center, The Hospital for Sick Children, Toronto, ON, Canada
| | - Martin Post
- Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada.,Translational Medicine Program, Peter Gilgan Center, The Hospital for Sick Children, Toronto, ON, Canada
| | - Isabella Caniggia
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada.,Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, ON, Canada
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26
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Ammendolia DA, Bement WM, Brumell JH. Plasma membrane integrity: implications for health and disease. BMC Biol 2021; 19:71. [PMID: 33849525 PMCID: PMC8042475 DOI: 10.1186/s12915-021-00972-y] [Citation(s) in RCA: 93] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Accepted: 02/01/2021] [Indexed: 12/12/2022] Open
Abstract
Plasma membrane integrity is essential for cellular homeostasis. In vivo, cells experience plasma membrane damage from a multitude of stressors in the extra- and intra-cellular environment. To avoid lethal consequences, cells are equipped with repair pathways to restore membrane integrity. Here, we assess plasma membrane damage and repair from a whole-body perspective. We highlight the role of tissue-specific stressors in health and disease and examine membrane repair pathways across diverse cell types. Furthermore, we outline the impact of genetic and environmental factors on plasma membrane integrity and how these contribute to disease pathogenesis in different tissues.
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Affiliation(s)
- Dustin A Ammendolia
- Cell Biology Program, Hospital for Sick Children, 686 Bay Street PGCRL, Toronto, ON, M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 1A1, Canada
| | - William M Bement
- Center for Quantitative Cell Imaging and Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - John H Brumell
- Cell Biology Program, Hospital for Sick Children, 686 Bay Street PGCRL, Toronto, ON, M5G 0A4, Canada. .,Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 1A1, Canada. .,Institute of Medical Science, University of Toronto, Toronto, ON, M5S 1A1, Canada. .,SickKids IBD Centre, Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada.
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27
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Function of Drosophila Synaptotagmins in membrane trafficking at synapses. Cell Mol Life Sci 2021; 78:4335-4364. [PMID: 33619613 PMCID: PMC8164606 DOI: 10.1007/s00018-021-03788-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/29/2021] [Accepted: 02/09/2021] [Indexed: 12/13/2022]
Abstract
The Synaptotagmin (SYT) family of proteins play key roles in regulating membrane trafficking at neuronal synapses. Using both Ca2+-dependent and Ca2+-independent interactions, several SYT isoforms participate in synchronous and asynchronous fusion of synaptic vesicles (SVs) while preventing spontaneous release that occurs in the absence of stimulation. Changes in the function or abundance of the SYT1 and SYT7 isoforms alter the number and route by which SVs fuse at nerve terminals. Several SYT family members also regulate trafficking of other subcellular organelles at synapses, including dense core vesicles (DCV), exosomes, and postsynaptic vesicles. Although SYTs are linked to trafficking of multiple classes of synaptic membrane compartments, how and when they interact with lipids, the SNARE machinery and other release effectors are still being elucidated. Given mutations in the SYT family cause disorders in both the central and peripheral nervous system in humans, ongoing efforts are defining how these proteins regulate vesicle trafficking within distinct neuronal compartments. Here, we review the Drosophila SYT family and examine their role in synaptic communication. Studies in this invertebrate model have revealed key similarities and several differences with the predicted activity of their mammalian counterparts. In addition, we highlight the remaining areas of uncertainty in the field and describe outstanding questions on how the SYT family regulates membrane trafficking at nerve terminals.
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28
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McElhanon KE, Young N, Hampton J, Paleo BJ, Kwiatkowski TA, Beck EX, Capati A, Jablonski K, Gurney T, Perez MAL, Aggarwal R, Oddis CV, Jarjour WN, Weisleder N. Autoantibodies targeting TRIM72 compromise membrane repair and contribute to inflammatory myopathy. J Clin Invest 2021; 130:4440-4455. [PMID: 32687067 DOI: 10.1172/jci131721] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 05/14/2020] [Indexed: 12/27/2022] Open
Abstract
Idiopathic inflammatory myopathies (IIM) involve chronic inflammation of skeletal muscle and subsequent muscle degeneration due to an uncontrolled autoimmune response; however, the mechanisms leading to pathogenesis are not well understood. A compromised sarcolemmal repair process could promote an aberrant exposure of intramuscular antigens with the subsequent initiation of an inflammatory response that contributes to IIM. Using an adoptive transfer mouse model of IIM, we show that sarcolemmal repair is significantly compromised in distal skeletal muscle in the absence of inflammation. We identified autoantibodies against TRIM72 (also known as MG53), a muscle-enriched membrane repair protein, in IIM patient sera and in our mouse model of IIM by ELISA. We found that patient sera with elevated levels of TRIM72 autoantibodies suppress sarcolemmal resealing in healthy skeletal muscle, and depletion of TRIM72 antibodies from these same serum samples rescues sarcolemmal repair capacity. Autoantibodies targeting TRIM72 lead to skeletal muscle fibers with compromised membrane barrier function, providing a continuous source of autoantigens to promote autoimmunity and further amplifying humoral responses. These findings reveal a potential pathogenic mechanism that acts as a feedback loop contributing to the progression of IIM.
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Affiliation(s)
- Kevin E McElhanon
- Dorothy M. Davis Heart and Lung Research Institute and Department of Physiology and Cell Biology, and
| | - Nicholas Young
- Division of Rheumatology and Immunology, Department of Internal Medicine, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Jeffrey Hampton
- Division of Rheumatology and Immunology, Department of Internal Medicine, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Brian J Paleo
- Dorothy M. Davis Heart and Lung Research Institute and Department of Physiology and Cell Biology, and
| | - Thomas A Kwiatkowski
- Dorothy M. Davis Heart and Lung Research Institute and Department of Physiology and Cell Biology, and
| | - Eric X Beck
- Dorothy M. Davis Heart and Lung Research Institute and Department of Physiology and Cell Biology, and
| | - Ana Capati
- Dorothy M. Davis Heart and Lung Research Institute and Department of Physiology and Cell Biology, and
| | - Kyle Jablonski
- Division of Rheumatology and Immunology, Department of Internal Medicine, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Travis Gurney
- Dorothy M. Davis Heart and Lung Research Institute and Department of Physiology and Cell Biology, and
| | - Miguel A Lopez Perez
- Dorothy M. Davis Heart and Lung Research Institute and Department of Physiology and Cell Biology, and
| | - Rohit Aggarwal
- Division of Rheumatology and Clinical Immunology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Chester V Oddis
- Division of Rheumatology and Clinical Immunology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Wael N Jarjour
- Division of Rheumatology and Immunology, Department of Internal Medicine, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Noah Weisleder
- Dorothy M. Davis Heart and Lung Research Institute and Department of Physiology and Cell Biology, and
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29
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Plasma membrane integrity in health and disease: significance and therapeutic potential. Cell Discov 2021; 7:4. [PMID: 33462191 PMCID: PMC7813858 DOI: 10.1038/s41421-020-00233-2] [Citation(s) in RCA: 88] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 10/23/2020] [Indexed: 12/13/2022] Open
Abstract
Maintenance of plasma membrane integrity is essential for normal cell viability and function. Thus, robust membrane repair mechanisms have evolved to counteract the eminent threat of a torn plasma membrane. Different repair mechanisms and the bio-physical parameters required for efficient repair are now emerging from different research groups. However, less is known about when these mechanisms come into play. This review focuses on the existence of membrane disruptions and repair mechanisms in both physiological and pathological conditions, and across multiple cell types, albeit to different degrees. Fundamentally, irrespective of the source of membrane disruption, aberrant calcium influx is the common stimulus that activates the membrane repair response. Inadequate repair responses can tip the balance between physiology and pathology, highlighting the significance of plasma membrane integrity. For example, an over-activated repair response can promote cancer invasion, while the inability to efficiently repair membrane can drive neurodegeneration and muscular dystrophies. The interdisciplinary view explored here emphasises the widespread potential of targeting plasma membrane repair mechanisms for therapeutic purposes.
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30
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Corrotte M, Cerasoli M, Maeda FY, Andrews NW. Endophilin-A2-dependent tubular endocytosis promotes plasma membrane repair and parasite invasion. J Cell Sci 2020; 134:jcs249524. [PMID: 33093240 PMCID: PMC7725609 DOI: 10.1242/jcs.249524] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 10/12/2020] [Indexed: 12/12/2022] Open
Abstract
Endocytosis of caveolae has previously been implicated in the repair of plasma membrane wounds. Here, we show that caveolin-1-deficient fibroblasts lacking caveolae upregulate a tubular endocytic pathway and have a reduced capacity to reseal after permeabilization with pore-forming toxins compared with wild-type cells. Silencing endophilin-A2 expression inhibited fission of endocytic tubules and further reduced plasma membrane repair in cells lacking caveolin-1, supporting a role for tubular endocytosis as an alternative pathway for the removal of membrane lesions. Endophilin-A2 was visualized in association with cholera toxin B-containing endosomes and was recruited to recently formed intracellular vacuoles containing Trypanosoma cruzi, a parasite that utilizes the plasma membrane wounding repair pathway to invade host cells. Endophilin-A2 deficiency inhibited T. cruzi invasion, and fibroblasts deficient in both caveolin-1 and endophilin-A2 did not survive prolonged exposure to the parasites. These findings reveal a novel crosstalk between caveolin-1 and endophilin-A2 in the regulation of clathrin-independent endocytosis and plasma membrane repair, a process that is subverted by T. cruzi parasites for cell invasion.
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Affiliation(s)
- Matthias Corrotte
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
- Department of Veterinary Medicine, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA
| | - Mark Cerasoli
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Fernando Y Maeda
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Norma W Andrews
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
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31
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Tang T, Yang ZY, Wang D, Yang XY, Wang J, Li L, Wen Q, Gao L, Bian XW, Yu SC. The role of lysosomes in cancer development and progression. Cell Biosci 2020; 10:131. [PMID: 33292489 PMCID: PMC7677787 DOI: 10.1186/s13578-020-00489-x] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Accepted: 10/29/2020] [Indexed: 01/01/2023] Open
Abstract
Lysosomes are an important component of the inner membrane system and participate in numerous cell biological processes, such as macromolecular degradation, antigen presentation, intracellular pathogen destruction, plasma membrane repair, exosome release, cell adhesion/migration and apoptosis. Thus, lysosomes play important roles in cellular activity. In addition, previous studies have shown that lysosomes may play important roles in cancer development and progression through the abovementioned biological processes and that the functional status and spatial distribution of lysosomes are closely related to cancer cell proliferation, energy metabolism, invasion and metastasis, immune escape and tumor-associated angiogenesis. Therefore, identifying the factors and mechanisms that regulate the functional status and spatial distribution of lysosomes and elucidating the relationship between lysosomes and the development and progression of cancer can provide important information for cancer diagnosis and prognosis prediction and may yield new therapeutic targets. This study briefly reviews the above information and explores the potential value of lysosomes in cancer therapy.
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Affiliation(s)
- Tao Tang
- Department of Stem Cell and Regenerative Medicine, Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Ze-Yu Yang
- Department of Stem Cell and Regenerative Medicine, Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Di Wang
- Department of Stem Cell and Regenerative Medicine, Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Xian-Yan Yang
- Department of Stem Cell and Regenerative Medicine, Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Jun Wang
- Department of Stem Cell and Regenerative Medicine, Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Lin Li
- Department of Stem Cell and Regenerative Medicine, Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Qian Wen
- Department of Stem Cell and Regenerative Medicine, Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Lei Gao
- Department of Hematology, Xinqiao Hospital, Third Military Medical University (Army Medical University), Chongqing, 400037, China
| | - Xiu-Wu Bian
- Department of Stem Cell and Regenerative Medicine, Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Shi-Cang Yu
- Department of Stem Cell and Regenerative Medicine, Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China.
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32
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McDade JR, Naylor MT, Michele DE. Sarcolemma wounding activates dynamin-dependent endocytosis in striated muscle. FEBS J 2020; 288:160-174. [PMID: 32893434 DOI: 10.1111/febs.15556] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 07/08/2020] [Accepted: 09/01/2020] [Indexed: 01/13/2023]
Abstract
Plasma membrane repair is an evolutionarily conserved mechanism by which cells can seal breaches in the plasma membrane. Mutations in several proteins with putative roles in sarcolemma integrity, membrane repair, and membrane transport result in several forms of muscle disease; however, the mechanisms that are activated and responsible for sarcolemma resealing are not well understood. Using the standard assays for membrane repair, which track the uptake of FM 1-43 dye into adult skeletal muscle fibers following laser-induced sarcolemma disruption, we show that labeling of resting fibers by FM1-43 prior to membrane wounding and the induced FM1-43 dye uptake after sarcolemma wounding occurs via dynamin-dependent endocytosis. Dysferlin-deficient muscle fibers show elevated dye uptake following wounding, which is the basis for the assertion that membrane repair is defective in this model. Our data show that dynamin inhibition mitigates the differences in FM1-43 dye uptake between dysferlin-null and wild-type muscle fibers, suggesting that elevated wound-induced FM1-43 uptake in dysferlin-deficient muscle may actually be due to enhanced dynamin-dependent endocytosis following wounding, though dynamin inhibition had no effect on dysferlin trafficking after wounding. By monitoring calcium flux after membrane wounding, we show that reversal of calcium precedes the sustained, slower increase of dynamin-dependent FM1-43 uptake in WT fibers, and that dysferlin-deficient muscle fibers have persistently increased calcium after wounding, consistent with its proposed role in resealing. These data highlight a previously unappreciated role for dynamin-dependent endocytosis in wounded skeletal muscle fibers and identify overactive dynamin-dependent endocytosis following sarcolemma wounding as a potential mechanism or consequence of dysferlin deficiency.
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Affiliation(s)
- Joel R McDade
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Molly T Naylor
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.,Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI, USA
| | - Daniel E Michele
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.,Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI, USA.,Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI, USA
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33
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Actin Polymerization and ESCRT Trigger Recruitment of the Fusogens Syntaxin-2 and EFF-1 to Promote Membrane Repair in C. elegans. Dev Cell 2020; 54:624-638.e5. [DOI: 10.1016/j.devcel.2020.06.027] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 05/08/2020] [Accepted: 06/19/2020] [Indexed: 12/20/2022]
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34
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Bendahmane M, Chapman-Morales A, Kreutzberger AJ, Schenk NA, Mohan R, Bakshi S, Philippe J, Zhang S, Kiessling V, Tamm LK, Giovannucci DR, Jenkins PM, Anantharam A. Synaptotagmin-7 enhances calcium-sensing of chromaffin cell granules and slows discharge of granule cargos. J Neurochem 2020; 154:598-617. [PMID: 32058590 PMCID: PMC7426247 DOI: 10.1111/jnc.14986] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 02/04/2020] [Accepted: 02/07/2020] [Indexed: 12/30/2022]
Abstract
Synaptotagmin-7 (Syt-7) is one of two major calcium sensors for exocytosis in adrenal chromaffin cells, the other being synaptotagmin-1 (Syt-1). Despite a broad appreciation for the importance of Syt-7, questions remain as to its localization, function in mediating discharge of dense core granule cargos, and role in triggering release in response to physiological stimulation. These questions were addressed using two distinct experimental preparations-mouse chromaffin cells lacking endogenous Syt-7 (KO cells) and a reconstituted system employing cell-derived granules expressing either Syt-7 or Syt-1. First, using immunofluorescence imaging and subcellular fractionation, it is shown that Syt-7 is widely distributed in organelles, including dense core granules. Total internal reflection fluorescence (TIRF) imaging demonstrates that the kinetics and probability of granule fusion in Syt-7 KO cells stimulated by a native secretagogue, acetylcholine, are markedly lower than in WT cells. When fusion is observed, fluorescent cargo proteins are discharged more rapidly when only Syt-1 is available to facilitate release. To determine the extent to which the aforementioned results are attributable purely to Syt-7, granules expressing only Syt-7 or Syt-1 were triggered to fuse on planar supported bilayers bearing plasma membrane SNARE proteins. Here, as in cells, Syt-7 confers substantially greater calcium sensitivity to granule fusion than Syt-1 and slows the rate at which cargos are released. Overall, this study demonstrates that by virtue of its high affinity for calcium and effects on fusion pore expansion, Syt-7 plays a central role in regulating secretory output from adrenal chromaffin cells.
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Affiliation(s)
- Mounir Bendahmane
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
| | | | - Alex J.B. Kreutzberger
- Center for Membrane and Cell Physiology and Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908
| | - Noah A. Schenk
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
| | - Ramkumar Mohan
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
| | - Shreeya Bakshi
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
| | - Julie Philippe
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
| | - Shuang Zhang
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
| | - Volker Kiessling
- Center for Membrane and Cell Physiology and Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908
| | - Lukas K. Tamm
- Center for Membrane and Cell Physiology and Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908
| | - David R. Giovannucci
- Department of Neuroscience, University of Toledo Medical School, Toledo, OH 43606
| | - Paul M. Jenkins
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
| | - Arun Anantharam
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
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35
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An in vitro model of temporal enhancement of epithelium barrier permeability by low-energy shock waves without contrast agents. Med Biol Eng Comput 2020; 58:1987-1993. [PMID: 32591989 DOI: 10.1007/s11517-020-02207-8] [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: 01/05/2019] [Accepted: 05/26/2020] [Indexed: 10/24/2022]
Abstract
One of the commonly used techniques for drug delivery is to temporarily increase the permeability of tissue barriers. Acoustic energies such as ultrasound and shock waves are known to modulate tissue permeability. Recently, it was found that shock waves modulate the blood-brain barrier in the rat brain without injection of contrast agents such as microbubbles. This finding implies that modulation of other tissue barriers by shock wave exposure without contrast agents may be possible. To examine whether the modulation is also possible with other tissue barriers, we here investigated whether shock waves would modulate an in vitro tissue barrier model consisting of epithelial cells cultured on culture inserts. The permeability of the epithelium sheets evaluated by trans-epithelial electrical resistance (TEER) was increased following shock waves at a peak pressure of 11 MPa. The increased permeability recovered within 2 h. This enhancement was realized with one-shot low-energy shock waves having an acoustic energy of 0.013 mJ/mm2. Monitoring the peak pressures in every exposure revealed that the minimum peak pressure required for the enhancement is 2.9 MPa. These results indicate that shock wave exposure has the potential to temporarily increase the permeability of epithelium barriers to enhance drug delivery without contrast agents. Graphical abstract Enhancements of epithelial barrier permeability were evaluated by trans-epithelial electrical resistance (TEER) before and after shock wave exposures.
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36
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Sleiman M, Stevens DR, Chitirala P, Rettig J. Cytotoxic Granule Trafficking and Fusion in Synaptotagmin7-Deficient Cytotoxic T Lymphocytes. Front Immunol 2020; 11:1080. [PMID: 32547563 PMCID: PMC7273742 DOI: 10.3389/fimmu.2020.01080] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 05/05/2020] [Indexed: 11/13/2022] Open
Abstract
Granules of cytotoxic T lymphocytes (CTL) are derived from the lysosomal compartment. Synaptotagmin7 (Syt7) appears to be the calcium sensor triggering fusion of lysosomes in fibroblasts. Syt7 has been proposed to control cytotoxic granule (CG) fusion in lymphocytes and mice lacking Syt7 have reduced ability to clear infections. However, fusion of CG persists in the absence of Syt7. To clarify the role of Syt7 in CTL function, we have examined the fusion of cytotoxic granules of CD8+ T-lymphocytes from Syt7 knock-out mice. We have recorded granule fusion in living CTL, using total internal reflection microscopy. Since Syt7 is considered a high affinity calcium-sensor specialized for fusion under low calcium conditions, we have compared cytotoxic granule fusion under low and high calcium conditions in the same CTL. There was no difference in latencies or numbers of fusion events per CTL under low-calcium conditions, indicating that Syt7 is not required for cytotoxic granule fusion. A deficit of fusion in Syt7 KO CTL was seen when a high-calcium solution was introduced. Expressing wild type Syt7 in Syt7 KO lymphocytes reversed this deficit, confirming its Syt7-dependence. Mutations of Syt7 which disrupt calcium binding to its C2A domain reduced the efficacy of this rescue. We counted the cytotoxic granules present at the plasma membrane to determine if the lack of fusion events in the Syt7 KO CTL was due to a lack of granules. In low calcium there were no differences in fusion events per CTL, and granule numbers were similar. In high calcium, granule number was similar though wild type CTL exhibited significantly more fusion than Syt7 KO CTL. The modest differences in granule counts do not account for the lack of fusion in high calcium in Syt7 KO CTL. In Syt7 KO CTL expressing wild type Syt7, delivery of cytotoxic granules to the plasma membrane was comparable to that of wild type CTL. Syt7 KO CTL expressing Syt7 with deficient calcium binding in the C2A domain had significantly less fusion and fewer CG at the plasma membrane. These results indicate that Syt7 is involved in trafficking of CG to the plasma membrane.
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Affiliation(s)
- Marwa Sleiman
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - David R Stevens
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Praneeth Chitirala
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Jens Rettig
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
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Trivedi PC, Bartlett JJ, Pulinilkunnil T. Lysosomal Biology and Function: Modern View of Cellular Debris Bin. Cells 2020; 9:cells9051131. [PMID: 32375321 PMCID: PMC7290337 DOI: 10.3390/cells9051131] [Citation(s) in RCA: 123] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 04/27/2020] [Accepted: 04/29/2020] [Indexed: 02/07/2023] Open
Abstract
Lysosomes are the main proteolytic compartments of mammalian cells comprising of a battery of hydrolases. Lysosomes dispose and recycle extracellular or intracellular macromolecules by fusing with endosomes or autophagosomes through specific waste clearance processes such as chaperone-mediated autophagy or microautophagy. The proteolytic end product is transported out of lysosomes via transporters or vesicular membrane trafficking. Recent studies have demonstrated lysosomes as a signaling node which sense, adapt and respond to changes in substrate metabolism to maintain cellular function. Lysosomal dysfunction not only influence pathways mediating membrane trafficking that culminate in the lysosome but also govern metabolic and signaling processes regulating protein sorting and targeting. In this review, we describe the current knowledge of lysosome in influencing sorting and nutrient signaling. We further present a mechanistic overview of intra-lysosomal processes, along with extra-lysosomal processes, governing lysosomal fusion and fission, exocytosis, positioning and membrane contact site formation. This review compiles existing knowledge in the field of lysosomal biology by describing various lysosomal events necessary to maintain cellular homeostasis facilitating development of therapies maintaining lysosomal function.
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Affiliation(s)
- Purvi C. Trivedi
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4H7, Canada; (P.C.T.); (J.J.B.)
- Dalhousie Medicine New Brunswick, Saint John, NB E2L 4L5, Canada
| | - Jordan J. Bartlett
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4H7, Canada; (P.C.T.); (J.J.B.)
- Dalhousie Medicine New Brunswick, Saint John, NB E2L 4L5, Canada
| | - Thomas Pulinilkunnil
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4H7, Canada; (P.C.T.); (J.J.B.)
- Dalhousie Medicine New Brunswick, Saint John, NB E2L 4L5, Canada
- Correspondence: ; Tel.: +1-(506)-636-6973
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Guan Z, Quiñones-Frías MC, Akbergenova Y, Littleton JT. Drosophila Synaptotagmin 7 negatively regulates synaptic vesicle release and replenishment in a dosage-dependent manner. eLife 2020; 9:e55443. [PMID: 32343229 PMCID: PMC7224696 DOI: 10.7554/elife.55443] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 04/28/2020] [Indexed: 01/03/2023] Open
Abstract
Synchronous neurotransmitter release is triggered by Ca2+ binding to the synaptic vesicle protein Synaptotagmin 1, while asynchronous fusion and short-term facilitation is hypothesized to be mediated by plasma membrane-localized Synaptotagmin 7 (SYT7). We generated mutations in Drosophila Syt7 to determine if it plays a conserved role as the Ca2+ sensor for these processes. Electrophysiology and quantal imaging revealed evoked release was elevated 2-fold. Syt7 mutants also had a larger pool of readily-releasable vesicles, faster recovery following stimulation, and intact facilitation. Syt1/Syt7 double mutants displayed more release than Syt1 mutants alone, indicating SYT7 does not mediate the residual asynchronous release remaining in the absence of SYT1. SYT7 localizes to an internal membrane tubular network within the peri-active zone, but does not enrich at active zones. These findings indicate the two Ca2+ sensor model of SYT1 and SYT7 mediating all phases of neurotransmitter release and facilitation is not applicable at Drosophila synapses.
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Affiliation(s)
- Zhuo Guan
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Monica C Quiñones-Frías
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Yulia Akbergenova
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
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Huson V, Regehr WG. Diverse roles of Synaptotagmin-7 in regulating vesicle fusion. Curr Opin Neurobiol 2020; 63:42-52. [PMID: 32278209 DOI: 10.1016/j.conb.2020.02.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/12/2020] [Accepted: 02/13/2020] [Indexed: 11/18/2022]
Abstract
Synaptotagmin 7 (Syt7) is a multifunctional calcium sensor expressed throughout the body. Its high calcium affinity makes it well suited to act in processes triggered by modest calcium increases within cells. In synaptic transmission, Syt7 has been shown to mediate asynchronous neurotransmitter release, facilitation, and vesicle replenishment. In this review we provide an update on recent developments, and the newly emerging roles of Syt7 in frequency invariant synaptic transmission and in suppressing spontaneous release. Additionally, we discuss Syt7's regulation of membrane fusion in non-neuronal cells, and its involvement in disease. How such diversity of functions is regulated remains an open question. We discuss several potential factors including temperature, presynaptic calcium signals, the localization of Syt7, and its interaction with other Syt isoforms.
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Synaptotagmin-7 is a key factor for bipolar-like behavioral abnormalities in mice. Proc Natl Acad Sci U S A 2020; 117:4392-4399. [PMID: 32041882 DOI: 10.1073/pnas.1918165117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The pathogenesis of bipolar disorder (BD) has remained enigmatic, largely because genetic animal models based on identified susceptible genes have often failed to show core symptoms of spontaneous mood cycling. However, pedigree and induced pluripotent stem cell (iPSC)-based analyses have implicated that dysfunction in some key signaling cascades might be crucial for the disease pathogenesis in a subpopulation of BD patients. We hypothesized that the behavioral abnormalities of patients and the comorbid metabolic abnormalities might share some identical molecular mechanism. Hence, we investigated the expression of insulin/synapse dually functioning genes in neurons derived from the iPSCs of BD patients and the behavioral phenotype of mice with these genes silenced in the hippocampus. By these means, we identified synaptotagmin-7 (Syt7) as a candidate risk factor for behavioral abnormalities. We then investigated Syt7 knockout (KO) mice and observed nocturnal manic-like and diurnal depressive-like behavioral fluctuations in a majority of these animals, analogous to the mood cycling symptoms of BD. We treated the Syt7 KO mice with clinical BD drugs including olanzapine and lithium, and found that the drug treatments could efficiently regulate the behavioral abnormalities of the Syt7 KO mice. To further verify whether Syt7 deficits existed in BD patients, we investigated the plasma samples of 20 BD patients and found that the Syt7 mRNA level was significantly attenuated in the patient plasma compared to the healthy controls. We therefore concluded that Syt7 is likely a key factor for the bipolar-like behavioral abnormalities.
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Kirichenko K, Zakharenko A, Pikula K, Chaika V, Markina Z, Orlova T, Medvedev S, Waissi G, Kholodov A, Tsatsakis A, Golokhvast K. Dependence of welding fume particle toxicity on electrode type and current intensity assessed by microalgae growth inhibition test. ENVIRONMENTAL RESEARCH 2019; 179:108818. [PMID: 31678725 DOI: 10.1016/j.envres.2019.108818] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 09/28/2019] [Accepted: 10/09/2019] [Indexed: 06/10/2023]
Abstract
Welding fumes are a major source of metal oxide particles, ozone, carbon monoxide, carbon dioxide, nitrogen oxides, and many other toxic substances. Hazardous properties and the level of toxicity of welding fumes depend mostly on the welding electrode type and the welding regime parameters. The specific objective of this study was to evaluate the aquatic toxicity of metal welding fume particles in vivo on microalga Heterosigma akashiwo. The quantity and size of particles were measured by flow cytometry using a scattering laser light with a wavelength of 405 nm. The number of microalgae cells after 72 h and 7 days exposition with welding fume particle suspensions was evaluated by flow cytometry. Morphological changes of the microalga were observed by optical microscopy. The toxic effect was demonstrated as a significant reduction of cell density after exposure of microalgae to welding fume particles. The greatest impact on the growth of microalga was caused by particles with high rutile content. It was shown that the adverse effect of metal oxide particles depends more on the chemical composition of particles in welding fume while the number and dispersity of particles had no noticeable toxic influence on microalgae. The findings of this research confirm the fact that the toxicity of welding fume particles can be significantly reduced by using rutile-cellulose coated electrodes.
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Affiliation(s)
| | | | - Konstantin Pikula
- Far Eastern Federal University, Vladivostok, 690950, Russian Federation.
| | - Vladimir Chaika
- Far Eastern Federal University, Vladivostok, 690950, Russian Federation
| | - Zhanna Markina
- Far Eastern Federal University, Vladivostok, 690950, Russian Federation; National Scientific Center of Marine Biology FEB RAS, 690014, Vladivostok, Russian Federation
| | - Tatiana Orlova
- National Scientific Center of Marine Biology FEB RAS, 690014, Vladivostok, Russian Federation
| | | | - Greta Waissi
- University of Eastern Finland, School of Pharmacy, POB 1627 70211, Kuopio, Finland
| | - Aleksey Kholodov
- Far Eastern Federal University, Vladivostok, 690950, Russian Federation
| | - Aristidis Tsatsakis
- Far Eastern Federal University, Vladivostok, 690950, Russian Federation; University of Crete, School of Medicine, Laboratory of Toxicology, 71003, Heraklion, Greece; I.M. Sechenov First Moscow State Medical University, 119048, Moscow, Russian Federation
| | - Kirill Golokhvast
- Far Eastern Federal University, Vladivostok, 690950, Russian Federation; Pacific Geographical Institute FEB RAS, 690014, Vladivostok, Russian Federation
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Synaptotagmin 7 Mediates Both Facilitation and Asynchronous Release at Granule Cell Synapses. J Neurosci 2019; 38:3240-3251. [PMID: 29593071 DOI: 10.1523/jneurosci.3207-17.2018] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 02/08/2018] [Accepted: 02/13/2018] [Indexed: 01/17/2023] Open
Abstract
When an action potential invades a presynaptic terminal it evokes large, brief Ca2+ signals that trigger vesicle fusion within milliseconds that is followed by a small residual Ca2+ (Cares) signal. At many synapses Cares produces synaptic facilitation that lasts up to hundreds of milliseconds and, although less common, Cares can also evoke asynchronous release (AR) that persists for tens of milliseconds. The properties of facilitation and AR are very different, which suggests that they are mediated by distinct mechanisms. However, recently it has been shown that the slow calcium sensor synaptotagmin 7 (Syt7) mediates facilitation at many synapses where AR does not occur, and conversely Syt7 can mediate AR without mediating facilitation. Here we study cerebellar granule cell synapses onto stellate cells and Purkinje cells in mice of both sexes to assess the role of Syt7 in these phenomena at the same synapse. This is of particular interest at granule cell synapses where AR is much more calcium dependent and shorter-lived than facilitation. We find that Syt7 can mediate these two processes despite their divergent properties. In Syt7 knock-out animals, facilitation and AR are smaller and shorter lived than in wild-type animals, even though the initial probability of release and Cares signals are unchanged. Although there are short-lived Syt7-independent mechanisms that mediate facilitation and AR in Syt7 KO animals, we find that at granule cell synapses AR and facilitation are both mediated primarily by Syt7.SIGNIFICANCE STATEMENT At synapses made by cerebellar granule cells, presynaptic activity elevates calcium for tens of milliseconds, which in turn evokes both asynchronous release (AR) and synaptic facilitation. AR is more calcium sensitive and shorter-lived than facilitation at these synapses, suggesting that they are mediated by different mechanisms. However, we find that the slow calcium sensor synaptotagmin 7 mediates both of these phenomena. Small, rapidly decaying components of AR and facilitation are present in Syt7 KO animals, indicating that additional mechanisms can contribute to both AR and facilitation at these synapses.
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Bittel DC, Jaiswal JK. Contribution of Extracellular Vesicles in Rebuilding Injured Muscles. Front Physiol 2019; 10:828. [PMID: 31379590 PMCID: PMC6658195 DOI: 10.3389/fphys.2019.00828] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 06/13/2019] [Indexed: 12/22/2022] Open
Abstract
Skeletal myofibers are injured due to mechanical stresses experienced during physical activity, or due to myofiber fragility caused by genetic diseases. The injured myofiber needs to be repaired or regenerated to restore the loss in muscle tissue function. Myofiber repair and regeneration requires coordinated action of various intercellular signaling factors-including proteins, inflammatory cytokines, miRNAs, and membrane lipids. It is increasingly being recognized release and transmission of these signaling factors involves extracellular vesicle (EV) released by myofibers and other cells in the injured muscle. Intercellular signaling by these EVs alters the phenotype of their target cells either by directly delivering the functional proteins and lipids or by modifying longer-term gene expression. These changes in the target cells activate downstream pathways involved in tissue homeostasis and repair. The EVs are heterogeneous with regards to their size, composition, cargo, location, as well as time-course of genesis and release. These differences impact on the subsequent repair and regeneration of injured skeletal muscles. This review focuses on how intracellular vesicle production, cargo packaging, and secretion by injured muscle, modulates specific reparative, and regenerative processes. Insights into the formation of these vesicles and their signaling properties offer new understandings of the orchestrated response necessary for optimal muscle repair and regeneration.
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Affiliation(s)
- Daniel C Bittel
- Children's National Health System, Center for Genetic Medicine Research, Washington, DC, United States
| | - Jyoti K Jaiswal
- Children's National Health System, Center for Genetic Medicine Research, Washington, DC, United States.,Department of Genomics and Precision Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC, United States
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Andrews NW. Solving the secretory acid sphingomyelinase puzzle: Insights from lysosome-mediated parasite invasion and plasma membrane repair. Cell Microbiol 2019; 21:e13065. [PMID: 31155842 DOI: 10.1111/cmi.13065] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 05/03/2019] [Accepted: 05/30/2019] [Indexed: 12/19/2022]
Abstract
Acid sphingomyelinase (ASM) is a lysosomal enzyme that cleaves the phosphorylcholine head group of sphingomyelin, generating ceramide. Recessive mutations in SMPD1, the gene encoding ASM, cause Niemann-Pick Disease Types A and B. These disorders are attributed not only to lipid accumulation inside lysosomes but also to changes on the outer leaflet of the plasma membrane, highlighting an extracellular role for ASM. Secretion of ASM occurs under physiological conditions, and earlier studies proposed two forms of the enzyme, one resident in lysosomes and another form that would be diverted to the secretory pathway. Such differential intracellular trafficking has been difficult to explain because there is only one SMPD1 transcript that generates an active enzyme, found primarily inside lysosomes. Unexpectedly, studies of cell invasion by the protozoan parasite Trypanosoma cruzi revealed that conventional lysosomes can fuse with the plasma membrane in response to elevations in intracellular Ca2+ , releasing their contents extracellularly. ASM exocytosed from lysosomes remodels the outer leaflet of the plasma membrane, promoting parasite invasion and wound repair. Here, we discuss the possibility that ASM release during lysosomal exocytosis, in response to various forms of stress, may represent a major source of the secretory form of this enzyme.
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Affiliation(s)
- Norma W Andrews
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland
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Brito C, Cabanes D, Sarmento Mesquita F, Sousa S. Mechanisms protecting host cells against bacterial pore-forming toxins. Cell Mol Life Sci 2019; 76:1319-1339. [PMID: 30591958 PMCID: PMC6420883 DOI: 10.1007/s00018-018-2992-8] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 12/06/2018] [Accepted: 12/10/2018] [Indexed: 12/19/2022]
Abstract
Pore-forming toxins (PFTs) are key virulence determinants produced and secreted by a variety of human bacterial pathogens. They disrupt the plasma membrane (PM) by generating stable protein pores, which allow uncontrolled exchanges between the extracellular and intracellular milieus, dramatically disturbing cellular homeostasis. In recent years, many advances were made regarding the characterization of conserved repair mechanisms that allow eukaryotic cells to recover from mechanical disruption of the PM membrane. However, the specificities of the cell recovery pathways that protect host cells against PFT-induced damage remain remarkably elusive. During bacterial infections, the coordinated action of such cell recovery processes defines the outcome of infected cells and is, thus, critical for our understanding of bacterial pathogenesis. Here, we review the cellular pathways reported to be involved in the response to bacterial PFTs and discuss their impact in single-cell recovery and infection.
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Affiliation(s)
- Cláudia Brito
- i3S-Instituto de Investigação e Inovação em Saúde, IBMC, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
- Programa Doutoral em Biologia Molecular e Celular (MCbiology), Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Rua Jorge de Viterbo Ferreira 228, 4050-313, Porto, Portugal
| | - Didier Cabanes
- i3S-Instituto de Investigação e Inovação em Saúde, IBMC, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
| | - Francisco Sarmento Mesquita
- i3S-Instituto de Investigação e Inovação em Saúde, IBMC, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal.
- Global Health Institute, School of Life Science, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
| | - Sandra Sousa
- i3S-Instituto de Investigação e Inovação em Saúde, IBMC, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal.
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Held RG, Kaeser PS. ELKS active zone proteins as multitasking scaffolds for secretion. Open Biol 2019; 8:rsob.170258. [PMID: 29491150 PMCID: PMC5830537 DOI: 10.1098/rsob.170258] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Accepted: 02/06/2018] [Indexed: 12/18/2022] Open
Abstract
Synaptic vesicle exocytosis relies on the tethering of release ready vesicles close to voltage-gated Ca2+ channels and specific lipids at the future site of fusion. This enables rapid and efficient neurotransmitter secretion during presynaptic depolarization by an action potential. Extensive research has revealed that this tethering is mediated by an active zone, a protein dense structure that is attached to the presynaptic plasma membrane and opposed to postsynaptic receptors. Although roles of individual active zone proteins in exocytosis are in part understood, the molecular mechanisms that hold the protein scaffold at the active zone together and link it to the presynaptic plasma membrane have remained unknown. This is largely due to redundancy within and across scaffolding protein families at the active zone. Recent studies, however, have uncovered that ELKS proteins, also called ERC, Rab6IP2 or CAST, act as active zone scaffolds redundant with RIMs. This redundancy has led to diverse synaptic phenotypes in studies of ELKS knockout mice, perhaps because different synapses rely to a variable extent on scaffolding redundancy. In this review, we first evaluate the need for presynaptic scaffolding, and we then discuss how the diverse synaptic and non-synaptic functional roles of ELKS support the hypothesis that ELKS provides molecular scaffolding for organizing vesicle traffic at the presynaptic active zone and in other cellular compartments.
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Affiliation(s)
- Richard G Held
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
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Barzilai-Tutsch H, Dewulf M, Lamaze C, Butler Browne G, Pines M, Halevy O. A promotive effect for halofuginone on membrane repair and synaptotagmin-7 levels in muscle cells of dysferlin-null mice. Hum Mol Genet 2019; 27:2817-2829. [PMID: 29771357 DOI: 10.1093/hmg/ddy185] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 05/09/2018] [Indexed: 11/14/2022] Open
Abstract
In the absence of dysferlin, skeletal muscle cells fail to reseal properly after injury, resulting in slow progress of the dysferlinopathy muscular dystrophy (MD). Halofuginone, a leading agent in preventing fibrosis in MDs, was tested for its effects on membrane resealing post-injury. A hypo-osmotic shock assay on myotubes derived from wild-type (Wt) and dysferlin-null (dysf-/-) mice revealed that pre-treatment with halofuginone reduces the percentage of membrane-ruptured myotubes only in dysf-/- myotubes. In laser-induced injury of isolated myofibers, halofuginone decreased the amount of FM1-43 at the injury site of dysf-/- myofibers while having no effect on Wt myofibers. These results implicate halofuginone in ameliorating muscle-cell membrane integrity in dysf-/- mice. Halofuginone increased lysosome scattering across the cytosol of dysf-/- primary myoblasts, in a protein kinase/extracellular signal-regulated protein kinase and phosphoinositide 3 kinase/Akt-dependent manner, in agreement with an elevation in lysosomal exocytotic activity in these cells. A spatial- and age-dependent synaptotagmin-7 (Syt-7) expression pattern was shown in dysf-/- versus Wt mice, suggesting that these pattern alterations are related to the disease progress and that sytnaptotagmin-7 may be compensating for the lack of dysferlin at least with regard to membrane resealing post-injury. While halofuginone did not affect patch-repair-complex key proteins, it further enhanced Syt-7 levels and its spread across the cytosol in dysf-/- myofibers and muscle tissue, and increased its co-localization with lysosomes. Together, the data imply a novel role for halofuginone in membrane-resealing events with Syt-7 possibly taking part in these events.
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Affiliation(s)
- Hila Barzilai-Tutsch
- Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Melissa Dewulf
- Membrane Dynamics and Mechanics of Intracellular Signaling Laboratory, Institut Curie-Centre de Recherche, PSL Research University, INSERM U1143, Centre national de la recherche scientifique, UMR 3666, Paris, France
| | - Christophe Lamaze
- Membrane Dynamics and Mechanics of Intracellular Signaling Laboratory, Institut Curie-Centre de Recherche, PSL Research University, INSERM U1143, Centre national de la recherche scientifique, UMR 3666, Paris, France
| | - Gillian Butler Browne
- Center for Research in Myology, CNRS FRE 3617, UPMC Univ Paris 06, UM76, INSERM U974, Sorbonne Universités, Paris, France
| | - Mark Pines
- The Volcani Center, Institute of Animal Science, Bet Dagan 52505, Israel
| | - Orna Halevy
- Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
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Turecek J, Regehr WG. Neuronal Regulation of Fast Synaptotagmin Isoforms Controls the Relative Contributions of Synchronous and Asynchronous Release. Neuron 2019; 101:938-949.e4. [PMID: 30733150 DOI: 10.1016/j.neuron.2019.01.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Revised: 10/30/2018] [Accepted: 01/03/2019] [Indexed: 10/27/2022]
Abstract
Neurotransmitter release can be synchronous and occur within milliseconds of action potential invasion, or asynchronous and persist for tens of milliseconds. The molecular determinants of release kinetics remain poorly understood. It has been hypothesized that asynchronous release dominates when fast Synaptotagmin isoforms are far from calcium channels or when specialized sensors, such as Synaptotagmin 7, are abundant. Here we test these hypotheses for GABAergic projections onto neurons of the inferior olive, where release in different subnuclei ranges from synchronous to asynchronous. Surprisingly, neither of the leading hypotheses accounts for release kinetics. Instead, we find that rapid Synaptotagmin isoforms are abundant in subnuclei with synchronous release but absent where release is asynchronous. Viral expression of Synaptotagmin 1 transforms asynchronous synapses into synchronous ones. Thus, the nervous system controls levels of fast Synaptotagmin isoforms to regulate release kinetics and thereby controls the ability of synapses to encode spike rates or precise timing.
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Affiliation(s)
- Josef Turecek
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Wade G Regehr
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA.
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Ray S, Thapa R, Keyel PA. Multiple Parameters Beyond Lipid Binding Affinity Drive Cytotoxicity of Cholesterol-Dependent Cytolysins. Toxins (Basel) 2018; 11:toxins11010001. [PMID: 30577571 PMCID: PMC6356533 DOI: 10.3390/toxins11010001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 12/14/2018] [Accepted: 12/18/2018] [Indexed: 02/06/2023] Open
Abstract
The largest superfamily of bacterial virulence factors is pore-forming toxins (PFTs). PFTs are secreted by both pathogenic and non-pathogenic bacteria. PFTs sometimes kill or induce pro-pathogen signaling in mammalian cells, all primarily through plasma membrane perforation, though the parameters that determine these outcomes are unclear. Membrane binding, calcium influx, pore size, and membrane repair are factors that influence PFT cytotoxicity. To test the contribution of membrane binding to cytotoxicity and repair, we compared the closely related, similarly-sized PFTs Perfringolysin O (PFO) from Clostridium perfringens and Streptolysin O (SLO) from Streptococcus pyogenes. Cell death kinetics for PFO and SLO were different because PFO increased in cytotoxicity over time. We introduced known L3 loop mutations that swap binding affinity between toxins and measured hemolytic activity, nucleated cell death kinetics and membrane repair using viability assays, and live cell imaging. Altered hemolytic activity was directly proportional to toxin binding affinity. In contrast, L3 loop alterations reduced nucleated cell death, and they had limited effects on cytotoxicity kinetics and membrane repair. This suggests other toxin structural features, like oligomerization, drives these parameters. Overall, these findings suggest that repair mechanisms and toxin oligomerization add constraints beyond membrane binding on toxin evolution and activity against nucleated cells.
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Affiliation(s)
- Sucharit Ray
- Department of Biological Sciences, College of Arts and Sciences, Texas Tech University, Box 43131, Lubbock, TX 79409, USA.
| | - Roshan Thapa
- Department of Biological Sciences, College of Arts and Sciences, Texas Tech University, Box 43131, Lubbock, TX 79409, USA.
| | - Peter A Keyel
- Department of Biological Sciences, College of Arts and Sciences, Texas Tech University, Box 43131, Lubbock, TX 79409, USA.
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Miyatake Y, Yamano T, Hanayama R. Myoferlin-Mediated Lysosomal Exocytosis Regulates Cytotoxicity by Phagocytes. THE JOURNAL OF IMMUNOLOGY 2018; 201:3051-3057. [PMID: 30333125 DOI: 10.4049/jimmunol.1800268] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 09/16/2018] [Indexed: 01/09/2023]
Abstract
During inflammation, phagocytes release digestive enzymes from lysosomes to degrade harmful cells such as pathogens and tumor cells. However, the molecular mechanisms regulating this process are poorly understood. In this study, we identified myoferlin as a critical regulator of lysosomal exocytosis by mouse phagocytes. Myoferlin is a type II transmembrane protein with seven C2 domains in the cytoplasmic region. It localizes to lysosomes and mediates their fusion with the plasma membrane upon calcium stimulation. Myoferlin promotes the release of lysosomal contents, including hydrolytic enzymes, which increase cytotoxicity. These data demonstrate myoferlin's critical role in lysosomal exocytosis by phagocytes, providing novel insights into the mechanisms of inflammation-related cellular injuries.
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Affiliation(s)
- Yuji Miyatake
- Department of Immunology, Kanazawa University Graduate School of Medical Sciences, Ishikawa 920-8640, Japan.,Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Tomoyoshi Yamano
- Department of Immunology, Kanazawa University Graduate School of Medical Sciences, Ishikawa 920-8640, Japan.,WPI Nano Life Science Institute (NanoLSI), Kanazawa University, Ishikawa 920-1192, Japan; and
| | - Rikinari Hanayama
- Department of Immunology, Kanazawa University Graduate School of Medical Sciences, Ishikawa 920-8640, Japan; .,WPI Nano Life Science Institute (NanoLSI), Kanazawa University, Ishikawa 920-1192, Japan; and.,Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Saitama 332-0012, Japan
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