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Korkmaz FT, Traber KE. Innate immune responses in pneumonia. Pneumonia (Nathan) 2023; 15:4. [PMID: 36829255 PMCID: PMC9957695 DOI: 10.1186/s41479-023-00106-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 01/05/2023] [Indexed: 02/26/2023] Open
Abstract
The lungs are an immunologically unique environment; they are exposed to innumerable pathogens and particulate matter daily. Appropriate clearance of pathogens and response to pollutants is required to prevent overwhelming infection, while preventing tissue damage and maintaining efficient gas exchange. Broadly, the innate immune system is the collection of immediate, intrinsic immune responses to pathogen or tissue injury. In this review, we will examine the innate immune responses of the lung, with a particular focus on their role in pneumonia. We will discuss the anatomic barriers and antimicrobial proteins of the lung, pathogen and injury recognition, and the role of leukocytes (macrophages, neutrophils, and innate lymphocytes) and lung stromal cells in innate immunity. Throughout the review, we will focus on new findings in innate immunity as well as features that are unique to the lung.
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Affiliation(s)
- Filiz T Korkmaz
- Department of Medicine, Division of Immunology & Infectious Disease, University of Massachusetts, Worcester, MA, USA
- Pulmonary Center, Boston University School of Medicine, Boston, MA, USA
| | - Katrina E Traber
- Pulmonary Center, Boston University School of Medicine, Boston, MA, USA.
- Department of Medicine, Boston University School of Medicine, Boston, MA, USA.
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2
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Sheng YH, Hasnain SZ. Mucus and Mucins: The Underappreciated Host Defence System. Front Cell Infect Microbiol 2022; 12:856962. [PMID: 35774401 PMCID: PMC9238349 DOI: 10.3389/fcimb.2022.856962] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 05/12/2022] [Indexed: 12/02/2022] Open
Abstract
The mucosal surfaces that form the boundary between the external environment and the underlying tissue are protected by a mucus barrier. Mucin glycoproteins, both secreted and cell surface mucins, are the major components of the barrier. They can exclude pathogens and toxins while hosting the commensal bacteria. In this review, we highlight the dynamic function of the mucins and mucus during infection, how this mucosal barrier is regulated, and how pathogens have evolved mechanisms to evade this defence system.
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Affiliation(s)
- Yong Hua Sheng
- Immunopathology Group, Mater Research Institute−The University of Queensland, Translational Research Institute, Brisbane, Qld, Australia
| | - Sumaira Z. Hasnain
- Immunopathology Group, Mater Research Institute−The University of Queensland, Translational Research Institute, Brisbane, Qld, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Qld, Australia
- *Correspondence: Sumaira Z. Hasnain,
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3
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Lillehoj EP, Luzina IG, Atamas SP. Mammalian Neuraminidases in Immune-Mediated Diseases: Mucins and Beyond. Front Immunol 2022; 13:883079. [PMID: 35479093 PMCID: PMC9035539 DOI: 10.3389/fimmu.2022.883079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 03/21/2022] [Indexed: 12/28/2022] Open
Abstract
Mammalian neuraminidases (NEUs), also known as sialidases, are enzymes that cleave off the terminal neuraminic, or sialic, acid resides from the carbohydrate moieties of glycolipids and glycoproteins. A rapidly growing body of literature indicates that in addition to their metabolic functions, NEUs also regulate the activity of their glycoprotein targets. The simple post-translational modification of NEU protein targets-removal of the highly electronegative sialic acid-affects protein folding, alters protein interactions with their ligands, and exposes or covers proteolytic sites. Through such effects, NEUs regulate the downstream processes in which their glycoprotein targets participate. A major target of desialylation by NEUs are mucins (MUCs), and such post-translational modification contributes to regulation of disease processes. In this review, we focus on the regulatory roles of NEU-modified MUCs as coordinators of disease pathogenesis in fibrotic, inflammatory, infectious, and autoimmune diseases. Special attention is placed on the most abundant and best studied NEU1, and its recently discovered important target, mucin-1 (MUC1). The role of the NEU1 - MUC1 axis in disease pathogenesis is discussed, along with regulatory contributions from other MUCs and other pathophysiologically important NEU targets.
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Affiliation(s)
- Erik P. Lillehoj
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Irina G. Luzina
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
- Research Service, Baltimore Veterans Affairs (VA) Medical Center, Baltimore, MD, United States
| | - Sergei P. Atamas
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
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4
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Carlier FM, de Fays C, Pilette C. Epithelial Barrier Dysfunction in Chronic Respiratory Diseases. Front Physiol 2021; 12:691227. [PMID: 34248677 PMCID: PMC8264588 DOI: 10.3389/fphys.2021.691227] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 05/20/2021] [Indexed: 12/15/2022] Open
Abstract
Mucosal surfaces are lined by epithelial cells, which provide a complex and adaptive module that ensures first-line defense against external toxics, irritants, antigens, and pathogens. The underlying mechanisms of host protection encompass multiple physical, chemical, and immune pathways. In the lung, inhaled agents continually challenge the airway epithelial barrier, which is altered in chronic diseases such as chronic obstructive pulmonary disease, asthma, cystic fibrosis, or pulmonary fibrosis. In this review, we describe the epithelial barrier abnormalities that are observed in such disorders and summarize current knowledge on the mechanisms driving impaired barrier function, which could represent targets of future therapeutic approaches.
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Affiliation(s)
- François M. Carlier
- Pole of Pneumology, ENT, and Dermatology, Institute of Experimental and Clinical Research, Université catholique de Louvain, Brussels, Belgium
- Department of Pneumology and Lung Transplant, Centre Hospitalier Universitaire UCL Namur, Yvoir, Belgium
| | - Charlotte de Fays
- Pole of Pneumology, ENT, and Dermatology, Institute of Experimental and Clinical Research, Université catholique de Louvain, Brussels, Belgium
| | - Charles Pilette
- Pole of Pneumology, ENT, and Dermatology, Institute of Experimental and Clinical Research, Université catholique de Louvain, Brussels, Belgium
- Department of Pneumology, Cliniques universitaires St-Luc, Brussels, Belgium
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5
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Chatterjee M, van Putten JPM, Strijbis K. Defensive Properties of Mucin Glycoproteins during Respiratory Infections-Relevance for SARS-CoV-2. mBio 2020; 11:e02374-20. [PMID: 33184103 PMCID: PMC7663010 DOI: 10.1128/mbio.02374-20] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mucus plays a pivotal role in protecting the respiratory tract against microbial infections. It acts as a primary contact site to entrap microbes and facilitates their removal from the respiratory tract via the coordinated beating of motile cilia. The major components of airway mucus are heavily O-glycosylated mucin glycoproteins, divided into gel-forming mucins and transmembrane mucins. The gel-forming mucins MUC5AC and MUC5B are the primary structural components of airway mucus, and they enable efficient clearance of pathogens by mucociliary clearance. MUC5B is constitutively expressed in the healthy airway, whereas MUC5AC is upregulated in response to inflammatory challenge. MUC1, MUC4, and MUC16 are the three major transmembrane mucins of the respiratory tracts which prevent microbial invasion, can act as releasable decoy receptors, and activate intracellular signal transduction pathways. Pathogens have evolved virulence factors such as adhesins that facilitate interaction with specific mucins and mucin glycans, for example, terminal sialic acids. Mucin expression and glycosylation are dependent on the inflammatory state of the respiratory tract and are directly regulated by proinflammatory cytokines and microbial ligands. Gender and age also impact mucin glycosylation and expression through the female sex hormone estradiol and age-related downregulation of mucin production. Here, we discuss what is currently known about the role of respiratory mucins and their glycans during bacterial and viral infections of the airways and their relevance for the novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Understanding the impact of microbe-mucin interaction in the respiratory tract could inspire the development of novel therapies to boost mucosal defense and combat respiratory infections.
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Affiliation(s)
- Maitrayee Chatterjee
- Department Biomolecular Health Sciences, Division Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Jos P M van Putten
- Department Biomolecular Health Sciences, Division Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Karin Strijbis
- Department Biomolecular Health Sciences, Division Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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6
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Increased MUC1 plus a larger quantity and complex size for MUC5AC in the peripheral airway lumen of long-term tobacco smokers. Clin Sci (Lond) 2020; 134:1107-1125. [PMID: 32400877 DOI: 10.1042/cs20191085] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 04/16/2020] [Accepted: 05/13/2020] [Indexed: 11/17/2022]
Abstract
There is little information on mucins versus potential regulatory factors in the peripheral airway lumen of long-term smokers with (LTS+) and without (LTS-) chronic obstructive pulmonary disease (COPD). We explored these matters in bronchoalveolar lavage (BAL) samples from two study materials, both including LTS+ and LTS- with a very similar historic exposure to tobacco smoke, and healthy non-smokers (HNSs; n=4-20/group). Utilizing slot blot and immunodetection of processed (filtered and centrifuged), as well as unprocessed BAL samples from one of the materials, we compared the quantity and fraction of large complexes of mucins. All LTS displayed an enhanced (median) level of MUC5AC compared with HNS. LTS- displayed a higher level of large MUC5AC complexes than HNS while LTS+ displayed a similar trend. In all LTS, total MUC5AC correlated with blood leukocytes, BAL neutrophil elastase and net gelatinase activity. Large mucin complexes accounted for most MUC5B, without clear group differences. In all LTS, total MUC5B correlated with total MUC5AC and local bacteria. In the same groups, large MUC5B complexes correlated with serum cotinine. MUC1 was increased and correlated with BAL leukocytes in all LTS whereas MUC2 was very low and without clear group differences. Thus, the main part of MUC5AC and MUC5B is present as large complexes in the peripheral airway lumen and historic as well as current exposure to tobacco smoke emerge as potential regulatory factors, regardless of COPD per se. Bacteria, leukocytes and proteinases also constitute potential regulatory factors, of interest for future therapeutic strategies.
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7
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Kato K, Chang EH, Chen Y, Lu W, Kim MM, Niihori M, Hecker L, Kim KC. MUC1 contributes to goblet cell metaplasia and MUC5AC expression in response to cigarette smoke in vivo. Am J Physiol Lung Cell Mol Physiol 2020; 319:L82-L90. [PMID: 32401676 DOI: 10.1152/ajplung.00049.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Goblet cell metaplasia (GCM) and mucin overproduction are a hallmark of chronic rhinosinusitis (CRS) and chronic obstructive pulmonary disease (COPD). In the airways, cigarette smoke (CS) induces activation of the epidermal growth factor receptor (EGFR) leading to GCM and overexpression of the gel-forming mucin MUC5AC. Although previous studies have demonstrated that a membrane-bound mucin, MUC1, modulates the activation of CS-induced EGFR, the role of MUC1 in CS-induced GCM and mucin overproduction has not been explored. In response to CS exposure, wild-type (WT) rats displayed Muc1 translocation from the apical surface of airway epithelium to the intracellular compartment of hyperplastic intermediate cells, EGFR phosphorylation, GCM, and Muc5ac overproduction. Similarly, human CRS sinonasal tissues demonstrated hyperplasia of intermediate cells enriched with MUC1 in the intracellular compartment, which was accompanied by GCM and increased MUC5AC expression. To further evaluate the role of Muc1 in vivo, a Muc1 knockout (KO) rat (MUC in humans and Muc in animals) was developed. In contrast to WT littermates, Muc1-KO rats exhibited no activation of EGFR, and were protected from GCM and Muc5ac overproduction. Genetic knockdown of MUC1 in human lung or Muc1 knockout in primary rat airway epithelial cells led to significantly diminished EGF-induced MUC5AC production. Together, these findings suggest that MUC1-dependent EGFR activation mediates CS-induced GCM and mucin overproduction. Strategies designed to suppress MUC1-dependent EGFR activation may provide a novel therapeutic approach for treating mucin hypersecretion in CRS and COPD.
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Affiliation(s)
- Kosuke Kato
- Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Arizona College of Medicine, Tucson, Arizona
| | - Eugene H Chang
- Department of Otolaryngology, University of Arizona College of Medicine, Tucson, Arizona
| | - Yin Chen
- Department of Pharmacology and Toxicology, University of Arizona College of Pharmacy, Tucson, Arizona
| | - Wenju Lu
- Department of Medicine, National Key Laboratory of Respiratory Disease, Guangzhou Medical University, Guangzhou, China
| | - Marianne M Kim
- Department of Otolaryngology, University of Arizona College of Medicine, Tucson, Arizona
| | - Maki Niihori
- Department of Otolaryngology, University of Arizona College of Medicine, Tucson, Arizona
| | - Louise Hecker
- Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Arizona College of Medicine, Tucson, Arizona.,Southern Arizona Veterans Affairs Health Care System, Tucson, Arizona
| | - Kwang Chul Kim
- Department of Otolaryngology, University of Arizona College of Medicine, Tucson, Arizona
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8
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Bose M, Mukherjee P. Microbe-MUC1 Crosstalk in Cancer-Associated Infections. Trends Mol Med 2020; 26:324-336. [PMID: 31753595 DOI: 10.1016/j.molmed.2019.10.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 10/03/2019] [Accepted: 10/08/2019] [Indexed: 02/07/2023]
Abstract
Infection-associated cancers account for ∼20% of all malignancies. Understanding the molecular mechanisms underlying infection-associated malignancies may help in developing diagnostic biomarkers and preventative vaccines against malignancy. During infection, invading microbes interact with host mucins lining the glandular epithelial cells and trigger inflammation. MUC1 is a transmembrane mucin glycoprotein that is present on the surface of almost all epithelial cells, and is known to interact with invading microbes. This interaction can trigger pro- or anti-inflammatory responses depending on the microbe and the cell type. In this review we summarize the mechanisms of microbe and MUC1 interactions, and highlight how MUC1 plays contrasting roles in different cells. We also share perspectives on future research that may support clinical advances in infection-associated cancers.
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Affiliation(s)
- Mukulika Bose
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA.
| | - Pinku Mukherjee
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
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9
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Abstract
Pneumonia is a type of acute lower respiratory infection that is common and severe. The outcome of lower respiratory infection is determined by the degrees to which immunity is protective and inflammation is damaging. Intercellular and interorgan signaling networks coordinate these actions to fight infection and protect the tissue. Cells residing in the lung initiate and steer these responses, with additional immunity effectors recruited from the bloodstream. Responses of extrapulmonary tissues, including the liver, bone marrow, and others, are essential to resistance and resilience. Responses in the lung and extrapulmonary organs can also be counterproductive and drive acute and chronic comorbidities after respiratory infection. This review discusses cell-specific and organ-specific roles in the integrated physiological response to acute lung infection, and the mechanisms by which intercellular and interorgan signaling contribute to host defense and healthy respiratory physiology or to acute lung injury, chronic pulmonary disease, and adverse extrapulmonary sequelae. Pneumonia should no longer be perceived as simply an acute infection of the lung. Pneumonia susceptibility reflects ongoing and poorly understood chronic conditions, and pneumonia results in diverse and often persistent deleterious consequences for multiple physiological systems.
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Affiliation(s)
- Lee J Quinton
- Pulmonary Center, Boston University School of Medicine , Boston, Massachusetts
| | - Allan J Walkey
- Pulmonary Center, Boston University School of Medicine , Boston, Massachusetts
| | - Joseph P Mizgerd
- Pulmonary Center, Boston University School of Medicine , Boston, Massachusetts
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10
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Agrawal B, Gupta N, Konowalchuk JD. MUC1 Mucin: A Putative Regulatory (Checkpoint) Molecule of T Cells. Front Immunol 2018; 9:2391. [PMID: 30405607 PMCID: PMC6204366 DOI: 10.3389/fimmu.2018.02391] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 09/26/2018] [Indexed: 01/30/2023] Open
Abstract
T lymphocytes are at the center of inducing an effective adaptive immune response and maintaining homeostasis. T cell responses are initiated through interactions between antigen presenting cells (APCs) and T cells. The type and strength of signals delivered through the T cell receptor (TCR) may modulate how the cells respond. The TCR-MHC (T cell receptor-major histocompatibility complex molecules) complex dictates the specificity, whereas co-stimulatory signals induced by interaction of various accessory cell surface molecules strengthen and optimize T cell responses. Multiple immune regulatory mechanisms brought about by co-inhibitory molecules expressed on T cells play a key role in orchestrating successful and non-damaging immunity. These co-inhibitory molecules are also referred to as initiators of immune check-points or co-inhibitory pathways. Knowledge of co-inhibitory pathways associated with activated T lymphocytes has allowed a better understanding of (a) the inflammatory and anti-inflammatory processes associated with infectious diseases and autoimmune diseases, and (b) mechanisms by which tumors evade immune attack. Many of these regulatory pathways are non-redundant and function in a highly concerted manner. Targeting them has provided effective approaches in treating cancer and autoimmune diseases. For this reason, it is valuable to identify any co-inhibitory molecules that affect these pathways. MUC1 mucin (CD227) has long been known to be expressed by epithelial cells and overexpressed by a multitude of adenocarcinomas. As long ago as 1998 we made a surprising discovery that MUC1 is also expressed by activated human T cells and we provided the first evidence of the role of MUC1 as a novel T cell regulator. Subsequent studies from different laboratories, as well as ours, supported an immuno-regulatory role of MUC1 in infections, inflammation, and autoimmunity that corroborated our original findings establishing MUC1 as a novel T cell regulatory molecule. In this article, we will discuss the experimental evidence supporting MUC1 as a putative regulatory molecule or a “checkpoint molecule” of T cells with implications as a novel biomarker and therapeutic target in chronic diseases such as autoimmunity, inflammation and cancer, and possibly infections.
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Affiliation(s)
- Babita Agrawal
- Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Nancy Gupta
- Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Jeffrey D Konowalchuk
- Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
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11
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Lock JY, Carlson TL, Carrier RL. Mucus models to evaluate the diffusion of drugs and particles. Adv Drug Deliv Rev 2018; 124:34-49. [PMID: 29117512 DOI: 10.1016/j.addr.2017.11.001] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 10/12/2017] [Accepted: 11/01/2017] [Indexed: 12/22/2022]
Abstract
Mucus is a complex hydrogel that acts as a natural barrier to drug delivery at different mucosal surfaces including the respiratory, gastrointestinal, and vaginal tracts. To elucidate the role mucus plays in drug delivery, different in vitro, in vivo, and ex vivo mucus models and techniques have been utilized. Drug and drug carrier diffusion can be studied using various techniques in either isolated mucus gels or mucus present on cell cultures and tissues. The species, age, and potential disease state of the animal from which mucus is derived can all impact mucus composition and structure, and therefore impact drug and drug carrier diffusion. This review provides an overview of the techniques used to characterize drug and drug carrier diffusion, and discusses the advantages and disadvantages of the different models available to highlight the information they can afford.
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12
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MUC1: The First Respiratory Mucin with an Anti-Inflammatory Function. J Clin Med 2017; 6:jcm6120110. [PMID: 29186029 PMCID: PMC5742799 DOI: 10.3390/jcm6120110] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 11/22/2017] [Accepted: 11/24/2017] [Indexed: 02/07/2023] Open
Abstract
MUC1 is a membrane-bound mucin expressed on the apical surfaces of most mucosal epithelial cells. In normal lung epithelia, MUC1 is a binding site for Pseudomonas aeruginosa, an opportunistic human pathogen of great clinical importance. It has now been established that MUC1 also serves an anti-inflammatory role in the airways that is initiated late in the course of a bacterial infection and is mediated through inhibition of Toll-like receptor (TLR) signaling. MUC1 expression was initially shown to interfere with TLR5 signaling in response to P. aeruginosa flagellin, but has since been extended to other TLRs. These new findings point to an immunomodulatory role for MUC1 during P. aeruginosa lung infection, particularly during the resolution phase of inflammation. This review briefly summarizes the recent characterization of MUC1’s anti-inflammatory properties in both the respiratory tract and extrapulmonary tissues.
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The cell surface mucin MUC1 limits the severity of influenza A virus infection. Mucosal Immunol 2017; 10:1581-1593. [PMID: 28327617 DOI: 10.1038/mi.2017.16] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 01/26/2017] [Indexed: 02/04/2023]
Abstract
Cell surface mucin (cs-mucin) glycoproteins are constitutively expressed at the surface of respiratory epithelia where pathogens such as influenza A virus (IAV) gain entry into cells. Different members of the cs-mucin family each express a large and heavily glycosylated extracellular domain that towers above other receptors on the epithelial cell surface, a transmembrane domain that enables shedding of the extracellular domain, and a cytoplasmic tail capable of triggering signaling cascades. We hypothesized that IAV can interact with the terminal sialic acids presented on the extracellular domain of cs-mucins, resulting in modulation of infection efficiency. Utilizing human lung epithelial cells, we found that IAV associates with the cs-mucin MUC1 but not MUC13 or MUC16. Overexpression of MUC1 by epithelial cells or the addition of sialylated synthetic MUC1 constructs, reduced IAV infection in vitro. In addition, Muc1-/- mice infected with IAV exhibited enhanced morbidity and mortality, as well as greater inflammatory mediator responses compared to wild type mice. This study implicates the cs-mucin MUC1 as a critical and dynamic component of the innate host response that limits the severity of influenza and provides the foundation for exploration of MUC1 in resolving inflammatory disease.
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Pseudomonas aeruginosa increases MUC1 expression in macrophages through the TLR4-p38 pathway. Biochem Biophys Res Commun 2017; 492:231-235. [PMID: 28822766 DOI: 10.1016/j.bbrc.2017.08.056] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 08/15/2017] [Indexed: 01/05/2023]
Abstract
Alveolar macrophages (AMs) play a critical role in the clearance of Pseudomonas aeruginosa (Pa) from the airways. However, hyper-activation of macrophages can impair bacterial clearance and contribute to morbidity and mortality. MUC1 mucin is a membrane-tethered, high molecular mass glycoprotein expressed on the apical surface of mucosal epithelial cells and some hematopoietic cells, including macrophages, where it counter-regulates inflammation. We recently reported that Pa up-regulates the expression of MUC1 in primary human AMs and THP-1 macrophages, and that increased MUC1 expression in these cells prevents hyper-activation of macrophages that appears to be important for host defense against severe pathology of Pa lung infection. The aims of this study were to elucidate the mechanism by which Pa increases MUC1 expression in macrophages. The results showed that: (a) Pa stimulation of THP-1 macrophages increased MUC1 expression both at transcriptional and protein levels in a dose-dependent manner; (b) Both Pa- and LPS-induced MUC1 expression in THP-1 cells were significantly diminished by an inhibitory peptide of TLR4; and (c) LPS-stimulated MUC1 expression was diminished at both the mRNA and protein levels by an inhibitor of the p38 mitogen-activated protein kinase, but not by inhibitors of ERK1/2, JNK, or IKK. We conclude that Pa-stimulated MUC1 expression in THP-1 macrophages is regulated mainly through the TLR4-p38 signaling pathway.
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15
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Experimental Pseudomonas aeruginosa mediated rhino sinusitis in mink. Int J Pediatr Otorhinolaryngol 2017; 96:156-163. [PMID: 28302328 DOI: 10.1016/j.ijporl.2016.12.037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 12/25/2016] [Accepted: 12/26/2016] [Indexed: 12/13/2022]
Abstract
OBJECTIVES The nasal and sinus cavities in children may serve as reservoirs for microorganisms that cause recurrent and chronic lung infections. This study evaluates whether the mink can be used as an animal model for studying Pseudomonas aeruginosa mediated rhino-sinusitis since there is no suitable traditional animal model for this disease. METHODS Nasal tissue samples from infected and control mink were fixed in formalin, demineralized, and embedded in paraffin. A histological examination of sections from the infected animals revealed disintegration of the respiratory epithelium lining the nasal turbinates and swelling and edema of the submucosa. The expression of mucins and sialylated glycans was examined using immunohistochemistry. RESULTS MUC1, MUC2 and MUC5AC were upregulated in the inoculated animals as a much stronger staining was present in the respiratory epithelium in the infected animals compared to the controls. The goblet cells in the nasal epithelium from the infected mink showed high affinity to the Maackia amurensis lectin and anti-asialo GM1 indicating a high concentration of α2-3 sialic acid respectively βGalNAc1-4Galβ containing glycans in these mucin producing cells. The nasal cavity in the infected mink shows features of carbohydrate expression comparable to what has been described in the respiratory system after Pseudomonas aeruginosa infection in humans. CONCLUSION It is suggested that the mink is suitable for studying Pseudomonas aeruginosa mediated rhino-sinusitis.
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16
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Rajabi H, Kufe D. MUC1-C Oncoprotein Integrates a Program of EMT, Epigenetic Reprogramming and Immune Evasion in Human Carcinomas. Biochim Biophys Acta Rev Cancer 2017; 1868:117-122. [PMID: 28302417 DOI: 10.1016/j.bbcan.2017.03.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 02/17/2017] [Accepted: 03/11/2017] [Indexed: 01/08/2023]
Abstract
The MUC1 gene evolved in mammalian species to provide protection of epithelia. The transmembrane MUC1 C-terminal subunit (MUC1-C) signals stress to the interior of the epithelial cell and, when overexpressed as in most carcinomas, functions as an oncoprotein. MUC1-C induces the epithelial-mesenchymal transition (EMT) by activating the inflammatory NF-κB p65 pathway and, in turn, the EMT-transcriptional repressor ZEB1. Emerging evidence has indicated that MUC1-C drives a program integrating the induction of EMT with activation of stem cell traits, epigenetic reprogramming and immune evasion. This mini-review focuses on the potential importance of this MUC1-C program in cancer progression.
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Affiliation(s)
- Hasan Rajabi
- Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, United States
| | - Donald Kufe
- Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, United States.
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17
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van Putten JPM, Strijbis K. Transmembrane Mucins: Signaling Receptors at the Intersection of Inflammation and Cancer. J Innate Immun 2017; 9:281-299. [PMID: 28052300 DOI: 10.1159/000453594] [Citation(s) in RCA: 170] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Accepted: 11/19/2016] [Indexed: 12/18/2022] Open
Abstract
Mucosal surfaces line our body cavities and provide the interaction surface between commensal and pathogenic microbiota and the host. The barrier function of the mucosal layer is largely maintained by gel-forming mucin proteins that are secreted by goblet cells. In addition, mucosal epithelial cells express cell-bound mucins that have both barrier and signaling functions. The family of transmembrane mucins consists of diverse members that share a few characteristics. The highly glycosylated extracellular mucin domains inhibit invasion by pathogenic bacteria and can form a tight mesh structure that protects cells in harmful conditions. The intracellular tails of transmembrane mucins can be phosphorylated and connect to signaling pathways that regulate inflammation, cell-cell interactions, differentiation, and apoptosis. Transmembrane mucins play important roles in preventing infection at mucosal surfaces, but are also renowned for their contributions to the development, progression, and metastasis of adenocarcinomas. In general, transmembrane mucins seem to have evolved to monitor and repair damaged epithelia, but these functions can be highjacked by cancer cells to yield a survival advantage. This review presents an overview of the current knowledge of the functions of transmembrane mucins in inflammatory processes and carcinogenesis in order to better understand the diverse functions of these multifunctional proteins.
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Affiliation(s)
- Jos P M van Putten
- Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands
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Zanin M, Baviskar P, Webster R, Webby R. The Interaction between Respiratory Pathogens and Mucus. Cell Host Microbe 2016; 19:159-68. [PMID: 26867175 DOI: 10.1016/j.chom.2016.01.001] [Citation(s) in RCA: 183] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The interaction between respiratory pathogens and their hosts is complex and incompletely understood. This is particularly true when pathogens encounter the mucus layer covering the respiratory tract. The mucus layer provides an essential first host barrier to inhaled pathogens that can prevent pathogen invasion and subsequent infection. Respiratory mucus has numerous functions and interactions, both with the host and with pathogens. This review summarizes the current understanding of respiratory mucus and its interactions with the respiratory pathogens Pseudomonas aeruginosa, respiratory syncytial virus and influenza viruses, with particular focus on influenza virus transmissibility and host-range specificity. Based on current findings we propose that respiratory mucus represents an understudied host-restriction factor for influenza virus.
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Affiliation(s)
- Mark Zanin
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
| | - Pradyumna Baviskar
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Robert Webster
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Richard Webby
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
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Kato K, Uchino R, Lillehoj EP, Knox K, Lin Y, Kim KC. Membrane-Tethered MUC1 Mucin Counter-Regulates the Phagocytic Activity of Macrophages. Am J Respir Cell Mol Biol 2016; 54:515-23. [PMID: 26393683 DOI: 10.1165/rcmb.2015-0177oc] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
MUC1 (MUC in human; Muc in animals) is a transmembrane mucin glycoprotein expressed in mucosal epithelial cells and hematopoietic cells. MUC1 is involved in the resolution of inflammation during airway Pseudomonas aeruginosa (Pa) infection by suppressing Toll-like receptor signaling in airway epithelial cells. Although alveolar macrophages are recognized as critical mediators of cell-mediated immunity against microorganisms inhaled into the airways, the role of MUC1 in regulating their response is unknown. The aims of this study were to determine whether macrophages express MUC1, and, if so, whether MUC1 expression might be associated with macrophage M0/M1/M2 differentiation or phagocytic activity. Human and mouse MUC1/Muc1 expression was drastically up-regulated in classically activated (M1) macrophages compared with nonactivated (M0) and alternatively activated (M2) macrophages. M1 polarization and Pa stimulation each increased MUC1 ectodomain shedding from the macrophage surface in a TNF-α-converting enzyme-dependent manner. MUC1/Muc1 deficiency in M0 macrophages increased adhesion and phagocytosis of Pa and Escherichia coli compared with MUC1/Muc1-expressing cells, and attenuation of phagocytosis by MUC1 was augmented after polarization into M1 macrophages compared with M0 macrophages. Finally, MUC1/Muc1 deficiency in macrophages increased reactive oxygen species production and TNF-α release in response to Pa compared with MUC1/Muc1-sufficient cells. These results indicate that MUC1/Muc1 expression by macrophages is predominantly in the M1 subtype, and that MUC1/Muc1 expression in these cells decreases their phagocytic activity in an antiinflammatory manner.
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Affiliation(s)
- Kosuke Kato
- 1 Department of Otolaryngology, University of Arizona College of Medicine, Tucson, Arizona.,2 Center for Inflammation, Translational and Clinical Lung Research, Temple University School of Medicine, Philadelphia, Pennsylvania
| | - Reina Uchino
- 2 Center for Inflammation, Translational and Clinical Lung Research, Temple University School of Medicine, Philadelphia, Pennsylvania
| | - Erik P Lillehoj
- 3 Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland
| | - Kenneth Knox
- 4 Department of Medicine, University of Arizona College of Medicine, Tucson, Arizona; and
| | - Yong Lin
- 5 Molecular Biology and Lung Cancer Program, Lovelace Respiratory Research Institute, Albuquerque, New Mexico(Received in original form May 28, 2015 and in final form September 15, 2015)
| | - K Chul Kim
- 1 Department of Otolaryngology, University of Arizona College of Medicine, Tucson, Arizona.,2 Center for Inflammation, Translational and Clinical Lung Research, Temple University School of Medicine, Philadelphia, Pennsylvania
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Regulation of Airway Inflammation by G-protein Regulatory Motif Peptides of AGS3 protein. Sci Rep 2016; 6:27054. [PMID: 27270970 PMCID: PMC4895231 DOI: 10.1038/srep27054] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 05/12/2016] [Indexed: 12/21/2022] Open
Abstract
Respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), and lung infections have critical consequences on mortality and morbidity in humans. The aims of the present study were to examine the mechanisms by which CXCL12 affects MUC1 transcription and airway inflammation, which depend on activator of G-protein signaling (AGS) 3 and to identify specific molecules that suppress CXCL12-induced airway inflammation by acting on G-protein-coupled receptors. Herein, AGS3 suppresses CXCL12-mediated upregulation of MUC1 and TNFα by regulating Gαi. We found that the G-protein regulatory (GPR) motif peptide in AGS3 binds to Gαi and downregulates MUC1 expression; in contrast, this motif upregulates TNFα expression. Mutated GPR Q34A peptide increased the expression of MUC1 and TGFβ but decreased the expression of TNFα and IL-6. Moreover, CXCR4-induced dendritic extensions in 2D and 3D matrix cultures were inhibited by the GPR Q34A peptide compared with a wild-type GPR peptide. The GPR Q34A peptide also inhibited CXCL12-induced morphological changes and inflammatory cell infiltration in the mouse lung, and production of inflammatory cytokines in bronchoalveolar lavage (BAL) fluid and the lungs. Our data indicate that the GPR motif of AGS3 is critical for regulating MUC1/Muc1 expression and cytokine production in the inflammatory microenvironment.
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Shirai K, Saika S. Ocular surface mucins and local inflammation--studies in genetically modified mouse lines. BMC Ophthalmol 2015; 15 Suppl 1:154. [PMID: 26818460 PMCID: PMC4895702 DOI: 10.1186/s12886-015-0137-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Mucins locate to the apical surfaces of all wet-surfaced epithelia including ocular surface. The functions of the mucins include anti-adhesive, lubrication, water retention, allergens and pathogen barrier function. Ocular surface pathologies, i.e. dry eye syndrome or allergic conjunctivitis, are reportedly associated with alteration of expression pattern of mucin components. Recent investigations indicated anti-bacterial adhesion or anti-inflammatory effects of members of mucins in non-ocular tissues, i.e., gastrointestinal tracts or airway tissues, by using genetically modified mouse lines that lacks an expression of a mucin member. However, examination of ocular phenotypes of each of mucin gene-ablated mouse lines has not yet fully performed. Muc16-dficient mouse is associated with spontaneous subclinical inflammation in conjunctiva. The article reviews the roles of mucin members in modulation of local inflammation in mucous membrane tissues and phenotype of mouse lines with the loss of a mucin gene. Analysis of ocular surface of mucin-gene related mutant mouse lines are to be further performed.
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Affiliation(s)
- Kumi Shirai
- Department of Ophthalmology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama, 641-0012, Japan.
| | - Shizuya Saika
- Department of Ophthalmology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama, 641-0012, Japan.
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Kato K, Lillehoj EP, Kim KC. Pseudomonas aeruginosa stimulates tyrosine phosphorylation of and TLR5 association with the MUC1 cytoplasmic tail through EGFR activation. Inflamm Res 2015; 65:225-33. [PMID: 26645913 DOI: 10.1007/s00011-015-0908-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 11/06/2015] [Accepted: 11/16/2015] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND MUC1 is a membrane-tethered mucin expressed on the surface of epithelial and hematopoietic cells. Previous studies have established that MUC1 attenuates airway inflammation in response to Pseudomonas aeruginosa (Pa) through suppression of Toll-like receptor (TLR) signaling. Here, we elucidate the mechanism through which the MUC1 cytoplasmic tail (CT) inhibits TLR5 signaling in response to Pa and its flagellin in primary normal human bronchial epithelial (NHBE) cells. METHODS NHBE and human and mouse macrophages were stimulated with Pa or flagellin and transforming growth factor-α (TGF-α) and tumor necrosis factor-α (TNF-α) levels in cell culture supernatants were measured by ELISA. NHBE cells were stimulated with Pa, flagellin, or TNF-α and MUC1-CT, and epidermal growth factor receptor (EGFR) levels were measured by immunoblotting. NHBE cells were stimulated with Pa and MUC1-CT/TLR5 and MUC1-CT/EGFR association were detected by co-immunoprecipitation. RESULTS Stimulation of NHBE cells with Pa and flagellin each increased release of the EGFR ligand, TGF-α, from NHBE cells. Both stimuli also activated EGFR tyrosine phosphorylation in these same cells. By contrast, stimulation of NHBE cells with Pa failed to induce TNF-α release, whereas stimulation of human or mouse macrophages with Pa promoted TNF-α release. Stimulation of NHBE cells with recombinant TNF-α increased both MUC1 and EGFR protein levels, and stimulation of these cells with Pa enhanced MUC1-CT tyrosine phosphorylation and increased MUC1-CT/TLR5 and MUC1-CT/EGFR protein association, in an EGFR-dependent manner. CONCLUSIONS These results indicate that in response to Pa or flagellin, EGFR associates with and tyrosine phosphorylates MUC1-CT in primary NHBE cells, leading to increased MUC1-CT association with TLR5. Based on prior studies in tumor cells, increased MUC1-CT/TLR5 association in NHBE cells is predicted to competitively inhibit Pa/flagellin-stimulated TLR5 activation, reduce TLR5-dependent cell signaling, and down-regulate airway inflammation. Given that MUC1 is a universal suppressor of TLR signaling, the results from this study suggest that abnormal interactions between MUC1 and EGFR or TLRs may lead to the development of chronic inflammatory diseases. Thus, this is an important finding from the clinical point of view.
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Affiliation(s)
- Kosuke Kato
- Department of Otolaryngology, University of Arizona College of Medicine, 1656 E Mabel St, MRB-419, Tucson, AZ, 85724, USA. .,Department of Physiology and Center for Inflammation, Translational and Clinical Lung Research, Temple University School of Medicine, Philadelphia, PA, 19140, USA.
| | - Erik P Lillehoj
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, 21201, USA.
| | - Kwang Chul Kim
- Department of Otolaryngology, University of Arizona College of Medicine, 1656 E Mabel St, MRB-419, Tucson, AZ, 85724, USA. .,Department of Physiology and Center for Inflammation, Translational and Clinical Lung Research, Temple University School of Medicine, Philadelphia, PA, 19140, USA.
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Kato K, Lillehoj EP, Kim KC. MUC1 regulates epithelial inflammation and apoptosis by PolyI:C through inhibition of Toll/IL-1 receptor-domain-containing adapter-inducing IFN-β (TRIF) recruitment to Toll-like receptor 3. Am J Respir Cell Mol Biol 2014; 51:446-54. [PMID: 24693944 DOI: 10.1165/rcmb.2014-0018oc] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
MUC1/Muc1 (MUC1 in humans, Muc1 in animals) is a membrane-tethered mucin expressed by airway epithelial cells and plays an antiinflammatory role during airway bacterial infection. We previously demonstrated that MUC1/Muc1 is a negative regulator of Toll-like receptor (TLR) inflammatory signaling mediated through the myeloid differentiation primary response gene 88 (MyD88) adaptor protein. In the present study, we determined whether MUC1 regulates MyD88-independent TLR signaling mediated through the TLR3-Toll/IL-1 receptor-domain-containing adapter-inducing IFN-β (TRIF) pathway in response to poly(I:C). Compared with MUC1/Muc1-expressing controls, cells deficient in MUC1/Muc1 were more prone to poly(I:C)-induced apoptosis; had increased poly(I:C)-driven activation of caspase-3, caspase-8, IFN regulatory factor-3, and NF-κB; and displayed heightened IFN-β gene expression. MUC1 overexpression by these cells had the opposite effects. Reciprocal coimmunoprecipitation experiments established constitutive TLR3/MUC1-CT (cytoplasmic tail) protein interaction in human embryonic kidney (HEK)293T cells overexpressing the two proteins and in lung epithelial cells expressing the endogenous proteins, the latter of which was confirmed by immunofluorescence colocalization of TLR3 with MUC1-CT. Coimmunoprecipitation studies also revealed that MUC1 overexpression by HEK293T cells reduced poly(I:C)-induced TLR3/TRIF protein interaction. Finally, MUC1 overexpression had no effect on TRIF-dependent auto-activation of TLR3 signaling, suggesting that the site of action of the MUC1-CT in TLR3 signaling is not downstream of TRIF. These data indicate that MUC1-CT counter-regulates apoptotic and inflammatory responses of airway epithelial cell through constitutive association with TLR3, thereby inhibiting poly(I:C)-induced recruitment of TRIF to TLR3.
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Affiliation(s)
- Kosuke Kato
- 1 Center for Inflammation, Translational and Clinical Lung Research, Temple University School of Medicine, Philadelphia, Pennsylvania; and
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Lillehoj EP, Kato K, Lu W, Kim KC. Cellular and molecular biology of airway mucins. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 303:139-202. [PMID: 23445810 PMCID: PMC5593132 DOI: 10.1016/b978-0-12-407697-6.00004-0] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Airway mucus constitutes a thin layer of airway surface liquid with component macromolecules that covers the luminal surface of the respiratory tract. The major function of mucus is to protect the lungs through mucociliary clearance of inhaled foreign particles and noxious chemicals. Mucus is comprised of water, ions, mucin glycoproteins, and a variety of other macromolecules, some of which possess anti-microbial, anti-protease, and anti-oxidant activities. Mucins comprise the major protein component of mucus and exist as secreted and cell-associated glycoproteins. Secreted, gel-forming mucins are mainly responsible for the viscoelastic property of mucus, which is crucial for effective mucociliary clearance. Cell-associated mucins shield the epithelial surface from pathogens through their extracellular domains and regulate intracellular signaling through their cytoplasmic regions. However, neither the exact structures of mucin glycoproteins, nor the manner through which their expression is regulated, are completely understood. This chapter reviews what is currently known about the cellular and molecular properties of airway mucins.
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Affiliation(s)
- Erik P. Lillehoj
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Kosuke Kato
- Center for Inflammation, Translational and Clinical Lung Research and Department of Physiology, Temple University School of Medicine, Philadelphia, PA, USA
| | - Wenju Lu
- Guangzhou Institute of Respiratory Diseases, State Key Laboratory of Respiratory Diseases, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, PR China
| | - Kwang C. Kim
- Center for Inflammation, Translational and Clinical Lung Research and Department of Physiology, Temple University School of Medicine, Philadelphia, PA, USA
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