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Chang HF, Schirra C, Pattu V, Krause E, Becherer U. Lytic granule exocytosis at immune synapses: lessons from neuronal synapses. Front Immunol 2023; 14:1177670. [PMID: 37275872 PMCID: PMC10233144 DOI: 10.3389/fimmu.2023.1177670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 05/09/2023] [Indexed: 06/07/2023] Open
Abstract
Regulated exocytosis is a central mechanism of cellular communication. It is not only the basis for neurotransmission and hormone release, but also plays an important role in the immune system for the release of cytokines and cytotoxic molecules. In cytotoxic T lymphocytes (CTLs), the formation of the immunological synapse is required for the delivery of the cytotoxic substances such as granzymes and perforin, which are stored in lytic granules and released via exocytosis. The molecular mechanisms of their fusion with the plasma membrane are only partially understood. In this review, we discuss the molecular players involved in the regulated exocytosis of CTL, highlighting the parallels and differences to neuronal synaptic transmission. Additionally, we examine the strengths and weaknesses of both systems to study exocytosis.
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Bourgeois-Jaarsma Q, Miaja Hernandez P, Groffen AJ. Ca 2+ sensor proteins in spontaneous release and synaptic plasticity: Limited contribution of Doc2c, rabphilin-3a and synaptotagmin 7 in hippocampal glutamatergic neurons. Mol Cell Neurosci 2021; 112:103613. [PMID: 33753311 DOI: 10.1016/j.mcn.2021.103613] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 03/09/2021] [Accepted: 03/13/2021] [Indexed: 11/28/2022] Open
Abstract
Presynaptic neurotransmitter release is strictly regulated by SNARE proteins, Ca2+ and a number of Ca2+ sensors including synaptotagmins (Syts) and Double C2 domain proteins (Doc2s). More than seventy years after the original description of spontaneous release, the mechanism that regulates this process is still poorly understood. Syt-1, Syt7 and Doc2 proteins contribute predominantly, but not exclusively, to synchronous, asynchronous and spontaneous phases of release. The proteins share a conserved tandem C2 domain architecture, but are functionally diverse in their subcellular location, Ca2+-binding properties and protein interactions. In absence of Syt-1, Doc2a and -b, neurons still exhibit spontaneous vesicle fusion which remains Ca2+-sensitive, suggesting the existence of additional sensors. Here, we selected Doc2c, rabphilin-3a and Syt-7 as three potential Ca2+ sensors for their sequence homology with Syt-1 and Doc2b. We genetically ablated each candidate gene in absence of Doc2a and -b and investigated spontaneous and evoked release in glutamatergic hippocampal neurons, cultured either in networks or on microglial islands (autapses). The removal of Doc2c had no effect on spontaneous or evoked release. Syt-7 removal also did not affect spontaneous release, although it altered short-term plasticity by accentuating short-term depression. The removal of rabphilin caused an increased spontaneous release frequency in network cultures, an effect that was not observed in autapses. Taken together, we conclude that Doc2c and Syt-7 do not affect spontaneous release of glutamate in hippocampal neurons, while our results suggest a possible regulatory role of rabphilin-3a in neuronal networks. These findings importantly narrow down the repertoire of synaptic Ca2+ sensors that may be implicated in the spontaneous release of glutamate.
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Affiliation(s)
- Quentin Bourgeois-Jaarsma
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
| | - Pablo Miaja Hernandez
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
| | - Alexander J Groffen
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands; Department of Clinical Genetics, VU Medical Center, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
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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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Phatarpekar PV, Billadeau DD. Molecular regulation of the plasma membrane-proximal cellular steps involved in NK cell cytolytic function. J Cell Sci 2020; 133:133/5/jcs240424. [PMID: 32086255 DOI: 10.1242/jcs.240424] [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: 12/20/2022] Open
Abstract
Natural killer (NK) cells, cytolytic lymphocytes of the innate immune system, play a crucial role in the immune response against infection and cancer. NK cells kill target cells through exocytosis of lytic granules that contain cytotoxic proteins, such as perforin and granzymes. Formation of a functional immune synapse, i.e. the interface between the NK cell and its target cell enhances lysis through accumulation of polymerized F-actin at the NK cell synapse, leading to convergence of lytic granules to the microtubule organizing center (MTOC) and its subsequent polarization along microtubules to deliver the lytic granules to the synapse. In this review, we focus on the molecular mechanisms regulating the cellular processes that occur after the lytic granules are delivered to the cytotoxic synapse. We outline how - once near the synapse - the granules traverse the clearings created by F-actin remodeling to dock, tether and fuse with the plasma membrane in order to secrete their lytic content into the synaptic cleft through exocytosis. Further emphasis is given to the role of Ca2+ mobilization during degranulation and, whenever applicable, we compare these mechanisms in NK cells and cytotoxic T lymphocytes (CTLs) as adaptive immune system effectors.
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Affiliation(s)
- Prasad V Phatarpekar
- Department of Immunology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Daniel D Billadeau
- Department of Immunology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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MacDougall DD, Lin Z, Chon NL, Jackman SL, Lin H, Knight JD, Anantharam A. The high-affinity calcium sensor synaptotagmin-7 serves multiple roles in regulated exocytosis. J Gen Physiol 2018; 150:783-807. [PMID: 29794152 PMCID: PMC5987875 DOI: 10.1085/jgp.201711944] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 05/07/2018] [Indexed: 12/19/2022] Open
Abstract
MacDougall et al. review the structure and function of the calcium sensor synaptotagmin-7 in exocytosis. Synaptotagmin (Syt) proteins comprise a 17-member family, many of which trigger exocytosis in response to calcium. Historically, most studies have focused on the isoform Syt-1, which serves as the primary calcium sensor in synchronous neurotransmitter release. Recently, Syt-7 has become a topic of broad interest because of its extreme calcium sensitivity and diversity of roles in a wide range of cell types. Here, we review the known and emerging roles of Syt-7 in various contexts and stress the importance of its actions. Unique functions of Syt-7 are discussed in light of recent imaging, electrophysiological, and computational studies. Particular emphasis is placed on Syt-7–dependent regulation of synaptic transmission and neuroendocrine cell secretion. Finally, based on biochemical and structural data, we propose a mechanism to link Syt-7’s role in membrane fusion with its role in subsequent fusion pore expansion via strong calcium-dependent phospholipid binding.
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Affiliation(s)
| | - Zesen Lin
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Nara L Chon
- Department of Chemistry, University of Colorado, Denver, CO
| | - Skyler L Jackman
- Vollum Institute, Oregon Health & Science University, Portland, OR
| | - Hai Lin
- Department of Chemistry, University of Colorado, Denver, CO
| | | | - Arun Anantharam
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
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Zhou X, Friedmann KS, Lyrmann H, Zhou Y, Schoppmeyer R, Knörck A, Mang S, Hoxha C, Angenendt A, Backes CS, Mangerich C, Zhao R, Cappello S, Schwär G, Hässig C, Neef M, Bufe B, Zufall F, Kruse K, Niemeyer BA, Lis A, Qu B, Kummerow C, Schwarz EC, Hoth M. A calcium optimum for cytotoxic T lymphocyte and natural killer cell cytotoxicity. J Physiol 2018; 596:2681-2698. [PMID: 29368348 DOI: 10.1113/jp274964] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 01/04/2018] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells are required to eliminate cancer cells. We analysed the Ca2+ dependence of CTL and NK cell cytotoxicity and found that in particular CTLs have a very low optimum of [Ca2+ ]i (between 122 and 334 nm) and [Ca2+ ]o (between 23 and 625 μm) for efficient cancer cell elimination, well below blood plasma Ca2+ levels. As predicted from these results, partial down-regulation of the Ca2+ channel Orai1 in CTLs paradoxically increases perforin-dependent cancer cell killing. Lytic granule release at the immune synapse between CTLs and cancer cells has a Ca2+ optimum compatible with this low Ca2+ optimum for efficient cancer cell killing, whereas the Ca2+ optimum for CTL migration is slightly higher and proliferation increases monotonously with increasing [Ca2+ ]o . We propose that a partial inhibition of Ca2+ signals by specific Orai1 blockers at submaximal concentrations could contribute to tumour elimination. ABSTRACT Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells are required to protect the human body against cancer. Ca2+ is a key metabolic factor for lymphocyte function and cancer homeostasis. We analysed the Ca2+ dependence of CTL and NK cell cytotoxicity against cancer cells and found that CTLs have a bell-shaped Ca2+ dependence with an optimum for cancer cell elimination at rather low [Ca2+ ]o (23-625 μm) and [Ca2+ ]i (122-334 nm). This finding predicts that a partial inhibition of Orai1 should increase (rather than decrease) cytotoxicity of CTLs at [Ca2+ ]o higher than 625 μm. We tested this hypothesis in CTLs and indeed found that partial down-regulation of Orai1 by siRNA increases the efficiency of cancer cell killing. We found two mechanisms that may account for the Ca2+ optimum of cancer cell killing: (1) migration velocity and persistence have a moderate optimum between 500 and 1000 μm [Ca2+ ]o in CTLs, and (2) lytic granule release at the immune synapse between CTLs and cancer cells is increased at 146 μm compared to 3 or 800 μm, compatible with the Ca2+ optimum for cancer cell killing. It has been demonstrated in many cancer cell types that Orai1-dependent Ca2+ signals enhance proliferation. We propose that a decrease of [Ca2+ ]o or partial inhibition of Orai1 activity by selective blockers in the tumour microenvironment could efficiently reduce cancer growth by simultaneously increasing CTL and NK cell cytotoxicity and decreasing cancer cell proliferation.
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Affiliation(s)
- Xiao Zhou
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Kim S Friedmann
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Hélène Lyrmann
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Yan Zhou
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Rouven Schoppmeyer
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Arne Knörck
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Sebastian Mang
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Cora Hoxha
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Adrian Angenendt
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Christian S Backes
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Carmen Mangerich
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Renping Zhao
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Sabrina Cappello
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany.,Cardiovascular Physiology, University Medical Center, University of Göttingen, Göttingen, 37073, Germany
| | - Gertrud Schwär
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Carmen Hässig
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Marc Neef
- Department of Theoretical Physics, Saarland University, Saarbrücken, 66041, Germany
| | - Bernd Bufe
- Physiology, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Frank Zufall
- Physiology, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Karsten Kruse
- Department of Theoretical Physics, Saarland University, Saarbrücken, 66041, Germany.,Department of Biochemistry and Theoretical Physics, University of Geneva, Geneva, 1211, Switzerland
| | - Barbara A Niemeyer
- Molecular Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Annette Lis
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Bin Qu
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Carsten Kummerow
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Eva C Schwarz
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
| | - Markus Hoth
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, 66421, Germany
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Tuosto L, Capuano C, Muscolini M, Santoni A, Galandrini R. The multifaceted role of PIP2 in leukocyte biology. Cell Mol Life Sci 2015; 72:4461-74. [PMID: 26265181 PMCID: PMC11113228 DOI: 10.1007/s00018-015-2013-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 07/31/2015] [Accepted: 08/06/2015] [Indexed: 10/23/2022]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP2) represents about 1 % of plasma membrane phospholipids and behaves as a pleiotropic regulator of a striking number of fundamental cellular processes. In recent years, an increasing body of literature has highlighted an essential role of PIP2 in multiple aspects of leukocyte biology. In this emerging picture, PIP2 is envisaged as a signalling intermediate itself and as a membrane-bound regulator and a scaffold of proteins with specific PIP2 binding domains. Indeed PIP2 plays a key role in several functions. These include directional migration in neutrophils, integrin-dependent adhesion in T lymphocytes, phagocytosis in macrophages, lysosomes secretion and trafficking at immune synapse in cytolytic effectors and secretory cells, calcium signals and gene transcription in B lymphocytes, natural killer cells and mast cells. The coordination of these different aspects relies on the spatio-temporal organisation of distinct PIP2 pools, generated by the main PIP2 generating enzyme, phosphatidylinositol 4-phosphate 5-kinase (PIP5K). Three different isoforms of PIP5K, named α, β and γ, and different splice variants have been described in leukocyte populations. The isoform-specific coupling of specific isoforms of PIP5K to different families of activating receptors, including integrins, Fc receptors, toll-like receptors and chemokine receptors, is starting to be reported. Furthermore, PIP2 is turned over by multiple metabolising enzymes including phospholipase C (PLC) γ and phosphatidylinositol 3-kinase (PI3K) which, along with Rho family small G proteins, is widely involved in strategic functions within the immune system. The interplay between PIP2, lipid-modifying enzymes and small G protein-regulated signals is also discussed.
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Affiliation(s)
- Loretta Tuosto
- Department of Biology and Biotechnology "Charles Darwin", Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University, Via dei Sardi 70, 00185, Rome, Italy.
| | - Cristina Capuano
- Department of Experimental Medicine, Sapienza University, Viale Regina Elena 324, 00185, Rome, Italy
| | - Michela Muscolini
- Department of Biology and Biotechnology "Charles Darwin", Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University, Via dei Sardi 70, 00185, Rome, Italy
| | - Angela Santoni
- Department of Molecular Medicine, Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University, Viale Regina Elena 291, 00185, Rome, Italy
| | - Ricciarda Galandrini
- Department of Experimental Medicine, Sapienza University, Viale Regina Elena 324, 00185, Rome, Italy.
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Mouchacca P, Chasson L, Frick M, Foray C, Schmitt-Verhulst AM, Boyer C. Visualization of granzyme B-expressing CD8 T cells during primary and secondary immune responses to Listeria monocytogenes. Immunology 2015; 145:24-33. [PMID: 25367158 DOI: 10.1111/imm.12420] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 10/22/2014] [Accepted: 10/23/2014] [Indexed: 12/17/2022] Open
Abstract
CD8 T cells contribute to long-term protection against Listeria monocytogenes infection by differentiating into memory T cells. These rapidly respond to antigen or inflammation upon secondary infection. In this study we used CD8 T cells from OT1 mice and CD4 T cells from OT2 mice expressing a fluorescent chimeric granzyme (GZMB-Tom) protein to monitor the primary response to infection with ovalbumin-expressing L. monocytogenes (Lm-OVA). We show that, unlike poorly responding CD4 T cells, CD8 T cells readily proliferated and expressed high levels of GZMB-Tom as early as 2 days after infection. FACS analysis showed GZMB-Tom expression in undivided CD8 T cells, with its level increasing over one to four divisions. OT1 T cells were visualized in the T-cell zone by confocal microscopy. This showed GZMB-Tom-containing granules oriented towards MHCII-positive cells. Twenty hours later, most OT1 T cells had divided but their level of GZMB-Tom expression was reduced. Recently divided OT1 cells failed to express GZMB-Tom. Fourteen hours after secondary infection, GZMB-Tom was re-expressed in memory OT1 T cells responding either to Lm-OVA or L. monocytogenes. Differences in the activation phenotype and in the splenic distribution of OT1 T cells were observed, depending on the challenge. Notably, OTI T cells with polarized granules were only observed after challenge with cognate antigen. This work showed that the GZMB-Tom knock-in mice in which GZMB-Tom faithfully reproduced GZMB expression, provide useful tools to dissect mechanisms leading to the development of anti-bacterial effector and memory CD8 T cells and reactivation of the memory response to cognate antigen or inflammatory signals.
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Affiliation(s)
- Pierre Mouchacca
- Centre d'Immunologie de Marseille-Luminy, UM2 Aix-Marseille Université, Marseille Cedex 9, France; INSERM U1104, Marseille, France; CNRS UMR7280, Marseille, France
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9
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Galandrini R, Capuano C, Santoni A. Activation of Lymphocyte Cytolytic Machinery: Where are We? Front Immunol 2013; 4:390. [PMID: 24312097 PMCID: PMC3832890 DOI: 10.3389/fimmu.2013.00390] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 11/06/2013] [Indexed: 11/13/2022] Open
Abstract
Target cell recognition by cytotoxic lymphocytes implies the simultaneous engagement and clustering of adhesion and activating receptors followed by the activation of an array of signal transduction pathways. The cytotoxic immune synapse represents the highly specialized dynamic interface formed between the cytolytic effector and its target that allows temporal and spatial integration of signals responsible for a defined sequence of processes culminating with the polarized secretion of lytic granules. Over the last decades, much attention has been given to the molecular signals coupling receptor ligation to the activation of cytolytic machinery. Moreover, in the last 10 years the discovery of genetic defects affecting cytotoxic responses greatly boosted our knowledge on the molecular effectors involved in the regulation of discrete phases of cytotoxic process at post-receptor levels. More recently, the use of super resolution and total internal reflection fluorescence imaging technologies added new insights on the dynamic reorganization of receptor and signaling molecules at lytic synapse as well as on the relationship between granule dynamics and cytoskeleton remodeling. To date we have a solid knowledge of the molecular mechanisms governing granule movement and secretion, being not yet fully unraveled the machinery that couples early receptor signaling to the late stage of synapse remodeling and granule dynamics. Here we highlight recent advances in our understanding of the molecular mechanisms acting in the activation of cytolytic machinery, also discussing similarities and differences between Natural killer cells and cytotoxic CD8+ T cells.
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Affiliation(s)
- Ricciarda Galandrini
- Department of Experimental Medicine, Istituto Pasteur-Fondazione Cenci-Bolognetti, Fondazione Eleonora Lorillard Spencer Cenci, Sapienza University , Rome , Italy
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Stimulation of MMP-1 and CCL2 by NAMPT in PDL cells. Mediators Inflamm 2013; 2013:437123. [PMID: 24058270 PMCID: PMC3766615 DOI: 10.1155/2013/437123] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 07/18/2013] [Indexed: 01/04/2023] Open
Abstract
Periodontitis is an inflammatory disease caused by pathogenic microorganisms and characterized by the destruction of the periodontium. Obese individuals have an increased risk of periodontitis, and elevated circulating levels of adipokines, such as nicotinamide phosphoribosyltransferase (NAMPT), may be a pathomechanistic link between both diseases. The aim of this in vitro study was to examine the regulation of periodontal ligament (PDL) cells by NAMPT and its production under inflammatory and infectious conditions. NAMPT caused a significant upregulation of 9 genes and downregulation of 3 genes, as analyzed by microarray analysis. Eight of these genes could be confirmed by real-time PCR: NAMPT induced a significant upregulation of EGR1, MMP-1, SYT7, ITPKA, CCL2, NTM, IGF2BP3, and NRP1. NAMPT also increased significantly the MMP-1 and CCL2 protein synthesis. NAMPT was significantly induced by interleukin-1β and the periodontal microorganism P. gingivalis. NAMPT may contribute to periodontitis through upregulation of MMP-1 and CCL2 in PDL cells. Increased NAMPT levels, as found in obesity, may therefore represent a mechanism whereby obesity could confer an increased risk of periodontitis. Furthermore, microbial and inflammatory signals may enhance the NAMPT synthesis in PDL cells and thereby contribute to the increased gingival and serum levels of this adipokine, as found in periodontitis.
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11
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Lopez JA, Jenkins MR, Rudd-Schmidt JA, Brennan AJ, Danne JC, Mannering SI, Trapani JA, Voskoboinik I. Rapid and unidirectional perforin pore delivery at the cytotoxic immune synapse. THE JOURNAL OF IMMUNOLOGY 2013; 191:2328-34. [PMID: 23885110 DOI: 10.4049/jimmunol.1301205] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The effective engagement of cytotoxic lymphocytes (CLs) with their target cells is essential for the removal of virus-infected and malignant cells from the body. The spatiotemporal properties that define CL engagement and killing of target cells remain largely uncharacterized due to a lack of biological reporters. We have used a novel live cell microscopy technique to visualize the engagement of primary human and mouse CL with their targets and the subsequent delivery of the lethal hit. Extensive quantitative real-time analysis of individual effector-target cell conjugates demonstrated that a single effector calcium flux event was sufficient for the degranulation of human CLs, resulting in the breach of the target cell membrane by perforin within 65-100 s. In contrast, mouse CLs demonstrated distinct calcium signaling profiles leading to degranulation: whereas mouse NKs required a single calcium flux event, CD8(+) T cells typically required several calcium flux events before perforin delivery. Irrespective of their signaling profile, every target cell that was damaged by perforin died by apoptosis. To our knowledge, we demonstrate for the first time that perforin pore delivery is unidirectional, occurring exclusively on the target cell membrane, but sparing the killer cell. Despite this, the CTL membrane was not intrinsically perforin resistant, as intact CTLs presented as targets to effector CTLs were capable of being killed by perforin-dependent mechanisms. Our results highlight the remarkable efficiency and specificity of perforin pore delivery by CLs.
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Affiliation(s)
- Jamie A Lopez
- Cancer Immunology Program, Peter MacCallum Cancer Centre, East Melbourne, Victoria 3002, Australia
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12
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Multiple roles for the actin cytoskeleton during regulated exocytosis. Cell Mol Life Sci 2012; 70:2099-121. [PMID: 22986507 DOI: 10.1007/s00018-012-1156-5] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/28/2012] [Accepted: 08/30/2012] [Indexed: 01/01/2023]
Abstract
Regulated exocytosis is the main mechanism utilized by specialized secretory cells to deliver molecules to the cell surface by virtue of membranous containers (i.e., secretory vesicles). The process involves a series of highly coordinated and sequential steps, which include the biogenesis of the vesicles, their delivery to the cell periphery, their fusion with the plasma membrane, and the release of their content into the extracellular space. Each of these steps is regulated by the actin cytoskeleton. In this review, we summarize the current knowledge regarding the involvement of actin and its associated molecules during each of the exocytic steps in vertebrates, and suggest that the overall role of the actin cytoskeleton during regulated exocytosis is linked to the architecture and the physiology of the secretory cells under examination. Specifically, in neurons, neuroendocrine, endocrine, and hematopoietic cells, which contain small secretory vesicles that undergo rapid exocytosis (on the order of milliseconds), the actin cytoskeleton plays a role in pre-fusion events, where it acts primarily as a functional barrier and facilitates docking. In exocrine and other secretory cells, which contain large secretory vesicles that undergo slow exocytosis (seconds to minutes), the actin cytoskeleton plays a role in post-fusion events, where it regulates the dynamics of the fusion pore, facilitates the integration of the vesicles into the plasma membrane, provides structural support, and promotes the expulsion of large cargo molecules.
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Becherer U, Medart MR, Schirra C, Krause E, Stevens D, Rettig J. Regulated exocytosis in chromaffin cells and cytotoxic T lymphocytes: How similar are they? Cell Calcium 2012; 52:303-12. [DOI: 10.1016/j.ceca.2012.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 03/27/2012] [Accepted: 04/09/2012] [Indexed: 10/28/2022]
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Boswell KL, James DJ, Esquibel JM, Bruinsma S, Shirakawa R, Horiuchi H, Martin TFJ. Munc13-4 reconstitutes calcium-dependent SNARE-mediated membrane fusion. ACTA ACUST UNITED AC 2012; 197:301-12. [PMID: 22508512 PMCID: PMC3328385 DOI: 10.1083/jcb.201109132] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Munc13-4 is a Ca2+-dependent membrane- and SNARE-binding protein that promotes membrane fusion. Munc13-4 is a widely expressed member of the CAPS/Munc13 protein family proposed to function in priming secretory granules for exocytosis. Munc13-4 contains N- and C-terminal C2 domains (C2A and C2B) predicted to bind Ca2+, but Ca2+-dependent regulation of Munc13-4 activity has not been described. The C2 domains bracket a predicted SNARE-binding domain, but whether Munc13-4 interacts with SNARE proteins is unknown. We report that Munc13-4 bound Ca2+ and restored Ca2+-dependent granule exocytosis to permeable cells (platelets, mast, and neuroendocrine cells) dependent on putative Ca2+-binding residues in C2A and C2B. Munc13-4 exhibited Ca2+-stimulated SNARE interactions dependent on C2A and Ca2+-dependent membrane binding dependent on C2B. In an apparent coupling of membrane and SNARE binding, Munc13-4 stimulated SNARE-dependent liposome fusion dependent on putative Ca2+-binding residues in both C2A and C2B domains. Munc13-4 is the first priming factor shown to promote Ca2+-dependent SNARE complex formation and SNARE-mediated liposome fusion. These properties of Munc13-4 suggest its function as a Ca2+ sensor at rate-limiting priming steps in granule exocytosis.
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Affiliation(s)
- Kristin L Boswell
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
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ORAI1-mediated calcium influx is required for human cytotoxic lymphocyte degranulation and target cell lysis. Proc Natl Acad Sci U S A 2011; 108:3324-9. [PMID: 21300876 DOI: 10.1073/pnas.1013285108] [Citation(s) in RCA: 160] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Lymphocytes mediate cytotoxicity by polarized release of the contents of cytotoxic granules toward their target cells. Here, we have studied the role of the calcium release-activated calcium channel ORAI1 in human lymphocyte cytotoxicity. Natural killer (NK) cells obtained from an ORAI1-deficient patient displayed defective store-operated Ca(2+) entry (SOCE) and severely defective cytotoxic granule exocytosis leading to impaired target cell lysis. Similar findings were obtained using NK cells from a stromal interaction molecule 1-deficient patient. The defect occurred at a late stage of the signaling process, because activation of leukocyte functional antigen (LFA)-1 and cytotoxic granule polarization were not impaired. Moreover, pharmacological inhibition of SOCE interfered with degranulation and target cell lysis by freshly isolated NK cells and CD8(+) effector T cells from healthy donors. In addition to effects on lymphocyte cytotoxicity, synthesis of the chemokine macrophage inflammatory protein-1β and the cytokines TNF-α and IFN-γ on target cell recognition was impaired in ORAI1-deficient NK cells, as previously described for T cells. By contrast, NK cell cytokine production induced by combinations of IL-12, IL-15, and IL-18 was not impaired by ORAI1 deficiency. Taken together, these results identify a critical role for ORAI1-mediated Ca(2+) influx in granule exocytosis for lymphocyte cytotoxicity as well as for cytokine production induced by target cell recognition.
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Schmidt H, Gelhaus C, Nebendahl M, Lettau M, Lucius R, Leippe M, Kabelitz D, Janssen O. Effector granules in human T lymphocytes: the luminal proteome of secretory lysosomes from human T cells. Cell Commun Signal 2011; 9:4. [PMID: 21255389 PMCID: PMC3034720 DOI: 10.1186/1478-811x-9-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 01/21/2011] [Indexed: 11/17/2022] Open
Abstract
Background Cytotoxic cells of the immune system have evolved a lysosomal compartment to store and mobilize effector molecules. In T lymphocytes and NK cells, the death factor FasL is one of the characteristic marker proteins of these so-called secretory lysosomes, which combine properties of conventional lysosomes and exocytotic vesicles. Although these vesicles are crucial for immune effector function, their protein content in T cells has so far not been investigated in detail. Results In the present study, intact membranous vesicles were enriched from homogenates of polyclonally activated T cells and initially characterized by Western blotting and electron microscopic inspection. The vesicular fraction that contained the marker proteins of secretory lysosomes was subsequently analyzed by 2D electrophoresis and mass spectrometry. The proteome analysis and data evaluation revealed that 70% of the 397 annotated proteins had been associated with different lysosome-related organelles in previous proteome studies. Conclusion We provide the first comprehensive proteome map of T cell-derived secretory lysosomes with only minor contaminations by cytosolic, nuclear or other proteins. This information will be useful to more precisely address the activation-dependent maturation and the specific distribution of effector organelles and proteins in individual T or NK cell populations in future studies.
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Affiliation(s)
- Hendrik Schmidt
- Institute of Immunology, Christian-Albrechts-University, UK S-H Campus Kiel, Kiel, Germany.
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Abstract
The majority of cells of the immune system are specialized secretory cells, whose function depends on regulated exocytosis. The latter is mediated by vesicular transport involving the sorting of specialized cargo into the secretory granules (SGs), thereby generating the transport vesicles; their transport along the microtubules and eventually their signal-dependent fusion with the plasma membrane. Each of these steps is tightly controlled by mechanisms, which involve the participation of specific sorting signals on the cargo proteins and their recognition by cognate adaptor proteins, posttranslational modifications of the cargo proteins and multiple GTPases and SNARE proteins. In some of the cells (i.e. mast cells, T killer cells) an intimate connection exists between the secretory system and the endocytic one, whereby the SGs are lysosome related organelles (LROs) also referred to as secretory lysosomes. Herein, we discuss these mechanisms in health and disease states.
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Affiliation(s)
- Anat Benado
- Department of Cell and Developmental Biology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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de Saint Basile G, Ménasché G, Fischer A. Molecular mechanisms of biogenesis and exocytosis of cytotoxic granules. Nat Rev Immunol 2010; 10:568-79. [PMID: 20634814 DOI: 10.1038/nri2803] [Citation(s) in RCA: 303] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cytotoxic T cells and natural killer cells are crucial for immune surveillance against virus-infected cells and tumour cells. Molecular studies of individuals with inherited defects that impair lymphocyte cytotoxic function have also highlighted the importance of cytotoxicity in the regulation and termination of immune responses. As discussed in this Review, characterization of these defects has contributed to our understanding of the key steps that are required for the maturation of cytotoxic granules and the secretion of their contents at the immunological synapse during target cell killing. This has revealed a marked similarity between cytotoxic granule exocytosis at the immunological synapse and synaptic vesicle exocytosis at the neurological synapse. We explore the possibility that comparison of these two kinetically and spatially regulated secretory pathways will provide clues to uncover additional effectors that regulate the cytotoxic function of lymphocytes.
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Affiliation(s)
- Geneviève de Saint Basile
- Institut National de la Santé et de la Recherche Médicale (INSERM), U768, Hôpital Necker Enfants Malades, 149 rue de Sèvres, 75015 Paris, France.
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Li J, Xiao Y, Zhou W, Wu Z, Zhang R, Xu T. Silence of Synaptotagmin VII inhibits release of dense core vesicles in PC12 cells. ACTA ACUST UNITED AC 2009; 52:1156-63. [PMID: 20016973 DOI: 10.1007/s11427-009-0160-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Accepted: 08/27/2009] [Indexed: 11/27/2022]
Abstract
Synaptotagmin VII (Syt VII), which has a higher Ca(2+) affinity and slower disassembly kinetics with lipid than Syt I and Syt IX, was regarded as being uninvolved in synaptic vesicle (SV) exocytosis but instead possibly as a calcium sensor for the slower kinetic phase of dense core vesicles (DCVs) release. By using high temporal resolution capacitance and amperometry measurements, it was demonstrated that the knockdown of endogenous Syt VII attenuated the fusion of DCV with the plasma membrane, reduced the amplitude of the exocytotic burst of the Ca(2+)-triggered DCV release without affecting the slope of the sustained component, and blocked the fusion pore expansion. This suggests that Syt VII is the Ca(2+) sensor of DCV fusion machinery and is an essential factor for the establishment and maintenance of the pool size of releasable DCVs in PC12 cells.
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Affiliation(s)
- JiangLi Li
- Key Laboratory of Molecular Biophysics of the Ministry of Education, Institute of Biophysics and Biochemistry, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
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Pores-Fernando AT, Zweifach A. Calcium influx and signaling in cytotoxic T-lymphocyte lytic granule exocytosis. Immunol Rev 2009; 231:160-73. [PMID: 19754896 DOI: 10.1111/j.1600-065x.2009.00809.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Cytotoxic T lymphocytes (CTLs) kill targets by releasing cytotoxic agents from lytic granules. Killing is a multi-step process. The CTL adheres to a target, allowing its T-cell receptors to recognize antigen. This triggers a signal transduction cascade that leads to the polarization of the microtubule cytoskeleton and granules towards the target, followed by exocytosis that occurs specifically at the site of contact. As with cytokine production by helper T cells (Th cells), target cell killing is absolutely dependent on Ca2+ influx, which is involved in regulating both reorientation and release. Current evidence suggests that Ca2+ influx in CTLs, as in Th cells, occurs via depletion-activated channels. The molecules that couple increases in Ca2+ to reorientation are unknown. The Ca2+/calmodulin-dependent phosphatase calcineurin, which plays a critical role in cytokine production by Th cells, is also involved in lytic granule exocytosis, although the relevant substrates remain to be identified and calcineurin activation is only one Ca2+-dependent step involved. There are thus striking similarities and important differences between Ca2+ signals in Th cells and CTLs, illustrating how cells can use similar signal transduction pathways to generate different functional outcomes.
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Affiliation(s)
- Arun T Pores-Fernando
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA
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Qu Y, Dubyak GR. P2X7 receptors regulate multiple types of membrane trafficking responses and non-classical secretion pathways. Purinergic Signal 2009; 5:163-73. [PMID: 19189228 DOI: 10.1007/s11302-009-9132-8] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Indexed: 02/04/2023] Open
Abstract
Activation of the P2X7 receptor (P2X7R) triggers a remarkably diverse array of membrane trafficking responses in leukocytes and epithelial cells. These responses result in altered profiles of cell surface lipid and protein composition that can modulate the direct interactions of P2X7R-expressing cells with other cell types in the circulation, in blood vessels, at epithelial barriers, or within sites of immune and inflammatory activation. Additionally, these responses can result in the release of bioactive proteins, lipids, and large membrane complexes into extracellular compartments for remote communication between P2X7R-expressing cells and other cells that amplify or modulate inflammation, immunity, and responses to tissue damages. This review will discuss P2X7R-mediated effects on membrane composition and trafficking in the plasma membrane (PM) and intracellular organelles, as well as actions of P2X7R in controlling various modes of non-classical secretion. It will review P2X7R regulation of: (1) phosphatidylserine distribution in the PM outer leaflet; (2) shedding of PM surface proteins; (3) release of PM-derived microvesicles or microparticles; (4) PM blebbing; (5) cell-cell fusion resulting in formation of multinucleate cells; (6) phagosome maturation and fusion with lysosomes; (7) permeability of endosomes with internalized pathogen-associated molecular patterns; (8) permeability/integrity of mitochondria; (9) exocytosis of secretory lysosomes; and (10) release of exosomes from multivesicular bodies.
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Affiliation(s)
- Yan Qu
- Department of Pharmacology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH, USA
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Ma JSY, Haydar TF, Radoja S. Protein kinase C delta localizes to secretory lysosomes in CD8+ CTL and directly mediates TCR signals leading to granule exocytosis-mediated cytotoxicity. THE JOURNAL OF IMMUNOLOGY 2008; 181:4716-22. [PMID: 18802074 DOI: 10.4049/jimmunol.181.7.4716] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Lytic granule exocytosis is the major effector function used by CD8(+) CTL in response to intracellular pathogens and tumors. Despite recent progress in the field, two important aspects of this cytotoxic mechanism remain poorly understood. First, TCR-signaling pathway(s) that selectively induces granule exocytosis in CTL has not been defined to date. Second, it is unclear how Ag receptor-induced signals are converted into mobilization of lytic granules. We recently demonstrated that protein kinase C delta (PKC delta) selectively regulates TCR-induced lytic granule polarization in mouse CD8(+) CTL. To better understand how PKC delta facilitates granule movement, here we studied dynamics of intracellular localization of PKC delta in living CD8(+) CTL. Strikingly, we found that PKC delta localizes to the secretory lysosomes and polarizes toward immunological synapse during the process of target cell killing. Also, biochemical and structure-function studies demonstrated that upon TCR ligation, PKC delta becomes rapidly phosphorylated on the activation loop and regulates granule exocytosis in a kinase-dependent manner. Altogether, our current studies provide new insights concerning the regulation of TCR-induced lytic granule exocytosis by revealing novel intracellular localization of PKC delta, providing the first example of colocalization of a kinase with secretory lysosomes in CD8(+) CTL and demonstrating that PKC delta directly transduces TCR signals leading to polarized granule secretion.
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Affiliation(s)
- Jennifer S Y Ma
- Center for Cancer and Immunology, Children's National Medical Center, Children's Research Institute, Washington, DC 20010, USA
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Beal AM, Anikeeva N, Varma R, Cameron TO, Norris PJ, Dustin ML, Sykulev Y. Protein kinase C theta regulates stability of the peripheral adhesion ring junction and contributes to the sensitivity of target cell lysis by CTL. THE JOURNAL OF IMMUNOLOGY 2008; 181:4815-24. [PMID: 18802085 DOI: 10.4049/jimmunol.181.7.4815] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Destruction of virus-infected cells by CTL is an extremely sensitive and efficient process. Our previous data suggest that LFA-1-ICAM-1 interactions in the peripheral supramolecular activation cluster (pSMAC) of the immunological synapse mediate formation of a tight adhesion junction that might contribute to the sensitivity of target cell lysis by CTL. Herein, we compared more (CD8(+)) and less (CD4(+)) effective CTL to understand the molecular events that promote efficient target cell lysis. We found that abrogation of the pSMAC formation significantly impaired the ability of CD8(+) but not CD4(+) CTL to lyse target cells despite having no effect of the amount of released granules by both CD8(+) and CD4(+) CTL. Consistent with this, CD4(+) CTL break their synapses more often than do CD8(+) CTL, which leads to the escape of the cytolytic molecules from the interface. CD4(+) CTL treatment with a protein kinase Ctheta inhibitor increases synapse stability and sensitivity of specific target cell lysis. Thus, formation of a stable pSMAC, which is partially controlled by protein kinase Ctheta, functions to confine the released lytic molecules at the synaptic interface and to enhance the effectiveness of target cell lysis.
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Affiliation(s)
- Allison M Beal
- Department of Microbiology and Immunology and Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, PA 19107, USA
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Idone V, Tam C, Andrews NW. Two-way traffic on the road to plasma membrane repair. Trends Cell Biol 2008; 18:552-9. [PMID: 18848451 DOI: 10.1016/j.tcb.2008.09.001] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Revised: 08/31/2008] [Accepted: 09/01/2008] [Indexed: 12/21/2022]
Abstract
Ca(2+) influx through plasma membrane wounds triggers a rapid-repair response that is essential for cell survival. Earlier studies showed that repair requires the exocytosis of intracellular vesicles. Exocytosis was thought to promote resealing by 'patching' the plasma membrane lesion or by facilitating bilayer restoration through reduction in membrane tension. However, cells also rapidly repair lesions created by pore-forming proteins, a form of injury that cannot be resealed solely by exocytosis. Recent studies indicate that, in cells injured by pores or mechanical abrasions, exocytosis is followed by lesion removal through endocytosis. Describing the relationship between wound-induced exocytosis and endocytosis has implications for the understanding of muscular degenerative diseases that are associated with defects in plasma membrane repair.
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Affiliation(s)
- Vincent Idone
- Section of Microbial Pathogenesis, Yale University School of Medicine, 295 Congress Street, New Haven, CT 06511, USA
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Coxon FP, Taylor A. Vesicular trafficking in osteoclasts. Semin Cell Dev Biol 2008; 19:424-33. [DOI: 10.1016/j.semcdb.2008.08.004] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Revised: 08/04/2008] [Accepted: 08/08/2008] [Indexed: 11/24/2022]
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Zhao H, Ito Y, Chappel J, Andrews NW, Teitelbaum SL, Ross FP. Synaptotagmin VII regulates bone remodeling by modulating osteoclast and osteoblast secretion. Dev Cell 2008; 14:914-25. [PMID: 18539119 DOI: 10.1016/j.devcel.2008.03.022] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Revised: 02/13/2008] [Accepted: 03/31/2008] [Indexed: 01/23/2023]
Abstract
Maintenance of bone mass and integrity requires a tight balance between resorption by osteoclasts and formation by osteoblasts. Exocytosis of functional proteins is a prerequisite for the activity of both cells. In the present study, we show that synaptotagmin VII, a calcium sensor protein that regulates exocytosis, is associated with lysosomes in osteoclasts and bone matrix protein-containing vesicles in osteoblasts. Absence of synaptotagmin VII inhibits cathepsin K secretion and formation of the ruffled border in osteoclasts and bone matrix protein deposition in osteoblasts, without affecting the differentiation of either cell. Reflecting these in vitro findings, synaptotagmin VII-deficient mice are osteopenic due to impaired bone resorption and formation. Therefore, synaptotagmin VII plays an important role in bone remodeling and homeostasis by modulating secretory pathways functionally important in osteoclasts and osteoblasts.
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Affiliation(s)
- Haibo Zhao
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Abstract
AbstractAlthough membrane phospholipid phosphatidylinositol-4,5bisphosphate (PIP2) plays a key role as signaling intermediate and coordinator of actin dynamics and vesicle trafficking, it remains completely unknown its involvement in the activation of cytolytic machinery. By live confocal imaging of primary human natural killer (NK) cells expressing the chimeric protein GFP-PH, we observed, during effector-target cell interaction, the consumption of a preexisting PIP2 pool, which is critically required for the activation of cytolytic machinery. We identified type I phosphatidylinositol-4-phosphate-5-kinase (PI5KI) α and γ isoforms as the enzymes responsible for PIP2 synthesis in NK cells. By hRNA-driven gene silencing, we observed that both enzymes are required for the proper activation of NK cytotoxicity and for inositol-1,4,5-trisphosphate (IP3) generation on receptor stimulation. In an attempt to elucidate the specific step controlled by PI5KIs, we found that lytic granule secretion but not polarization resulted in impaired PI5KIα- and PI5KIγ-silenced cells. Our findings delineate a novel mechanism implicating PI5KIα and PI5KIγ isoforms in the synthesis of PIP2 pools critically required for IP3-dependent Ca2+ response and lytic granule release.
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Higashio H, Nishimura N, Ishizaki H, Miyoshi J, Orita S, Sakane A, Sasaki T. Doc2α and Munc13-4 Regulate Ca2+-Dependent Secretory Lysosome Exocytosis in Mast Cells. THE JOURNAL OF IMMUNOLOGY 2008; 180:4774-84. [DOI: 10.4049/jimmunol.180.7.4774] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Grybko MJ, Bartnik JP, Wurth GA, Pores-Fernando AT, Zweifach A. Calcineurin activation is only one calcium-dependent step in cytotoxic T lymphocyte granule exocytosis. J Biol Chem 2007; 282:18009-18017. [PMID: 17478429 DOI: 10.1074/jbc.m702222200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have tested the idea that calcineurin, a calcium-dependent phosphatase that is critical for activating cytokine gene expression in helper T cells, plays a role in lytic granule exocytosis in cytotoxic T lymphocytes (CTLs). We used TALL-104 human leukemic CTLs as a model. Our results confirm an earlier report (Dutz, J. P., Fruman, D. A., Burakoff, S. J., and Bierer, B. E. (1993) J. Immunol. 150, 2591-2598) that immunosuppressive drugs inhibit exocytosis in CTLs stimulated either via the T cell receptor (TCR) or via TCR-independent soluble agents. Of the two recently reported alternate targets of immunosuppressive drugs (Matsuda, S., Shibasaki, F., Takehana, K., Mori, H., Nishida, E., and Koyasu, S. (2000) EMBO Rep. 1, 428-434 and Matsuda, S., and Koyasu, S. (2000) Immunopharmacology 47, 119-125), JNK is not required for lytic granule exocytosis, but we were not able to exclude a role for P38. Exocytosis could be inhibited by expressing GFP fused to a C-terminal fragment of CAIN (cabin 1), but not by expressing VIVIT-GFP. Finally, expressing either full-length or truncated constitutively active mutant calcineurin A enhanced lytic granule exocytosis. However, the mutant calcineurin was unable to support exocytosis when cells were stimulated in the absence of Ca2+ influx. Taken together, our results support the idea that activation of calcineurin is required for lytic granule exocytosis but suggest that it is not the sole Ca2+-dependent step.
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Affiliation(s)
- Michael J Grybko
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06268-3125
| | - Jakub P Bartnik
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06268-3125
| | - Georjeana A Wurth
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06268-3125
| | - Arun T Pores-Fernando
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06268-3125
| | - Adam Zweifach
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06268-3125.
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