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Jaramillo AM, Vladar EK, Holguin F, Dickey BF, Evans CM. Emerging cell and molecular targets for treating mucus hypersecretion in asthma. Allergol Int 2024:S1323-8930(24)00046-7. [PMID: 38692992 DOI: 10.1016/j.alit.2024.04.002] [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: 03/14/2024] [Accepted: 04/03/2024] [Indexed: 05/03/2024] Open
Abstract
Mucus provides a protective barrier that is crucial for host defense in the lungs. However, excessive or abnormal mucus can have pathophysiological consequences in many pulmonary diseases, including asthma. Patients with asthma are treated with agents that relax airway smooth muscle and reduce airway inflammation, but responses are often inadequate. In part, this is due to the inability of existing therapeutic agents to directly target mucus. Accordingly, there is a critical need to better understand how mucus hypersecretion and airway plugging are affected by the epithelial cells that synthesize, secrete, and transport mucus components. This review highlights recent advances in the biology of mucin glycoproteins with a specific focus on MUC5AC and MUC5B, the chief macromolecular components of airway mucus. An improved mechanistic understanding of key steps in mucin production and secretion will help reveal novel potential therapeutic strategies.
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Affiliation(s)
- Ana M Jaramillo
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado School of Medicine, Aurora, CO, USA
| | - Eszter K Vladar
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado School of Medicine, Aurora, CO, USA
| | - Fernando Holguin
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado School of Medicine, Aurora, CO, USA
| | - Burton F Dickey
- Department of Pulmonary Medicine, Anderson Cancer Center, University of Texas M.D., Houston, TX, USA
| | - Christopher M Evans
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado School of Medicine, Aurora, CO, USA.
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2
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Stefani I, Iwaszkiewicz J, Fasshauer D. Exploring the conformational changes of the Munc18-1/syntaxin 1a complex. Protein Sci 2023; 33:e4870. [PMID: 38109275 PMCID: PMC10895456 DOI: 10.1002/pro.4870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 11/30/2023] [Accepted: 12/07/2023] [Indexed: 12/20/2023]
Abstract
Neurotransmitters are released from synaptic vesicles, the membrane of which fuses with the plasma membrane upon calcium influx. This membrane fusion reaction is driven by the formation of a tight complex comprising the plasma membrane N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins syntaxin-1a and SNAP-25 with the vesicle SNARE protein synaptobrevin. The neuronal protein Munc18-1 forms a stable complex with syntaxin-1a. Biochemically, syntaxin-1a cannot escape the tight grip of Munc18-1, so formation of the SNARE complex is inhibited. However, Munc18-1 is essential for the release of neurotransmitters in vivo. It has therefore been assumed that Munc18-1 makes the bound syntaxin-1a available for SNARE complex formation. Exactly how this occurs is still unclear, but it is assumed that structural rearrangements occur. Here, we used a series of mutations to specifically weaken the complex at different positions in order to induce these rearrangements biochemically. Our approach was guided through sequence and structural analysis and supported by molecular dynamics simulations. Subsequently, we created a homology model showing the complex in an altered conformation. This conformation presumably represents a more open arrangement of syntaxin-1a that permits the formation of a SNARE complex to be initiated while still bound to Munc18-1. In the future, research should investigate how this central reaction for neuronal communication is controlled by other proteins.
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Affiliation(s)
- Ioanna Stefani
- Department of Computational BiologyUniversity of LausanneLausanneSwitzerland
| | | | - Dirk Fasshauer
- Department of Computational BiologyUniversity of LausanneLausanneSwitzerland
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3
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Boeglin M, Leyva-Díaz E, Hobert O. Expression and function of Caenorhabditis elegans UNCP-18, a paralog of the SM protein UNC-18. Genetics 2023; 225:iyad180. [PMID: 37793339 PMCID: PMC10697816 DOI: 10.1093/genetics/iyad180] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/01/2023] [Accepted: 09/26/2023] [Indexed: 10/06/2023] Open
Abstract
Sec1/Munc18 (SM) proteins are important regulators of SNARE complex assembly during exocytosis throughout all major animal tissue types. However, expression of a founding member of the SM family, UNC-18, is mostly restricted to the nervous system of the nematode Caenorhabditis elegans, where it is important for synaptic transmission. Moreover, unc-18 null mutants do not display the lethality phenotype associated with (a) loss of all Drosophila and mouse orthologs of unc-18 and (b) with complete elimination of synaptic transmission in C. elegans. We investigated whether a previously uncharacterized unc-18 paralog, which we named uncp-18, may be able to explain the restricted expression and limited phenotypes of unc-18 null mutants. A reporter allele shows ubiquitous expression of uncp-18. Analysis of uncp-18 null mutants, unc-18 and uncp-18 double null mutants, as well as overexpression of uncp-18 in an unc-18 null mutant background, shows that these 2 genes can functionally compensate for one another and are redundantly required for embryonic viability. Our results indicate that the synaptic transmission defects of unc-18 null mutants cannot necessarily be interpreted as constituting a null phenotype for SM protein function at the synapse.
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Affiliation(s)
- Marion Boeglin
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, NewYork, NY 10027, USA
- Department of Development and Stem Cells, IGBMC, CNRS UMR 7104/INSERM U1258, Université de Strasbourg, Strasbourg 67081, France
| | - Eduardo Leyva-Díaz
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, NewYork, NY 10027, USA
| | - Oliver Hobert
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, NewYork, NY 10027, USA
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4
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Zhou M, Tian T, Wu C. Mechanism Underlying the Regulation of Mucin Secretion in the Uterus during Pregnancy. Int J Mol Sci 2023; 24:15896. [PMID: 37958878 PMCID: PMC10647571 DOI: 10.3390/ijms242115896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 10/23/2023] [Accepted: 10/28/2023] [Indexed: 11/15/2023] Open
Abstract
The function of endometrial epithelial cells is to secrete various substances that are rich in growth factors and nutrients. These substances support both embryo implantation and its subsequent development into a fetus. A vast number of mucins are expressed in endometrial epithelial cells, and they play an important role in regulating the processes of embryo implantation, pregnancy, and parturition. Previous studies have shown that mucin forms a mucus layer covering endometrial epithelial cells, which helps resist damage from foreign bacteria and their toxins. Therefore, this article aims to investigate the location of mucins in the endometrium, the mechanism of mucin secretion by the endometrium, and the regulation of mucins in the uterine epithelium by reproductive hormones, as well as the role of mucins in the protection of the epithelium's structure. This research aims to provide a foundational understanding for future studies on the role and mechanism of endometrial mucins throughout the pregnancy cycle.
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Affiliation(s)
| | | | - Chenchen Wu
- College of Animal Veterinary Medicine, Northwest A&F University, Yangling 712100, China; (M.Z.); (T.T.)
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5
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Song C, Chai Z, Chen S, Zhang H, Zhang X, Zhou Y. Intestinal mucus components and secretion mechanisms: what we do and do not know. Exp Mol Med 2023; 55:681-691. [PMID: 37009791 PMCID: PMC10167328 DOI: 10.1038/s12276-023-00960-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 12/26/2022] [Indexed: 04/04/2023] Open
Abstract
Damage to the colon mucus barrier, the first line of defense against microorganisms, is an important determinant of intestinal diseases such as inflammatory bowel disease and colorectal cancer, and disorder in extraintestinal organs. The mucus layer has attracted the attention of the scientific community in recent years, and with the discovery of new mucosal components, it has become increasingly clear that the mucosal barrier is a complex system composed of many components. Moreover, certain components are jointly involved in regulating the structure and function of the mucus barrier. Therefore, a comprehensive and systematic understanding of the functional components of the mucus layer is clearly warranted. In this review, we summarize the various functional components of the mucus layer identified thus far and describe their unique roles in shaping mucosal structure and function. Furthermore, we detail the mechanisms underlying mucus secretion, including baseline and stimulated secretion. In our opinion, baseline secretion can be categorized into spontaneous Ca2+ oscillation-mediated slow and continuous secretion and stimulated secretion, which is mediated by massive Ca2+ influx induced by exogenous stimuli. This review extends the current understanding of the intestinal mucus barrier, with an emphasis on host defense strategies based on fortification of the mucus layer.
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Affiliation(s)
- Chunyan Song
- Department of Preventive Medicine, Health Science Center, Ningbo University, Zhejiang Key Laboratory of Pathophysiology, Ningbo, Zhejiang, 315211, China
| | - Zhenglong Chai
- Department of Preventive Medicine, Health Science Center, Ningbo University, Zhejiang Key Laboratory of Pathophysiology, Ningbo, Zhejiang, 315211, China
| | - Si Chen
- Department of Preventive Medicine, Health Science Center, Ningbo University, Zhejiang Key Laboratory of Pathophysiology, Ningbo, Zhejiang, 315211, China
| | - Hui Zhang
- Department of Preventive Medicine, Health Science Center, Ningbo University, Zhejiang Key Laboratory of Pathophysiology, Ningbo, Zhejiang, 315211, China
| | - Xiaohong Zhang
- Department of Preventive Medicine, Health Science Center, Ningbo University, Zhejiang Key Laboratory of Pathophysiology, Ningbo, Zhejiang, 315211, China.
- The Affiliated Hospital of Medical School, Ningbo University, Institute of Digestive Disease of Ningbo University, Ningbo, Zhejiang, 315020, China.
| | - Yuping Zhou
- The Affiliated Hospital of Medical School, Ningbo University, Institute of Digestive Disease of Ningbo University, Ningbo, Zhejiang, 315020, China.
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6
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Lai Y, Tuvim MJ, Leitz J, Peters J, Pfuetzner RA, Esquivies L, Zhou Q, Czako B, Cross JB, Jones P, Dickey BF, Brunger AT. Screening of Hydrocarbon-Stapled Peptides for Inhibition of Calcium-Triggered Exocytosis. Front Pharmacol 2022; 13:891041. [PMID: 35814209 PMCID: PMC9258623 DOI: 10.3389/fphar.2022.891041] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 04/14/2022] [Indexed: 11/13/2022] Open
Abstract
The so-called primary interface between the SNARE complex and synaptotagmin-1 (Syt1) is essential for Ca2+-triggered neurotransmitter release in neuronal synapses. The interacting residues of the primary interface are conserved across different species for synaptotagmins (Syt1, Syt2, Syt9), SNAP-25, and syntaxin-1A homologs involved in fast synchronous release. This Ca2+-independent interface forms prior to Ca2+-triggering and plays a role in synaptic vesicle priming. This primary interface is also conserved in the fusion machinery that is responsible for mucin granule membrane fusion. Ca2+-stimulated mucin secretion is mediated by the SNAREs syntaxin-3, SNAP-23, VAMP8, Syt2, and other proteins. Here, we designed and screened a series of hydrocarbon-stapled peptides consisting of SNAP-25 fragments that included some of the key residues involved in the primary interface as observed in high-resolution crystal structures. We selected a subset of four stapled peptides that were highly α-helical as assessed by circular dichroism and that inhibited both Ca2+-independent and Ca2+-triggered ensemble lipid-mixing with neuronal SNAREs and Syt1. In a single-vesicle content-mixing assay with reconstituted neuronal SNAREs and Syt1 or with reconstituted airway SNAREs and Syt2, the selected peptides also suppressed Ca2+-triggered fusion. Taken together, hydrocarbon-stapled peptides that interfere with the primary interface consequently inhibit Ca2+-triggered exocytosis. Our inhibitor screen suggests that these compounds may be useful to combat mucus hypersecretion, which is a major cause of airway obstruction in the pathophysiology of COPD, asthma, and cystic fibrosis.
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Affiliation(s)
- Ying Lai
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, United States,*Correspondence: Axel T. Brunger, ; Ying Lai, ; Burton F. Dickey,
| | - Michael J. Tuvim
- Department of Pulmonary Medicine, MD Anderson Cancer Center, University of Texas, Houston, TX, United States
| | - Jeremy Leitz
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, United States
| | - John Peters
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, United States
| | - Richard A. Pfuetzner
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, United States,Howard Hughes Medical Institute, Stanford University, Stanford, CA, United States
| | - Luis Esquivies
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, United States,Howard Hughes Medical Institute, Stanford University, Stanford, CA, United States
| | - Qiangjun Zhou
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, United States
| | - Barbara Czako
- Institute for Applied Cancer Science, MD Anderson Cancer Center, University of Texas, Houston, TX, United States
| | - Jason B. Cross
- Institute for Applied Cancer Science, MD Anderson Cancer Center, University of Texas, Houston, TX, United States
| | - Philip Jones
- Institute for Applied Cancer Science, MD Anderson Cancer Center, University of Texas, Houston, TX, United States
| | - Burton F. Dickey
- Department of Pulmonary Medicine, MD Anderson Cancer Center, University of Texas, Houston, TX, United States,*Correspondence: Axel T. Brunger, ; Ying Lai, ; Burton F. Dickey,
| | - Axel T. Brunger
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, United States,Howard Hughes Medical Institute, Stanford University, Stanford, CA, United States,*Correspondence: Axel T. Brunger, ; Ying Lai, ; Burton F. Dickey,
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7
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Inhibition of calcium-triggered secretion by hydrocarbon-stapled peptides. Nature 2022; 603:949-956. [PMID: 35322233 PMCID: PMC8967716 DOI: 10.1038/s41586-022-04543-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 02/11/2022] [Indexed: 02/06/2023]
Abstract
Membrane fusion triggered by Ca2+ is orchestrated by a conserved set of proteins to mediate synaptic neurotransmitter release, mucin secretion and other regulated exocytic processes1–4. For neurotransmitter release, the Ca2+ sensitivity is introduced by interactions between the Ca2+ sensor synaptotagmin and the SNARE complex5, and sequence conservation and functional studies suggest that this mechanism is also conserved for mucin secretion6. Disruption of Ca2+-triggered membrane fusion by a pharmacological agent would have therapeutic value for mucus hypersecretion as it is the major cause of airway obstruction in the pathophysiology of respiratory viral infection, asthma, chronic obstructive pulmonary disease and cystic fibrosis7–11. Here we designed a hydrocarbon-stapled peptide that specifically disrupts Ca2+-triggered membrane fusion by interfering with the so-called primary interface between the neuronal SNARE complex and the Ca2+-binding C2B domain of synaptotagmin-1. In reconstituted systems with these neuronal synaptic proteins or with their airway homologues syntaxin-3, SNAP-23, VAMP8, synaptotagmin-2, along with Munc13-2 and Munc18-2, the stapled peptide strongly suppressed Ca2+-triggered fusion at physiological Ca2+ concentrations. Conjugation of cell-penetrating peptides to the stapled peptide resulted in efficient delivery into cultured human airway epithelial cells and mouse airway epithelium, where it markedly and specifically reduced stimulated mucin secretion in both systems, and substantially attenuated mucus occlusion of mouse airways. Taken together, peptides that disrupt Ca2+-triggered membrane fusion may enable the therapeutic modulation of mucin secretory pathways. Peptides that disrupt Ca2+-triggered membrane fusion may enable the therapeutic modulation of mucin secretory pathways.
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8
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Sauvola CW, Littleton JT. SNARE Regulatory Proteins in Synaptic Vesicle Fusion and Recycling. Front Mol Neurosci 2021; 14:733138. [PMID: 34421538 PMCID: PMC8377282 DOI: 10.3389/fnmol.2021.733138] [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: 06/29/2021] [Accepted: 07/20/2021] [Indexed: 01/01/2023] Open
Abstract
Membrane fusion is a universal feature of eukaryotic protein trafficking and is mediated by the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) family. SNARE proteins embedded in opposing membranes spontaneously assemble to drive membrane fusion and cargo exchange in vitro. Evolution has generated a diverse complement of SNARE regulatory proteins (SRPs) that ensure membrane fusion occurs at the right time and place in vivo. While a core set of SNAREs and SRPs are common to all eukaryotic cells, a specialized set of SRPs within neurons confer additional regulation to synaptic vesicle (SV) fusion. Neuronal communication is characterized by precise spatial and temporal control of SNARE dynamics within presynaptic subdomains specialized for neurotransmitter release. Action potential-elicited Ca2+ influx at these release sites triggers zippering of SNAREs embedded in the SV and plasma membrane to drive bilayer fusion and release of neurotransmitters that activate downstream targets. Here we discuss current models for how SRPs regulate SNARE dynamics and presynaptic output, emphasizing invertebrate genetic findings that advanced our understanding of SRP regulation of SV cycling.
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Affiliation(s)
- Chad W Sauvola
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
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9
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So WY, Liu WN, Teo AKK, Rutter GA, Han W. Paired box 6 programs essential exocytotic genes in the regulation of glucose-stimulated insulin secretion and glucose homeostasis. Sci Transl Med 2021; 13:13/600/eabb1038. [PMID: 34193609 DOI: 10.1126/scitranslmed.abb1038] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 01/25/2021] [Accepted: 05/26/2021] [Indexed: 01/26/2023]
Abstract
The paired box 6 (PAX6) transcription factor is crucial for normal pancreatic islet development and function. Heterozygous mutations of PAX6 are associated with impaired insulin secretion and early-onset diabetes mellitus in humans. However, the molecular mechanism of PAX6 in controlling insulin secretion in human beta cells and its pathophysiological role in type 2 diabetes (T2D) remain ambiguous. We investigated the molecular pathway of PAX6 in the regulation of insulin secretion and the potential therapeutic value of PAX6 in T2D by using human pancreatic beta cell line EndoC-βH1, the db/db mouse model, and primary human pancreatic islets. Through loss- and gain-of-function approaches, we uncovered a mechanism by which PAX6 modulates glucose-stimulated insulin secretion (GSIS) through a cAMP response element-binding protein (CREB)/Munc18-1/2 pathway. Moreover, under diabetic conditions, beta cells and pancreatic islets displayed dampened PAX6/CREB/Munc18-1/2 pathway activity and impaired GSIS, which were reversed by PAX6 replenishment. Adeno-associated virus-mediated PAX6 overexpression in db/db mouse pancreatic beta cells led to a sustained amelioration of glycemic perturbation in vivo but did not affect insulin resistance. Our study highlights the pathophysiological role of PAX6 in T2D-associated beta cell dysfunction in humans and suggests the potential of PAX6 gene transfer in preserving and restoring beta cell function.
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Affiliation(s)
- Wing Yan So
- Institute of Molecular and Cell Biology, Agency for Science Technology and Research, Singapore 138673, Singapore
| | - Wai Nam Liu
- Institute of Molecular and Cell Biology, Agency for Science Technology and Research, Singapore 138673, Singapore
| | - Adrian Kee Keong Teo
- Institute of Molecular and Cell Biology, Agency for Science Technology and Research, Singapore 138673, Singapore.,Departments of Biochemistry and Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117596, Singapore
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics and Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London W12 0NN, UK
| | - Weiping Han
- Institute of Molecular and Cell Biology, Agency for Science Technology and Research, Singapore 138673, Singapore. .,Center for Neuro-Metabolism and Regeneration Research, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou 510700, China
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10
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SNAP23 is essential for platelet and mast cell development and required in connective tissue mast cells for anaphylaxis. J Biol Chem 2021; 296:100268. [PMID: 33837726 PMCID: PMC7948755 DOI: 10.1016/j.jbc.2021.100268] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 12/31/2020] [Accepted: 01/06/2021] [Indexed: 11/23/2022] Open
Abstract
Degranulation, a fundamental effector response from mast cells (MCs) and platelets, is an example of regulated exocytosis. This process is mediated by SNARE proteins and their regulators. We have previously shown that several of these proteins are essential for exocytosis in MCs and platelets. Here, we assessed the role of the SNARE protein SNAP23 using conditional knockout mice, in which SNAP23 was selectively deleted from either the megakaryocyte/platelet or connective tissue MC lineages. We found that removal of SNAP23 in platelets results in severe defects in degranulation of all three platelet secretory granule types, i.e., alpha, dense, and lysosomal granules. The mutation also induces thrombocytopenia, abnormal platelet morphology and activation, and reduction in the number of alpha granules. Therefore, the degranulation defect might not be secondary to an intrinsic failure of the machinery mediating regulated exocytosis in platelets. When we removed SNAP23 expression in MCs, there was a complete developmental failure in vitro and in vivo. The developmental defects in platelets and MCs and the abnormal translocation of membrane proteins to the surface of platelets indicate that SNAP23 is also involved in constitutive exocytosis in these cells. The MC conditional deletant animals lacked connective tissue MCs, but their mucosal MCs were normal and expanded in response to an antigenic stimulus. We used this mouse to show that connective tissue MCs are required and mucosal MCs are not sufficient for an anaphylactic response.
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11
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Abstract
Exocytosis of secreted mucins is the final step in their intracellular processing, resulting in their release into the airway lumen to interact with water and ions to form mucus. Mucins are secreted at a low baseline rate and a high stimulated rate, and both rates are regulated by second messengers acting on components of the exocytic machinery. The principal physiologic function of the low baseline rate is to support steady-state mucociliary clearance of inhaled particles and pathogens that enter the airways during normal breathing. Even in the setting of mucin hyperproduction, baseline secretion generally does not induce mucus occlusion. The principal physiologic function of the high stimulated rate of secretion from both submucosal glands and surface goblet cells in proximal airways appears to be to sweep away larger particles, whereas in distal airways it appears to act in concert with mucin hyperproduction to induce mucus occlusion to trap migrating helminths. Pathophysiologically, stimulated mucin secretion in the setting of mucin hyperproduction from allergic or other types of airway inflammation in the absence of helminth infection causes airflow obstruction and infection. Molecular components of the mucin exocytic machinery are increasingly being identified, and surprisingly, many components are not shared between baseline and stimulated machines. The physiologic significance of the presence of two distinct molecular machines is not yet known, such as whether these interact selectively with secretory granules of different sizes or contents. A full understanding of the mechanism and regulation of airway mucin secretion will provide further insight into pathophysiologic processes and may identify therapeutic strategies to alleviate obstructive airway diseases.
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12
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Jaramillo AM, Piccotti L, Velasco WV, Delgado ASH, Azzegagh Z, Chung F, Nazeer U, Farooq J, Brenner J, Parker-Thornburg J, Scott BL, Evans CM, Adachi R, Burns AR, Kreda SM, Tuvim MJ, Dickey BF. Different Munc18 proteins mediate baseline and stimulated airway mucin secretion. JCI Insight 2019; 4:124815. [PMID: 30721150 PMCID: PMC6483006 DOI: 10.1172/jci.insight.124815] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 01/31/2019] [Indexed: 12/15/2022] Open
Abstract
Airway mucin secretion is necessary for ciliary clearance of inhaled particles and pathogens but can be detrimental in pathologies such as asthma and cystic fibrosis. Exocytosis in mammals requires a Munc18 scaffolding protein, and airway secretory cells express all 3 Munc18 isoforms. Using conditional airway epithelial cell-deletant mice, we found that Munc18a has the major role in baseline mucin secretion, Munc18b has the major role in stimulated mucin secretion, and Munc18c does not function in mucin secretion. In an allergic asthma model, Munc18b deletion reduced airway mucus occlusion and airflow resistance. In a cystic fibrosis model, Munc18b deletion reduced airway mucus occlusion and emphysema. Munc18b deficiency in the airway epithelium did not result in any abnormalities of lung structure, particle clearance, inflammation, or bacterial infection. Our results show that regulated secretion in a polarized epithelial cell may involve more than one exocytic machine at the apical plasma membrane and that the protective roles of mucin secretion can be preserved while therapeutically targeting its pathologic roles.
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Affiliation(s)
- Ana M. Jaramillo
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
- Institute of Bioscience and Technology, Texas A&M University Health Science Center, Houston, Texas, USA
| | - Lucia Piccotti
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Walter V. Velasco
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | | | - Zoulikha Azzegagh
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Felicity Chung
- Marsico Lung Institute/Cystic Fibrosis Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Usman Nazeer
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Junaid Farooq
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Josh Brenner
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Jan Parker-Thornburg
- Department of Genetics, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Brenton L. Scott
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Christopher M. Evans
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Denver School of Medicine, Aurora, Colorado, USA
| | - Roberto Adachi
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Alan R. Burns
- College of Optometry, University of Houston, Houston, Texas, USA
| | - Silvia M. Kreda
- Marsico Lung Institute/Cystic Fibrosis Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Michael J. Tuvim
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Burton F. Dickey
- Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
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13
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Sanchez E, Gonzalez EA, Moreno DS, Cardenas RA, Ramos MA, Davalos AJ, Manllo J, Rodarte AI, Petrova Y, Moreira DC, Chavez MA, Tortoriello A, Lara A, Gutierrez BA, Burns AR, Heidelberger R, Adachi R. Syntaxin 3, but not syntaxin 4, is required for mast cell-regulated exocytosis, where it plays a primary role mediating compound exocytosis. J Biol Chem 2019; 294:3012-3023. [PMID: 30563839 PMCID: PMC6398129 DOI: 10.1074/jbc.ra118.005532] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 11/30/2018] [Indexed: 11/06/2022] Open
Abstract
Mast cells (MCs) participate in allergy, inflammation, and defense against pathogens. They release multiple immune mediators via exocytosis, a process that requires SNARE proteins, including syntaxins (Stxs). The identity of the Stxs involved in MC exocytosis remains controversial. Here, we studied the roles of Stx3 and -4 in fully developed MCs from conditional knockout mice by electrophysiology and EM, and found that Stx3, and not Stx4, is crucial for MC exocytosis. The main defect seen in Stx3-deficient MCs was their inability to engage multigranular compound exocytosis, while leaving most single-vesicle fusion events intact. We used this defect to show that this form of exocytosis is not only required to accelerate MC degranulation but also essential to achieve full degranulation. The exocytic defect was severe but not absolute, indicating that an Stx other than Stx3 and -4 is also required for exocytosis in MCs. The removal of Stx3 affected only regulated exocytosis, leaving other MC effector responses intact, including the secretion of cytokines via constitutive exocytosis. Our in vivo model of passive systemic anaphylaxis showed that the residual exocytic function of Stx3-deficient MCs was sufficient to drive a full anaphylactic response in mice.
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Affiliation(s)
- Elizabeth Sanchez
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Erika A Gonzalez
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - David S Moreno
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Rodolfo A Cardenas
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Marco A Ramos
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Alfredo J Davalos
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - John Manllo
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Alejandro I Rodarte
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Youlia Petrova
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Daniel C Moreira
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Miguel A Chavez
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Alejandro Tortoriello
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Adolfo Lara
- the Department of Neurobiology and Anatomy, McGovern Medical School at the University of Texas Health Science Center, Houston, Texas 77030, and
| | - Berenice A Gutierrez
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Alan R Burns
- the College of Optometry, University of Houston, Houston, Texas 77204
| | - Ruth Heidelberger
- the Department of Neurobiology and Anatomy, McGovern Medical School at the University of Texas Health Science Center, Houston, Texas 77030, and
| | - Roberto Adachi
- From the Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030,
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14
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Pezzulo AA, Tudas RA, Stewart CG, Buonfiglio LGV, Lindsay BD, Taft PJ, Gansemer ND, Zabner J. HSP90 inhibitor geldanamycin reverts IL-13- and IL-17-induced airway goblet cell metaplasia. J Clin Invest 2019; 129:744-758. [PMID: 30640172 PMCID: PMC6355221 DOI: 10.1172/jci123524] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 11/20/2018] [Indexed: 12/29/2022] Open
Abstract
Goblet cell metaplasia, a disabling hallmark of chronic lung disease, lacks curative treatments at present. To identify novel therapeutic targets for goblet cell metaplasia, we studied the transcriptional response profile of IL-13-exposed primary human airway epithelia in vitro and asthmatic airway epithelia in vivo. A perturbation-response profile connectivity approach identified geldanamycin, an inhibitor of heat shock protein 90 (HSP90) as a candidate therapeutic target. Our experiments confirmed that geldanamycin and other HSP90 inhibitors prevented IL-13-induced goblet cell metaplasia in vitro and in vivo. Geldanamycin also reverted established goblet cell metaplasia. Geldanamycin did not induce goblet cell death, nor did it solely block mucin synthesis or IL-13 receptor-proximal signaling. Geldanamycin affected the transcriptome of airway cells when exposed to IL-13, but not when exposed to vehicle. We hypothesized that the mechanism of action probably involves TGF-β, ERBB, or EHF, which would predict that geldanamycin would also revert IL-17-induced goblet cell metaplasia, a prediction confirmed by our experiments. Our findings suggest that persistent airway goblet cell metaplasia requires HSP90 activity and that HSP90 inhibitors will revert goblet cell metaplasia, despite active upstream inflammatory signaling. Moreover, HSP90 inhibitors may be a therapeutic option for airway diseases with goblet cell metaplasia of unknown mechanism.
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Affiliation(s)
- Alejandro A. Pezzulo
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, and
- Pappajohn Biomedical Institute, University of Iowa, Iowa City, Iowa, USA
| | - Rosarie A. Tudas
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, and
- Pappajohn Biomedical Institute, University of Iowa, Iowa City, Iowa, USA
| | - Carley G. Stewart
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, and
- Pappajohn Biomedical Institute, University of Iowa, Iowa City, Iowa, USA
| | | | - Brian D. Lindsay
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, and
| | - Peter J. Taft
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, and
- Pappajohn Biomedical Institute, University of Iowa, Iowa City, Iowa, USA
| | - Nicholas D. Gansemer
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, and
- Pappajohn Biomedical Institute, University of Iowa, Iowa City, Iowa, USA
| | - Joseph Zabner
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, and
- Pappajohn Biomedical Institute, University of Iowa, Iowa City, Iowa, USA
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15
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Cardenas EI, Gonzalez R, Breaux K, Da Q, Gutierrez BA, Ramos MA, Cardenas RA, Burns AR, Rumbaut RE, Adachi R. Munc18-2, but not Munc18-1 or Munc18-3, regulates platelet exocytosis, hemostasis, and thrombosis. J Biol Chem 2019; 294:4784-4792. [PMID: 30696774 DOI: 10.1074/jbc.ra118.006922] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/24/2019] [Indexed: 12/17/2022] Open
Abstract
Platelet degranulation, a form of regulated exocytosis, is crucial for hemostasis and thrombosis. Exocytosis in platelets is mediated by SNARE proteins, and in most mammalian cells this process is controlled by Munc18 (mammalian homolog of Caenorhabditis elegans uncoordinated gene 18) proteins. Platelets express all Munc18 paralogs (Munc18-1, -2, and -3), but their roles in platelet secretion and function have not been fully characterized. Using Munc18-1, -2, and -3 conditional knockout mice, here we deleted expression of these proteins in platelets and assessed granule exocytosis. We measured products secreted by each type of platelet granule and analyzed EM platelet profiles by design-based stereology. We observed that the removal of Munc18-2 ablates the release of alpha, dense, and lysosomal granules from platelets, but we found no exocytic role for Munc18-1 or -3 in platelets. In vitro, Munc18-2-deficient platelets exhibited defective aggregation at low doses of collagen and impaired thrombus formation under shear stress. In vivo, megakaryocyte-specific Munc18-2 conditional knockout mice had a severe hemostatic defect and prolonged arterial and venous bleeding times. They were also protected against arterial thrombosis in a chemically induced model of arterial injury. Taken together, our results indicate that Munc18-2, but not Munc18-1 or Munc18-3, is essential for regulated exocytosis in platelets and platelet participation in thrombosis and hemostasis.
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Affiliation(s)
- Eduardo I Cardenas
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.,the Escuela de Ingenieria y Ciencias, Instituto Tecnologico de Monterrey, Monterrey, Nuevo Leon 64849, Mexico
| | - Ricardo Gonzalez
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.,the Escuela de Ingenieria y Ciencias, Instituto Tecnologico de Monterrey, Monterrey, Nuevo Leon 64849, Mexico
| | - Keegan Breaux
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Qi Da
- the Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas 77030.,the Department of Medicine, Baylor College of Medicine, Houston, Texas 77030
| | - Berenice A Gutierrez
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.,the Escuela de Ingenieria y Ciencias, Instituto Tecnologico de Monterrey, Monterrey, Nuevo Leon 64849, Mexico
| | - Marco A Ramos
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Rodolfo A Cardenas
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.,the Escuela de Medicina y Ciencias de la Salud, Instituto Tecnologico de Monterrey, Monterrey, Nuevo León 64710, México, and
| | - Alan R Burns
- the College of Optometry, University of Houston, Houston, Texas 77204
| | - Rolando E Rumbaut
- the Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas 77030.,the Department of Medicine, Baylor College of Medicine, Houston, Texas 77030
| | - Roberto Adachi
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030,
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16
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Winkelmann VE, Thompson KE, Neuland K, Jaramillo AM, Fois G, Schmidt H, Wittekindt OH, Han W, Tuvim MJ, Dickey BF, Dietl P, Frick M. Inflammation-induced upregulation of P2X 4 expression augments mucin secretion in airway epithelia. Am J Physiol Lung Cell Mol Physiol 2018; 316:L58-L70. [PMID: 30358443 DOI: 10.1152/ajplung.00157.2018] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mucus clearance provides an essential innate defense mechanism to keep the airways and lungs free of particles and pathogens. Baseline and stimulated mucin secretion from secretory airway epithelial cells need to be tightly regulated to prevent mucus hypersecretion and mucus plugging of the airways. It is well established that extracellular ATP is a potent stimulus for regulated mucus secretion. Previous studies revealed that ATP acts via metabotropic P2Y2 purinoreceptors on goblet cells. Extracellular ATP, however, is also a potent agonist for ionotropic P2X purinoreceptors. Expression of several P2X isoforms has been reported in airways, but cell type-specific expression and the function thereof remained elusive. With this study, we now provide evidence that P2X4 is the predominant P2X isoform expressed in secretory airway epithelial cells. After IL-13 treatment of either human primary tracheal epithelial cells or mice, P2X4 expression is upregulated in vitro and in vivo under conditions of chronic inflammation, mucous metaplasia, and hyperplasia. Upregulation of P2X4 is strongest in MUC5AC-positive goblet cells. Moreover, activation of P2X4 by extracellular ATP augments intracellular Ca2+ signals and mucin secretion, whereas Ca2+ signals and mucin secretion are dampened by inhibition of P2X4 receptors. These data provide new insights into the purinergic regulation of mucin secretion and add to the emerging picture that P2X receptors modulate exocytosis of large secretory organelles and secretion of macromolecular vesicle cargo.
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Affiliation(s)
| | - Kristin E Thompson
- Centre de Recherche Saint-Antoine, INSERM, Université Pierre et Marie Curie-Université Paris 06, Sorbonne Universités, Paris , France
| | - Kathrin Neuland
- Institute of General Physiology, Ulm University , Ulm , Germany
| | - Ana M Jaramillo
- Department of Pulmonary Medicine, MD Anderson Cancer Center , Houston, Texas
| | - Giorgio Fois
- Institute of General Physiology, Ulm University , Ulm , Germany
| | - Hanna Schmidt
- Institute of General Physiology, Ulm University , Ulm , Germany
| | | | - Wei Han
- Department of Pulmonary Medicine, MD Anderson Cancer Center , Houston, Texas
| | - Michael J Tuvim
- Department of Pulmonary Medicine, MD Anderson Cancer Center , Houston, Texas
| | - Burton F Dickey
- Department of Pulmonary Medicine, MD Anderson Cancer Center , Houston, Texas
| | - Paul Dietl
- Institute of General Physiology, Ulm University , Ulm , Germany
| | - Manfred Frick
- Institute of General Physiology, Ulm University , Ulm , Germany
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17
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Suzuki A, Iwata J. Molecular Regulatory Mechanism of Exocytosis in the Salivary Glands. Int J Mol Sci 2018; 19:E3208. [PMID: 30336591 PMCID: PMC6214078 DOI: 10.3390/ijms19103208] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 10/10/2018] [Accepted: 10/11/2018] [Indexed: 12/12/2022] Open
Abstract
Every day, salivary glands produce about 0.5 to 1.5 L of saliva, which contains salivary proteins that are essential for oral health. The contents of saliva, 0.3% proteins (1.5 to 4.5 g) in fluid, help prevent oral infections, provide lubrication, aid digestion, and maintain oral health. Acinar cells in the lobular salivary glands secrete prepackaged secretory granules that contain salivary components such as amylase, mucins, and immunoglobulins. Despite the important physiological functions of salivary proteins, we know very little about the regulatory mechanisms of their secretion via exocytosis, which is a process essential for the secretion of functional proteins, not only in salivary glands, but also in other secretory organs, including lacrimal and mammary glands, the pancreas, and prostate. In this review, we discuss recent findings that elucidate exocytosis by exocrine glands, especially focusing on the salivary glands, in physiological and pathological conditions.
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Affiliation(s)
- Akiko Suzuki
- Department of Diagnostic & Biomedical Sciences, The University of Texas Health Science Center at Houston School of Dentistry, Houston, TX 77054, USA.
- Center for Craniofacial Research, The University of Texas Health Science Center at Houston School of Dentistry, Houston, TX 77054, USA.
| | - Junichi Iwata
- Department of Diagnostic & Biomedical Sciences, The University of Texas Health Science Center at Houston School of Dentistry, Houston, TX 77054, USA.
- Center for Craniofacial Research, The University of Texas Health Science Center at Houston School of Dentistry, Houston, TX 77054, USA.
- Program of Biochemistry and Cell Biology, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX 77030, USA.
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18
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Su Y, Wang J, Zou J, Han W, Li S. miR-330 regulates interleukin-13-induced MUC5AC secretion by targeting Munc18b in human bronchial epithelial cells. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2018; 11:3463-3470. [PMID: 31949724 PMCID: PMC6962880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 03/28/2018] [Indexed: 06/10/2023]
Abstract
Mucus hypersecretion by airway epithelium and plugging of the airways are primary reasons of mortality in asthma patients and major causes of asthma disease progression and exacerbation. MUC5AC protein is a major component of airway mucus. MicroRNAs (miRNAs), a class of small noncoding RNAs, have emerged as moderators of MUC5AC production and secretion and are implicated in the pathogenesis of asthma. Recently, miR-330 has been reported to be downregulated in the blood of asthmatic patients, acting as a biomarker for asthma. The role of miR-330 in asthma, however, is unclear. Here, we showed that interleukin (IL)-13 induced MUC5AC secretion and inhibited miR-330 expression in a concentration-dependent manner in human bronchial epithelial cells (HBE16). Upregulation of miR-330 in HBE16 cells inhibited IL-13-induced MUC5AC secretion while, conversely, depletion of endogenous miR-330 exacerbated MUC5AC secretion. Munc18b (Syntaxin-Binding Protein 2; STXBP2) is a limiting component of the exocytic machinery of airway epithelial cells. We identified and validated that Munc18b was a direct target of miR-330 and miR-330 regulated MUC5AC secretion in HBE16 cells by acting directly on the 3'UTR of Munc18b mRNA. Collectively, these data reveal that miR-330 inhibits IL-13-induced MUC5AC secretion in human bronchial epithelial cells by targeting Munc18b, encouraging us to further explore the potential of manipulating miR-330 in treatment of airway diseases with mucus hypersecretion.
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Affiliation(s)
- Yi Su
- Department of Pulmonary Medicine, Qingdao Municipal Hospital, School of Medicine, Qingdao UniversityQingdao, China
| | - Jing Wang
- Department of Pulmonary Medicine, Qingdao Municipal Hospital, School of Medicine, Qingdao UniversityQingdao, China
| | - Jianhong Zou
- Department of Health Education, Shibei District Center for Disease Prevention and Control of QingdaoQingdao, China
| | - Wei Han
- Department of Pulmonary Medicine, Qingdao Municipal Hospital, School of Medicine, Qingdao UniversityQingdao, China
| | - Shuangbao Li
- Department of Pulmonary Medicine, Qingdao Municipal Hospital, School of Medicine, Qingdao UniversityQingdao, China
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19
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Gutierrez BA, Chavez MA, Rodarte AI, Ramos MA, Dominguez A, Petrova Y, Davalos AJ, Costa RM, Elizondo R, Tuvim MJ, Dickey BF, Burns AR, Heidelberger R, Adachi R. Munc18-2, but not Munc18-1 or Munc18-3, controls compound and single-vesicle-regulated exocytosis in mast cells. J Biol Chem 2018; 293:7148-7159. [PMID: 29599294 DOI: 10.1074/jbc.ra118.002455] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 03/20/2018] [Indexed: 11/06/2022] Open
Abstract
Mast cells (MCs) play pivotal roles in many inflammatory conditions including infections, anaphylaxis, and asthma. MCs store immunoregulatory compounds in their large cytoplasmic granules and, upon stimulation, secrete them via regulated exocytosis. Exocytosis in many cells requires the participation of Munc18 proteins (also known as syntaxin-binding proteins), and we found that mature MCs express all three mammalian isoforms: Munc18-1, -2, and -3. To study their functions in MC effector responses and test the role of MC degranulation in anaphylaxis, we used conditional knockout (cKO) mice in which each Munc18 protein was deleted exclusively in MCs. Using recordings of plasma membrane capacitance for high-resolution analysis of exocytosis in individual MCs, we observed an almost complete absence of exocytosis in Munc18-2-deficient MCs but intact exocytosis in MCs lacking Munc18-1 or Munc18-3. Stereological analysis of EM images of stimulated MCs revealed that the deletion of Munc18-2 also abolishes the homotypic membrane fusion required for compound exocytosis. We confirmed the severe defect in regulated exocytosis in the absence of Munc18-2 by measuring the secretion of mediators stored in MC granules. Munc18-2 cKO mice had normal morphology, development, and distribution of their MCs, indicating that Munc18-2 is not essential for the migration, retention, and maturation of MC-committed progenitors. Despite that, we found that Munc18-2 cKO mice were significantly protected from anaphylaxis. In conclusion, MC-regulated exocytosis is required for the anaphylactic response, and Munc18-2 is the sole Munc18 isoform that mediates membrane fusion during MC degranulation.
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Affiliation(s)
- Berenice A Gutierrez
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030; Escuela de Ingeniería y Ciencias, Tecnologico de Monterrey, Monterrey NL 64849 México
| | - Miguel A Chavez
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030; Escuela de Medicina y Ciencias de la Salud, Tecnologico de Monterrey, Monterrey NL 64710 México
| | - Alejandro I Rodarte
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030; Escuela de Medicina y Ciencias de la Salud, Tecnologico de Monterrey, Monterrey NL 64710 México
| | - Marco A Ramos
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Andrea Dominguez
- Escuela de Medicina y Ciencias de la Salud, Tecnologico de Monterrey, Monterrey NL 64710 México
| | - Youlia Petrova
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Alfredo J Davalos
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Renan M Costa
- Graduate School of Biomedical Sciences, Houston, Texas 77030
| | - Ramon Elizondo
- Escuela de Medicina y Ciencias de la Salud, Tecnologico de Monterrey, Monterrey NL 64710 México
| | - Michael J Tuvim
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Burton F Dickey
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Alan R Burns
- College of Optometry, University of Houston, Houston, Texas 77204
| | - Ruth Heidelberger
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas Health Science Center, Houston, Texas 77030
| | - Roberto Adachi
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.
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20
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Rodarte EM, Ramos MA, Davalos AJ, Moreira DC, Moreno DS, Cardenas EI, Rodarte AI, Petrova Y, Molina S, Rendon LE, Sanchez E, Breaux K, Tortoriello A, Manllo J, Gonzalez EA, Tuvim MJ, Dickey BF, Burns AR, Heidelberger R, Adachi R. Munc13 proteins control regulated exocytosis in mast cells. J Biol Chem 2017; 293:345-358. [PMID: 29141910 DOI: 10.1074/jbc.m117.816884] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 11/02/2017] [Indexed: 01/01/2023] Open
Abstract
Mast cells (MCs) are involved in host defenses against pathogens and inflammation. Stimulated MCs release substances stored in their granules via regulated exocytosis. In other cell types, Munc13 (mammalian homolog of Caenorhabditis elegans uncoordinated gene 13) proteins play essential roles in regulated exocytosis. Here, we found that MCs express Munc13-2 and -4, and we studied their roles using global and conditional knock-out (KO) mice. In a model of systemic anaphylaxis, we found no difference between WT and Munc13-2 KO mice, but global and MC-specific Munc13-4 KO mice developed less hypothermia. This protection correlated with lower plasma histamine levels and with histological evidence of defective MC degranulation but not with changes in MC development, distribution, numbers, or morphology. In vitro assays revealed that the defective response in Munc13-4-deficient MCs was limited to regulated exocytosis, leaving other MC secretory effector responses intact. Single cell capacitance measurements in MCs from mouse mutants differing in Munc13-4 expression levels in their MCs revealed that as levels of Munc13-4 decrease, the rate of exocytosis declines first, and then the total amount of exocytosis decreases. A requirement for Munc13-2 in MC exocytosis was revealed only in the absence of Munc13-4. Electrophysiology and EM studies uncovered that the number of multigranular compound events (i.e. granule-to-granule homotypic fusion) was severely reduced in the absence of Munc13-4. We conclude that although Munc13-2 plays a minor role, Munc13-4 is essential for regulated exocytosis in MCs, and that this MC effector response is required for a full anaphylactic response.
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Affiliation(s)
- Elsa M Rodarte
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Marco A Ramos
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Alfredo J Davalos
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Daniel C Moreira
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - David S Moreno
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Eduardo I Cardenas
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Alejandro I Rodarte
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Youlia Petrova
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Sofia Molina
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Luis E Rendon
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Elizabeth Sanchez
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Keegan Breaux
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Alejandro Tortoriello
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - John Manllo
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Erika A Gonzalez
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Michael J Tuvim
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Burton F Dickey
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Alan R Burns
- College of Optometry, University of Houston, Houston, Texas 77204
| | - Ruth Heidelberger
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Roberto Adachi
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030.
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21
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Morey C, Kienle CN, Klöpper TH, Burkhardt P, Fasshauer D. Evidence for a conserved inhibitory binding mode between the membrane fusion assembly factors Munc18 and syntaxin in animals. J Biol Chem 2017; 292:20449-20460. [PMID: 29046354 DOI: 10.1074/jbc.m117.811182] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 10/10/2017] [Indexed: 12/30/2022] Open
Abstract
The membrane fusion necessary for vesicle trafficking is driven by the assembly of heterologous SNARE proteins orchestrated by the binding of Sec1/Munc18 (SM) proteins to specific syntaxin SNARE proteins. However, the precise mode of interaction between SM proteins and SNAREs is debated, as contrasting binding modes have been found for different members of the SM protein family, including the three vertebrate Munc18 isoforms. While different binding modes could be necessary, given their roles in different secretory processes in different tissues, the structural similarity of the three isoforms makes this divergence perplexing. Although the neuronal isoform Munc18a is well-established to bind tightly to both the closed conformation and the N-peptide of syntaxin 1a, thereby inhibiting SNARE complex formation, Munc18b and -c, which have a more widespread distribution, are reported to mainly interact with the N-peptide of their partnering syntaxins and are thought to instead promote SNARE complex formation. We have reinvestigated the interaction between Munc18c and syntaxin 4 (Syx4). Using isothermal titration calorimetry, we found that Munc18c, like Munc18a, binds to both the closed conformation and the N-peptide of Syx4. Furthermore, using a novel kinetic approach, we found that Munc18c, like Munc18a, slows down SNARE complex formation through high-affinity binding to syntaxin. This strongly suggests that secretory Munc18s in general control the accessibility of the bound syntaxin, probably preparing it for SNARE complex assembly.
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Affiliation(s)
- Czuee Morey
- From the Département des neurosciences fondamentales, Université de Lausanne, Rue du Bugnon 9, CH-1005 Lausanne, Switzerland
| | - C Nickias Kienle
- From the Département des neurosciences fondamentales, Université de Lausanne, Rue du Bugnon 9, CH-1005 Lausanne, Switzerland
| | - Tobias H Klöpper
- Whitehat Life Sciences Ltd., 20 Wenlock Road, N1 7GU London, United Kingdom, and
| | - Pawel Burkhardt
- the Marine Biological Association, Citadel Hill Marine Laboratory, Plymouth PL1 2PB, United Kingdom
| | - Dirk Fasshauer
- From the Département des neurosciences fondamentales, Université de Lausanne, Rue du Bugnon 9, CH-1005 Lausanne, Switzerland,
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22
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Leptin positively regulates MUC5AC production and secretion induced by interleukin-13 in human bronchial epithelial cells. Biochem Biophys Res Commun 2017; 493:979-984. [PMID: 28942146 DOI: 10.1016/j.bbrc.2017.09.106] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 09/19/2017] [Indexed: 01/16/2023]
Abstract
Mucus hypersecretion and plugging of lower respiratory tract airways due to mucus plugs have long been recognized as the leading cause of the morbidity and mortality in asthma. MUC5AC protein is a major component of airway mucus. Here, we showed that interleukin (IL)-13 induced MUC5AC production and secretion, and leptin expression in the human bronchial epithelial cell line-16 (HBE16) cells in a concentration-dependent manner. Leptin knockdown suppressed MUC5AC production and secretion induced by IL-13. We further investigated the molecular mechanism by which leptin functioned, and found that leptin regulated IL-13-induced MUC5AC production and secretion via the JAK2-STAT3 pathway. Subsequently, Munc18b, a limiting component of the exocytic machinery of airway epithelial and mast cells, was found that when knockdown, MUC5AC secretion was significantly inhibited. SABiosciences ChIP search tool identified three STAT3 binding sites with Munc18b promoter. Chromatin immunoprecipitation analysis further confirmed that Stat3 upregulated Munc18b expression by directly binding to its promoter. These data suggested that leptin promotes MUC5AC secretion via JAK2-STAT3-MUNC18b regulatory network. Taken together, our data highlight a positive feedback role and molecular mechanism for leptin in the control of MUC5AC production and secretion from airway epithelial cells stimulated by IL-13, which encourage further exploration of the therapeutic potentials of manipulating leptin in the treatment of mucus hypersecretion in chronic inflammation lung diseases.
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23
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Qin T, Liang T, Zhu D, Kang Y, Xie L, Dolai S, Sugita S, Takahashi N, Ostenson CG, Banks K, Gaisano HY. Munc18b Increases Insulin Granule Fusion, Restoring Deficient Insulin Secretion in Type-2 Diabetes Human and Goto-Kakizaki Rat Islets with Improvement in Glucose Homeostasis. EBioMedicine 2017; 16:262-274. [PMID: 28163042 PMCID: PMC5474508 DOI: 10.1016/j.ebiom.2017.01.030] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 01/09/2017] [Accepted: 01/20/2017] [Indexed: 01/22/2023] Open
Abstract
Reduced pancreatic islet levels of Munc18a/SNARE complex proteins have been postulated to contribute to the deficient glucose-stimulated insulin secretion (GSIS) in type-2 diabetes (T2D). Whereas much previous work has purported Munc18a/SNARE complex (Syntaxin-1A/VAMP-2/SNAP25) to be primarily involved in predocked secretory granule (SG) fusion, less is known about newcomer SGs that undergo minimal docking time at the plasma membrane before fusion. Newcomer SG fusion has been postulated to involve a distinct SM/SNARE complex (Munc18b/Syntaxin-3/VAMP8/SNAP25), whose levels we find also reduced in islets of T2D humans and T2D Goto-Kakizaki (GK) rats. Munc18b overexpression by adenovirus infection (Ad-Munc18b), by increasing assembly of Munc18b/SNARE complexes, mediated increased fusion of not only newcomer SGs but also predocked SGs in T2D human and GK rat islets, resulting in rescue of the deficient biphasic GSIS. Infusion of Ad-Munc18b into GK rat pancreas led to sustained improvement in glucose homeostasis. However, Munc18b overexpression in normal islets increased only newcomer SG fusion. Therefore, Munc18b could potentially be deployed in human T2D to rescue the deficient GSIS. Human T2D islet β-cells exhibit reduced fusion of predocked & newcomer secretory granules (SGs). Munc18b increases SNARE complexes involved in fusions of both newcomer & predocked SGs. Munc18b rescue of newcomer & predocked SGs increased biphasic secretion in human T2D β-cells. Munc18b rescue of T2D Goto-Kakizaki rat β-cell secretion improves glucose homeostasis.
Deficient insulin secretion from pancreatic islet β-cells in type-2 diabetes (T2D) is partly due to reduced expression of many proteins that assemble into specific complexes that mediate fusion of insulin secretory granules (SGs) with plasma membrane, termed exocytosis. We here show we can infuse a virus that contains the construct of one of the SG fusion proteins, Munc18b, into pancreatic ducts of T2D rats to reach the islets, which restored insulin secretion and improved glycemic control. Munc18b acts to promote the assembly of SG fusion complexes. This strategy could potentially be applied to treat human T2D by endoscopic infusion.
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Affiliation(s)
- Tairan Qin
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Tao Liang
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Dan Zhu
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Youhou Kang
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Li Xie
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Subhankar Dolai
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Shuzo Sugita
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Division of Fundamental Neurobiology, University Health Network, Toronto, ON M5T 2S8, Canada
| | - Noriko Takahashi
- Laboratory of Physiological Chemistry, Institute of Medicinal Chemistry, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
| | - Claes-Goran Ostenson
- Department of Molecular Medicine and Surgery, Endocrinology and Diabetology Unit, Karolinska Institutet, Karolinska University Hospital, SE-171 76 Stockholm, Sweden
| | - Kate Banks
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Division of Comparative Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Herbert Y Gaisano
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada.
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24
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SNAP23 is selectively expressed in airway secretory cells and mediates baseline and stimulated mucin secretion. Biosci Rep 2015; 35:BSR20150004. [PMID: 26182382 PMCID: PMC4613665 DOI: 10.1042/bsr20150004] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 04/14/2015] [Indexed: 11/17/2022] Open
Abstract
Airway mucin secretion is important pathophysiologically and as a model of polarized epithelial regulated exocytosis. We find the trafficking protein, SNAP23 (23-kDa paralogue of synaptosome-associated protein of 25 kDa), selectively expressed in secretory cells compared with ciliated and basal cells of airway epithelium by immunohistochemistry and FACS, suggesting that SNAP23 functions in regulated but not constitutive epithelial secretion. Heterozygous SNAP23 deletant mutant mice show spontaneous accumulation of intracellular mucin, indicating a defect in baseline secretion. However mucins are released from perfused tracheas of mutant and wild-type (WT) mice at the same rate, suggesting that increased intracellular stores balance reduced release efficiency to yield a fully compensated baseline steady state. In contrast, acute stimulated release of intracellular mucin from mutant mice is impaired whether measured by a static imaging assay 5 min after exposure to the secretagogue ATP or by kinetic analysis of mucins released from perfused tracheas during the first 10 min of ATP exposure. Together, these data indicate that increased intracellular stores cannot fully compensate for the defect in release efficiency during intense stimulation. The lungs of mutant mice develop normally and clear bacteria and instilled polystyrene beads comparable to WT mice, consistent with these functions depending on baseline secretion that is fully compensated.
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25
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Bin NR, Jung CH, Kim B, Chandrasegram P, Turlova E, Zhu D, Gaisano HY, Sun HS, Sugita S. Chaperoning of closed syntaxin-3 through Lys46 and Glu59 in domain 1 of Munc18 proteins is indispensable for mast cell exocytosis. J Cell Sci 2015; 128:1946-60. [PMID: 25795302 DOI: 10.1242/jcs.165662] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 03/16/2015] [Indexed: 11/20/2022] Open
Abstract
Understanding how Munc18 proteins govern exocytosis is crucial because mutations of this protein cause severe secretion deficits in neuronal and immune cells. Munc18-2 has indispensable roles in the degranulation of mast cell, partly by binding and chaperoning a subset of syntaxin isoforms. However, the key syntaxin that, crucially, participates in the degranulation – whose levels and intracellular localization are regulated by Munc18-2 – remains unknown. Here, we demonstrate that double knockdown of Munc18-1 and Munc-2 in mast cells results in greatly reduced degranulation accompanied with strikingly compromised expression levels and localization of syntaxin-3. This phenotype is fully rescued by wild-type Munc18 proteins but not by the K46E, E59K and K46E/E59K mutants of Munc-18 domain 1, each of which exhibits completely abolished binding to 'closed' syntaxin-3. Furthermore, knockdown of syntaxin-3 strongly impairs degranulation. Collectively, our data argue that residues Lys46 and Glu59 of Munc18 proteins are indispensable for mediating the interaction between Munc18 and closed syntaxin-3, which is essential for degranulation by chaperoning syntaxin-3. Our results also indicate that the functional contribution of these residues differs between immune cell degranulation and neuronal secretion.
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Affiliation(s)
- Na-Ryum Bin
- Division of Fundamental Neurobiology, Toronto Western Research Institute, University Health Network, Krembil Discovery Tower, Toronto, ON M5T 2S8, Canada Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Chang Hun Jung
- Division of Fundamental Neurobiology, Toronto Western Research Institute, University Health Network, Krembil Discovery Tower, Toronto, ON M5T 2S8, Canada Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Byungjin Kim
- Division of Fundamental Neurobiology, Toronto Western Research Institute, University Health Network, Krembil Discovery Tower, Toronto, ON M5T 2S8, Canada
| | - Prashanth Chandrasegram
- Division of Fundamental Neurobiology, Toronto Western Research Institute, University Health Network, Krembil Discovery Tower, Toronto, ON M5T 2S8, Canada
| | - Ekaterina Turlova
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada Department of Surgery, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Dan Zhu
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Herbert Y Gaisano
- Division of Fundamental Neurobiology, Toronto Western Research Institute, University Health Network, Krembil Discovery Tower, Toronto, ON M5T 2S8, Canada Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Hong-Shuo Sun
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada Department of Surgery, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Shuzo Sugita
- Division of Fundamental Neurobiology, Toronto Western Research Institute, University Health Network, Krembil Discovery Tower, Toronto, ON M5T 2S8, Canada Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
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26
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Gaisano HY. Here come the newcomer granules, better late than never. Trends Endocrinol Metab 2014; 25:381-8. [PMID: 24746186 DOI: 10.1016/j.tem.2014.03.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Revised: 03/06/2014] [Accepted: 03/14/2014] [Indexed: 01/03/2023]
Abstract
Exocytosis in pancreatic β-cells employs Munc18/soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes that mediate the priming and docking onto the plasma membrane (PM) of insulin granules, called predocked granules, that sit on the PM until Ca(2+) influx evokes fusion. This accounts for most of the initial peak secretory response. However, the subsequent sustained phase of glucose-stimulated insulin secretion arises from newcomer granules that have a minimal residence time at the PM before fusion. In this Opinion I discuss recent work that has begun to decipher the components of the exocytotic machinery of newcomer granules, including a Munc18/SNARE complex that is different from that mediating the fusion of predocked granules and which can potentially rescue defective insulin secretion in diabetes. These insights are applicable to other neuroendocrine cells that exhibit sustained secretion.
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Affiliation(s)
- Herbert Y Gaisano
- Department of Medicine, University of Toronto, M5S 1A8, Toronto, Canada.
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27
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Haddock BJ, Zhu Y, Doyle SP, Abdullah LH, Davis CW. Role of MARCKS in regulated secretion from mast cells and airway goblet cells. Am J Physiol Lung Cell Mol Physiol 2014; 306:L925-36. [PMID: 24705720 DOI: 10.1152/ajplung.00213.2013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
MARCKS (myristoylated alanine-rich C kinase substrate) is postulated to regulate the passage of secretory granules through cortical actin in the early phase of exocytosis. There are, however, three proposed mechanisms of action, all of which were derived from studies using synthetic peptides representing either the central phosphorylation site domain or the upstream, NH2-terminal domain: it tethers actin to the plasma membrane and/or to secretory granules, and/or it sequesters PIP2. Using MARCKS-null mice, we probed for a loss of function secretory phenotype in mast cells harvested from embryonic livers and maturated in vivo [embryonic hepatic-derived mast cells (eHMCs)]. Both wild-type (WT) and MARCKS-null eHMCs exhibited full exocytic responses upon FcϵRI receptor activation with DNP-BSA (2,4-dinitrophenyl-BSA), whether they were in suspension or adherent. The secretory responses of MARCKS-null eHMCs were consistently higher than those of WT cells, but the differences had sporadic statistical significance. The MARCKS-null cells exhibited faster secretory kinetics, however, achieving the plateau phase of the response with a t½ ∼2.5-fold faster. Hence, MARCKS appears to be a nonessential regulatory protein in mast cell exocytosis but exerts a negative modulation. Surprisingly, the MARCKS NH2-terminal peptide, MANS, which has been reported to inhibit mucin secretion from airway goblet cells (Li Y, Martin LD, Spizz G, Adler KB. J Biol Chem 276: 40982-40990, 2001), inhibited hexosaminidase secretion from WT and MARCKS-null eHMCs, leading us to reexamine its effects on mucin secretion. Results from studies using peptide inhibitors with human bronchial epithelial cells and with binding assays using purified mucins suggested that MANS inhibited the mucin binding assay, rather than the secretory response.
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Affiliation(s)
- Brookelyn J Haddock
- Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina and Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina
| | - Yunxiang Zhu
- Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina and
| | - Sean P Doyle
- Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina and
| | - Lubna H Abdullah
- Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina and
| | - C William Davis
- Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina and Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina
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28
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Brochetta C, Suzuki R, Vita F, Soranzo MR, Claver J, Madjene LC, Attout T, Vitte J, Varin-Blank N, Zabucchi G, Rivera J, Blank U. Munc18-2 and syntaxin 3 control distinct essential steps in mast cell degranulation. THE JOURNAL OF IMMUNOLOGY 2013; 192:41-51. [PMID: 24323579 DOI: 10.4049/jimmunol.1301277] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Mast cell degranulation requires N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) and mammalian uncoordinated18 (Munc18) fusion accessory proteins for membrane fusion. However, it is still unknown how their interaction supports fusion. In this study, we found that small interfering RNA-mediated silencing of the isoform Munc18-2 in mast cells inhibits cytoplasmic secretory granule (SG) release but not CCL2 chemokine secretion. Silencing of its SNARE-binding partner syntaxin 3 (STX3) also markedly inhibited degranulation, whereas combined knockdown produced an additive inhibitory effect. Strikingly, while Munc18-2 silencing impaired SG translocation, silencing of STX3 inhibited fusion, demonstrating unique roles of each protein. Immunogold studies showed that both Munc18-2 and STX3 are located on the granule surface, but also within the granule matrix and in small nocodazole-sensitive clusters of the cytoskeletal meshwork surrounding SG. After stimulation, clusters containing both effectors were detected at fusion sites. In resting cells, Munc18-2, but not STX3, interacted with tubulin. This interaction was sensitive to nocodazole treatment and decreased after stimulation. Our results indicate that Munc18-2 dynamically couples the membrane fusion machinery to the microtubule cytoskeleton and demonstrate that Munc18-2 and STX3 perform distinct, but complementary, functions to support, respectively, SG translocation and membrane fusion in mast cells.
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Affiliation(s)
- Cristiana Brochetta
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| | - Ryo Suzuki
- Laboratory of Molecular Immunogenetics, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, 20892
| | - Francesca Vita
- Department of Life Sciences Department of Physiology and Pathology, University of Trieste, Italy
| | - Maria Rosa Soranzo
- Department of Life Sciences Department of Physiology and Pathology, University of Trieste, Italy
| | - Julien Claver
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| | - Lydia Celia Madjene
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| | - Tarik Attout
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| | - Joana Vitte
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| | - Nadine Varin-Blank
- Inserm U978, 93000 Bobigny, France.,Laboratoire d'excellence "Inflamex," Unité de Formation et de Recherche Santé-Médecine-Biologie Humaine, 93000 Bobigny, France
| | - Giuliano Zabucchi
- Department of Life Sciences Department of Physiology and Pathology, University of Trieste, Italy
| | - Juan Rivera
- Laboratory of Molecular Immunogenetics, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, 20892
| | - Ulrich Blank
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
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29
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van der Sluijs P, Zibouche M, van Kerkhof P. Late steps in secretory lysosome exocytosis in cytotoxic lymphocytes. Front Immunol 2013; 4:359. [PMID: 24302923 PMCID: PMC3831147 DOI: 10.3389/fimmu.2013.00359] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 10/22/2013] [Indexed: 12/16/2022] Open
Abstract
Natural Killer cells are a subset of cytotoxic lymphocytes that are important in host defense against infections and transformed cells. They exert this function through recognition of target cells by cell surface receptors, which triggers a signaling program that results in a re-orientation of the microtubule organizing center and secretory lysosomes toward the target cell. Upon movement of secretory lysosomes to the plasma membrane and subsequent fusion, toxic proteins are released by secretory lysosomes in the immunological synapse which then enter and kill the target cell. In this minireview we highlight recent progress in our knowledge of late steps in this specialized secretion pathway and address important open questions.
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Affiliation(s)
- Peter van der Sluijs
- Department of Cell Biology, University Medical Center Utrecht , Utrecht , Netherlands
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30
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Adler KB, Tuvim MJ, Dickey BF. Regulated mucin secretion from airway epithelial cells. Front Endocrinol (Lausanne) 2013; 4:129. [PMID: 24065956 PMCID: PMC3776272 DOI: 10.3389/fendo.2013.00129] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 09/03/2013] [Indexed: 12/18/2022] Open
Abstract
Secretory epithelial cells of the proximal airways synthesize and secrete gel-forming polymeric mucins. The secreted mucins adsorb water to form mucus that is propelled by neighboring ciliated cells, providing a mobile barrier which removes inhaled particles and pathogens from the lungs. Several features of the intracellular trafficking of mucins make the airway secretory cell an interesting comparator for the cell biology of regulated exocytosis. Polymeric mucins are exceedingly large molecules (up to 3 × 10(6) Da per monomer) whose folding and initial polymerization in the ER requires the protein disulfide isomerase Agr2. In the Golgi, mucins further polymerize to form chains and possibly branched networks comprising more than 20 monomers. The large size of mucin polymers imposes constraints on their packaging into transport vesicles along the secretory pathway. Sugar side chains account for >70% of the mass of mucins, and their attachment to the protein core by O-glycosylation occurs in the Golgi. Mature polymeric mucins are stored in large secretory granules ∼1 μm in diameter. These are translocated to the apical membrane to be positioned for exocytosis by cooperative interactions among myristoylated alanine-rich C kinase substrate, cysteine string protein, heat shock protein 70, and the cytoskeleton. Mucin granules undergo exocytic fusion with the plasma membrane at a low basal rate and a high stimulated rate. Both rates are mediated by a regulated exocytic mechanism as indicated by phenotypes in both basal and stimulated secretion in mice lacking Munc13-2, a sensor of the second messengers calcium and diacylglycerol (DAG). Basal secretion is induced by low levels of activation of P2Y2 purinergic and A3 adenosine receptors by extracellular ATP released in paracrine fashion and its metabolite adenosine. Stimulated secretion is induced by high levels of the same ligands, and possibly by inflammatory mediators as well. Activated receptors are coupled to phospholipase C by Gq, resulting in the generation of DAG and of IP3 that releases calcium from apical ER. Stimulated secretion requires activation of the low affinity calcium sensor Synaptotagmin-2, while a corresponding high affinity calcium sensor in basal secretion is not known. The core exocytic machinery is comprised of the SNARE proteins VAMP8, SNAP23, and an unknown Syntaxin protein, together with the scaffolding protein Munc18b. Common and distinct features of this exocytic system in comparison to neuroendocrine cells and neurons are highlighted.
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Affiliation(s)
- Kenneth B. Adler
- Department of Molecular Biomedical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, NC, USA
| | - Michael J. Tuvim
- Department of Pulmonary Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Burton F. Dickey
- Department of Pulmonary Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- *Correspondence: Burton F. Dickey, Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Unit 1462, 1515 Holcombe Boulevard, Houston, TX 77030-4009, USA e-mail:
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