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Wahl AM, Takano T, Su S, Warner BM, Perez P, Sneyd J, Yule DI. Structural and functional analysis of salivary intercalated duct cells reveals a secretory phenotype. J Physiol 2023; 601:4539-4556. [PMID: 37724716 PMCID: PMC10591963 DOI: 10.1113/jp285104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 08/30/2023] [Indexed: 09/21/2023] Open
Abstract
Currently, all salivary ducts (intercalated, striated and collecting) are assumed to function broadly in a similar manner, reclaiming ions that were secreted by the secretory acinar cells while preserving fluid volume and delivering saliva to the oral cavity. Nevertheless, there has been minimal investigation into the structural and functional differences between distinct types of salivary duct cells. Therefore, in this study, the expression profile of proteins involved in stimulus-secretion coupling, as well as the function of the intercalated duct (ID) and striated duct cells, was examined. Particular focus was placed on defining differences between distinct duct cell populations. To accomplish this, immunohistochemistry and in situ hybridization were utilized to examine the localization and expression of proteins involved in reabsorption and secretion of ions and fluid. Further, in vivo calcium imaging was employed to investigate cellular function. Based on the protein expression profile and functional data, marked differences between the IDs and striated ducts were observed. Specifically, the ID cells express proteins native to the secretory acinar cells while lacking proteins specifically expressed in the striated ducts. Further, the ID and striated duct cells display different calcium signalling characteristics, with the IDs responding to a neural stimulus in a manner similar to the acinar cells. Overall, our data suggest that the IDs have a distinct role in the secretory process, separate from the reabsorptive striated ducts. Instead, based on our evidence, the IDs express proteins found in secretory cells, generate calcium signals in a manner similar to acinar cells, and, therefore, are likely secretory cells. KEY POINTS: Current studies examining salivary intercalated duct cells are limited, with minimal documentation of the ion transport machinery and the overall role of the cells in fluid generation. Salivary intercalated duct cells are presumed to function in the same manner as other duct cells, reclaiming ions, maintaining fluid volume and delivering the final saliva to the oral cavity. Here we systematically examine the structure and function of the salivary intercalated duct cells using immunohistochemistry, in situ hybridization and by monitoring in vivo Ca2+ dynamics. Structural data revealed that the intercalated duct cells lack proteins vital for reabsorption and express proteins necessary for secretion. Ca2+ dynamics in the intercalated duct cells were consistent with those observed in secretory cells and resulted from GPCR-mediated IP3 production.
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Affiliation(s)
- Amanda M Wahl
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY, USA
| | - Takahiro Takano
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY, USA
| | - Shan Su
- Department of Mathematics, University of Auckland, Auckland, New Zealand
| | | | - Paola Perez
- Salivary Disorders Unit, NIDCR, Bethesda, MD, USA
| | - James Sneyd
- Department of Mathematics, University of Auckland, Auckland, New Zealand
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY, USA
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Shin Y, Lee SW, Namkoong E, An W, Lee JH, Brown PD, Park K. Epigenetic Modification as a Regulatory Mechanism for Spatiotemporal Dynamics of ANO1 Expression in Salivary Glands. Int J Mol Sci 2019; 20:E6298. [PMID: 31847128 PMCID: PMC6940850 DOI: 10.3390/ijms20246298] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 12/10/2019] [Accepted: 12/11/2019] [Indexed: 12/20/2022] Open
Abstract
Anoctamin1 (ANO1), a calcium activated chloride channel, is known to play a critical role in salivary secretion. In the salivary gland, ANO1 is expressed exclusively in the acinar cells, with no expression in the ductal cells. However, the mechanisms that determine this distinctive cell type-dependent expression pattern of ANO1 remain unknown. In this study, we discovered that the cell-dependent expression of ANO1 during salivary gland organogenesis is regulated by DNA methylation of ANO1 CpG islands. ANO1 CpG islands in e12 embryonic submandibular glands (eSMG) are highly methylated, but those in e14 eSMG or adult SMG are significantly unmethylated. The differential expression pattern of ANO1 in duct and acini is defined at e14. Artificial demethylation by treatment with the demethylating agent 5-aza-2'-deoxycytidine (5-Aza-CdR), induced the expression of ANO1 in both the ductal cell line Human Submandibular Gland (HSG) and in the duct cells of adult mouse SMG. During the trans-differentiation in Matrigel of duct-origin HSG cells into acinar-like phenotype, significant demethylation of ANO1 CpG islands is observed. This may be due to the reduced expression of DNA methyltransferase (DNMT) 3a and 3b. These results suggest that the differential expression of ANO1 in salivary glands during organogenesis and differentiation is mainly regulated by epigenetic demethylation of the ANO1 gene.
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Affiliation(s)
- Yonghwan Shin
- Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul 110-749, Korea; (Y.S.); (S.-W.L.); (E.N.)
- Department of Biochemistry and Molecular Biology, Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA 90033, USA;
| | - Sang-Woo Lee
- Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul 110-749, Korea; (Y.S.); (S.-W.L.); (E.N.)
| | - Eun Namkoong
- Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul 110-749, Korea; (Y.S.); (S.-W.L.); (E.N.)
| | - Woojin An
- Department of Biochemistry and Molecular Biology, Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA 90033, USA;
| | - Jong-Ho Lee
- Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital, Seoul 110-749, Korea
| | - Peter D Brown
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, UK;
| | - Kyungpyo Park
- Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul 110-749, Korea; (Y.S.); (S.-W.L.); (E.N.)
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Tachow A, Thoungseabyoun W, Phuapittayalert L, Petcharat K, Sakagami H, Kondo H, Hipkaeo W. Co-localization of endogenous Arf6 and its activator EFA6D in the granular convoluted tubule cells of mouse submandibular glands under normal conditions and when stimulated by isoproterenol, noradrenaline and carbachol. Arch Oral Biol 2017. [PMID: 28645101 DOI: 10.1016/j.archoralbio.2017.06.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE This study proposed to investigate the localization at light and electron microscopic levels of Arf6 and its activator EFA6D in the mouse submandibular gland (SMG) under normal conditions and when stimulated by adrenergic or cholinergic agonists. MATERIALS AND METHODS SMGs of male adult mice were utilized for immunoblotting and immuno-light and -electron microscopic analyses. Isoproterenol and noradrenalin were used as adrenergics, while carbachol was used for the cholinergic stimulant. SMGs were examined at 15, 30, 60 and 120min after intraperitoneal injection of these agents. RESULTS Immunoreactivities for both Arf6 and its activator EFA6D were similarly intense in the basolateral domain of GCTs, but no significant immunoreactivities were seen in the apical domain of GCT cells or any domain of acinar cells under normal conditions. In immuno-electron microscopy, the immunoreactive materials were mainly deposited on the basolateral plasma membranes and subjacent cytoplasm. Shortly after injection of isoproterenol and noradrenaline, but not carbachol, the immunoreactivities for both molecules were additionally seen on the apical plasmalemma of most, if not all, GCT cells, but not acinar cells. CONCLUSION The present findings suggest that the direct involvement of Arf6/EFA6D in regulatory exocytosis at the apical plasma membrane of acinar and GCT cells is apparently to be smaller, if present, than that of endocytosis at the basolateral membranes of GCT cells under normal conditions. This also suggests that the two molecules function additionally at the apical membrane of GCT cells for modulation of saliva secretion under β-adrenoceptor stimulation.
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Affiliation(s)
- Apussara Tachow
- Nanomorphology-Based Apply Research Group & Electron Microscopy Unit, Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Wipawee Thoungseabyoun
- Nanomorphology-Based Apply Research Group & Electron Microscopy Unit, Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | | | - Kanoktip Petcharat
- Biochemistry and Nutrition, School of Medical Science, University of Phayao, Phayao, Thailand
| | - Hiroyuki Sakagami
- Department of Anatomy, School of Medicine, Kitasato University, Tokyo, Japan
| | - Hisatake Kondo
- Nanomorphology-Based Apply Research Group & Electron Microscopy Unit, Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand; Department of Organ Anatomy, Graduate School of Medicine, Tohoku University, Sendai, Japan
| | - Wiphawi Hipkaeo
- Nanomorphology-Based Apply Research Group & Electron Microscopy Unit, Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
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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: 271] [Impact Index Per Article: 22.6] [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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Tanimura A, Shitara A, Tojyo Y. Diversity and Spatio-Temporal Properties of Calcium Responses in Salivary Ducts. J Oral Biosci 2011. [DOI: 10.1016/s1349-0079(11)80035-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Cotroneo E, Proctor GB, Carpenter GH. Regeneration of acinar cells following ligation of rat submandibular gland retraces the embryonic-perinatal pathway of cytodifferentiation. Differentiation 2010; 79:120-30. [PMID: 20056310 PMCID: PMC2841285 DOI: 10.1016/j.diff.2009.11.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Revised: 11/20/2009] [Accepted: 11/29/2009] [Indexed: 11/19/2022]
Abstract
Rat submandibular gland can regenerate following ligation-induced atrophy, eventually recovering its normal morphology and function. Previous studies have suggested that the regeneration process implies both self-proliferation of existing acini and formation of new acinar cells. One hypothesis is that new acinar cells may differentiate from the ductal cells in a similar fashion to the process of cytodifferentiation occurring during submandibular glandular development. In this study atrophy was induced, under recovery anaesthesia, by applying a metal clip on the main duct of the submandibular gland without including the chorda lingual nerve. After 2 weeks the duct was deligated for 3, 5 or 7 days or 8 weeks and the glands collected. Tissue was prepared for immunohistochemistry, biochemical analysis and RNA extraction. The histology of the regenerated glands shows several normal-looking acini, which have regained their glycoprotein content (AB/PAS positive), data also confirmed by biochemical analysis (SDS-PAGE/PAS). Regenerating tissue was characterized by the presence of embryonic-like branched structures ending with AB/PAS positive acinar cells. The proteins SMG-B and PSP are normally expressed in acinar cell precursors during development but only by intercalated ductal cells in the adult stage. In the adult regenerating gland mRNA levels of both SMG-B and PSP were found to be up-regulated compared to ligated glands and SMG-B expression localized to acinar cells whilst the ductal cells were negative. This study of rat submandibular gland regeneration suggests new acinar cells have differentiated from ducts and express markers of acinar cell precursors in a similar manner to the cytodifferentiation process occurring during glandular development.
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Affiliation(s)
| | | | - Guy H. Carpenter
- Salivary Research Unit, floor 17 Tower Wing, King's College London Dental Institute, London,UK, SE1 9RT
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Inagaki T, Ono K, Masuda W, Iida T, Hosokawa R, Inenaga K. Differences in the Ca2+ response resulting from neurotransmitter stimulations of rat parotid acini and ducts. Auton Neurosci 2010; 154:102-7. [PMID: 20096649 DOI: 10.1016/j.autneu.2009.12.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 11/19/2009] [Accepted: 12/09/2009] [Indexed: 10/19/2022]
Abstract
There are few data available regarding the differences in intracellular Ca2+ responses of parotid acinar and ductal cells. This study investigated the Ca2+ mobilization that was induced by the chemical stimulation of acinar and ductal cells from rat parotid glands. In fura-2 loaded parotid cells, carbachol increased the intracellular Ca2+ concentration ([Ca2+](i)) to a greater extent in the acinar cells than in the ductal cells, but noradrenaline increased the [Ca2+](i) in the ductal cells more than in the acinar cells. Although there was no difference in the alpha1-adrenergic receptor agonist phenylephrine-induced Ca2+ mobilization between acini and ducts, the beta-adrenergic receptor agonist isoproterenol increased the [Ca2+](i) in only the ductal cells. Additionally, the effects of non-adrenergic, non-cholinergic neurotransmitters were investigated. Substance P and ATP increased the [Ca2+](i) in parotid acini and/or ducts. A substance P-induced Ca2+ response was observed in only acini, while the ATP-induced Ca2+ response was significantly higher in ducts than in acini. These results suggest that parotid acini have a greater sensitivity to cholinergic and substance P stimulation and a lesser sensitivity to beta-adrenergic and ATP stimulation than the ductal cells. In light of these results, substance P and isoproterenol will be useful for identifying parotid acini and ducts, respectively.
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Affiliation(s)
- Tomohiro Inagaki
- Department of Biosciences, Kyushu Dental College, 2-6-1 Manazuru, Kokurakitaku, Kitakyushu, Fukuoka 803-8580, Japan
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Shitara A, Tanimura A, Sato A, Tojyo Y. Spontaneous oscillations in intracellular Ca(2+) concentration via purinergic receptors elicit transient cell swelling in rat parotid ducts. Am J Physiol Gastrointest Liver Physiol 2009; 297:G1198-205. [PMID: 19779019 DOI: 10.1152/ajpgi.00168.2009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Using multiphoton microscopy, we established that rat parotid ductal cells exhibit spontaneous oscillations in intracellular Ca(2+) concentration ([Ca(2+)](i)). These oscillatory Ca(2+) responses were observed during continuous perfusion with a physiological salt solution at 37 degrees C in the absence of calcium mobilizing agonist stimulation. The timing and patterns of these spontaneous Ca(2+) oscillations varied among individual ductal cells, and the average number of Ca(2+) responses in a single responding ductal cell was 2.1 in a 10-min recording period. High-speed scanning (0.6 s/image) revealed that most spontaneous elevations in [Ca(2+)](i) were initiated at the luminal side of ductal cells and spread toward the basal side within 2 s. Electron microscopic analysis after Ca(2+) imaging indicated that spontaneously oscillating ducts contained numerous granules at the luminal side, which is characteristic of granular ducts. These Ca(2+) oscillations were completely blocked by the purinergic receptor inhibitors 4-[[4-formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl]-2-pyridinyl]azo]-1,3-benzenedisulfonic acid (PPADS) and suramin but were not blocked by the muscarinic antagonist atropine or the alpha-adrenergic antagonist phentolamine. Simultaneous observation of fura-2 fluorescence and differential interference contrast (DIC) images showed that spontaneous elevations of [Ca(2+)](i) were well correlated with changes in shape of ductal cells. Using a plasma membrane fluorescence probe, SynaptoGreen C4, we found that the changes in DIC images reflected spontaneous cell swelling of ductal cells. Our findings present the possibility that purinergic receptors mediate spontaneous Ca(2+) oscillations in parotid ductal cells and regulate electrolyte reabsorption from the primary saliva in the resting state.
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Affiliation(s)
- Akiko Shitara
- Dept. of Pharmacology, Health Sciences Univ. of Hokkaido, Japan
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Correia PN, Carpenter GH, Paterson KL, Proctor GB. Inducible nitric oxide synthase increases secretion from inflamed salivary glands. Rheumatology (Oxford) 2009; 49:48-56. [PMID: 19933597 PMCID: PMC2789584 DOI: 10.1093/rheumatology/kep313] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Objective. Salivary gland secretion is dependent on cholinergic stimulation via autonomic nerves and calcium signalling in acinar cells. Secretory dysfunction associated with SS may be partly caused by the damaging effects of increased glandular concentrations of nitric oxide (NO) derived from up-regulation of inducible NO synthase (iNOS) that accompanies glandular inflammation. The present study examines the effects of increased iNOS expression on salivary gland secretory function. Methods. The inflammogen lipopolysaccharide (LPS) was introduced intraductally into rat submandibular glands, and glandular responsiveness to cholinergic stimulation was determined. Results. LPS provoked a rapid, long-lasting inflammation, increasing gland weight (by almost 20%) and inflammatory cell infiltration at 3 and 24 h. Immunoblotting of glandular homogenates indicated that iNOS expression was increased ∼4-fold, and immunohistochemistry of frozen tissue sections showed increased iNOS expression in acinar cells. Salivary secretion from inflamed glands was significantly increased in response to low doses of methacholine and accompanied by increased acinar cell calcium signalling in vitro. Prior administration of the iNOS inhibitors, aminoguanidine or l-NIL [l-N6-(1-iminoethyl)-lysine dihydrochloride] abolished increased secretion and acinar cell calcium signalling. Conclusions. Up-regulation of glandular iNOS expression can increase cholinergically evoked salivary secretion and appears to offset any secretory hypofunction linked with glandular inflammation. It seems unlikely that increased glandular levels of NO are responsible for the secretory hypofunction that accompanies SS.
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Affiliation(s)
- Patricia N Correia
- Salivary Research Unit, King's College London Dental Institute, Guy's and St Thomas' Hospitals, Great Maze Pond, London SE1 9RT, UK
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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: 111] [Impact Index Per Article: 6.9] [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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Cotroneo E, Proctor GB, Paterson KL, Carpenter GH. Early markers of regeneration following ductal ligation in rat submandibular gland. Cell Tissue Res 2008; 332:227-35. [PMID: 18335244 PMCID: PMC2493059 DOI: 10.1007/s00441-008-0588-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Accepted: 01/21/2008] [Indexed: 11/26/2022]
Abstract
Rat submandibular glands can recover their function and secretory protein content following ductal ligation-induced atrophy. Morphological studies have established that following ligation, deligation of the gland allows the regeneration of new salivary gland tissue. However, little is known about changes happening during early regeneration following intra-oral duct ligation, which does not damage the parasympathetic nerves. Glands that had been 2 weeks ligated or 2 weeks ligated + 3 days deligated were compared. Tissue was prepared for histological, immunohistochemical (SMG-B and Ki-67) and immunocytochemical analyses (smooth muscle actin, aquaporin 5). Haematoxylin and eosin staining of deligated glands showed that some acini regained their cytoplasmic volume; moreover, the loss of Alcian blue/periodic acid-Schiff's staining from the lumen of ducts suggested successful deligation. The deligated gland was characterized by atypical acinar-ductal branched structures, which were less frequent in the ligated gland and rarely seen in normal unoperated tissue. Myoepithelial cells were also investigated since changes in their morphology reflected changes in the acini morphology not readily detected by conventional staining. Actin staining revealed the presence of some shrunken acini in the atrophic tissue, whereas they had regained their normal morphology in the deligated gland suggesting that the acini were recovering. Some acini during deligation regained aquaporin 5 expression, which had decreased during atrophy. SMG-B protein, located in the pro-acinar cell during gland development and usually found in the intercalated duct cells in the adult, was detected in the newly formed acini of the deligated gland. This study suggests that morphological markers of regeneration appear as early as 3 days following ligation removal.
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Affiliation(s)
- Emanuele Cotroneo
- Salivary Research Unit, King's College London, Floor 17, Guy's Tower, Dental Institute at Guy's, King's College and St Thomas' Hospital, London SE1 9RT, UK.
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Jo H, Byun HM, Lee SI, Shin DM. Initiation site of Ca(2+) entry evoked by endoplasmic reticulum Ca(2+) depletion in mouse parotid and pancreatic acinar cells. Yonsei Med J 2007; 48:526-30. [PMID: 17594163 PMCID: PMC2628100 DOI: 10.3349/ymj.2007.48.3.526] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
PURPOSE In non-excitable cells, which include parotid and pancreatic acinar cells, Ca(2+) entry is triggered via a mechanism known as capacitative Ca(2+) entry, or store-operated Ca(2+) entry. This process is initiated by the perception of the filling state of endoplasmic reticulum (ER) and the depletion of internal Ca(2+) stores, which acts as an important factor triggering Ca(2+) entry. However, both the mechanism of store-mediated Ca(2+) entry and the molecular identity of store-operated Ca(2+) channel (SOCC) remain uncertain. MATERIALS AND METHODS In the present study we investigated the Ca(2+) entry initiation site evoked by depletion of ER to identify the localization of SOCC in mouse parotid and pancreatic acinar cells with microfluorometeric imaging system. RESULTS Treatment with thapsigargin (Tg), an inhibitor of sarco/endoplasmic reticulum Ca(2+)-ATPase, in an extracellular Ca(2+) free state, and subsequent exposure to a high external calcium state evoked Ca(2+) entry, while treatment with lanthanum, a non-specific blocker of plasma Ca(2+) channel, completely blocked Tg-induced Ca(2+) entry. Microfluorometric imaging showed that Tg-induced Ca(2+) entry started at a basal membrane, not a apical membrane. CONCLUSION These results suggest that Ca2+ entry by depletion of the ER initiates at the basal pole in polarized exocrine cells and may help to characterize the nature of SOCC.
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Affiliation(s)
- Hae Jo
- Yonsei University College of Dentistry, 250 Seongsanno, Seodaemon-gu, Seoul 120-752, Korea
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Pochet S, Garcia-Marcos M, Seil M, Otto A, Marino A, Dehaye JP. Contribution of two ionotropic purinergic receptors to ATP responses in submandibular gland ductal cells. Cell Signal 2007; 19:2155-64. [PMID: 17651941 DOI: 10.1016/j.cellsig.2007.06.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Accepted: 06/15/2007] [Indexed: 11/19/2022]
Abstract
The effect of extracellular ATP on salivary gland function was compared in wild-type (WT) and P2X(7) knockout (KO) mice. The increase in the intracellular concentration of calcium ([Ca(2+)](i)) in response to carbachol was similar in submandibular ductal cells of WT and KO mice. ATP and its analog, benzoyl-ATP, induced a sustained increase in the [Ca(2+)](i) in WT animals. In KO mice, ATP slightly and transiently increased the [Ca(2+)](i) and benzoyl-ATP had no effect. The response to ATP of WT but not KO mice was blocked by KN-62, Coomassie blue and magnesium. The small response of ATP observed in KO mice was completely blocked in the absence of extracellular calcium, unchanged by U73122 and potentiated by ivermectin indicating the probable involvement of a P2X(4) receptor. A RT-PCR and a Western blot confirmed the presence of these receptors in ducts of both WT and KO mice. ATP increased the permeability of the cells to ethidium bromide and stimulated a phospholipase A(2) activity in WT but not KO mice. Mice submandibular gland cells secreted IL-1beta but this secretion was not modified by ATP and was similar in both groups of animals. The volume of saliva provoked by pilocarpine and the concentration of proteins, sodium and chloride in this saliva was similar in both groups of animals. The concentration of potassium was higher in KO mice. We can conclude that the major purinergic receptors expressed in mice submandibular ductal cells are P2X(7) receptors but that P2X(4) receptors are also involved in some ATP effects.
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Affiliation(s)
- Stéphanie Pochet
- Laboratoire de Biochimie et de Biologie Cellulaire, Institut de Pharmacie, C.P. 205/3, Université libre de Bruxelles (ULB), Campus de la Plaine, Boulevard du Triomphe B1050, Brussels, Belgium.
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Shitara A, Tanimura A, Nezu A, Morita T, Tojyo Y. Multi-photon microscopic imaging of rat parotid ducts demonstrates cellular heterogeneity in Ca2+ responsiveness. Arch Oral Biol 2007; 52:1072-8. [PMID: 17586459 DOI: 10.1016/j.archoralbio.2007.05.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 05/11/2007] [Accepted: 05/15/2007] [Indexed: 11/24/2022]
Abstract
The heterogeneity of salivary ductal cells, with regard to their sensitivity to Ca(2+)-mobilizing agonists, was visualized by multi-photon microscopy. Stimulation of isolated parotid ducts with 0.1 and 1 microM epinephrine (Epi) elevated the intracellular Ca(2+) levels ([Ca(2+)](i)) in approximately 30% and >90% of the ductal cells, respectively. Of the 0.1 microM Epi-responsive cells, 80% responded rapidly to subsequent stimulation with 1 microM Epi. Similarly, threshold concentrations (0.5 or 1 microM) of phenylephrine (PhL), carbachol (CCh) or ATP, induced responses in approximately 20% of the ductal cells, and subsequent stimulations with 10 microM of the same agonist activated approximately 80% of ductal cells. These observations indicate that parotid ducts contain a certain subpopulation of cells, which exhibits particularly high sensitivity to these Ca(2+)-mobilizing agonists, compared to the remaining ductal cells. Sequential stimulation with threshold concentrations of PhL, CCh, and ATP induced Ca(2+) responses in approximately 33% of ductal cells. Of these responsive cells, the majority (69%) could only respond to one of the three agonists; while a small minority (9%) were capable of responding to all three agonists. These results indicate that low concentrations of PhL, CCh, and ATP activate different subpopulations of parotid ductal cells.
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Affiliation(s)
- Akiko Shitara
- Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
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16
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Wang X, Zeng W, Kim MS, Allen PB, Greengard P, Muallem S. Spinophilin/neurabin reciprocally regulate signaling intensity by G protein-coupled receptors. EMBO J 2007; 26:2768-76. [PMID: 17464283 PMCID: PMC1888664 DOI: 10.1038/sj.emboj.7601701] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2006] [Accepted: 04/03/2007] [Indexed: 11/09/2022] Open
Abstract
Spinophilin (SPL) and neurabin (NRB) are structurally similar scaffolding proteins with several protein binding modules, including actin and PP1 binding motifs and PDZ and coiled-coil domains. SPL also binds regulators of G protein signaling (RGS) proteins and the third intracellular loop (3iL) of G protein-coupled receptors (GPCRs) to reduce the intensity of Ca(2+) signaling by GPCRs. The role of NRB in Ca(2+) signaling is not known. In the present work, we used biochemical and functional assays in model systems and in SPL(-/-) and NRB(-/-) mice to show that SPL and NRB reciprocally regulate Ca(2+) signaling by GPCRs. Thus, SPL and NRB bind all members of the R4 subfamily of RGS proteins tested (RGS1, RGS2, RGS4, RGS16) and GAIP. By contract, SPL, but not NRB, binds the 3iL of the GPCRs alpha(1B)-adrenergic (alpha(1B)AR), dopamine, CCKA, CCKB and the muscarinic M3 receptors. Coexpression of SPL or NRB with the alpha(1B)AR in Xenopus oocytes revealed that SPL reduces, whereas NRB increases, the intensity of Ca(2+) signaling by alpha(1B)AR. Accordingly, deletion of SPL in mice enhanced binding of RGS2 to NRB and Ca(2+) signaling by alphaAR, whereas deletion of NRB enhanced binding of RGS2 to SPL and reduced Ca(2+) signaling by alphaAR. This was due to reciprocal modulation by SPL and NRB of the potency of RGS2 to inhibit Ca(2+) signaling by alphaAR. These findings suggest a novel mechanism of regulation of GPCR-mediated Ca(2+) signaling in which SPL/NRB forms a functional pair of opposing regulators that modulates Ca(2+) signaling intensity by GPCRs by determining the extent of inhibition by the R4 family of RGS proteins.
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Affiliation(s)
- Xinhua Wang
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
| | - Weizhong Zeng
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
| | - Min Seuk Kim
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
| | - Patrick B Allen
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - Paul Greengard
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, NY, USA
| | - Shmuel Muallem
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
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17
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Carpenter GH, Osailan SM, Correia P, Paterson KP, Proctor GB. Rat salivary gland ligation causes reversible secretory hypofunction. Acta Physiol (Oxf) 2007; 189:241-9. [PMID: 17305704 PMCID: PMC1859985 DOI: 10.1111/j.1365-201x.2006.01662.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM To determine the influence of inflammation on salivary secretion. Secretion by salivary glands involves interactions between nerves, blood vessels and salivary cells. The present study investigated the effects of inflammation on rat submandibular gland function following acute ductal obstruction. METHODS Under recovery anaesthesia a metal clip was placed on the main duct of the submandibular gland. After 24 h salivary secretion was evoked by nerve and methacholine stimulation. For recovery experiments the clip was removed after 24 h and the animal left to recover for 3 days when salivary function was again assessed. RESULTS By 24 h of obstruction an inflammatory infiltrate had developed within the obstructed gland and stimulated salivary flows were just 20% of the normal secretion, whilst protein secretion and ion reabsorption were also severely impaired. If ductal obstruction was removed after 24 h the salivary function returned to normal after 3 days of recovery. In vitro analysis of cells from 24-h ligated glands revealed normal changes in intracellular calcium (the main secondary messenger involved in fluid secretion) in response to methacholine stimulation. Protein secretion from isolated cells indicated some changes in particular to methacholine-induced protein secretion although a significant protein secretion was still seen in response to isoprenaline - the main stimulus for protein secretion. CONCLUSION This report demonstrates reversible salivary inhibition associated with an inflammatory infiltrate within the salivary gland.
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Affiliation(s)
- G H Carpenter
- Salivary Research Unit, Floor 17, Guy's Tower, King's College London, London, UK.
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18
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Cox SW, Ebersole LE, Carpenter GH, Proctor GB. Effects of autonomic agonists and immunomodulatory cytokines on polymeric immunoglobulin receptor expression by cultured rat and human salivary and colonic cell lines. Arch Oral Biol 2006; 52:411-6. [PMID: 17118334 DOI: 10.1016/j.archoralbio.2006.10.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2006] [Revised: 09/13/2006] [Accepted: 10/07/2006] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Immunoglobulin A (IgA) is transported across glandular epithelial cells by polymeric immunoglobulin receptor (plgR), with each receptor molecule participating in only one round of transcytosis. Nerve-related stimuli rapidly increase salivary secretion of IgA, while concentrations are increased in the autoimmune disease Sjögren's syndrome. Our aim here was to determine whether autonomic agonists and cytokines present in Sjögren's-affected glands can up-regulate salivary cell plgR expression. METHODS Cultures of rat parotid acinar cells (PAR C5) and human submandibular gland ductal cells (HSG) were exposed to carbachol or adrenaline for 24 h and to interleukin-4 and/or interferon-gamma for 48 h. The human colonic cell line HT-29 served as a positive control for cytokine response. plgR mRNA was quantified by reverse transcription and real-time PCR and protein expression was examined by immunoblotting. RESULTS Carbachol increased plgR mRNA levels significantly in all cells but adrenaline did so only with PAR cells (P<0.05). HSG and HT-29 cells both up-regulated plgR gene transcription on exposure to interleukin-4 and interferon-gamma either alone or in combination (P<0.05). By contrast, production of plgR mRNA in PAR cells tended to decrease in response to all cytokine treatments. plgR protein levels rose in line with mRNA expression in cytokine-treated HT-29 cultures (P<0.05). CONCLUSIONS Autonomimetics can up-regulate plgR transcription in transformed and neoplastic salivary and colonic cells, although intracellular coupling mechanisms require further investigation. Immunomodulatory cytokines increased plgR expression in one of the salivary cell lines, but additional work is needed to establish whether this occurs in Sjögren's patients.
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Affiliation(s)
- S W Cox
- Salivary Research Unit, King's College London Dental Institute at Guy's, King's College and St Thomas' Hospitals, London, UK.
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19
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Jo H, Byun HM, Kim JH, Kim MS, Kim SH, Hong JH, Seo JT, Lee SI, Shin DM, Son HK. Expression of Ca2+-dependent synaptotagmin isoforms in mouse and rat parotid acinar cells. Yonsei Med J 2006; 47:70-7. [PMID: 16502487 PMCID: PMC2687583 DOI: 10.3349/ymj.2006.47.1.70] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Synaptotagmin is a Ca2+ sensing protein, which triggers a fusion of synaptic vesicles in neuronal transmission. Little is known regarding the expression of Ca2+-dependent synaptotagmin isoforms and their contribution to the release of secretory vesicles in mouse and rat parotid acinar cells. We investigated a type of Ca2+-dependent synaptotagmin and Ca2+ signaling in both rat and mouse parotid acinar cells using RT-PCR, microfluorometry, and amylase assay. Mouse parotid acinar cells exhibited much more sensitive amylase release in response to muscarinic stimulation than did rat parotid acinar cells. However, transient [Ca2+]i increases and Ca2+ influx in response to muscarinic stimulation in both cells were identical, suggesting that the expression or activity of the Ca2+ sensing proteins is different. Seven Ca2+-dependent synaptotagmins, from 1 to 7, were expressed in the mouse parotid acinar cells. However, in the rat parotid acinar cells, only synaptotagmins 1, 3, 4 and 7 were expressed. These results indicate that the expression of Ca2+-dependent synaptotagmins may contribute to the release of secretory vesicles in parotid acinar cells.
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Affiliation(s)
- Hae Jo
- Department of Oral Biology, Brain Korea 21 Project of Medical Science, Yonsei University College of Dentistry, Seoul, Korea
| | - Hae Mi Byun
- Department of Oral Biology, Brain Korea 21 Project of Medical Science, Yonsei University College of Dentistry, Seoul, Korea
| | - Jong-Hoon Kim
- Department of Pedodontics, Yonsei University College of Dentistry, Seoul, Korea
| | - Min Seuk Kim
- Department of Oral Biology, Brain Korea 21 Project of Medical Science, Yonsei University College of Dentistry, Seoul, Korea
| | - Seung-Hyeoi Kim
- Department of Oral Biology, Brain Korea 21 Project of Medical Science, Yonsei University College of Dentistry, Seoul, Korea
| | - Jeong Hee Hong
- Department of Oral Biology, Brain Korea 21 Project of Medical Science, Yonsei University College of Dentistry, Seoul, Korea
| | - Jeong Taeg Seo
- Department of Oral Biology, Brain Korea 21 Project of Medical Science, Yonsei University College of Dentistry, Seoul, Korea
| | - Syng-Ill Lee
- Department of Oral Biology, Brain Korea 21 Project of Medical Science, Yonsei University College of Dentistry, Seoul, Korea
| | - Dong Min Shin
- Department of Oral Biology, Brain Korea 21 Project of Medical Science, Yonsei University College of Dentistry, Seoul, Korea
| | - Heung-Kyu Son
- Department of Pedodontics, Yonsei University College of Dentistry, Seoul, Korea
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20
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Takemura H, Horio Y. Spatial microenvironment defines Ca2+ entry and Ca2+ release in salivary gland cells. Biochem Biophys Res Commun 2005; 336:223-31. [PMID: 16137661 DOI: 10.1016/j.bbrc.2005.07.200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2005] [Accepted: 07/25/2005] [Indexed: 10/25/2022]
Abstract
The difference of Ca(2+) mobilization induced by muscarinic receptor activation between parotid acinar and duct cells was examined. Oxotremorine, a muscarinic-cholinergic agonist, induced intracellular Ca(2+) release and extracellular Ca(2+) entry through store-operated Ca(2+) entry (SOC) and non-SOC channels in acinar cells, but it activated only Ca(2+) entry from non-SOC channels in duct cells. RT-PCR experiments showed that both types of cells expressed the same muscarinic receptor, M3. Given that ATP activated the intracellular Ca(2+) stores, the machinery for intracellular Ca(2+) release was intact in the duct cells. By immunocytochemical experiments, IP(3)R2 colocalized with M3 receptors in the plasma membrane area of acinar cells; in duct cells, IP(3)R2 resided in the region on the opposite side of the M3 receptors. On the other hand, purinergic P2Y2 receptors were found in the apical area of duct cells where they colocalized with IP(3)R2. These results suggest that the expression of the IP(3)Rs near G-protein-coupled receptors is necessary for the activation of intracellular Ca(2+) stores. Therefore, the microenvironment probably affects intracellular Ca(2+) release and Ca(2+) entry.
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Affiliation(s)
- Haruo Takemura
- Department of Pharmacology, Sapporo Medical University, South 1, West 17, Sapporo 060-8556, Japan.
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21
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Nezu A, Morita T, Tanimura A, Tojyo Y. Comparison of agonist-induced Ca2+ responses in rat submandibular acini and ducts. Arch Oral Biol 2005; 50:585-92. [PMID: 15848152 DOI: 10.1016/j.archoralbio.2004.07.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2004] [Accepted: 07/19/2004] [Indexed: 10/26/2022]
Abstract
Changes in intracellular Ca(2+) concentration ([Ca(2+)]i) induced by agonists were simultaneously monitored in rat submandibular acini and ducts using a Ca(2+) imaging system. Substance P (SP) elicited marked increases in [Ca(2+)]i in acini but not in ducts. Carbachol (CCh) increased [Ca(2+)]i in both acini and ducts, but the maximal level was higher in acini than in ducts. In contrast, epinephrine (Epi) also induced an increase in [Ca(2+)]i in acini and ducts, but to a greater extent in ducts than in acini. Isoproterenol (ISO) caused a small but significant increase in [Ca(2+)]i in ducts but not acini. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis using total RNA extracted from highly purified acinar and ductal cells showed that substance P receptor mRNA was present in acini at higher levels than in ducts. In contrast, alpha(1a)-adrenoceptor mRNA was more strongly expressed in ducts than in acini. The muscarinic receptors (M(3) and M(5)) and beta-adrenoceptors (beta(1) and beta(2)) were expressed at equivalent levels in both cell types. These results confirm that acini and ducts exhibit significant differences in agonist-induced Ca(2+) responses. Furthermore, substance P- and epinephrine-induced Ca(2+) responses were consistent with receptor mRNA expression in acini and ducts, but carbachol- and isoproterenol-induced [Ca(2+)]i increases were not.
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Affiliation(s)
- Akihiro Nezu
- Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan.
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22
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Li Q, Luo X, Muallem S. Regulation of the P2X7 receptor permeability to large molecules by extracellular Cl- and Na+. J Biol Chem 2005; 280:26922-7. [PMID: 15923180 DOI: 10.1074/jbc.m504966200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Upon continuous stimulation, the pore of the monovalent cation-selective P2X7 receptor (P2X7R) expands to accommodate large molecules such as N-methyl-D-glucamine (NMDG+). How the change in P2X7R permeability is regulated is not known. Here we report that extracellular Cl- (Cl-(o)) regulates the outward current, whereas extracellular Na+ (Na+(o)) regulates the inward current of large molecules by P2X7Rs. The P2X7R-mediated current was measured in parotid acinar and duct cells of wild type and P2X7R-/- mice and in HEK293 cells expressing the human or mouse P2X7R isoforms. In symmetrical NaCl, triethylammonium chloride, and NMDG+ chloride solutions, the P2X7R current followed a linear current/voltage relationship. In symmetrical NaCl, removal of Cl-(o) reduced the inward Na+ current by approximately 35% and the outward Na+ current by only 10%. By contrast, in the absence of Na+(i) and the presence of Na+(o) or NMDG+(o), the removal of Cl-(o) reduced the inward Na+ or NMDG+ currents by 35% but the outward NMDG+ current by >95%. The effect of Cl-(o) was half-maximal at approximately 60 mm. Reducing Cl-(i) from 150 to 10 mm did not reproduce the effects of Cl-(o). All currents were eliminated in P2X7R-/- cells and reproduced by expressing the P2X7Rs in HEK cells. These findings suggest that Cl-(o) primarily regulates the outward P2X7R current of large molecules. When cells dialyzed with NMDG+ were stimulated in the presence of Na+(o), subsequent removal of Na+(o) resulted in a strongly outward rectifying NMDG+ current, indicating maintained high selectivity for Na+ over NMDG+. During continuous incubation in Na+-free medium, the permeability of the P2X7Rs to NMDG+ gradually increased. On the other hand, when the cells were incubated in symmetrical NMDG+ and only then stimulated with ATP, the NMDG+ current by P2X7Rs followed a linear current/voltage relationship and did not change with time. These findings suggest that the P2X7R has a "Na+(o) memory" and that Na+(o) regulates the inward permeability of P2X7Rs to large molecules. The novel regulation of P2X7R outward and inward permeability to large molecules by Cl-(o) and Na+(o), respectively, may have an important protective function, particularly in secretory epithelial cells.
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Affiliation(s)
- Qin Li
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA
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23
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Bandyopadhyay BC, Swaim WD, Liu X, Redman RS, Patterson RL, Ambudkar IS. Apical Localization of a Functional TRPC3/TRPC6-Ca2+-Signaling Complex in Polarized Epithelial Cells. J Biol Chem 2005; 280:12908-16. [PMID: 15623527 DOI: 10.1074/jbc.m410013200] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Receptor-coupled [Ca2+]i increase is initiated in the apical region of epithelial cells and has been associated with apically localized Ca2+-signaling proteins. However, localization of Ca2+ channels that are regulated by such Ca2+-signaling events has not yet been established. This study examines the localization of TRPC channels in polarized epithelial cells and demonstrates a role for TRPC3 in apical Ca2+ uptake. Endogenously and exogenously expressed TRPC3 was localized apically in polarized Madin-Darby canine kidney cells (MDCK) and salivary gland epithelial cells. In contrast, TRPC1 was localized basolaterally, whereas TRPC6 was detected in both locations. Localization of Galpha(q/11), inositol 1,4,5-trisphosphate receptor-3, and phospholipase Cbeta1 and -beta2 was also predominantly apical. TRPC3 co-immunoprecipitated with endogenous TRPC6, phospholipase Cbetas, Galpha(q/11), inositol 1,4,5-trisphosphate receptor-3, and syntaxin 3 but not with TRPC1. Furthermore, 1-oleoyl-2-acetyl-sn-glycerol (OAG)-stimulated apical 45Ca2+ uptake was higher in TRPC3-MDCK cells compared with control (MDCK) cells. Bradykinin-stimulated apical 45Ca2+ uptake and transepithelial 45Ca2+ flux were also higher in TRPC3-expressing cells. Consistent with this, OAG induced [Ca2+]i increase in the apical, but not basal, region of TRPC3-MDCK cells that was blocked by EGTA addition to the apical medium. Most importantly, (i) TRPC3 was detected in the apical region of rat submandibular gland ducts, whereas TRPC6 was present in apical as well as basolateral regions of ducts and acini; and (ii) OAG stimulated Ca2+ influx into dispersed ductal cells. These data demonstrate functional localization of TRPC3/TRPC6 channels in the apical region of polarized epithelial cells. In salivary gland ducts this could contribute to the regulation of salivary [Ca2+] and secretion.
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Affiliation(s)
- Bidhan C Bandyopadhyay
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892, USA
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Kanno T. Compound exocytosis of secretory granules containing salivary chromogranin A in granular duct cells in rat submandibular gland: the last study in collaboration with the late Professor Noboru Yanaihara at Yanaihara Institute. ACTA ACUST UNITED AC 2005; 123:3-7. [PMID: 15518886 DOI: 10.1016/j.regpep.2004.03.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Chromogranin A (CgA) is a member of a family of chromogranins, which are co-stored and co-released with adrenaline and noradrenalin (NAd) in the adrenal medulla in response to stimulation of the splanchnic nerve. Double immunohistochemical staining is carried out by use of antibodies against CgA and 1,4,5-trisphosphate receptor type 2 (IP3R2) on the same sections prepared from the isolated and perfused submandibulllar gland of rat. In the control sections prepared from resting state, an intense IP3R2 immunoreactivity (IR) appeared preferentially at the apical pole of subpopulation of the granulated duct cells, in which CgA-like IR distributed throughout the cytoplasm. Electron-micrograph showed that the granular cells in the resting state stored numerous membrane-bound granules in the apical cytoplasm. Stimulation with 1 microM NAd caused rapid immediate increase in secretory responses. Sections prepared from the gland at the peak of secretory responses exhibited that, in the granular duct cells, the apically converge IP3R2 IR became diffuse and indistinguishable, and that the apical half of the cells was occupied, indicating that mobilization of Ca2+ from the IP3-sensitive pool may preferentially be involved in the secretory responses to alpha-adrenergic agonist.
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Affiliation(s)
- Tomio Kanno
- Department of Physiology, School of Veterinary Medicine, Hokkaido University, Kita 18-jo Nishi 9-chome, Kita, Sapporo 060-0818, Japan.
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25
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Wang X, Zeng W, Soyombo AA, Tang W, Ross EM, Barnes AP, Milgram SL, Penninger JM, Allen PB, Greengard P, Muallem S. Spinophilin regulates Ca2+ signalling by binding the N-terminal domain of RGS2 and the third intracellular loop of G-protein-coupled receptors. Nat Cell Biol 2005; 7:405-11. [PMID: 15793568 DOI: 10.1038/ncb1237] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2004] [Accepted: 01/10/2005] [Indexed: 11/08/2022]
Abstract
Signalling by G proteins is controlled by the regulator of G-protein signalling (RGS) proteins that accelerate the GTPase activity of Galpha subunits and act in a G-protein-coupled receptor (GPCR)-specific manner. The conserved RGS domain accelerates the G subunit GTPase activity, whereas the variable amino-terminal domain participates in GPCR recognition. How receptor recognition is achieved is not known. Here, we show that the scaffold protein spinophilin (SPL), which binds the third intracellular loop (3iL) of several GPCRs, binds the N-terminal domain of RGS2. SPL also binds RGS1, RGS4, RGS16 and GAIP. When expressed in Xenopus laevis oocytes, SPL markedly increased inhibition of alpha-adrenergic receptor (alphaAR) Ca2+ signalling by RGS2. Notably, the constitutively active mutant alphaAR(A293E) (the mutation being in the 3iL) did not bind SPL and was relatively resistant to inhibition by RGS2. Use of betaAR-alphaAR chimaeras identified the 288REKKAA293 sequence as essential for the binding of SPL and inhibition of Ca2+ signalling by RGS2. Furthermore, alphaAR-evoked Ca2+ signalling is less sensitive to inhibition by SPL in rgs2-/- cells and less sensitive to inhibition by RGS2 in spl-/- cells. These findings provide a general mechanism by which RGS proteins recognize GPCRs to confer signalling specificity.
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Affiliation(s)
- Xinhua Wang
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9040, USA
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26
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Carpenter GH, Proctor GB, Garrett JR. Preganglionic parasympathectomy decreases salivary SIgA secretion rates from the rat submandibular gland. J Neuroimmunol 2005; 160:4-11. [PMID: 15710452 DOI: 10.1016/j.jneuroim.2004.10.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2004] [Revised: 10/20/2004] [Accepted: 10/20/2004] [Indexed: 10/26/2022]
Abstract
Immunoglobulin A (IgA) is transported into saliva by salivary cells expressing the polymeric immunoglobulin receptor (pIgR). In rat salivary glands, autonomic nerves stimulate this process. To examine how nerves affect pIgR-mediated IgA secretion, the chorda-lingual nerve was sectioned. One week after preganglionic parasympathectomy, both the stimulated and unstimulated rates of salivary IgA secretion were reduced, despite similar glandular amounts of IgA. Biochemical analysis of cells from parasympathectomised and control glands indicated reduced membrane expression of pIgR. It appears the removal of long-term parasympathetic input has affected the routing of pIgR within salivary cells and reduced the SIgA transport into saliva.
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Affiliation(s)
- G H Carpenter
- Salivary Research Group, Division Oral Medicine, Guy's King's and St Thomas' School of Dentistry, United Kingdom.
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27
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Brown DA, Bruce JIE, Straub SV, Yule DI. cAMP potentiates ATP-evoked calcium signaling in human parotid acinar cells. J Biol Chem 2004; 279:39485-94. [PMID: 15262999 DOI: 10.1074/jbc.m406201200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In salivary acinar cells, intracellular calcium ([Ca(2+)](i)) signaling plays an important role in eliciting fluid secretion through the activation of Ca(2+)-activated ionic conductances. Ca(2+) and cAMP have synergistic effects on fluid secretion such that peak secretion is elicited following activation of both parasympathetic and sympathetic pathways. We have recently demonstrated that cAMP exerts effects on Ca(2+) release, through protein kinase A (PKA)-mediated phosphorylation of inositol 1,4,5-trisphosphate receptors (InsP(3)R) in mouse parotid acinar cells. To extend these findings, in the present study cross-talk between Ca(2+) signaling and cAMP pathways in human parotid acinar cells was investigated. In human parotid acinar cells, carbachol stimulation evoked increases in the [Ca(2+)](i) and the initial peak amplitude was enhanced following PKA activation, consistent with reports from mouse parotid. Stimulation with ATP also evoked an increase in [Ca(2+)](i). The ATP-evoked Ca(2+) elevation was largely dependent on extracellular Ca(2+), suggesting the involvement of the P2X family of purinergic receptors. Pharmacological elevation of cAMP resulted in a approximately 5-fold increase in the peak [Ca(2+)](i) change evoked by ATP stimulation. This enhanced [Ca(2+)](i) increase was not dependent on intracellular release from InsP(3)R or ryanodine receptors, suggesting a direct effect on P2XR. Reverse transcription-polymerase chain reaction and Western blot analysis confirmed the presence of P2X(4)R and P2X(7)R mRNA and protein in human parotid acinar cells. ATP-activated cation currents were studied using whole cell patch clamp techniques in HEK-293 cells, a null background for P2XR. Raising cAMP resulted in a approximately 4.5-fold enhancement of ATP-activated current in HEK-293 cells transfected with P2X(4)R DNA but had no effects on currents in cells expressing P2X(7)R. These data indicate that in human parotid acinar cells, in addition to modulation of Ca(2+) release, Ca(2+) influx through P2X(4)R may constitute a further locus for the synergistic effects of Ca(2+) and PKA activation.
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Affiliation(s)
- David A Brown
- Department of Pharmacology & Physiology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, New York 14642, USA
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Nakamura T, Matsui M, Uchida K, Futatsugi A, Kusakawa S, Matsumoto N, Nakamura K, Manabe T, Taketo MM, Mikoshiba K. M(3) muscarinic acetylcholine receptor plays a critical role in parasympathetic control of salivation in mice. J Physiol 2004; 558:561-75. [PMID: 15146045 PMCID: PMC1664962 DOI: 10.1113/jphysiol.2004.064626] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The M(1) and M(3) subtypes are the major muscarinic acetylcholine receptors in the salivary gland and M(3) is reported to be more abundant. However, despite initial reports of salivation abnormalities in M(3)-knockout (M(3)KO) mice, it is still unclear which subtype is functionally relevant in physiological salivation. In the present study, salivary secretory function was examined using mice lacking specific subtype(s) of muscarinic receptor. The carbachol-induced [Ca(2+)](i) increase was markedly impaired in submandibular gland cells from M(3)KO mice and completely absent in those from M(1)/M(3)KO mice. This demonstrates that M(3) and M(1) play major and minor roles, respectively, in the cholinergically induced [Ca(2+)](i) increase. Two-dimensional Ca(2+)-imaging analysis revealed the patchy distribution of M(1) in submandibular gland acini, in contrast to the ubiquitous distribution of M(3). In vivo administration of a high dose of pilocarpine (10 mg kg(-1), s.c.) to M(3)KO mice caused salivation comparable to that in wild-type mice, while no salivation was induced in M(1)/M(3)KO mice, indicating that salivation in M(3)KO mice is caused by an M(1)-mediated [Ca(2+)](i) increase. In contrast, a lower dose of pilocarpine (1 mg kg(-1), s.c.) failed to induce salivation in M(3)KO mice, but induced abundant salivation in wild-type mice, indicating that M(3)-mediated salivation has a lower threshold than M(1)-mediated salivation. In addition, M(3)KO mice, but not M(1)KO mice, had difficulty in eating dry food, as shown by frequent drinking during feeding, suggesting that salivation during eating is mediated by M(3) and that M(1) plays no practical role in it. These results show that the M(3) subtype is essential for parasympathetic control of salivation and a reasonable target for the drug treatment and gene therapy of xerostomia, including Sjögren's syndrome.
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Affiliation(s)
- Takeshi Nakamura
- Calcium Oscillation Project, Japan Science and Technology Agency, Tokyo, Japan
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29
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Ostuni MA, Ferrero AJ, Bereciartu A, Houssay AB, Tumilasci OR. Modulation by somatostatin of rat submandibular salivary secretion. Arch Oral Biol 2003; 48:205-12. [PMID: 12648558 DOI: 10.1016/s0003-9969(02)00205-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Although somatostatin (somatotrophin release inhibitory factor; SRIF) is a well-known inhibitory peptide, there are only a few reports of it acting as a positive modulator. In this work, the action of somatostatin upon rat submandibular protein secretion was studied. In vivo somatostatin infusion (35 microg/(kg h)) raised protein secretion stimulated by adrenergic and peptidergic agents. To rule out possible systemic effects of somatostatin, in vitro experiments were performed. Somatostatin (90 nmol/l) augmented protein release stimulated by noradrenaline (19 micromol/l) and substance P (10 micromol/l), but it did not affect isoprenaline (400 micromol/l)-induced protein release. Phenoxybenzamine (20 micromol/l) reduced the effect of somatostatin on noradrenaline-stimulated protein release. Propranolol (20 micromol/l) increased the noradrenaline-stimulated protein release and this effect was synergistic with the action of somatostatin. The absence of extracellular calcium did not significantly reduce somatostatin enhancement of agonist-induced secretion. Fluorescence measurements of the Ca(2+)-sensitive dye fluo3 showed that cytosolic calcium in acinar cells remained elevated during stimuli when somatostatin was present in the medium. It was concluded that somatostatin modulates rat submandibular protein secretion by prolonging the time that the cytosolic calcium signal remains high after stimulus.
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Affiliation(s)
- M A Ostuni
- Facultad de Odontología, Cátedra de Biofísica, Universidad de Buenos Aires, M.T. de Alvear 2142 (C1122AAH), Argentina.
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30
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Segawa A, Takemura H, Yamashina S. Calcium signalling in tissue: diversity and domain-specific integration of individual cell response in salivary glands. J Cell Sci 2002; 115:1869-76. [PMID: 11956318 DOI: 10.1242/jcs.115.9.1869] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Organ function requires coordinated multicellular activities, which may require proper control of cell signalling dynamics at the supracellular level. By using high-speed confocal microscopy, we studied how calcium signalling is organised in the dissociated rat parotid gland. Salivary gland function is accomplished primarily by the compartmentalized epithelial domains, acini and ducts, the former involved in the production of primary saliva and the latter involved in its modification. Upon muscarinic stimulation with carbachol, both domains showed an increase in intracellular free calcium concentration ([Ca(2+)]i) with distinctive spatiotemporal kinetics, as indicated by the fluo-3 fluorescence. Acini responded initially, and the ducts followed with a time lag of more than 0.3 second. Cells comprising an acinus responded synchronously, whereas those in the ducts responded heterogeneously with respect to the latency period, magnitude of response and the requirement of extracellular calcium to raise [Ca(2+)]i. ATP also elicited a non-synchronous [Ca(2+)]i response in the duct domain, under a pattern different from that of carbachol. The synchronous oscillations seen in the acinar domain were made asynchronous by octanol, an agent known to inhibit gap-junction function. Accordingly, a gap junction component, connexin 32, was immunolocalised predominantly between the acinar cells. Moreover, expression of the type 2 inositol (1,4,5)-trisphosphate receptor [Ins(1,4,5)P(3)R] was homogeneous in the acinar domain but heterogeneous in the duct domain. Together, these data suggest that the calcium signalling system in salivary glands is constructed specifically according to the tissue architecture.
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Affiliation(s)
- Akihisa Segawa
- Department of Anatomy, School of Medicine, Kitasato University, 1-15-1 Kitasato, Sagamihara, Kanagawa 228-8555, Japan.
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Nezu A, Tanimura A, Tojyo Y. Characterization of the ca2 + response mediated by activation of beta-adrenoceptors in rat submandibular ducts. JAPANESE JOURNAL OF PHARMACOLOGY 2000; 84:25-31. [PMID: 11043449 DOI: 10.1254/jjp.84.25] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The Ca2+ signaling mediated by activation of beta-adrenoceptors was studied in a purified preparation of ducts from rat submandibular glands. At concentrations above 1 nM, isoproterenol (ISO) caused a small but significant increase in cytosolic Ca2+ concentration ([Ca2+]i). The ISO-induced increase in [Ca2+]i was completely inhibited by the beta-adrenoceptor antagonist propranolol but not by the alpha-adrenoceptor antagonist phentolamine. Forskolin was able to mimic the Ca2+ response to ISO. These results suggest that the ISO-induced increase in [Ca2+]i in rat submandibular ducts is mediated by an accumulation of cAMP resulting from activation of beta-adrenoceptors. In the absence of extracellular Ca2+, ISO or forskolin caused a transient increase in [Ca2+]i, indicating Ca2+ mobilization from intracellular Ca2+ stores. Further, stimulation with ISO failed to mobilize Ca2+ after the depletion of intracellular Ca2+ stores by phenylephrine or carbachol, suggesting that the cAMP-mediated increase in [Ca2+]i is due to a Ca2+ release from inositol trisphosphate (IP3)-sensitive Ca2+ stores. As ISO did not stimulate a detectable production of IP3, the cAMP-mediated Ca2+ mobilization may be evoked by a mechanism different from activation of phosphoinositide hydrolysis.
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Affiliation(s)
- A Nezu
- Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Japan
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Morán-Jiménez MJ, Matute C. Immunohistochemical localization of the P2Y(1) purinergic receptor in neurons and glial cells of the central nervous system. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 78:50-8. [PMID: 10891584 DOI: 10.1016/s0169-328x(00)00067-x] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This study reports the characterization of a polyclonal antiserum to a carboxy-terminal epitope of the P2Y(1) receptor and its use in immunolocalization studies of this receptor in the CNS. The antibody recognized a major band of 42 kDa in Western blot of tissue homogenates from rat and bovine brain. Immunohistochemical studies confirmed early reports about the presence of the P2Y(1) receptor in the corpus callosum, habenula and ductal cells of the salivary gland. In addition, we found that the P2Y(1) receptor is intensely expressed in Purkinje cells, in deep layers of the cerebral cortex and in ischemic-sensitive areas of the hippocampus. Moreover, oligodendrocytes and astrocytes in brain white matter tracts and optic nerve were also immunoreactive. The intense expression of the P2Y(1) peptide in the aforementioned cell types suggests that this receptor may play fundamental roles in glial physiology. This antiserum should be a useful tool to study the presence of the P2Y(1) receptor in different tissues and cell cultures as well as in expression systems, and to distinguish the P2Y(1) from other subtypes of P2Y receptors.
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Affiliation(s)
- M J Morán-Jiménez
- Departamento de Neurociencias, Facultad de Medicina y Odontología, Universidad del País Vasco, 48940 Leioa, Vizcaya, Spain
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Turner JT, Landon LA, Gibbons SJ, Talamo BR. Salivary gland P2 nucleotide receptors. CRITICAL REVIEWS IN ORAL BIOLOGY AND MEDICINE : AN OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION OF ORAL BIOLOGISTS 2000; 10:210-24. [PMID: 10759423 DOI: 10.1177/10454411990100020701] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The effects of ATP on salivary glands have been recognized since 1982. Functional and pharmacological studies of the P2 nucleotide receptors that mediate the effects of ATP and other extracellular nucleotides have been supported by the cloning of receptor cDNAs, by the expression of the receptor proteins, and by the identification in salivary gland cells of multiple P2 receptor subtypes. Currently, there is evidence obtained from pharmacological and molecular biology approaches for the expression in salivary gland of two P2X ligand-gated ion channels, P2Z/P2X7 and P2X4, and two P2Y G protein-coupled receptors, P2Y1 and P2Y2. Activation of each of these receptor subtypes increases intracellular Ca2+, a second messenger with a key role in the regulation of salivary gland secretion. Through Ca2+ regulation and other mechanisms, P2 receptors appear to regulate salivary cell volume, ion and protein secretion, and increased permeability to small molecules that may be involved in cytotoxicity. Some localization of the various salivary P2 receptor subtypes to specific cells and membrane subdomains has been reported, along with evidence for the co-expression of multiple P2 receptor subtypes within specific salivary acinar or duct cells. However, additional studies in vivo and with intact organ preparations are required to define clearly the roles the various P2 receptor subtypes play in salivary gland physiology and pathology. Opportunities for eventual utilization of these receptors as pharmacotherapeutic targets in diseases involving salivary gland dysfunction appear promising.
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Affiliation(s)
- J T Turner
- Department of Pharmacology, University of Missouri-Columbia School of Medicine, 65212, USA
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Liu X, Singh BB, Ambudkar IS. ATP-dependent activation of K(Ca) and ROMK-type K(ATP) channels in human submandibular gland ductal cells. J Biol Chem 1999; 274:25121-9. [PMID: 10455193 DOI: 10.1074/jbc.274.35.25121] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
[Ca(2+)](i) and membrane current were measured in human submandibular gland ductal (HSG) cells to determine the regulation of salivary cell function by ATP. 1-10 microM ATP activated internal Ca(2+) release, outward Ca(2+)-dependent K(+) channel (K(Ca)), and inward store-operated Ca(2+) current (I(SOC)). The subsequent addition of 100 microM ATP activated an inwardly rectifying K(+) current, without increasing [Ca(2+)](i). The K(+) current was also stimulated by ATP in cells treated with thapsigargin in a Ca(2+)-free medium and was blocked by glibenclamide and tolbutamide, but not by charybdotoxin. This suggests the involvement of a Ca(2+)-independent, sulfonylurea-sensitive K(+) channel (K(ATP)). UTP mimicked the low [ATP] effects, while benzoyl-ATP activated internal Ca(2+) release, a Ca(2+) influx pathway, and K(Ca). Thus, ATP acts via P(2U) (P2Y(2)) and P(2Z) (P2X(7)) receptors to increase [Ca(2+)](i) and activate K(Ca), but not K(ATP). Importantly, (i) ROMK1 and the cystic fibrosis transmembrane regulator protein (but not SUR1, SUR2A, or SUR2B) and (ii) cAMP-stimulated Cl(-) and K(+) currents were detected in HSG cells. These data demonstrate for the first time that a ROMK-type K(ATP) channel is present in salivary gland duct cells that is regulated by extracellular ATP and possibly by the cystic fibrosis transmembrane regulator. This reveals a potentially novel mechanism for K(+) secretion in these cells.
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Affiliation(s)
- X Liu
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892, USA
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35
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Luo X, Zheng W, Yan M, Lee MG, Muallem S. Multiple functional P2X and P2Y receptors in the luminal and basolateral membranes of pancreatic duct cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:C205-15. [PMID: 10444396 DOI: 10.1152/ajpcell.1999.277.2.c205] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Purinergic receptors in the basolateral and luminal membranes of the pancreatic duct can act by a feedback mechanism to coordinate transport activity in the two membranes during ductal secretion. The goal of the present work was to identify and localize the functional P2 receptors (P2R) in the rat pancreatic duct. The lack of selective agonists and/or antagonists for any of the cloned P2R dictated the use of molecular and functional approaches to the characterization of ductal P2R. For the molecular studies, RNA was prepared from microdissected pancreatic intralobular ducts and was shown to be free of mRNA for amylase and endothelial nitric oxide synthase (markers for acinar and endothelial cells, respectively). A new procedure is described to obtain an enriched preparation of single duct cells suitable for electrophysiological studies. Localization of P2R was achieved by testing the effect of various P2R agonists on intracellular Ca(2+) concentration ([Ca(2+)](i)) of microperfused intralobular ducts. RT-PCR analysis suggested the expression of six subtypes of P2R in the pancreatic duct: three P2YR and three P2XR. Activation of Cl(-) current by various nucleotides and coupling of the receptors activated by these nucleotides to G proteins confirmed the expression of multiple P2R in duct cells. Measurement of [Ca(2+)](i) in microperfused intralobular ducts suggested the expression of P2X(1)R, P2X(4)R, probably P2X(7)R, and as yet unidentified P2YR, possibly P2Y(1)R, in the basolateral membrane. Expression of P2Y(2)R, P2Y(4)R, and P2X(7)R was found in the luminal membrane. The unprecedented expression of such a variety of P2R in one cell type, many capable of activating Cl(-) channels, suggests that these receptors may have an important role in pancreatic duct cell function.
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Affiliation(s)
- X Luo
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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36
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Sugita K, Mörk AC, Zhang GH, Martinez JR. Modulation of Ca2+ mobilization by protein kinase C in the submandibular duct cell line A253. Mol Cell Biochem 1999; 198:39-46. [PMID: 10497876 DOI: 10.1023/a:1006925408055] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The expression of protein kinase C (PKC) isoforms and the modulation of Ca2+ mobilization by PKC were investigated in the human submandibular duct cell line A253. Three new PKC (nPKC) isoforms (delta, epsilon, and theta) and one atypical PKC (aPKC) isoform (lambda) are expressed in this cell line. No classical PKC (cPKC) isoforms were present. The effects of the PKC activator phorbol 12-myristate-13-acetate (PMA) and of the PKC inhibitors calphostin C (CC) and bisindolymaleimide I (BSM) on inositol 1,4,5-trisphosphate (IP3) and Ca2+ responses to ATP and to thapsigargin (TG) were investigated. Pre-exposure to PMA inhibited IP3 formation, Ca2+ release and Ca2+ influx in response to ATP. Pre-exposure to CC or BSM slightly enhanced IP3 formation but inhibited the Ca2+ release and the Ca2+ influx induced by ATP. In contrast, pre-exposure to PMA did not modify the Ca2+ release induced by TG, but reduced the influx of Ca2+ seen in the presence of this Ca2+-ATPase inhibitor. These results suggest that PKC modulates elements of the IP3/Ca2+ signal transduction pathway in A253 cells by (1) inhibiting phosphatidylinositol turnover and altering the sensitivity of the Ca2+ channels to IP3, (2) altering the activity, the sensitivity to inhibitors, or the distribution of the TG-sensitive Ca2+ ATPase, and (3) modulating Ca2+ entry pathways.
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Affiliation(s)
- K Sugita
- Department of Pediatrics, University of Texas Health Science Center, San Antonio 78284-7827, USA
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Luo X, Zeng W, Xu X, Popov S, Davignon I, Wilkie TM, Mumby SM, Muallem S. Alternate coupling of receptors to Gs and Gi in pancreatic and submandibular gland cells. J Biol Chem 1999; 274:17684-90. [PMID: 10364208 DOI: 10.1074/jbc.274.25.17684] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Many Gs-coupled receptors can activate both cAMP and Ca2+ signaling pathways. Three mechanisms for dual activation have been proposed. One is receptor coupling to both Gs and G15 (a Gq class heterotrimeric G protein) to initiate independent signaling cascades that elevate intracellular levels of cAMP and Ca+2, respectively. The other two mechanisms involve cAMP-dependent protein kinase-mediated activation of phospholipase Cbeta either directly or by switching receptor coupling from Gs to Gi. These mechanisms were primarily inferred from studies with transfected cell lines. In native cells we found that two Gs-coupled receptors (the vasoactive intestinal peptide and beta-adrenergic receptors) in pancreatic acinar and submandibular gland duct cells, respectively, evoke a Ca2+ signal by a mechanism involving both Gs and Gi. This inference was based on the inhibitory action of antibodies specific for Galphas, Galphai, and phosphatidylinositol 4,5-bisphosphate, pertussis toxin, RGS4, a fragment of beta-adrenergic receptor kinase and inhibitors of cAMP-dependent protein kinase. By contrast, Ca2+ signaling evoked by Gs-coupled receptor agonists was not blocked by Gq class-specific antibodies and was unaffected in Galpha15 -/- knockout mice. We conclude that sequential activation of Gs and Gi, mediated by cAMP-dependent protein kinase, may represent a general mechanism in native cells for dual stimulation of signaling pathways by Gs-coupled receptors.
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Affiliation(s)
- X Luo
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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38
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39
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Kabré E, Chaïb N, Boussard P, Mérino G, Devleeschouwer M, Dehaye JP. Study on the activation of phospholipases A2 by purinergic agonists in rat submandibular ductal cells. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1436:616-27. [PMID: 9989292 DOI: 10.1016/s0005-2760(98)00158-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Extracellular ATP and benzoyl-ATP (Bz-ATP) increased the release of [3H]arachidonic acid ([3H]AA) from prelabeled rat submandibular gland (RSMG) ductal cells respectively two- and threefold. Both agonists also increased the release of [3H]AA from acini but at a lower level (+50% and +100% respectively). Carbachol had no significant effect on either cellular population. In ductal cells phorbol myristate acetate, an activator of protein kinase C, slightly increased the basal release of [3H]AA but did not affect the release of [3H]AA in response to ATP. Staurosporine, an inhibitor of protein kinases, inhibited the response to the purines. The removal of calcium from the extracellular medium decreased the response to ATP and Bz-ATP. Only barium could partly substitute for calcium to restore the purinergic response. Zinc inhibited the release of [3H]AA. Permeabilization of the cells with streptolysin O (SLO) activated the calcium-independent phospholipase A2 activity (iPLA2). The iPLA2, not the calcium-dependent PLA2 (cPLA2), released [3H]oleic acid ([3H]OA) from RSMG ductal cells. It is concluded that RSMG ducts have a higher PLA2 activity when compared to acini. This activity is accounted for by iPLA2 and cPLA2. Both enzymes are activated by P2X agonists by a staurosporine-sensitive mechanism. Cells permeabilized with SLO or membranes from Escherichia coli as a substrate are not good models to study the regulation of these enzymes. In intact RSMG ductal cells the two activities can be distinguished by rather specific inhibitors, by different ionic conditions and also by the fatty acid used to label the cells.
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Affiliation(s)
- E Kabré
- Laboratoire de Biochimie Générale et Humaine, Université Libre de Bruxelles, Belgium
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40
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Lee MG, Schultheis PJ, Yan M, Shull GE, Bookstein C, Chang E, Tse M, Donowitz M, Park K, Muallem S. Membrane-limited expression and regulation of Na+-H+ exchanger isoforms by P2 receptors in the rat submandibular gland duct. J Physiol 1998; 513 ( Pt 2):341-57. [PMID: 9806987 PMCID: PMC2231293 DOI: 10.1111/j.1469-7793.1998.341bb.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/1998] [Accepted: 08/24/1998] [Indexed: 11/26/2022] Open
Abstract
1. Cell-specific reverse transcriptase-polymerase chain reaction (RT-PCR), immunolocalization and microspectrofluorometry were used to identify and localize the Na+-H+ exchanger (NHE) isoforms expressed in the submandibular gland (SMG) acinar and duct cells and their regulation by basolateral and luminal P2 receptors in the duct. 2. The molecular and immunofluorescence analysis showed that SMG acinar and duct cells expressed NHE1 in the basolateral membrane (BLM). Duct cells also expressed NHE2 and NHE3 in the luminal membrane (LM). 3. Expression of NHE3 was unequivocally established by the absence of staining in SMG from NHE3 knockout mice. NHE3 was expressed in the LM and in subluminal regions of the duct. 4. Measurement of the inhibition of NHE activity by the amiloride analogue HOE 694 (HOE) suggested expression of NHE1-like activity in the BLM and NHE2-like activity in the LM of the SMG duct. Several acute and chronic treatments tested failed to activate NHE activity with low affinity for HOE as expected for NHE3. Hence, the physiological function and role of NHE3 in the SMG duct is not clear at present. 5. Activation of P2 receptors resulted in activation of an NHE-independent, luminal H+ transport pathway that markedly and rapidly acidified the cells. This pathway could be blocked by luminal but not basolateral Ba2+. 6. Stimulation of P2U receptors expressed in the BLM activated largely NHE1-like activity, and stimulation of P2Z receptors expressed in the LM activated largely NHE2-like activity. 7. The interrelation between basolateral and luminal NHE activities and their respective regulation by P2U and P2Z receptors can be used to co-ordinate membrane transport events in the LM and BLM during active Na+ reabsorption by the SMG duct.
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Affiliation(s)
- M G Lee
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
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41
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Xu X, Croy JT, Zeng W, Zhao L, Davignon I, Popov S, Yu K, Jiang H, Offermanns S, Muallem S, Wilkie TM. Promiscuous coupling of receptors to Gq class alpha subunits and effector proteins in pancreatic and submandibular gland cells. J Biol Chem 1998; 273:27275-9. [PMID: 9765251 DOI: 10.1074/jbc.273.42.27275] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mice with deficiencies in one or more Gq class alpha subunit genes were used to examine the role of the alpha subunit in regulating Ca2+ signaling in pancreatic and submandibular gland cells. Western blot analysis showed that these cells express three of the four Gq class subunits, Galphaq, Galpha11, and Galpha14 but not Galpha15. Surprisingly, all parameters of Ca2+ signaling were identical in cells from wild type and four lines of mutant mice: 1) Galpha11-/-, 2) Galpha11-/-/Galpha14-/-, 3) Galpha14-/-/Galpha15-/-, and 4) Galphaq-/-/Galpha15-/-. These parameters included the Kapp for several Gq class coupled receptors, induction of [Ca2+]i oscillations by weak stimulation, and a biphasic [Ca2+]i response by strong stimulation. Furthermore, Ca2+ release from internal stores and Ca2+ entry were not affected in cells from any of the mutant mice. We conclude that Galphaq, Galpha11, and Galpha14 promiscuously couple several receptors (m3 muscarinic, bombesin, cholecystokinin, and alpha1 adrenergic) to effector proteins that activate both Ca2+ release from internal stores and Ca2+ entry.
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Affiliation(s)
- X Xu
- Department, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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42
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Sévigny J, Grondin G, Gendron FP, Roy J, Beaudoin AR. Demonstration and immunolocalization of ATP diphosphohydrolase in the pig digestive system. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:G473-82. [PMID: 9724258 DOI: 10.1152/ajpgi.1998.275.3.g473] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Two isoforms of ATP diphosphohydrolase (ATPDase; EC 3.6.1.5) have been previously characterized, purified, and identified. This enzyme is an ectonucleotidase that catalyzes the sequential release of gamma- and beta-phosphate groups of triphospho- and diphosphonucleosides. One of its putative roles is to modulate the extracellular concentrations of purines in different physiological systems. The purpose of this study was to define, identify, and localize these two isoforms of ATPDase in the pig digestive system. ATPDase activity was measured in pig stomach, duodenum, pancreas, and parotid gland. Enzyme assays, electrophoretograms, and Western blots with a polyclonal antibody that recognizes both isoforms demonstrate the presence of ATPDase in these organs. Immunolocalization showed intense reactions with gastric glands (parietal and chief cells), intestine (columnar epithelial cells), parotid gland, and pancreas. Smooth muscle cells all along the digestive tract were also highly reactive. Considering the variety of purinoceptors associated with the digestive system, the ATPDase is strategically positioned to modulate purine-mediated actions such as electrolyte secretion, glandular secretion, smooth muscle contraction, and blood flow.
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Affiliation(s)
- J Sévigny
- Département de Biologie, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1
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43
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Chaïb N, Kabré E, Métioui M, Alzola E, Dantinne C, Marino A, Dehaye JP. Differential sensitivity to nickel and SK&F96365 of second messenger-operated and receptor-operated calcium channels in rat submandibular ductal cells. Cell Calcium 1998; 23:395-404. [PMID: 9924631 DOI: 10.1016/s0143-4160(98)90096-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The intracellular concentration of calcium ([Ca2+]i) of rat submandibular ductal cells was measured with the intracellular fluorescent dye Fura-2. Carbachol (100 microM) and ATP (1 mM) both increased the [Ca2+]i. The late response to ATP was blocked by 0.5 mM Ni2+. This concentration of Ni2+ also blocked the increase of the [Ca2+]i and the uptake of manganese and calcium in response to 2'- and 3'-O-(4-benzoylbenzoyl) adenosine 5'-triphosphate (BzATP, 100 microM), a specific agonist of P2X receptors from salivary glands. The increase of the [Ca2+]i in response to 2-methylthioadenosine 5'-triphosphate (2-MeSATP, 100 microM) a specific P2Y agonist in salivary glands or to a muscarinic agonist (carbachol) was not affected by 0.5 mM Ni2+. Only higher concentrations of Ni2+ (in the millimolar range) inhibited the uptake of extracellular calcium in response to carbachol. SK&F96365, a blocker of store-operated calcium channels, inhibited the uptake of extracellular calcium in response to carbachol without affecting the response to BzATP. It is concluded that at low concentrations (below 0.5 mM), Ni2+ inhibits the non-specific cation channel coupled to P2X receptors. The uptake of extracellular calcium by store-operated calcium channels is inhibited by higher concentrations of Ni2+ and by SK&F96365.
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Affiliation(s)
- N Chaïb
- Laboratoire de Biochimie générale et humaine, Institut de Pharmacie, Université libre de Bruxelles, Belgium.
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44
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Yamamoto-Hino M, Miyawaki A, Segawa A, Adachi E, Yamashina S, Fujimoto T, Sugiyama T, Furuichi T, Hasegawa M, Mikoshiba K. Apical vesicles bearing inositol 1,4,5-trisphosphate receptors in the Ca2+ initiation site of ductal epithelium of submandibular gland. J Cell Biol 1998; 141:135-42. [PMID: 9531553 PMCID: PMC2132724 DOI: 10.1083/jcb.141.1.135] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In polarized epithelial cells, agonists trigger Ca2+ waves and oscillations. These patterns may be caused by the compartmentalization of inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ pools into specific regions. We have investigated the relationship between the distribution of IP3 receptors (IP3Rs) and the spatiotemporal pattern of Ca2+ signaling in the duct cells of the rat submandibular gland (SMG). Using immunofluorescence, although labeling was somewhat heterogeneous, the IP3Rs were colocalized to the apical pole of the duct cells. Immunoelectron microscopy identified small apical vesicles bearing IP3R2 in some types of duct cells. Real-time confocal imaging of intact ducts demonstrated that, after carbachol stimulation, an initial Ca2+ spike occurred in the apical region. Subsequently, repetitive Ca2+ spikes spread from the apical to the middle cytoplasm. These apical Ca2+ initiation sites were found only in some "pioneer cells," rather than in all duct cells. We performed both Ca2+ imaging and immunofluorescence on the same ducts and detected the strongest immunosignals of IP3R2 in the Ca2+ initiation sites of the pioneer cells. The subcellular localization and expression level of IP3Rs correlated strongly with the spatiotemporal nature of the intracellular Ca2+ signal and distinct Ca2+ responses among the rat SMG duct cells.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium Channels/analysis
- Calcium Channels/biosynthesis
- Calcium Channels/physiology
- Carbachol/pharmacology
- Cell Membrane/drug effects
- Cell Membrane/physiology
- Cell Membrane/ultrastructure
- Cell Polarity
- Epithelial Cells/drug effects
- Epithelial Cells/physiology
- Epithelial Cells/ultrastructure
- Inositol 1,4,5-Trisphosphate Receptors
- Kinetics
- Microscopy, Electron
- Microscopy, Immunoelectron
- Microscopy, Video
- RNA, Messenger/metabolism
- Rats
- Receptors, Cytoplasmic and Nuclear/analysis
- Receptors, Cytoplasmic and Nuclear/biosynthesis
- Receptors, Cytoplasmic and Nuclear/physiology
- Signal Transduction
- Submandibular Gland/cytology
- Submandibular Gland/physiology
- Transcription, Genetic
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Affiliation(s)
- M Yamamoto-Hino
- Developmental Neurobiology Laboratory, RIKEN Brain Science Institute, Wako-City, Saitama 351, Japan
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45
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Zeng W, Lee MG, Muallem S. Membrane-specific regulation of Cl- channels by purinergic receptors in rat submandibular gland acinar and duct cells. J Biol Chem 1997; 272:32956-65. [PMID: 9407075 DOI: 10.1074/jbc.272.52.32956] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Measurement of [Cl-]i and the Cl- current in the rat salivary submandibular gland (SMG) acinar and duct cells was used to evaluate the role of Cl- channels in the regulation of [Cl-]i during purinergic stimulation. Under resting conditions [Cl-]i averaged 56 +/- 8 and 26 +/- 7 mM in acinar and duct cells, respectively. In both cells, stimulation with 1 mM ATP resulted in Cl- efflux and subsequent influx. Inhibition of NaKCl2 cotransport had no effect on [Cl-]i changes in duct cells and inhibited only about 50% of Cl- uptake in acinar cells. Accordingly, low levels of expression of NaKCl2 cotransporter protein were found in duct cells. Acinar cells expressed high levels of the cotransporter. Measurement of Cl- current under selective conditions revealed that acinar and duct cells express at least five distinct Cl- channels; a ClCO-like, volume-sensitive, inward rectifying, Ca2+-activated and CFTR-like Cl- currents. ATP acting on both cell types activated at least two channels, the Ca2+-activated Cl- channel and a Ca2+-independent glibenclamide-sensitive Cl--current, possibly cystic fibrosis transmembrane regulator (CFTR). Of the many nucleotides tested only 2'-3'-benzoylbenzoyl (Bz)-ATP and UTP activated Cl- channels in SMG cells. Despite their relative potency in increasing [Ca2+]i, BzATP in both SMG cell types largely activated the Ca2+-independent, glibenclamide-sensitive Cl- current, whereas UTP activated only the Ca2+-dependent Cl- current. We interpret this to suggest that BzATP and UTP largely activate Cl- channels residing in the membrane expressing the receptor for the active nucleotide. The present studies reveal a potentially new mechanism for transcellular Cl- transport in a CFTR-expressing tissue, the SMG. Coordinated action of the P2z (luminal) and P2u (basolateral) receptors can mediate part of the transcellular Cl- transport by acinar and duct cells to determine the final electrolyte composition of salivary fluid.
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Affiliation(s)
- W Zeng
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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46
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Lee MG, Zeng W, Muallem S. Characterization and localization of P2 receptors in rat submandibular gland acinar and duct cells. J Biol Chem 1997; 272:32951-5. [PMID: 9407074 DOI: 10.1074/jbc.272.52.32951] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
[Ca2+]i and the Cl- current were measured in isolated submandibular gland acinar and duct cells to characterize and localize the purinergic receptors expressed in these cells. In both cell types 2'-3'-benzoylbenzoyl (Bz)-ATP and ATP increased [Ca2+]i mainly by activation of Ca2+ influx. UTP had only minimal effect on [Ca2+]i at concentrations between 0.1 and 1 mM. However, a whole cell current recording showed that all nucleotides effectively activated Cl- currents. Inhibition of signal transduction through G proteins by guanyl-5'-beta-thiophosphate revealed that the effect of ATP on Cl- current was mediated in part by activation of a G protein-coupled and in part by a G protein-independent receptor. BzATP activated exclusively the G protein-independent portion, whereas UTP activated only the G protein-dependent portion of the Cl- current. Measurement of [Ca2+]i in the microperfused duct showed that ATP stimulated a [Ca2+]i increase when applied to the luminal or the basolateral sides. BzATP increased [Ca2+]i only when applied to the luminal side, whereas UTP at 100 microM increased -Ca2+-i only when applied to the basolateral side. The combined results suggest that duct and possibly acinar cells express P2z receptors in the luminal and P2u receptors in the basolateral membrane.
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Affiliation(s)
- M G Lee
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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47
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Xu X, Zeng W, Diaz J, Lau KS, Gukovskaya AC, Brown RJ, Pandol SJ, Muallem S. nNOS and Ca2+ influx in rat pancreatic acinar and submandibular salivary gland cells. Cell Calcium 1997; 22:217-28. [PMID: 9330792 DOI: 10.1016/s0143-4160(97)90015-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Regulation of agonist-activated Ca2+ influx by the NOS pathway through generation of cGMP is being found in an increasing number of cell types. In the present work, we examined the role of the NOS pathway in agonist-evoked [Ca2+]i oscillations and attempted to identify the NOS isoform most likely to regulate Ca2+ influx. For this, we first show that two Ca(2+)-mobilizing agonists acting on pancreatic acinar cells, bombesin (BS) and the cholecystokinin analog CCK-JMV-180 (CCKJ), evokes different type of [Ca2+]i oscillations. The BS-evoked [Ca2+]i oscillations rapidly became acutely dependent on the presence of extracellular Ca2+, whereas the CCKJ-evoked oscillations continue for long periods of time in the absence of Ca2+ influx. This differential behavior allowed us to isolate Ca2+ influx and study its regulation while controlling for non specific effects on all other Ca2+ transporting events involved in generating [Ca2+]i oscillations. Inhibitors of selective steps in the NOS pathway inhibited agonist-induced cGMP production. The inhibitors were then used to show that scavenging NO with reduced hemoglobin, inhibition of guanylyl cyclase with 1H-[1,2,4] oxadiazolo[4,3-a] quinoxaline-1-one (ODQ) and inhibition of protein kinase G with Rp-8-pCPT-cGMPS inhibited [Ca2+]i oscillations evoked by BS but not those evoked by CCKJ. These findings were extended to duct and acinar cells of the SMG. In these cells, Ca(2+)-mobilizing agonists stimulate large Ca2+ influx, which was inhibited by all inhibitors of the NOS pathway. Western blot analysis and immunolocalization revealed that the cells did not express iNOS, eNOS was expressed only in blood vessels and capillaries whereas nNOS was expressed at high levels next to the plasma membrane of all cells. Accordingly, the nNOS inhibitor 7-nitroindazole (7-NI) inhibited BS- but not CCKJ-evoked [Ca2+]i oscillations and Ca2+ influx into SMG acinar and duct cells. Thus, together, our findings favor nNOS as the isoform activated by the Ca2+ released from internal stores to generate cGMP and regulate Ca2+ influx.
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Affiliation(s)
- X Xu
- Department of Physiology, University of Texas, Southwestern Medical Center, Dallas 75235, USA
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48
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Lee MG, Xu X, Zeng W, Diaz J, Kuo TH, Wuytack F, Racymaekers L, Muallem S. Polarized expression of Ca2+ pumps in pancreatic and salivary gland cells. Role in initiation and propagation of [Ca2+]i waves. J Biol Chem 1997; 272:15771-6. [PMID: 9188473 DOI: 10.1074/jbc.272.25.15771] [Citation(s) in RCA: 160] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The present study was aimed at localization of plasma membrane (PMCA) and intracellular (SERCA) Ca2+ pumps and characterizing their role in initiation and propagation of Ca2+ waves. Specific and polarized expression of Ca2+ pumps was observed in all epithelial cells examined. Immunolocalization revealed expression of PMCA in both the basolateral and luminal membranes of all cell types. SERCA2a appeared to be expressed in the luminal pole, whereas SERCA2b was expressed in the basal pole and the nuclear envelope of pancreatic acini. Interestingly, SERCA2b was found in the luminal pole of submandibular salivary gland acinar and duct cells. These cells expressed SERCA3 in the basal pole. To examine the significance of the polarized expression of SERCA and perhaps PMCA pumps in secretory cells, we compared the effect of inhibition of SERCA pumps with thapsigargine and partial Ca2+ release with ionomycin on Ca2+ release evoked by agonists and Ca2+ uptake induced by antagonists. Despite their polarized expression, Ca2+ uptake by SERCA pumps and Ca2+ efflux by PMCA resulted in uniform reduction in [Ca2+]i. Surprisingly, inhibition of the SERCA pumps, but not Ca2+ release by ionomycin, eliminated the distinct initiation sites and propagated Ca2+ waves, leading to a uniform increase in [Ca2+]i. In addition, inhibition of SERCA pumps reduced the rate of Ca2+ release from internal stores. The implication of these findings to rates of Ca2+ diffusion in the cytosol, compartmentalization of Ca2+ signaling complexes, and mechanism of Ca2+ wave propagation are discussed.
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Affiliation(s)
- M G Lee
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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49
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Lee MG, Xu X, Zeng W, Diaz J, Wojcikiewicz RJ, Kuo TH, Wuytack F, Racymaekers L, Muallem S. Polarized expression of Ca2+ channels in pancreatic and salivary gland cells. Correlation with initiation and propagation of [Ca2+]i waves. J Biol Chem 1997; 272:15765-70. [PMID: 9188472 DOI: 10.1074/jbc.272.25.15765] [Citation(s) in RCA: 229] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In polarized epithelial cells [Ca2+]i waves are initiated in discrete regions and propagate through the cytosol. The structural basis for these compartmentalized and coordinated events are not well understood. In the present study we used a combination of [Ca2+]i imaging at high temporal resolution, recording of Ca2+-activated Cl- current, and immunolocalization by confocal microscopy to study the correlation between initiation and propagation of [Ca2+]i waves and localization of Ca2+ release channels in pancreatic acini and submandibular acinar and duct cells. In all cells Ca2+ waves are initiated in the luminal pole and propagate through the cell periphery to the basal pole. All three cell types express the three known inositol 1,4,5-trisphosphate receptors (IP3Rs). Expression of IP3Rs was confined to the area just underneath the luminal and lateral membranes, with no detectable receptors in the basal pole or other regions of the cells. In pancreatic acini and SMG ducts IP3R3 was also found in the nuclear envelope. Expression of ryanodine receptor was detected in submandibular salivary gland cells but not pancreatic acini. Accordingly, cyclic ADP ribose was very effective in mobilizing Ca2+ from internal stores of submandibular salivary gland but not pancreatic acinar cells. Measurement of [Ca2+]i and localization of IP3Rs in the same cells suggests that only a small part of IP3Rs participate in the initiation of the Ca2+ wave, whereas most receptors in the cell periphery probably facilitate the propagation of the Ca2+ wave. The combined results together with our previous studies on this subject lead us to conclude that the internal Ca2+ pool is highly compartmentalized and that compartmentalization is achieved in part by polarized expression of Ca2+ channels.
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Affiliation(s)
- M G Lee
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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50
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Ko WH, Wilson SM, Wong PY. Purine and pyrimidine nucleotide receptors in the apical membranes of equine cultured epithelia. Br J Pharmacol 1997; 121:150-6. [PMID: 9146899 PMCID: PMC1564646 DOI: 10.1038/sj.bjp.0701093] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
1. The short circuit current (ISC) technique was used to quantify electrolyte transport by equine cultured sweat gland epithelia. Adenosine 5'-triphosphate (ATP) and certain related compounds, caused transient increases in ISC when added to the apical solution. The order of potency was uridine triphosphate (UTP) > ATP > ADP > > AMP = adenosine. 2. The responses to apical nucleotides were due to chloride and bicarbonate secretion and were reduced in pertussis toxin-treated cells. P2-receptors sensitive to uridine 5'-triphosphate (UTP), that interact with inhibitory G proteins, therefore appear to be present in the apical membrane. 3. Responses to ATP and UTP were reduced in cells loaded with BAPTA, a calcium chelator. BAPTA attenuated the response to ATP more than the response to UTP suggesting that these nucleotides may not act via a common pathway. 4. Cross-desensitization experiments indicated that two populations of UTP-sensitive receptor were present. One was sensitive to UTP and ATP, whereas the second was sensitive only to UTP. Uridine diphosphate appeared to activate the ATP-insensitive receptor population selectively. 5. These data suggest that apical pyrimidinoceptors may be expressed by these cells. The physiological role of these receptors is unknown but they may allow the autocrine regulation of epithelial function.
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Affiliation(s)
- W H Ko
- Department of Physiology, Chinese University of Hong Kong, New Territories, Hong Kong
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