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Chibly AM, Aure MH, Patel VN, Hoffman MP. Salivary gland function, development, and regeneration. Physiol Rev 2022; 102:1495-1552. [PMID: 35343828 PMCID: PMC9126227 DOI: 10.1152/physrev.00015.2021] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 11/27/2021] [Accepted: 03/17/2022] [Indexed: 02/08/2023] Open
Abstract
Salivary glands produce and secrete saliva, which is essential for maintaining oral health and overall health. Understanding both the unique structure and physiological function of salivary glands, as well as how they are affected by disease and injury, will direct the development of therapy to repair and regenerate them. Significant recent advances, particularly in the OMICS field, increase our understanding of how salivary glands develop at the cellular, molecular, and genetic levels: the signaling pathways involved, the dynamics of progenitor cell lineages in development, homeostasis, and regeneration, and the role of the extracellular matrix microenvironment. These provide a template for cell and gene therapies as well as bioengineering approaches to repair or regenerate salivary function.
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Affiliation(s)
- Alejandro M Chibly
- Matrix and Morphogenesis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
| | - Marit H Aure
- Matrix and Morphogenesis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
| | - Vaishali N Patel
- Matrix and Morphogenesis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
| | - Matthew P Hoffman
- Matrix and Morphogenesis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
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2
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Mao QY, Xie S, Wu LL, Xiang RL, Cai ZG. Aberrantly expressed lncRNAs and mRNAs after botulinum toxin type A inhibiting salivary secretion. Oral Dis 2020; 27:1171-1183. [PMID: 32892462 DOI: 10.1111/odi.13633] [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: 05/15/2020] [Revised: 07/25/2020] [Accepted: 08/24/2020] [Indexed: 11/24/2022]
Abstract
OBJECTIVE In this study, we sought to determine the expression profiles of long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) and construct functional networks to analyze their potential roles following botulinum toxin type A (BTXA)-mediated inhibition of salivary secretion. METHODS The submandibular gland of rats in the BTXA and control groups was injected with BTXA and saline, respectively. Microarray analysis was used to identify the differentially expressed lncRNAs and mRNAs. Gene ontology and pathway analysis were performed to examine the biological functions. Functional networks, including lncRNA-mRNA co-expression and competing endogenous RNA (ceRNA) networks, were constructed to reveal the interaction between the coding and non-coding genes. RESULTS Microarray analysis revealed that 254 lncRNAs and 631 mRNAs were differentially expressed between the BTXA and control groups. Bioinformatic analysis revealed that most of the mRNAs were closely related to transmembrane transporter activity. lncRNA-mRNA co-expression and ceRNA networks were constructed, and several critical mRNA-lncRNA axes and key microRNAs related to salivary secretion were identified. CONCLUSIONS Our study identified differentially expressed lncRNAs and mRNAs through microarray analysis and explored the interactions between the coding and non-coding genes through bioinformatic analysis. These findings provide new insights into the mechanism of BTXA-mediated inhibition of salivary secretion.
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Affiliation(s)
- Qian-Ying Mao
- Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing, China
| | - Shang Xie
- Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing, China
| | - Li-Ling Wu
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing, China
| | - Ruo-Lan Xiang
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing, China
| | - Zhi-Gang Cai
- Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing, China
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3
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Ahuja M, Chung WY, Lin WY, McNally BA, Muallem S. Ca 2+ Signaling in Exocrine Cells. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a035279. [PMID: 31636079 DOI: 10.1101/cshperspect.a035279] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Calcium (Ca2+) and cyclic AMP (cAMP) signaling cross talk and synergize to stimulate the cardinal functions of exocrine cells, regulated exocytosis, and fluid and electrolyte secretion. This physiological process requires the organization of the two signaling pathways into complexes at defined cellular domains and close placement. Such domains are formed by membrane contact sites (MCS). This review discusses the basic properties of Ca2+ signaling in exocrine cells, the role of MCS in the organization of cell signaling and in cross talk and synergism between the Ca2+ and cAMP signaling pathways and, finally, the mechanism by which the Ca2+ and cAMP pathways synergize to stimulate epithelial fluid and electrolyte secretion.
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Affiliation(s)
- Malini Ahuja
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892
| | - Woo Young Chung
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892
| | - Wei-Yin Lin
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892
| | - Beth A McNally
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892
| | - Shmuel Muallem
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892
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4
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Kondo Y, Melvin JE, Catalan MA. Physiological cAMP-elevating secretagogues differentially regulate fluid and protein secretions in mouse submandibular and sublingual glands. Am J Physiol Cell Physiol 2019; 316:C690-C697. [PMID: 30840492 DOI: 10.1152/ajpcell.00421.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The mechanisms underlying the functional differences in sympathetic and parasympathetic regulation of the major salivary glands have received little attention. The acute effects of parasympathetic muscarinic (carbachol)-dependent and combined parasympathetic-dependent plus cAMP-dependent pathways on fluid secretion rates, ion composition, and protein content were assessed using a newly developed ex vivo preparation that allows the simultaneous perfusion of the mouse submandibular (SMGs) and sublingual glands (SLGs). Our results confirm that the muscarinic-dependent pathway accounts for the bulk of salivation in SMGs and SLGs, whereas costimulation with a cAMP-increasing agent (forskolin, isoproterenol, or vasoactive intestinal peptide) did not increase the flow rate. Costimulation with carbachol plus the β-adrenergic agonist isoproterenol decreased the concentration of NaCl and produced a substantial increase in the protein and Ca2+ content of SMG but not SLG saliva, consistent with a sparse sympathetic innervation of the SLGs. On the other hand, forskolin, which bypasses receptors to increase intracellular cAMP by directly activating the enzyme adenylate cyclase, enhanced the secretion of protein and Ca2+ by both the SMGs and SLGs. In contrast, isoproterenol and vasoactive intestinal peptide specifically stimulated protein secretion in SMG and SLG salivas, respectively. In summary, cAMP-dependent signaling does not play a major role in the stimulation of fluid secretion in SMGs and SLGs, whereas each cAMP-increasing agonist behaves differently in a gland-specific manner suggesting differential expression of G protein-coupled receptors in the epithelial cells of SMGs and SLGs.
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Affiliation(s)
- Yusuke Kondo
- Secretory Mechanisms and Dysfunction Section, Division of Intramural Research, National Institute of Dental and Craniofacial Research, National Institutes of Health , Bethesda, Maryland.,Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University , Fukuoka , Japan
| | - James E Melvin
- Secretory Mechanisms and Dysfunction Section, Division of Intramural Research, National Institute of Dental and Craniofacial Research, National Institutes of Health , Bethesda, Maryland
| | - Marcelo A Catalan
- Secretory Mechanisms and Dysfunction Section, Division of Intramural Research, National Institute of Dental and Craniofacial Research, National Institutes of Health , Bethesda, Maryland.,Facultad de Ciencias de la Salud, Universidad Arturo Prat , Iquique , Chile
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Pedersen AML, Sørensen CE, Proctor GB, Carpenter GH, Ekström J. Salivary secretion in health and disease. J Oral Rehabil 2018; 45:730-746. [PMID: 29878444 DOI: 10.1111/joor.12664] [Citation(s) in RCA: 217] [Impact Index Per Article: 36.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/01/2018] [Indexed: 12/16/2022]
Abstract
Saliva is a complex fluid produced by 3 pairs of major salivary glands and by hundreds of minor salivary glands. It comprises a large variety of constituents and physicochemical properties, which are important for the maintenance of oral health. Saliva not only protects the teeth and the oropharyngeal mucosa, it also facilitates articulation of speech, and is imperative for mastication and swallowing. Furthermore, saliva plays an important role in maintaining a balanced microbiota. Thus, the multiple functions provided by saliva are essential for proper protection and functioning of the body as a whole and for the general health. A large number of diseases and medications can affect salivary secretion through different mechanisms, leading to salivary gland dysfunction and associated oral problems, including xerostomia, dental caries and fungal infections. The first part of this review article provides an updated insight into our understanding of salivary gland structure, the neural regulation of salivary gland secretion, the mechanisms underlying the formation of saliva, the various functions of saliva and factors that influence salivary secretion under normal physiological conditions. The second part focuses on how various diseases and medical treatment including commonly prescribed medications and cancer therapies can affect salivary gland structure and function. We also provide a brief insight into how to diagnose salivary gland dysfunction.
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Affiliation(s)
- A M L Pedersen
- Oral Medicine, Oral Pathology & Clinical Oral Physiology, University of Copenhagen, Copenhagen, Denmark
| | - C E Sørensen
- Oral Biochemistry, Cariology & Endodontics, Department of Odontology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - G B Proctor
- Mucosal & Salivary Biology Division, King's College London Dental Institute, London, UK
| | - G H Carpenter
- Mucosal & Salivary Biology Division, King's College London Dental Institute, London, UK
| | - J Ekström
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden
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New saliva secretion model based on the expression of Na +-K + pump and K + channels in the apical membrane of parotid acinar cells. Pflugers Arch 2018; 470:613-621. [PMID: 29344775 DOI: 10.1007/s00424-018-2109-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 12/13/2017] [Accepted: 01/08/2018] [Indexed: 12/28/2022]
Abstract
The plasma membrane of parotid acinar cells is functionally divided into apical and basolateral regions. According to the current model, fluid secretion is driven by transepithelial ion gradient, which facilitates water movement by osmosis into the acinar lumen from the interstitium. The osmotic gradient is created by the apical Cl- efflux and the subsequent paracellular Na+ transport. In this model, the Na+-K+ pump is located exclusively in the basolateral membrane and has essential role in salivary secretion, since the driving force for Cl- transport via basolateral Na+-K+-2Cl- cotransport is generated by the Na+-K+ pump. In addition, the continuous electrochemical gradient for Cl- flow during acinar cell stimulation is maintained by the basolateral K+ efflux. However, using a combination of single-cell electrophysiology and Ca2+-imaging, we demonstrate that photolysis of Ca2+ close to the apical membrane of parotid acinar cells triggered significant K+ current, indicating that a substantial amount of K+ is secreted into the lumen during stimulation. Nevertheless, the K+ content of the primary saliva is relatively low, suggesting that K+ might be reabsorbed through the apical membrane. Therefore, we investigated the localization of Na+-K+ pumps in acinar cells. We show that the pumps appear evenly distributed throughout the whole plasma membrane, including the apical pole of the cell. Based on these results, a new mathematical model of salivary fluid secretion is presented, where the pump reabsorbs K+ from and secretes Na+ to the lumen, which can partially supplement the paracellular Na+ pathway.
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Knockout of the LRRC26 subunit reveals a primary role of LRRC26-containing BK channels in secretory epithelial cells. Proc Natl Acad Sci U S A 2017; 114:E3739-E3747. [PMID: 28416688 DOI: 10.1073/pnas.1703081114] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Leucine-rich-repeat-containing protein 26 (LRRC26) is the regulatory γ1 subunit of Ca2+- and voltage-dependent BK-type K+ channels. BK channels that contain LRRC26 subunits are active near normal resting potentials even without Ca2+, suggesting they play unique physiological roles, likely limited to very specific cell types and cellular functions. By using Lrrc26 KO mice with a β-gal reporter, Lrrc26 promoter activity is found in secretory epithelial cells, especially acinar epithelial cells in lacrimal and salivary glands, and also goblet and Paneth cells in intestine and colon, although absent from neurons. We establish the presence of LRRC26 protein in eight secretory tissues or tissues with significant secretory epithelium and show that LRRC26 protein coassembles with the pore-forming BK α-subunit in at least three tissues: lacrimal gland, parotid gland, and colon. In lacrimal, parotid, and submandibular gland acinar cells, LRRC26 KO shifts BK gating to be like α-subunit-only BK channels. Finally, LRRC26 KO mimics the effect of SLO1/BK KO in reducing [K+] in saliva. LRRC26-containing BK channels are competent to contribute to resting K+ efflux at normal cell membrane potentials with resting cytosolic Ca2+ concentrations and likely play a critical physiological role in supporting normal secretory function in all secretory epithelial cells.
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8
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Kshatri AS, Li Q, Yan J, Large RJ, Sergeant GP, McHale NG, Thornbury KD, Hollywood MA. Differential efficacy of GoSlo-SR compounds on BKα and BKαγ 1-4 channels. Channels (Austin) 2016; 11:66-78. [PMID: 27440457 DOI: 10.1080/19336950.2016.1213930] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Large conductance, voltage and Ca2+ activated K+ channels (BK channels) are abundantly expressed throughout the body and are important regulators of smooth muscle tone and neuronal excitability. Their dysfunction is implicated in various diseases including overactive bladder, hypertension and erectile dysfunction. Therefore, BK channel openers bear significant therapeutic potential to treat the above diseases. GoSlo-SR compounds were designed to be potent and efficacious BK channel openers. Although their structural activity relationships, activation in both BKα and BKαβ channels and the hypothetical mode of action of these compounds has been studied in detail in recent years, their effectiveness to open the BKαγ channels still remains unexplored. In this study, we have examined the efficacy of 3 closely related GoSlo-SR openers, GoSlo-SR-5-6 (SR-5-6), GoSlo-SR-5-44 (SR-5-44) and GoSlo-SR-5-130 (SR-5-130) using inside out patches on BKα channels coexpressed with 4 different LRRC (γ1-4) subunits in HEK293 cells. Our data suggests that the activation effects due to SR-5-6 were not significantly affected in the presence of γ1-4 subunits. Interestingly, the effects of more efficacious BK channel opener SR-5-44 were altered by different γ subunits. In cells expressing BKα channels, the shift in V1/2 (ΔV1/2) induced by SR-5-44 (3 μM) was -76 ± 3 mV, whereas it was significantly reduced by ∼70 % in BKαγ1 channels (ΔV1/2= -23 ± 3, p < 0.001, ANOVA). In BKαγ2 channels the ΔV1/2 was -36 ± 1 mV, which was less than that observed in BKαγ3 and BKαγ4 channels where the ΔV1/2 was -47 ± 5 mV, and -82 ± 5 mV, respectively. Additionally, the excitatory effects of a 'β specific' BK channel opener, SR-5-130 were only partially restored in the patches containing BKαγ1-4 channels. Together this data highlights that subtle modifications in GoSlo-SR structures alter their effectiveness on BK channels with accessory γ subunits and this study might provide a scaffold for the development of more tissue specific BK channel openers.
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Affiliation(s)
- Aravind S Kshatri
- a The Smooth Muscle Research Center, Dundalk Institute of Technology , Dundalk , Ireland
| | - Qin Li
- b Department of Anesthesiology and Preoperative Medicine , The University of Texas MD Anderson Cancer Center , Houston , TX , USA
| | - Jiusheng Yan
- b Department of Anesthesiology and Preoperative Medicine , The University of Texas MD Anderson Cancer Center , Houston , TX , USA
| | - Roddy J Large
- a The Smooth Muscle Research Center, Dundalk Institute of Technology , Dundalk , Ireland.,c Ion Channel Biotechnology Center, Dundalk Institute of Technology , Dundalk , Ireland
| | - Gerard P Sergeant
- a The Smooth Muscle Research Center, Dundalk Institute of Technology , Dundalk , Ireland.,c Ion Channel Biotechnology Center, Dundalk Institute of Technology , Dundalk , Ireland
| | - Noel G McHale
- a The Smooth Muscle Research Center, Dundalk Institute of Technology , Dundalk , Ireland.,c Ion Channel Biotechnology Center, Dundalk Institute of Technology , Dundalk , Ireland
| | - Keith D Thornbury
- a The Smooth Muscle Research Center, Dundalk Institute of Technology , Dundalk , Ireland.,c Ion Channel Biotechnology Center, Dundalk Institute of Technology , Dundalk , Ireland
| | - Mark A Hollywood
- a The Smooth Muscle Research Center, Dundalk Institute of Technology , Dundalk , Ireland.,c Ion Channel Biotechnology Center, Dundalk Institute of Technology , Dundalk , Ireland
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9
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Son A, Park S, Shin DM, Muallem S. Orai1 and STIM1 in ER/PM junctions: roles in pancreatic cell function and dysfunction. Am J Physiol Cell Physiol 2016; 310:C414-22. [PMID: 26739495 DOI: 10.1152/ajpcell.00349.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Membrane contact sites (MCS) are critical junctions that form between the endoplasmic reticulum (ER) and membranes of various organelles, including the plasma membrane (PM). Signaling complexes, including mediators of Ca(2+) signaling, are assembled within MCS, such as the ER/PM junction. This is most evident in polarized epithelial cells, such as pancreatic cells. Core Ca(2+) signaling proteins cluster at the apical pole, the site of inositol 1,4,5-trisphosphate-mediated Ca(2+) release and Orai1/transient receptor potential canonical-mediated store-dependent Ca(2+) entry. Recent advances have characterized the proteins that tether the membranes at MCS and the role of these proteins in modulating physiological and pathological intracellular signaling. This review discusses recent advances in the characterization of Ca(2+) signaling at ER/PM junctions and the relation of these junctions to physiological and pathological Ca(2+) signaling in pancreatic acini.
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Affiliation(s)
- Aran Son
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
| | - Seonghee Park
- Department of Physiology, School of Medicine, Ewha Womans University, Seoul, Korea
| | - Dong Min Shin
- Department of Oral Biology, BK 21 PLUS Project, Yonsei University College of Dentistry, Seoul, Korea
| | - Shmuel Muallem
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland;
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Ferreira LGB, Faria RX. TRPing on the pore phenomenon: what do we know about transient receptor potential ion channel-related pore dilation up to now? J Bioenerg Biomembr 2016; 48:1-12. [PMID: 26728159 DOI: 10.1007/s10863-015-9634-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 12/02/2015] [Indexed: 01/06/2023]
Abstract
Ion channels allow for rapid ion diffusion through the plasma membrane. In some conditions, ion channels induce changes in the critical plasma membrane permeability that permit 900-Da solutes to enter cells. This process is known as the pore phenomenon. Some transient receptor potential (TRP) channel subtypes have been highlighted such as the P2X7 receptor, plasma membrane VDAC-1 channel, and pannexin hemichannels. The TRP ion channels are considered multimodal transducers that respond to several kinds of stimuli. In addition, many TRP channel subtypes are involved in physiological and pathophysiological processes such as inflammation, pain, and cancer. The TRPA1, TRPM8, and TRPV1-4 subtypes have been shown to promote large-molecular-weight solute uptake, including impermeable fluorescent dyes, QX-314 hydrophilic lidocaine derivative, gabapentin, and antineoplastic drugs. This review discusses the current knowledge of TRP-associated pores and encourages scientists to study their features and explore them as novel therapeutic tools.
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Affiliation(s)
- L G B Ferreira
- Laboratory of Inflammation, Oswaldo Cruz Institute, FIOCRUZ, Av. Brasil, n° 4365, Manguinhos, CEP 21045-900, Rio de Janeiro, Brazil.
| | - R X Faria
- Laboratory of Cellular Communication, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Av. Brasil, n° 4365, Manguinhos, CEP 21045-900, Rio de Janeiro, Brazil
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Physiological role of aquaporin 5 in salivary glands. Pflugers Arch 2015; 468:519-39. [DOI: 10.1007/s00424-015-1749-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 10/15/2015] [Accepted: 10/16/2015] [Indexed: 12/18/2022]
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12
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Nezu A, Morita T, Tanimura A. In vitro and in vivo imaging of intracellular Ca2+ responses in salivary gland cells. J Oral Biosci 2015. [DOI: 10.1016/j.job.2015.02.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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13
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Kidokoro M, Nakamoto T, Mukaibo T, Kondo Y, Munemasa T, Imamura A, Masaki C, Hosokawa R. Na(+)-K(+)-2Cl(-) cotransporter-mediated fluid secretion increases under hypotonic osmolarity in the mouse submandibular salivary gland. Am J Physiol Renal Physiol 2014; 306:F1155-60. [PMID: 24623142 DOI: 10.1152/ajprenal.00709.2012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Water-handling epithelia are sensitive to the osmotic environment. In this study, the effects of a hypo-osmotic challenge on carbachol (CCh)-induced fluid secretion was investigated using an ex vivo submandibular gland perfusion technique and intracellular pH and Ca(2+) measurements. The osmolality of the perfusion solution was altered to examine the response of the gland to a hypotonic challenge. The flow rate was increased by 34% with a 30% hypotonic solution (225 mosmol/kgH2O), although the Ca(2+) response was unchanged. The lowering of the external Cl(-) by 50% abolished this increase in the 30% hypotonic solution. Furthermore, bumetanide, an inhibitor of the Na(+)-K(+)-2Cl(-) cotransporter (NKCC1), completely inhibited the fluid secretion increase caused by the 30% hypotonic solution, and both the total amount of fluid and the flow rate were identical to those of the isotonic solution. This finding was confirmed by measuring the NKCC1 bumetanide-dependent NH4 (+) transport; Na(+)-K(+)-2Cl(-) transport was upregulated >40% by a 30% hypotonic challenge. Therefore, the increase in CCh-induced fluid secretion in response to hypotonic conditions can be attributed, to a large extent, to the specific activation of the NKCC1.
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Affiliation(s)
- Manami Kidokoro
- Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan
| | - Tetsuji Nakamoto
- Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan
| | - Taro Mukaibo
- Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan
| | - Yusuke Kondo
- Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan
| | - Takashi Munemasa
- Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan
| | - Atsushi Imamura
- Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan
| | - Chihiro Masaki
- Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan
| | - Ryuji Hosokawa
- Department of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu City, Fukuoka, Japan
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Catalán MA, Peña-Munzenmayer G, Melvin JE. Ca²⁺-dependent K⁺ channels in exocrine salivary glands. Cell Calcium 2014; 55:362-8. [PMID: 24559652 DOI: 10.1016/j.ceca.2014.01.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Revised: 01/14/2014] [Accepted: 01/21/2014] [Indexed: 11/28/2022]
Abstract
In the last 15 years, remarkable progress has been realized in identifying the genes that encode the ion-transporting proteins involved in exocrine gland function, including salivary glands. Among these proteins, Ca(2+)-dependent K(+) channels take part in key functions including membrane potential regulation, fluid movement and K(+) secretion in exocrine glands. Two K(+) channels have been identified in exocrine salivary glands: (1) a Ca(2+)-activated K(+) channel of intermediate single channel conductance encoded by the KCNN4 gene, and (2) a voltage- and Ca(2+)-dependent K(+) channel of large single channel conductance encoded by the KCNMA1 gene. This review focuses on the physiological roles of Ca(2+)-dependent K(+) channels in exocrine salivary glands. We also discuss interesting recent findings on the regulation of Ca(2+)-dependent K(+) channels by protein-protein interactions that may significantly impact exocrine gland physiology.
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Affiliation(s)
- Marcelo A Catalán
- Secretory Mechanisms and Dysfunction Section (SMDS), National Institute of Dental and Craniofacial Research, National Institutes of Health, 10 Center Drive, Building 10/Room 5N102, Bethesda, MD 20892, USA.
| | - Gaspar Peña-Munzenmayer
- Secretory Mechanisms and Dysfunction Section (SMDS), National Institute of Dental and Craniofacial Research, National Institutes of Health, 10 Center Drive, Building 10/Room 5N102, Bethesda, MD 20892, USA
| | - James E Melvin
- Secretory Mechanisms and Dysfunction Section (SMDS), National Institute of Dental and Craniofacial Research, National Institutes of Health, 10 Center Drive, Building 10/Room 5N102, Bethesda, MD 20892, USA.
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15
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Ohana E. Transepithelial ion transport across duct cells of the salivary gland. Oral Dis 2013; 21:826-35. [DOI: 10.1111/odi.12201] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 09/24/2013] [Accepted: 09/25/2013] [Indexed: 01/16/2023]
Affiliation(s)
- E Ohana
- Epithelial Signaling and Transport Section; Molecular Physiology and Therapeutics Branch; National Institute of Dental and Craniofacial Research; National Institutes of Health; Bethesda MD USA
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16
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Genomic analyses identify distinct patterns of selection in domesticated pigs and Tibetan wild boars. Nat Genet 2013; 45:1431-8. [DOI: 10.1038/ng.2811] [Citation(s) in RCA: 341] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 10/04/2013] [Indexed: 12/28/2022]
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Park HW, Lee MG. Transepithelial bicarbonate secretion: lessons from the pancreas. Cold Spring Harb Perspect Med 2012; 2:2/10/a009571. [PMID: 23028131 DOI: 10.1101/cshperspect.a009571] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Many cystic fibrosis transmembrane conductance regulator (CFTR)-expressing epithelia secrete bicarbonate (HCO(3)(-))-containing fluids. Recent evidence suggests that defects in epithelial bicarbonate secretion are directly involved in the pathogenesis of cystic fibrosis, in particular by building up hyperviscous mucus in the ductal structures of the lung and pancreas. Pancreatic juice is one of the representative fluids that contain a very high concentration of bicarbonate among bodily fluids that are secreted from CFTR-expressing epithelia. We introduce up-to-date knowledge on the basic principles of transepithelial bicarbonate transport by showing the mechanisms involved in pancreatic bicarbonate secretion. The model of pancreatic bicarbonate secretion described herein may also apply to other exocrine epithelia. As a central regulator of bicarbonate transport at the apical membrane, CFTR plays an essential role in both direct and indirect bicarbonate secretion. The major role of CFTR in bicarbonate secretion would be variable depending on the tissue and cell type. For example, in epithelial cells that produce a low concentration of bicarbonate-containing fluid (up to 80 mm), either CFTR-dependent Cl(-)/HCO(3)(-) exchange or CFTR anion channel with low bicarbonate permeability would be sufficient to generate such fluid. However, in cells that secrete high-bicarbonate-containing fluids, a highly selective CFTR bicarbonate channel activity is required. Therefore, understanding the molecular mechanism of transepithelial bicarbonate transport and the role of CFTR in each specific epithelium will provide therapeutic strategies to recover from epithelial defects induced by hyposecretion of bicarbonate in cystic fibrosis.
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Affiliation(s)
- Hyun Woo Park
- Department of Pharmacology, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, Korea
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18
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Kajiya M, Ichimonji I, Min C, Zhu T, Jin JO, Yu Q, Almazrooa SA, Cha S, Kawai T. Muscarinic type 3 receptor induces cytoprotective signaling in salivary gland cells through epidermal growth factor receptor transactivation. Mol Pharmacol 2012; 82:115-24. [PMID: 22511543 DOI: 10.1124/mol.111.077354] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Muscarinic type 3 receptor (M3R) plays a pivotal role in the induction of glandular fluid secretions. Although M3R is often the target of autoantibodies in Sjögren's syndrome (SjS), chemical agonists for M3R are clinically used to stimulate saliva secretion in patients with SjS. Aside from its activity in promoting glandular fluid secretion, however, it is unclear whether activation of M3R is related to other biological events in SjS. This study aimed to investigate the cytoprotective effect of chemical agonist-mediated M3R activation on apoptosis induced in human salivary gland (HSG) cells. Carbachol (CCh), a muscarinic receptor-specific agonist, abrogated tumor necrosis factor α/interferon γ-induced apoptosis through pathways involving caspase 3/7, but its cytoprotective effect was decreased by a M3R antagonist, a mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (ERK) inhibitor, a phosphatidylinositol 3-kinase/Akt inhibitor, or an epidermal growth factor receptor (EGFR) inhibitor. Ligation of M3R with CCh transactivated EGFR and phosphorylated ERK and Akt, the downstream targets of EGFR. Inhibition of intracellular calcium release or protein kinase C δ, both of which are involved in the cell signaling of M3R-mediated fluid secretion, did not affect CCh-induced ERK or Akt phosphorylation. CCh stimulated Src phosphorylation and binding to EGFR. A Src inhibitor attenuated the CCh/M3R-induced cytoprotective effect and EGFR transactivation cascades. Overall, these results indicated that CCh/M3R induced transactivation of EGFR through Src activation leading to ERK and Akt phosphorylation, which in turn suppressed caspase 3/7-mediated apoptotic signals in HSG cells. This study, for the first time, proposes that CCh-mediated M3R activation can promote not only fluid secretion but also survival of salivary gland cells in the inflammatory context of SjS.
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Affiliation(s)
- Mikihito Kajiya
- Department of Immunology, Forsyth Institute, Cambridge, Massachusetts 02142, USA
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19
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Lee MG, Ohana E, Park HW, Yang D, Muallem S. Molecular mechanism of pancreatic and salivary gland fluid and HCO3 secretion. Physiol Rev 2012; 92:39-74. [PMID: 22298651 DOI: 10.1152/physrev.00011.2011] [Citation(s) in RCA: 273] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Fluid and HCO(3)(-) secretion is a vital function of all epithelia and is required for the survival of the tissue. Aberrant fluid and HCO(3)(-) secretion is associated with many epithelial diseases, such as cystic fibrosis, pancreatitis, Sjögren's syndrome, and other epithelial inflammatory and autoimmune diseases. Significant progress has been made over the last 20 years in our understanding of epithelial fluid and HCO(3)(-) secretion, in particular by secretory glands. Fluid and HCO(3)(-) secretion by secretory glands is a two-step process. Acinar cells secrete isotonic fluid in which the major salt is NaCl. Subsequently, the duct modifies the volume and electrolyte composition of the fluid to absorb the Cl(-) and secrete HCO(3)(-). The relative volume secreted by acinar and duct cells and modification of electrolyte composition of the secreted fluids varies among secretory glands to meet their physiological functions. In the pancreas, acinar cells secrete a small amount of NaCl-rich fluid, while the duct absorbs the Cl(-) and secretes HCO(3)(-) and the bulk of the fluid in the pancreatic juice. Fluid secretion appears to be driven by active HCO(3)(-) secretion. In the salivary glands, acinar cells secrete the bulk of the fluid in the saliva that is driven by active Cl(-) secretion and contains high concentrations of Na(+) and Cl(-). The salivary glands duct absorbs both the Na(+) and Cl(-) and secretes K(+) and HCO(3)(-). In this review, we focus on the molecular mechanism of fluid and HCO(3)(-) secretion by the pancreas and salivary glands, to highlight the similarities of the fundamental mechanisms of acinar and duct cell functions, and to point out the differences to meet gland-specific secretions.
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Affiliation(s)
- Min Goo Lee
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Korea
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20
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Almassy J, Begenisich T. The LRRC26 protein selectively alters the efficacy of BK channel activators. Mol Pharmacol 2011; 81:21-30. [PMID: 21984254 DOI: 10.1124/mol.111.075234] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Large conductance, Ca(2+)-activated K channel proteins are involved in a wide range of physiological activities, so there is considerable interest in the pharmacology of large conductance calcium-activated K (BK) channels. One potent activator of BK channels is mallotoxin (MTX), which produces a very large hyperpolarizing shift of the voltage gating of heterologously expressed BK channels and causes a dramatic increase in the activity of BK channels in human smooth muscle cells. However, we found that MTX shifted the steady-state activation of BK channels in native parotid acinar cells by only 6 mV. This was not because the parotid BK isoform (parSlo) is inherently insensitive to MTX as MTX shifted the activation of heterologously expressed parSlo channels by 70 mV. Even though MTX had a minimal effect on steady-state activation of parotid BK channels, it produced an approximate 2-fold speeding of the channel-gating kinetics. The BK channels in parotid acinar cells have a much more hyperpolarized voltage activation range than BK channels in most other cell types. We found that this is probably attributable to an accessory protein, LRRC26, which is expressed in parotid glands: expressed parSlo + LRRC26 channels were resistant to the actions of MTX. Another class of BK activators is the benzimidazalones that includes 1,3-dihydro-1-(2-hydroxy-5-(trifluoromethyl)phenyl)-5-(trifluoromethyl)-2H-benzimidazol-2-one (NS-1619). Although the LRRC26 accessory protein strongly inhibited the ability of MTX to activate BK channels, we found that it had only a small effect on the action of NS-1619 on BK channels. Thus, the LRRC26 BK channel accessory protein selectively alters the pharmacology of BK channels.
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Affiliation(s)
- Janos Almassy
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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21
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Roussa E. Channels and transporters in salivary glands. Cell Tissue Res 2010; 343:263-87. [PMID: 21120532 DOI: 10.1007/s00441-010-1089-y] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Accepted: 11/03/2010] [Indexed: 01/04/2023]
Abstract
According to the two-stage hypothesis, primary saliva, a NaCl-rich plasma-like isotonic fluid is secreted by salivary acinar cells and its ionic composition becomes modified in the duct system. The ducts secrete K(+) and HCO (3) (-) and reabsorb Na(+) and Cl(-) without any water movement, thus establishing a hypotonic final saliva. Salivary secretion depends on the coordinated action of several channels and transporters localized in the apical and basolateral membrane of acinar and duct cells. Early functional studies in perfused glands, followed by the molecular cloning of several transport proteins and the subsequent analysis of mutant mice, have greatly contributed to our understanding of salivary fluid and the electrolyte secretion process. With a few exceptions, most of the key channels and transporters involved in salivary secretion have now been identified and characterized. However, the picture that has emerged from all these studies is one of a complex molecular network characterized by redundancy for several transport proteins, compensatory mechanisms, and adaptive changes in health and disease. Current research is directed to the molecular interactions between the determinants and the ways in which they are regulated by extracellular signals and intracellular mediators. This review focuses on the functionally and molecularly best-characterized channels and transporters that are considered to be involved in transepithelial fluid and electrolyte transport in salivary glands.
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Affiliation(s)
- Eleni Roussa
- Anatomy and Cell Biology II, Department of Molecular Embryology, Albert Ludwigs University Freiburg, 79104, Freiburg i. Br., Germany.
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22
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Okamura K, Kato K, Uchida R, Ohkubo T, Taniguchi K, Yamazaki J. Specific expression of salivary maxi-K channel variant is augmented in diabetic mice. Arch Oral Biol 2010; 55:848-54. [PMID: 20732675 DOI: 10.1016/j.archoralbio.2010.07.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 06/04/2010] [Accepted: 07/28/2010] [Indexed: 10/19/2022]
Abstract
BACKGROUND AND OBJECTIVE A genetically diabetic mouse strain (db/db) exhibits severe obesity and a syndrome resembling human non-insulin-dependent diabetes mellitus. Our histological study of submandibular glands revealed that the size and area of the granular convoluted tubules was substantially decreased in db/db mice. We hypothesized that this structural difference reflected a specific alteration in salivary duct function. METHODS The saliva evoked by pilocarpine was used for the measurement of ion concentrations, and submandibular glands were dissected out for the immunohistochemistry and real-time PCR study. RESULTS The K(+) concentration of the salivary secretion was higher in db/db than in control m+/m+ mice, while neither saliva volume nor the concentrations of Na(+) or Cl⁻ differed between these strains. In db/db mice (vs. m+/m+ mice): quantitative PCR analysis revealed an increased mRNA expression of large-conductance Ca²(+)-activated K(+) (maxi-K) channels, immunohistochemistry revealed an increase in the luminal surface expression of the maxi-K channel protein, and a particularly interesting finding was that there was a substantial increase in the salivary tissue-specific splice variant ParSlo. CONCLUSION These results suggest that in db/db mice, the K(+) content of saliva may be elevated due to an expression of a maxi-K channel variant, which results from a modification of ductal structure. GENERAL SIGNIFICANCE Our data may shed some light on the mechanism responsible for determining the dynamics of salivary K(+) concentration increased in diabetic patients.
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Affiliation(s)
- Kazuhiko Okamura
- Department of Morphological Biology, Fukuoka Dental College, Tamura, Sawara-ku, Japan.
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Romanenko VG, Thompson J, Begenisich T. Ca2+-activated K channels in parotid acinar cells: The functional basis for the hyperpolarized activation of BK channels. Channels (Austin) 2010; 4:278-88. [PMID: 20519930 DOI: 10.4161/chan.4.4.12197] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Fluid secretion relies on a close interplay between Ca(2+)-activated Cl and K channels. Salivary acinar cells contain both large conductance, BK, and intermediate conductance, IK1, K channels. Physiological fluid secretion occurs with only modest (<500 nM) increases in intracellular Ca(2+) levels but BK channels in many cell types and in heterologous expression systems require very high concentrations for significant activation. We report here our efforts to understand this apparent contradiction. We determined the Ca(2+) dependence of IK1 and BK channels in mouse parotid acinar cells. IK1 channels activated with an apparent Ca(2+) affinity of about 350 nM and a Hill coefficient near 3. Native parotid BK channels activated at similar Ca(2+) levels unlike the BK channels in other cell types. Since the parotid BK channel is encoded by an uncommon splice variant, we examined this clone in a heterologous expression system. In contrast to the native parotid channel, activation of this expressed "parSlo" channel required very high levels of Ca(2+). In order to understand the functional basis for the special properties of the native channels, we analyzed the parotid BK channel in the context of the Horrigan-Aldrich model of BK channel gating. We found that the shifted activation of parotid BK channels resulted from a hyperpolarizing shift of the voltage dependence of voltage sensor activation and channel opening and included a large change in the coupling of these two processes.
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Affiliation(s)
- Victor G Romanenko
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
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Catalán MA, Nakamoto T, Melvin JE. The salivary gland fluid secretion mechanism. THE JOURNAL OF MEDICAL INVESTIGATION 2010; 56 Suppl:192-6. [PMID: 20224180 DOI: 10.2152/jmi.56.192] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Fluid secretion by exocrine glands requires the coordinated activity of multiple water and ion transporter and channel proteins. The molecular cloning of many of the transporter molecules involved in fluid secretion has yielded a better understanding of the fluid secretion process. Mouse salivary glands are easily accessible model systems for the study of exocrine gland secretion at the cellular and organ level. Indeed, the characterization of mice with null mutations in many of the water and ion transporter and channel genes has demonstrated the physiological roles of individual proteins. This overview will focus on recent developments in determining the molecular identification of the proteins that are involved in the fluid secretion process.
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Affiliation(s)
- Marcelo A Catalán
- Department of Pharmacology and Physiology, University of Rochester Medical Center, New York, NY 14642, USA
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25
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Thompson J, Begenisich T. Mechanistic details of BK channel inhibition by the intermediate conductance, Ca2+-activated K channel. Channels (Austin) 2009; 3:194-204. [PMID: 19574736 DOI: 10.4161/chan.3.3.9043] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Salivary gland acinar cells have two types of Ca(2+)-activated K channels required for fluid secretion: the intermediate conductance (IK1) channel and the large conductance (BK) channel. Activation of IK1 inhibits BK channels including in small, cell-free, excised membrane patches. As a first step toward understanding the mechanism underlying this interaction, we examined its voltage sensitivity. We found that the IK1-induced inhibition of BK channels was only weakly voltage dependent and not accompanied by alteration in BK gating kinetics. These actions of IK1 on BK channels are not consistent with a mechanism whereby activation of IK1 causes a shift of the BK channel's voltage dependence as occurs for many BK modulatory processes. In a search for other clues about the interaction mechanism, we noted that the N-terminus of the IK1 channel shares some chemical features with the N-terminal regions of two BK subunits known to inhibit BK activity by blocking the cytoplasmic end of the BK pore. Thus, we tested the idea that the N-terminus of IK1 channels may act similarly. We found that a peptide derived from the N-terminal region of the IK1 protein blocked BK channels. Significantly, we also found that the activation of IK1 channels competed with block by the N-terminus peptide. Thus, the activation of IK1 channels inhibits BK channels by a mechanism that involves block of the cytoplasmic pore, not an alteration in the voltage dependence of BK gating. The mediator of this cytoplasmic pore block may be the IK1 N-terminus.
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Affiliation(s)
- Jill Thompson
- Department of Pharmacology and Physiology and the Center for Oral Biology, University of Rochester Medical Center, Rochester, NY 14642, USA
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26
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Romanenko VG, Roser KS, Melvin JE, Begenisich T. The role of cell cholesterol and the cytoskeleton in the interaction between IK1 and maxi-K channels. Am J Physiol Cell Physiol 2009; 296:C878-88. [PMID: 19176762 DOI: 10.1152/ajpcell.00438.2008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Recently, we demonstrated a novel interaction between large-conductance (maxi-K or K(Ca)1.1) and intermediate-conductance (IK1 or K(Ca)3.1) Ca(2+)-activated K channels: activation of IK1 channels causes the inhibition of maxi-K activity (Thompson J and Begenisich T. J Gen Physiol 127: 159-169, 2006). Here we show that the interaction between these two channels can be regulated by the membrane cholesterol level in parotid acinar cells. Depletion of cholesterol using methyl-beta-cyclodextrin weakened, while cholesterol enrichment increased, the ability of IK1 activation to inhibit maxi-K channels. Cholesterol's stereoisomer, epicholesterol, was unable to substitute for cholesterol in the interaction between the two K channels, suggesting a specific cholesterol-protein interaction. This suggestion was strengthened by the results of experiments in which cholesterol was replaced by coprostanol and epicoprostanol. These two sterols have nearly identical effects on membrane physical properties and cholesterol-rich microdomain stability, but had very different effects on the IK1/maxi-K interaction. In addition, the IK1/maxi-K interaction was unaltered in cells lacking caveolin, the protein essential for formation and stability of caveolae. Finally, disruption of the actin cytoskeleton restored the IK1-induced maxi-K inhibition that was lost with cell cholesterol depletion, demonstrating the importance of an intact cytoskeleton for the cholesterol-dependent regulation of the IK1/maxi-K interaction.
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Affiliation(s)
- Victor G Romanenko
- Dept. of Pharmacology, Box 711, Univ. of Rochester Medical Center, Rochester, NY 14642, USA
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27
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Nakamoto T, Brown DA, Catalán MA, Gonzalez-Begne M, Romanenko VG, Melvin JE. Purinergic P2X7 receptors mediate ATP-induced saliva secretion by the mouse submandibular gland. J Biol Chem 2008; 284:4815-22. [PMID: 19097994 DOI: 10.1074/jbc.m808597200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Salivary glands express multiple isoforms of P2X and P2Y nucleotide receptors, but their in vivo physiological roles are unclear. P2 receptor agonists induced salivation in an ex vivo submandibular gland preparation. The nucleotide selectivity sequence of the secretion response was BzATP >> ATP > ADP >> UTP, and removal of external Ca(2+) dramatically suppressed the initial ATP-induced fluid secretion ( approximately 85%). Together, these results suggested that P2X receptors are the major purinergic receptor subfamily involved in the fluid secretion process. Mice with targeted disruption of the P2X(7) gene were used to evaluate the role of the P2X(7) receptor in nucleotide-evoked fluid secretion. P2X(7) receptor protein and BzATP-activated inward cation currents were absent, and importantly, purinergic receptor agonist-stimulated salivation was suppressed by more than 70% in submandibular glands from P2X(7)-null mice. Consistent with these observations, the ATP-induced increases in [Ca(2+)](i) were nearly abolished in P2X(7)(-/-) submandibular acinar and duct cells. ATP appeared to also act through the P2X(7) receptor to inhibit muscarinic-induced fluid secretion. These results demonstrate that the ATP-sensitive P2X(7) receptor regulates fluid secretion in the mouse submandibular gland.
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Affiliation(s)
- Tetsuji Nakamoto
- Center for Oral Biology, University of Rochester Medical Center, Rochester, New York 14642, USA
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28
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Heitzmann D, Warth R. Physiology and pathophysiology of potassium channels in gastrointestinal epithelia. Physiol Rev 2008; 88:1119-82. [PMID: 18626068 DOI: 10.1152/physrev.00020.2007] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Epithelial cells of the gastrointestinal tract are an important barrier between the "milieu interne" and the luminal content of the gut. They perform transport of nutrients, salts, and water, which is essential for the maintenance of body homeostasis. In these epithelia, a variety of K(+) channels are expressed, allowing adaptation to different needs. This review provides an overview of the current literature that has led to a better understanding of the multifaceted function of gastrointestinal K(+) channels, thereby shedding light on pathophysiological implications of impaired channel function. For instance, in gastric mucosa, K(+) channel function is a prerequisite for acid secretion of parietal cells. In epithelial cells of small intestine, K(+) channels provide the driving force for electrogenic transport processes across the plasma membrane, and they are involved in cell volume regulation. Fine tuning of salt and water transport and of K(+) homeostasis occurs in colonic epithelia cells, where K(+) channels are involved in secretory and reabsorptive processes. Furthermore, there is growing evidence for changes in epithelial K(+) channel expression during cell proliferation, differentiation, apoptosis, and, under pathological conditions, carcinogenesis. In the future, integrative approaches using functional and postgenomic/proteomic techniques will help us to gain comprehensive insights into the role of K(+) channels of the gastrointestinal tract.
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Affiliation(s)
- Dirk Heitzmann
- Institute of Physiology and Clinic and Policlinic for Internal Medicine II, Regensburg, Germany
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Abstract
Membrane transport proteins are integral membrane proteins and considered as potential drug targets. Activity assay of transport proteins is essential for developing drugs to target these proteins. Major issues related to activity assessment of transport proteins include availability of transporters, transport activity of transporters, and interactions between ligands and transporters. Researchers need to consider the physiological status of proteins (bound in lipid membranes or purified), availability and specificity of substrates, and the purpose of the activity assay (screening, identifying, or comparing substrates and inhibitors) before choosing appropriate assay strategies and techniques. Transport proteins bound in vesicular membranes can be assayed for transporting substrate across membranes by means of uptake assay or entrance counterflow assay. Alternatively, transport proteins can be assayed for interactions with ligands by using techniques such as isothermal titration calorimetry, nuclear magnetic resonance spectroscopy, or surface plasmon resonance. Other methods and techniques such as fluorometry, scintillation proximity assay, electrophysiological assay, or stopped-flow assay could also be used for activity assay of transport proteins. In this paper the major strategies and techniques for activity assessment of membrane transport proteins are reviewed.
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Affiliation(s)
- Hao Xie
- Department of Biological Science and Biotechnology, Institute of Science, Wuhan University of Technology, Wuhan 430070, China.
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30
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Nakamoto T, Romanenko VG, Takahashi A, Begenisich T, Melvin JE. Apical maxi-K (KCa1.1) channels mediate K+ secretion by the mouse submandibular exocrine gland. Am J Physiol Cell Physiol 2008; 294:C810-9. [PMID: 18216162 DOI: 10.1152/ajpcell.00511.2007] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The exocrine salivary glands of mammals secrete K+ by an unknown pathway that has been associated with HCO3(-) efflux. However, the present studies found that K+ secretion in the mouse submandibular gland did not require HCO3(-), demonstrating that neither K+/HCO3(-) cotransport nor K+/H+ exchange mechanisms were involved. Because HCO3(-) did not appear to participate in this process, we tested whether a K channel is required. Indeed, K+ secretion was inhibited >75% in mice with a null mutation in the maxi-K, Ca2+-activated K channel (KCa1.1) but was unchanged in mice lacking the intermediate-conductance IKCa1 channel (KCa3.1). Moreover, paxilline, a specific maxi-K channel blocker, dramatically reduced the K+ concentration in submandibular saliva. The K+ concentration of saliva is well known to be flow rate dependent, the K+ concentration increasing as the flow decreases. The flow rate dependence of K+ secretion was nearly eliminated in KCa1.1 null mice, suggesting an important role for KCa1.1 channels in this process as well. Importantly, a maxi-K-like current had not been previously detected in duct cells, the theoretical site of K+ secretion, but we found that KCa1.1 channels localized to the apical membranes of both striated and excretory duct cells, but not granular duct cells, using immunohistochemistry. Consistent with this latter observation, maxi-K currents were not detected in granular duct cells. Taken together, these results demonstrate that the secretion of K+ requires and is likely mediated by KCa1.1 potassium channels localized to the apical membranes of striated and excretory duct cells in the mouse submandibular exocrine gland.
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Affiliation(s)
- Tetsuji Nakamoto
- Center for Oral Biology, Department of Pharmacology and Physiology, Univ. of Rochester Medical Center, Box 611, 601 Elmwood Ave, Rochester, NY 14642, USA
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31
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Gin E, Crampin EJ, Brown DA, Shuttleworth TJ, Yule DI, Sneyd J. A mathematical model of fluid secretion from a parotid acinar cell. J Theor Biol 2007; 248:64-80. [PMID: 17559884 PMCID: PMC2001236 DOI: 10.1016/j.jtbi.2007.04.021] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2006] [Revised: 04/04/2007] [Accepted: 04/26/2007] [Indexed: 10/23/2022]
Abstract
Salivary fluid secretion is crucial for preventing problems such as dryness of mouth, difficulty with mastication and swallowing, as well as oral pain and dental cavities. Fluid flow is driven primarily by the transepithelial movement of chloride and sodium ions into the parotid acinus lumen. The activation of Cl(-) channels is calcium dependent, with the average elevated calcium concentration during calcium oscillations increasing the conductance of the channels, leading to an outflow of Cl(-). The accumulation of NaCl in the lumen drives water flow by osmosis. We construct a mathematical model of the calcium concentration oscillations and couple this to a model for Cl(-) efflux. We also construct a model governing fluid flow in an isolated parotid acinar cell, which includes a description of the rate of change of intracellular ion concentrations, cell volume, membrane potential and water flow rate. We find that [Ca(2+)] oscillations lead to oscillations in fluid flow, and that the rate of fluid flow is regulated by the average calcium concentration and not the frequency of the oscillations.
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Affiliation(s)
- Elan Gin
- Department of Mathematics, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
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32
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Flores CA, Melvin JE, Figueroa CD, Sepúlveda FV. Abolition of Ca2+-mediated intestinal anion secretion and increased stool dehydration in mice lacking the intermediate conductance Ca2+-dependent K+ channel Kcnn4. J Physiol 2007; 583:705-17. [PMID: 17584847 PMCID: PMC2277011 DOI: 10.1113/jphysiol.2007.134387] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Intestinal fluid secretion is driven by apical membrane, cystic fibrosis transmembrane conductance regulator (CFTR)-mediated efflux of Cl- that is concentrated in cells by basolateral Na(+)-K(+)-2Cl- cotransporters (NKCC1). An absolute requirement for Cl- efflux is the parallel activation of K(+) channels which maintain a membrane potential that sustains apical anion secretion. Both cAMP and Ca(2+) are intracellular signals for intestinal Cl- secretion. The K(+) channel involved in cAMP-dependent secretion has been identified as the KCNQ1-KCNE3 complex, but the identity of the K(+) channel driving Ca(2+)-activated Cl- secretion is controversial. We have now used a Kcnn4 null mouse to show that the intermediate conductance IK1 K(+) channel is necessary and sufficient to support Ca(2+)-dependent Cl- secretion in large and small intestine. Ussing chambers were used to monitor transepithelial potential, resistance and equivalent short-circuit current in colon and jejunum from control and Kcnn4 null mice. Na(+), K(+) and water content of stools was also measured. Distal colon and small intestinal epithelia from Kcnn4 null mice had normal cAMP-dependent Cl- secretory responses. In contrast, they completely lacked Cl- secretion in response to Ca(2+)-mobilizing agonists. Ca(2+)-activated electrogenic K(+) secretion was increased in colon epithelium of mice deficient in the IK1 channel. Na(+) and water content of stools was diminished in IK1-null animals. The use of Kcnn4 null mice has allowed us to demonstrate that IK1 K(+) channels are solely responsible for driving intestinal Ca(2+)-activated Cl- secretion. The absence of this channel leads to a marked reduction in water content in the stools, probably as a consequence of decreased electrolyte and water secretion.
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Affiliation(s)
- Carlos A Flores
- Centro de Estudios Científicos, Avenida Arturo Prat 514, Valdivia, Chile
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Romanenko VG, Nakamoto T, Srivastava A, Begenisich T, Melvin JE. Regulation of membrane potential and fluid secretion by Ca2+-activated K+ channels in mouse submandibular glands. J Physiol 2007; 581:801-17. [PMID: 17379640 PMCID: PMC2075181 DOI: 10.1113/jphysiol.2006.127498] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We have recently shown that the IK1 and maxi-K channels in parotid salivary gland acinar cells are encoded by the K(Ca)3.1 and K(Ca)1.1 genes, respectively, and in vivo stimulated parotid secretion is severely reduced in double-null mice. The current study tested whether submandibular acinar cell function also relies on these channels. We found that the K(+) currents in submandibular acinar cells have the biophysical and pharmacological footprints of IK1 and maxi-K channels and their molecular identities were confirmed by the loss of these currents in K(Ca)3.1- and K(Ca)1.1-null mice. Unexpectedly, the pilocarpine-stimulated in vivo fluid secretion from submandibular glands was essentially normal in double-null mice. This result and the possibility of side-effects of pilocarpine on the nervous system, led us to develop an ex vivo fluid secretion assay. Fluid secretion from the ex vivo assay was substantially (about 75%) reduced in animals with both K(+) channel genes ablated - strongly suggesting systemic complications with the in vivo assay. Additional experiments focusing on the membrane potential in isolated submandibular acinar cells revealed mechanistic details underlying fluid secretion in K(+) channel-deficient mice. The membrane potential of submandibular acinar cells from wild-type mice remained strongly hyperpolarized (-55 +/- 2 mV) relative to the Cl(-) equilibrium potential (-24 mV) during muscarinic stimulation. Similar hyperpolarizations were observed in K(Ca)3.1- and K(Ca)1.1-null mice (-51 +/- 3 and -48 +/- 3 mV, respectively), consistent with the normal fluid secretion produced ex vivo. In contrast, acinar cells from double K(Ca)3.1/K(Ca)1.1-null mice were only slightly hyperpolarized (-35 +/- 2 mV) also consistent with the ex vivo (but not in vivo) results. Finally, we found that the modest hyperpolarization of cells from the double-null mice was maintained by the electrogenic Na(+),K(+)-ATPase.
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Affiliation(s)
- Victor G Romanenko
- Center for Oral Biology in the Aab Institute of Biomedical Sciences and Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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Nakamoto T, Srivastava A, Romanenko VG, Ovitt CE, Perez-Cornejo P, Arreola J, Begenisich T, Melvin JE. Functional and molecular characterization of the fluid secretion mechanism in human parotid acinar cells. Am J Physiol Regul Integr Comp Physiol 2007; 292:R2380-90. [PMID: 17347411 DOI: 10.1152/ajpregu.00591.2006] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The strategies available for treating salivary gland hypofunction are limited because relatively little is known about the secretion process in humans. An initial microarray screen detected ion transport proteins generally accepted to be critically involved in salivation. We tested for the activity of some of these proteins, as well as for specific cell properties required to support fluid secretion. The resting membrane potential of human acinar cells was near -51 mV, while the intracellular [Cl-] was approximately 62 mM, about fourfold higher than expected if Cl ions were passively distributed. Active Cl- uptake mechanisms included a bumetanide-sensitive Na+ -K+ -2Cl- cotransporter and paired DIDS-sensitive Cl-/HCO3- and EIPA-sensitive Na+/H+ exchangers that correlated with expression of NKCC1, AE2, and NHE1 transcripts, respectively. Intracellular Ca2+ stimulated a niflumic acid-sensitive Cl- current with properties similar to the Ca2+ -gated Cl channel BEST2. In addition, intracellular Ca2+ stimulated a paxilline-sensitive and voltage-dependent, large-conductance K channel and a clotrimazole-sensitive, intermediate-conductance K channel, consistent with the detection of transcripts for KCNMA1 and KCNN4, respectively. Our results demonstrate that the ion transport mechanisms in human parotid glands are equivalent to those in the mouse, confirming that animal models provide valuable systems for testing therapies to prevent salivary gland dysfunction.
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Affiliation(s)
- Tetsuji Nakamoto
- The Center for Oral Biology in the Aab Institute of Biomedical Sciences, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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McManaman JL, Reyland ME, Thrower EC. Secretion and fluid transport mechanisms in the mammary gland: comparisons with the exocrine pancreas and the salivary gland. J Mammary Gland Biol Neoplasia 2006; 11:249-68. [PMID: 17136613 DOI: 10.1007/s10911-006-9031-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Milk is a complex fluid composed of proteins, sugars, lipids and minerals, in addition to a wide variety of bioactive molecules including vitamins, trace elements and growth factors. The composition of these components reflects the integrated activities of distinct synthetic, secretion and transport processes found in mammary epithelial cells, and mirrors the differing nutritional and developmental requirements of mammalian neonates. Five general pathways have been described for secretion of milk components. With the exception of lipids, which are secreted a unique pathway, milk components are thought to be secreted by adaptations of pathways found in other secretory organs. However little is known about the molecular and cellular mechanisms that constitute these pathways or the physiological mechanisms by which they are regulated. Comparisons of current secretion and transport models in the mammary gland, exocrine pancreas and salivary gland indicate that significant differences exist between the mammary gland and other exocrine organs in how proteins and lipids are packaged and secreted, and how fluid is transported.
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Affiliation(s)
- James L McManaman
- Department of Obstetrics and Gynecology, University of Colorado Health Sciences Center at Fitzsimons, Mail Stop 8309, P.O. Box 6511, Aurora, CO 80045, USA.
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