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Martínez-Carrasco R, Fini ME. Dynasore modulates store-operated calcium entry and mitochondrial calcium release in corneal epithelial cells. Exp Eye Res 2024; 247:110029. [PMID: 39127237 DOI: 10.1016/j.exer.2024.110029] [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: 04/02/2024] [Revised: 07/15/2024] [Accepted: 08/07/2024] [Indexed: 08/12/2024]
Abstract
Dysregulation of calcium homeostasis can precipitate a cascade of pathological events that lead to tissue damage and cell death. Dynasore is a small molecule that inhibits endocytosis by targeting classic dynamins. In a previous study, we showed that dynasore can protect human corneal epithelial cells from damage due to tert-butyl hydroperoxide (tBHP) exposure by restoring cellular calcium (Ca2+) homeostasis. Here we report results of a follow-up study aimed at identifying the source of the damaging Ca2+. Store-operated Ca2+ entry (SOCE) is a cellular mechanism to restore intracellular calcium stores from the extracellular milieu. We found that dynasore effectively blocks SOCE in cells treated with thapsigargin (TG), a small molecule that inhibits pumping of Ca2+ into the endoplasmic reticulum (ER). Unlike dynasore however, SOCE inhibitor YM-58483 did not interfere with the cytosolic Ca2+ overload caused by tBHP exposure. We also found that dynasore effectively blocks Ca2+ release from internal sources. The inefficacy of inhibitors of ER Ca2+ channels suggested that this compartment was not the source of the Ca2+ surge caused by tBHP exposure. However, using a Ca2+-measuring organelle-entrapped protein indicator (CEPIA) reporter targeted to mitochondria, we found that dynasore can block mitochondrial Ca2+ release due to tBHP exposure. Our results suggest that dynasore exerts multiple effects on cellular Ca2+ homeostasis, with inhibition of mitochondrial Ca2+ release playing a key role in protection of corneal epithelial cells against oxidative stress due to tBHP exposure.
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Affiliation(s)
- Rafael Martínez-Carrasco
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine, 800 Washington St, Boston, MA, 02111, USA
| | - M Elizabeth Fini
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine, 800 Washington St, Boston, MA, 02111, USA; Program in Genetics, Molecular & Cellular Biology, Tufts Graduate School of Biomedical Sciences, Tufts University, 136 Harrison Ave, Boston, MA, USA; Program in Pharmacology & Drug Development, Tufts Graduate School of Biomedical Sciences, 136 Harrison Ave, Tufts University, Boston, MA, USA.
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2
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Xu A, Wang Y, Luo D, Xia Y, Xue H, Yao H, Li S. By regulating the IP3R/GRP75/VDAC1 complex to restore mitochondrial dynamic balance, selenomethionine reduces lipopolysaccharide-induced neuronal apoptosis. J Cell Physiol 2024; 239:e31190. [PMID: 38219075 DOI: 10.1002/jcp.31190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 12/09/2023] [Accepted: 12/23/2023] [Indexed: 01/15/2024]
Abstract
Selenium (Se), as one of the essential trace elements, plays an anti-inflammatory, antioxidation, and immune-enhancing effect in the body. In addition, Se can also improve nervous system damage induced by various factors. Earlier studies have described the important role of mitochondrial dynamic imbalance in lipopolysaccharide (LPS)-induced nerve injury. The inositol 1,4,5-triphosphate receptor (IP3R)/glucose-regulated protein 75 (GRP75)/voltage-dependent anion channel 1 (VDAC1) complex is considered to be the key to regulating mitochondrial dynamics. However, it is not clear whether Selenomethionine (SeMet) has any influence on the IP3R/GRP75/VDAC1 complex. Therefore, the aim of this investigation was to determine whether SeMet can alleviate LPS-induced brain damage and to elucidate the function of the IP3R/GRP75/VDAC1 complex in it. We established SeMet and/or LPS exposure models in vivo and in vitro using laying hens and primary chicken nerve cells. We noticed that SeMet reversed endoplasmic reticulum stress (ERS) and the imbalance in mitochondrial dynamics and significantly prevented the occurrence of neuronal apoptosis. We made this finding by morphological observation of the brain tissue of laying hens and the detection of related genes such as ERS, the IP3R/GRP75/VDAC1 complex, calcium signal (Ca2+), mitochondrial dynamics, and apoptosis. Other than that, we also discovered that the IP3R/GRP75/VDAC1 complex was crucial in controlling Ca2+ transport between the endoplasmic reticulum and the mitochondrion when SeMet functions as a neuroprotective agent. In summary, our results revealed the specific mechanism by which SeMet alleviated LPS-induced neuronal apoptosis for the first time. As a consequence, SeMet has great potential in the treatment and prevention of neurological illnesses (like neurodegenerative diseases).
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Affiliation(s)
- Anqi Xu
- College of Veterinary Medicine, Northeast Agricultural University, Harbin, China
| | - Yixuan Wang
- College of Veterinary Medicine, Northeast Agricultural University, Harbin, China
| | - Dongliu Luo
- College of Veterinary Medicine, Northeast Agricultural University, Harbin, China
| | - Yu Xia
- College of Veterinary Medicine, Northeast Agricultural University, Harbin, China
| | - Hua Xue
- National Selenium-Rich Product Quality Supervision and Inspection Center, Enshi, People's Republic of China
| | - Haidong Yao
- Department of Biosciences and Nutrition, Karolinska Institutet, Stockholm, Sweden
| | - Shu Li
- College of Veterinary Medicine, Northeast Agricultural University, Harbin, China
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Pan J, Pany S, Martinez-Carrasco R, Fini ME. Differential Efficacy of Small Molecules Dynasore and Mdivi-1 for the Treatment of Dry Eye Epitheliopathy or as a Countermeasure for Nitrogen Mustard Exposure of the Ocular Surface. J Pharmacol Exp Ther 2024; 388:506-517. [PMID: 37442618 PMCID: PMC10801785 DOI: 10.1124/jpet.123.001697] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 05/19/2023] [Accepted: 06/05/2023] [Indexed: 07/15/2023] Open
Abstract
The ocular surface comprises the wet mucosal epithelia of the cornea and conjunctiva, the associated glands, and the overlying tear film. Epitheliopathy is the common pathologic outcome when the ocular surface is subjected to oxidative stress. Whether different stresses act via the same or different mechanisms is not known. Dynasore and dyngo-4a, small molecules developed to inhibit the GTPase activity of classic dynamins DNM1, DNM2, and DNM3, but not mdivi-1, a specific inhibitor of DNM1L, protect corneal epithelial cells exposed to the oxidant tert-butyl hydroperoxide (tBHP). Here we report that, while dyngo-4a is the more potent inhibitor of endocytosis, dynasore is the better cytoprotectant. Dynasore also protects corneal epithelial cells against exposure to high salt in an in vitro model of dysfunctional tears in dry eye. We now validate this finding in vivo, demonstrating that dynasore protects against epitheliopathy in a mouse model of dry eye. Knockdown of classic dynamin DNM2 was also cytoprotective against tBHP exposure, suggesting that dynasore's effect is at least partially on target. Like tBHP and high salt, exposure of corneal epithelial cells to nitrogen mustard upregulated the unfolded protein response and inflammatory markers, but dynasore did not protect against nitrogen mustard exposure. In contrast, mdivi-1 was cytoprotective. Interestingly, mdivi-1 did not inhibit the nitrogen mustard-induced expression of inflammatory cytokines. We conclude that exposure to tBHP or nitrogen mustard, two different oxidative stress agents, cause corneal epitheliopathy via different pathologic pathways. SIGNIFICANCE STATEMENT: Results presented in this paper, for the first time, implicate the dynamin DNM2 in ocular surface epitheliopathy. The findings suggest that dynasore could serve as a new topical treatment for dry eye epitheliopathy and that mdivi-1 could serve as a medical countermeasure for epitheliopathy due to nitrogen mustard exposure, with potentially increased efficacy when combined with anti-inflammatory agents and/or UPR modulators.
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Affiliation(s)
- Jinhong Pan
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine (J.P., S.P., R.M.-C., M.E.F.) and Program in Pharmacology and Drug Development, Tufts Graduate School of Biomedical Sciences (M.E.F.), Tufts University, Boston, Massachusetts
| | - Satyabrata Pany
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine (J.P., S.P., R.M.-C., M.E.F.) and Program in Pharmacology and Drug Development, Tufts Graduate School of Biomedical Sciences (M.E.F.), Tufts University, Boston, Massachusetts
| | - Rafael Martinez-Carrasco
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine (J.P., S.P., R.M.-C., M.E.F.) and Program in Pharmacology and Drug Development, Tufts Graduate School of Biomedical Sciences (M.E.F.), Tufts University, Boston, Massachusetts
| | - M Elizabeth Fini
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine (J.P., S.P., R.M.-C., M.E.F.) and Program in Pharmacology and Drug Development, Tufts Graduate School of Biomedical Sciences (M.E.F.), Tufts University, Boston, Massachusetts
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Song A, Phandthong R, Talbot P. Endocytosis inhibitors block SARS-CoV-2 pseudoparticle infection of mink lung epithelium. Front Microbiol 2023; 14:1258975. [PMID: 38033586 PMCID: PMC10682793 DOI: 10.3389/fmicb.2023.1258975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 10/27/2023] [Indexed: 12/02/2023] Open
Abstract
Introduction Both spill over and spill back of SARS-CoV-2 virus have been reported on mink farms in Europe and the United States. Zoonosis is a public health concern as dangerous mutated forms of the virus could be introduced into the human population through spillback. Methods The purpose of our study was to determine the SARS-CoV-2 entry mechanism using the mink lung epithelial cell line (Mv1Lu) and to block entry with drug inhibitors. Results Mv1Lu cells were susceptible to SARS-CoV-2 viral pseudoparticle infection, validating them as a suitable disease model for COVID-19. Inhibitors of TMPRSS2 and of endocytosis, two pathways of viral entry, were tested to identify those that blocked infection. TMPRSS2 inhibitors had minimal impact, which can be explained by the apparent lack of activity of this enzyme in the mink and its localization within the cell, not on the cell surface. Discussion Dyngo4a, a small molecule endocytosis inhibitor, significantly reduced infection, supporting the conclusion that the entry of the SARS-CoV-2 virus into Mv1Lu cells occurs primarily through endocytosis. The small molecule inhibitors that were effective in this study could potentially be used therapeutically to prevent SARS-CoV-2 infection in mink populations. This study will facilitate the development of therapeutics to prevent zoonotic transmission of SARS-CoV-2 variants to other animals, including humans.
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Affiliation(s)
- Ann Song
- Cell, Molecular, and Developmental Biology Graduate Program, University of California, Riverside, Riverside, CA, United States
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, CA, United States
| | - Rattapol Phandthong
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, CA, United States
| | - Prue Talbot
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, CA, United States
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Hao S, Huang H, Ma RY, Zeng X, Duan CY. Multifaceted functions of Drp1 in hypoxia/ischemia-induced mitochondrial quality imbalance: from regulatory mechanism to targeted therapeutic strategy. Mil Med Res 2023; 10:46. [PMID: 37833768 PMCID: PMC10571487 DOI: 10.1186/s40779-023-00482-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 09/21/2023] [Indexed: 10/15/2023] Open
Abstract
Hypoxic-ischemic injury is a common pathological dysfunction in clinical settings. Mitochondria are sensitive organelles that are readily damaged following ischemia and hypoxia. Dynamin-related protein 1 (Drp1) regulates mitochondrial quality and cellular functions via its oligomeric changes and multiple modifications, which plays a role in mediating the induction of multiple organ damage during hypoxic-ischemic injury. However, there is active controversy and gaps in knowledge regarding the modification, protein interaction, and functions of Drp1, which both hinder and promote development of Drp1 as a novel therapeutic target. Here, we summarize recent findings on the oligomeric changes, modification types, and protein interactions of Drp1 in various hypoxic-ischemic diseases, as well as the Drp1-mediated regulation of mitochondrial quality and cell functions following ischemia and hypoxia. Additionally, potential clinical translation prospects for targeting Drp1 are discussed. This review provides new ideas and targets for proactive interventions on multiple organ damage induced by various hypoxic-ischemic diseases.
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Affiliation(s)
- Shuai Hao
- Department of Anesthesiology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010 China
- Research Institute of General Surgery, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, 210002 China
| | - He Huang
- Department of Anesthesiology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010 China
| | - Rui-Yan Ma
- Department of Anesthesiology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010 China
- Department of Cardiovascular Surgery, Xinqiao Hospital, Army Medical University, Chongqing, 400037 China
| | - Xue Zeng
- Department of Anesthesiology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010 China
- Institute for Brain Science and Disease, Chongqing Medical University, Chongqing, 400010 China
| | - Chen-Yang Duan
- Department of Anesthesiology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010 China
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Oda JM, den Hartigh AB, Jackson SM, Tronco AR, Fink SL. The unfolded protein response components IRE1α and XBP1 promote human coronavirus infection. mBio 2023; 14:e0054023. [PMID: 37306512 PMCID: PMC10470493 DOI: 10.1128/mbio.00540-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 04/20/2023] [Indexed: 06/13/2023] Open
Abstract
The cellular processes that support human coronavirus replication and contribute to the pathogenesis of severe disease remain incompletely understood. Many viruses, including coronaviruses, cause endoplasmic reticulum (ER) stress during infection. IRE1α is a component of the cellular response to ER stress that initiates non-conventional splicing of XBP1 mRNA. Spliced XBP1 encodes a transcription factor that induces the expression of ER-related targets. Activation of the IRE1α-XBP1 pathway occurs in association with risk factors for severe human coronavirus infection. In this study, we found that the human coronaviruses HCoV-OC43 (human coronavirus OC43) and SARS-CoV-2 (severe acute respiratory syndrome coronavirus-2) both robustly activate the IRE1α-XBP1 branch of the unfolded protein response in cultured cells. Using IRE1α nuclease inhibitors and genetic knockdown of IRE1α and XBP1, we found that these host factors are required for optimal replication of both viruses. Our data suggest that IRE1α supports infection downstream of initial viral attachment and entry. In addition, we found that ER stress-inducing conditions are sufficient to enhance human coronavirus replication. Furthermore, we found markedly increased XBP1 in circulation in human patients with severe coronavirus disease 2019 (COVID-19). Together, these results demonstrate the importance of IRE1α and XBP1 for human coronavirus infection. IMPORTANCE There is a critical need to understand the cellular processes co-opted during human coronavirus replication, with an emphasis on identifying mechanisms underlying severe disease and potential therapeutic targets. Here, we demonstrate that the host proteins IRE1α and XBP1 are required for robust infection by the human coronaviruses, SARS-CoV-2 and HCoV-OC43. IRE1α and XBP1 participate in the cellular response to ER stress and are activated during conditions that predispose to severe COVID-19. We found enhanced viral replication with exogenous IRE1α activation, and evidence that this pathway is activated in humans during severe COVID-19. Together, these results demonstrate the importance of IRE1α and XBP1 for human coronavirus infection.
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Affiliation(s)
- Jessica M. Oda
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, Washington, USA
| | - Andreas B. den Hartigh
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, Washington, USA
| | - Shoen M. Jackson
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, Washington, USA
| | - Ana R. Tronco
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, Washington, USA
| | - Susan L. Fink
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, Washington, USA
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Martinez-Carrasco R, Rachagani S, Batra SK, Argüeso P, Fini ME. Roles unveiled for membrane-associated mucins at the ocular surface using a Muc4 knockout mouse model. Sci Rep 2023; 13:13558. [PMID: 37604830 PMCID: PMC10442421 DOI: 10.1038/s41598-023-40491-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 08/11/2023] [Indexed: 08/23/2023] Open
Abstract
Membrane-associated mucins (MAMs) are proposed to play critical roles at the ocular surface; however, in vivo evidence has been lacking. Here we investigate these roles by phenotyping of a Muc4 KO mouse. Histochemical analysis for expression of the beta-galactosidase transgene replacing Muc4 revealed a spiraling ribbon pattern across the corneal epithelium, consistent with centripetal cell migration from the limbus. Depletion of Muc4 compromised transcellular barrier function, as evidenced by an increase in rose bengal staining. In addition, the corneal surface was less smooth, consistent with disruption of tear film stability. While surface cells presented with well-developed microprojections, an increase in the number of cells with fewer microprojections was observed. Moreover, an increase in skin-type keratin K10 and a decrease in transcription factor Pax6 was observed, suggesting an incipient transdifferentiation. Despite this, no evidence of inflammatory dry eye disease was apparent. In addition, Muc4 had no effect on signaling by toll-like receptor Tlr4, unlike reports for MUC1 and MUC16. Results of this study provide the first in vivo evidence for the role of MAMs in transcellular barrier function, tear film stability, apical epithelial cell architecture, and epithelial mucosal differentiation at the ocular surface.
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Affiliation(s)
- Rafael Martinez-Carrasco
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine, Boston, MA, 02111, USA
| | - Satyanarayan Rachagani
- Department of Biochemistry & Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Surinder K Batra
- Department of Biochemistry & Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
- Department of Pathology, University of Nebraska Medical Center, Omaha, NE, USA
- Buffett Cancer Center, Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, USA
| | - Pablo Argüeso
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine, Boston, MA, 02111, USA
- Program in Immunology, Tufts Graduate School of Biomedical Sciences, Tufts University, Boston, MA, USA
- Program in Genetics, Molecular & Cellular Biology, Tufts Graduate School of Biomedical Sciences, Tufts University, Boston, MA, USA
- Program in Pharmacology & Drug Development, Tufts Graduate School of Biomedical Sciences, Tufts University, Boston, MA, USA
| | - M Elizabeth Fini
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine, Boston, MA, 02111, USA.
- Program in Genetics, Molecular & Cellular Biology, Tufts Graduate School of Biomedical Sciences, Tufts University, Boston, MA, USA.
- Program in Pharmacology & Drug Development, Tufts Graduate School of Biomedical Sciences, Tufts University, Boston, MA, USA.
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Martinez-Carrasco R, Fini ME. Dynasore Protects Corneal Epithelial Cells Subjected to Hyperosmolar Stress in an In Vitro Model of Dry Eye Epitheliopathy. Int J Mol Sci 2023; 24:ijms24054754. [PMID: 36902183 PMCID: PMC10003680 DOI: 10.3390/ijms24054754] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 02/19/2023] [Accepted: 02/20/2023] [Indexed: 03/06/2023] Open
Abstract
Epitheliopathy at the ocular surface is a defining sign of dry eye disease, a common disorder that affects 10% to 30% of the world's population. Hyperosmolarity of the tear film is one of the main drivers of pathology, with subsequent endoplasmic reticulum (ER) stress, the resulting unfolded protein response (UPR), and caspase-3 activation implicated in the pathway to programmed cell death. Dynasore, is a small molecule inhibitor of dynamin GTPases that has shown therapeutic effects in a variety of disease models involving oxidative stress. Recently we showed that dynasore protects corneal epithelial cells exposed to the oxidant tBHP, by selective reduction in expression of CHOP, a marker of the UPR PERK branch. Here we investigated the capacity of dynasore to protect corneal epithelial cells subjected to hyperosmotic stress (HOS). Similar to dynasore's capacity to protect against tBHP exposure, dynasore inhibits the cell death pathway triggered by HOS, protecting against ER stress and maintaining a homeostatic level of UPR activity. However, unlike with tBHP exposure, UPR activation due to HOS is independent of PERK and mostly driven by the UPR IRE1 branch. Our results demonstrate the role of the UPR in HOS-driven damage, and the potential of dynasore as a treatment to prevent dry eye epitheliopathy.
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Affiliation(s)
- Rafael Martinez-Carrasco
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine, Boston, MA 02111, USA
- Correspondence: (R.M.-C.); (M.E.F.)
| | - M. Elizabeth Fini
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine, Boston, MA 02111, USA
- Graduate School of Biomedical Sciences, Tufts University, Boston, MA 02111, USA
- Correspondence: (R.M.-C.); (M.E.F.)
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Martinez-Carrasco R, Argüeso P, Fini ME. Membrane-associated mucins of the human ocular surface in health and disease. Ocul Surf 2021; 21:313-330. [PMID: 33775913 PMCID: PMC8328898 DOI: 10.1016/j.jtos.2021.03.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 03/02/2021] [Accepted: 03/08/2021] [Indexed: 02/06/2023]
Abstract
Mucins are a family of high molecular weight, heavily-glycosylated proteins produced by wet epithelial tissues, including the ocular surface epithelia. Densely-packed O-linked glycan chains added post-translationally confer the biophysical properties of hydration, lubrication, anti-adhesion and repulsion. Membrane-associated mucins (MAMs) are the distinguishing components of the mucosal glycocalyx. At the ocular surface, MAMs maintain wetness, lubricate the blink, stabilize the tear film, and create a physical barrier to the outside world. In addition, it is increasingly appreciated that MAMs function as cell surface receptors that transduce information from the outside to the inside of the cell. Recently, our team published a comprehensive review/perspectives article for molecular scientists on ocular surface MAMs, including previously unpublished data and analyses on two new genes MUC21 and MUC22, as well as new MAM functions and biological roles, comparing human and mouse (PMID: 31493487). The current article is a refocus for the audience of The Ocular Surface. First, we update the gene and protein information in a more concise form, and include a new section on glycosylation. Next, we discuss biological roles, with some new sections and further updating from our previous review. Finally, we provide a new chapter on MAM involvement in ocular surface disease. We end this with discussion of an emerging mechanism responsible for damage to the epithelia and their mucosal glycocalyces: the unfolded protein response (UPR). The UPR offers a novel target for therapeutic intervention.
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Affiliation(s)
- Rafael Martinez-Carrasco
- Department of Ophthalmology, Tufts University School of Medicine at New England Eye Center, Tufts Medical Center, Boston, MA, 02111, USA.
| | - Pablo Argüeso
- Department of Ophthalmology, Harvard Medical School at Schepens Eye Research Institute of Mass, Eye and Ear, Boston, MA, 02114, USA.
| | - M Elizabeth Fini
- Department of Ophthalmology, Tufts University School of Medicine at New England Eye Center, Tufts Medical Center: Program in Pharmacology & Drug Development, Graduate School of Biomedical Sciences, Tufts University, Boston, MA, O2111, USA.
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