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Amaya MJ, Nathanson MH. Calcium signaling and the secretory activity of bile duct epithelia. Cell Calcium 2014; 55:317-24. [PMID: 24612866 DOI: 10.1016/j.ceca.2014.02.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 02/03/2014] [Accepted: 02/04/2014] [Indexed: 12/20/2022]
Abstract
Cytosolic calcium (Cai(2+)) is a second messenger that is important for the regulation of secretion in many types of tissues. Bile duct epithelial cells, or cholangiocytes, are polarized epithelia that line the biliary tree in liver and are responsible for secretion of bicarbonate and other solutes into bile. Cai(2+) signaling plays an important role in the regulation of secretion by cholangiocytes, and this review discusses the machinery involved in the formation of Ca(2+) signals in cholangiocytes, along with the evidence that these signals regulate ductular secretion. Finally, this review discusses the evidence that impairments in cholangiocyte Ca(2+) signaling play a primary role in the pathogenesis of cholestatic disorders, in which hepatic bile secretion is impaired.
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Affiliation(s)
- Maria Jimena Amaya
- Section of Digestive Diseases, Department of Internal Medicine, Yale University, 333 Cedar Street, PO Box 208019, New Haven, CT 06520-8019, USA
| | - Michael H Nathanson
- Section of Digestive Diseases, Department of Internal Medicine, Yale University, 333 Cedar Street, PO Box 208019, New Haven, CT 06520-8019, USA.
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Acidocalcisomes of Trypanosoma brucei have an inositol 1,4,5-trisphosphate receptor that is required for growth and infectivity. Proc Natl Acad Sci U S A 2013; 110:1887-92. [PMID: 23319604 DOI: 10.1073/pnas.1216955110] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Acidocalcisomes are acidic calcium stores rich in polyphosphate and found in a diverse range of organisms. The mechanism of Ca(2+) release from these organelles was unknown. Here we present evidence that Trypanosoma brucei acidocalcisomes possess an inositol 1,4,5-trisphosphate receptor (TbIP(3)R) for Ca(2+) release. Localization studies in cell lines expressing TbIP(3)R in its endogenous locus fused to an epitope tag revealed its partial colocalization with the vacuolar proton pyrophosphatase, a marker of acidocalcisomes. IP(3) was able to stimulate Ca(2+) release from a chicken B-lymphocyte cell line in which the genes for all three vertebrate IP(3)Rs have been stably ablated (DT40-3KO) and that were stably expressing TbIP(3)R, providing evidence of its function. IP(3) was also able to release Ca(2+) from permeabilized trypanosomes or isolated acidocalcisomes and photolytic release of IP(3) in intact trypanosomes loaded with Fluo-4 elicited a transient Ca(2+) increase in their cytosol. Ablation of TbIP(3)R by RNA interference caused a significant reduction of IP(3)-mediated Ca(2+) release in trypanosomes and resulted in defects in growth in culture and infectivity in mice. Taken together, the data provide evidence of the presence of a functional IP(3)R as a Ca(2+) release channel in acidocalcisomes of trypanosomes and suggest that a Ca(2+) signaling pathway that involves acidocalcisomes is required for growth and establishment of infection.
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Abstract
Ca2+ transfer from endoplasmic reticulum (ER) to mitochondria can trigger apoptotic pathways by inducing release of mitochondrial pro-apoptotic factors. Three different types of inositol 1,4,5-trisphosphate receptor (IP3R) serve to discharge Ca2+ from ER, but possess some peculiarities, especially in apoptosis induction. The anti-apoptotic protein Akt can phosphorylate all IP3R isoforms and protect cells from apoptosis, reducing ER Ca2+ release. However, it has not been elucidated which IP3R subtypes mediate these effects. Here, we show that Akt activation in COS7 cells, which lack of IP3R I, strongly suppresses IP3-mediated Ca2+ release and apoptosis. Conversely, in SH-SY 5Y cells, which are type III-deficient, Akt is unable to modulate ER Ca2+ flux, losing its anti-apoptotic activity. In SH-SY 5Y-expressing subtype III, Akt recovers its protective function on cell death, by reduction of Ca2+ release. Moreover, regulating Ca2+ flux to mitochondria, Akt maintains the mitochondrial integrity and delays the trigger of apoptosis, in a type III-dependent mechanism. These results demonstrate a specific activity of Akt on IP3R III, leading to diminished Ca2+ transfer to mitochondria and protection from apoptosis, suggesting an additional level of cell death regulation mediated by Akt.
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Chaloux B, Caron AZ, Guillemette G. Protein kinase A increases the binding affinity and the Ca2+ release activity of the inositol 1,4,5-trisphosphate receptor type 3 in RINm5F cells. Biol Cell 2012; 99:379-88. [PMID: 17373911 DOI: 10.1042/bc20060121] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION In endocrine cells, IP(3)R (inositol 1,4,5-trisphosphate receptor), a ligand-gated Ca2+ channel, plays an important role in the control of intracellular Ca2+ concentration. There are three subtypes of IP(3)R that are distributed differentially among cell types. RINm5F cells express almost exclusively the IP(3)R-3 subtype. The purpose of the present study was to investigate the effect of PKA (protein kinase A) on the activity of IP(3)R-3 in RINm5F cells. RESULTS We show that immunoprecipitated IP(3)R-3 is a good substrate for PKA. Using a back-phosphorylation approach, we show that endogenous PKA phosphorylates IP(3)R-3 in intact RINm5F cells. [(3)H]IP(3) (inositol 1,4,5-trisphosphate) binding affinity and IP(3)-induced Ca2+ release activity were enhanced in permeabilized cells that were pre-treated with forskolin or PKA. The PKA-induced enhancement of IP(3)R-3 activity was also observed in intact RINm5F cells stimulated with carbachol and epidermal growth factor, two agonists that use different receptor types to activate phospholipase C. CONCLUSION The results of the present study reveal a converging step where the cAMP and the Ca2+ signalling systems act co-operatively in endocrine cell responses to external stimuli.
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Affiliation(s)
- Benoit Chaloux
- Department of Pharmacology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec, Canada
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Guido M, Fagundes DJ, Ynouye CM, Pontes ERJC, Takita LC, Amaral EGSD, Teruya R, Paes MC, Brasileiro JL, Aydos RD. Apoptotic effects of inositol hexaphosphate on biomarker Itpr3 in induced colon rat carcinogenesis. Acta Cir Bras 2008; 23:157-64. [DOI: 10.1590/s0102-86502008000200008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Accepted: 12/11/2007] [Indexed: 11/22/2022] Open
Abstract
PURPOSE: To study the effect of the modulation of inositol hexaphosphate (IP6) in the biological immunohistochemistry expression of cellular signaling marker apoptosis, in model of carcinogenesis of colon induced by azoxymethane (AOM). METHODS: Wistar rats (N=112) distributed in 4 groups (n=28): Control; B, AOM (5 mg kg-1, 2x, to break week 3); C, IP6 (in water 1%, six weeks); D, IP6+AOM. Weekly euthanasia (n=7), from week three. Immunohistochemistry of ascendant colon with biological marker inositol 1,4,5 triphosphate receptor type III (Itpr3). Quantification of the immune-expression with use of computer-assisted image processing. Analysis statistics of the means between groups, weeks in groups, groups in weeks, and established significance when p<0.05. RESULTS: One proved significant difference between groups in the expression of Itpr3, p<0.0001; with Itpr3 reduction of BxD group, p<0.001. CONCLUSION: Inositol hexaphosphate promotes modulation of biological markers with reduction of Itpr3 in carcinogenesis of colon.
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Roedding AS, Li PP, Warsh JJ. Characterization of the transient receptor potential channels mediating lysophosphatidic acid-stimulated calcium mobilization in B lymphoblasts. Life Sci 2006; 80:89-97. [PMID: 16979191 DOI: 10.1016/j.lfs.2006.08.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Revised: 08/03/2006] [Accepted: 08/17/2006] [Indexed: 11/19/2022]
Abstract
Altered 1-oleoyl-lysophosphatidic acid (LPA, 100 microM)-stimulated calcium responses occur in B-lymphoblast cell lines from bipolar disorder patients, but the mechanism(s) involved is uncertain. Lysophosphatidic acid shares a structurally similar fatty acid side chain with the diacylglycerol analogue, 1-oleoyl-2-acetyl-sn-glycerol (OAG), a known activator of subtypes 3, 6 and 7 of the canonical transient receptor potential (TRPC) cation channel subfamily. Accordingly, the objective of this study was to determine whether the LPA-stimulated calcium response in B-lymphoblasts is mediated, in part, through this TRPC channel subfamily. Divalent cation selectivity in response to thapsigargin, LPA and OAG were used to distinguish TRPC-like character of the responses to these agents in BLCLs. The sensitivity to gadolinium, an inhibitor of capacitative calcium channels, was used to determine the store-operated nature of the responses. The TRPC isoforms that are present in BLCLs as identified by immunoblotting and/or PCR include TRPC1, 3 and 5. Minimal barium influx in calcium-free buffer was observed following thapsigargin stimulation. However, LPA stimulated barium influx of a magnitude similar to that induced by OAG. Thapsigargin-provoked calcium influx was completely inhibited by gadolinium (10 microM), whereas LPA and OAG-stimulated responses were partially inhibited and potentiated, respectively. The results suggest that 100 microM LPA stimulates calcium entry through channels with characteristics similar to TRPC3, as TRPC6 and 7 are absent in B-lymphoblasts.
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Affiliation(s)
- Angela S Roedding
- Laboratory of Cellular and Molecular Pathophysiology, Centre for Addiction and Mental Health, Toronto, ON, Canada M5T 1R8
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Singer RH, Lawrence DS, Ovryn B, Condeelis J. Imaging of gene expression in living cells and tissues. JOURNAL OF BIOMEDICAL OPTICS 2005; 10:051406. [PMID: 16292943 DOI: 10.1117/1.2103032] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
It is possible to observe gene expression within single cells using a tetracycline inducible promoter for activation. Transcription can be observed by using a fluorescent fusion protein to bind nascent RNA. Ultimately, it is desirable to activate a reporter gene within a single cell with only photons. This is achieved by preparing a chemically altered transcription factor that is functionally unable to activate a reporter gene until it is exposed to photon excitation. We apply two-photon imaging to visualize tumor cells expressing a transgene and ultimately this approach will provide the means to activate a specific gene within a single cell within any tissue to ultimately observe its functional significance in situ.
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Affiliation(s)
- Robert H Singer
- Albert Einstein College of Medicine, Department of Anatomy and Structural Biology and Biochemistry, Biophotonics Center, 1300 Morris Park Avenue, Bronx, New York 10461, USA.
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Aromolaran AAS, Blatter LA. Modulation of intracellular Ca2+ release and capacitative Ca2+ entry by CaMKII inhibitors in bovine vascular endothelial cells. Am J Physiol Cell Physiol 2005; 289:C1426-36. [PMID: 16093279 DOI: 10.1152/ajpcell.00262.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of inhibitors of CaMKII on intracellular Ca2+ signaling were examined in single calf pulmonary artery endothelial (CPAE) cells using indo-1 microfluorometry to measure cytoplasmic Ca2+ concentration ([Ca2+]i). The three CaMKII inhibitors, KN-93, KN-62, and autocamtide-2-related inhibitory peptide (AIP), all reduced the plateau phase of the [Ca2+]i transient evoked by stimulation with extracellular ATP. Exposure to KN-93 or AIP alone in the presence of 2 mM extracellular Ca2+ resulted in a dose-dependent increase of [Ca2+]i consisting of a rapid and transient Ca2+ spike followed by a small sustained plateau phase of elevated [Ca2+]i. Exposure to KN-93 in the absence of extracellular Ca2+ caused a transient rise of [Ca2+]i, suggesting that exposure to CaMKII inhibitors directly triggered release of Ca2+ from intracellular endoplasmic reticulum (ER) Ca2+ stores. Repetitive stimulation with KN-93 and ATP, respectively, revealed that both components released Ca2+ largely from the same store. Pretreatment of CPAE cells with the membrane-permeable inositol 1,4,5-trisphosphate (IP3) receptor blocker 2-aminoethoxydiphenyl borate caused a significant inhibition of the KN-93-induced Ca2+ response, suggesting that exposure to KN-93 affects Ca2+ release from an IP3-sensitive store. Depletion of Ca2+ stores by exposure to ATP or to the ER Ca2+ pump inhibitor thapsigargin triggered robust capacitative Ca2+ entry (CCE) signals in CPAE cells that could be blocked effectively with KN-93. The data suggest that in CPAE cells, CaMKII modulates Ca2+ handling at different levels. The use of CaMKII inhibitors revealed that in CPAE cells, the most profound effects of CaMKII are inhibition of release of Ca2+ from intracellular stores and activation of CCE.
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Rossi AM, Picotto G, de Boland AR, Boland RL. Evidence on the operation of ATP-induced capacitative calcium entry in breast cancer cells and its blockade by 17beta-estradiol. J Cell Biochem 2004; 87:324-33. [PMID: 12397614 DOI: 10.1002/jcb.10303] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Little is known about the regulation of cytosolic calcium Ca(2+) levels ([Ca(2+)](i)) in breast cancer cells. We investigated the existence of capacitative calcium entry (CCE) in the tumorigenic cell line MCF-7 and its responsiveness to ATP. MCF-7 cells express purinergic receptors as well as estrogen receptors (ER). Depletion of calcium stores with thapsigargin (TG, 500 nM) or ATP (10 microM) in the absence of extracellular Ca(2+), resulted in a rapid and transient elevation in [Ca(2+)](i). After recovery of basal levels, Ca(2+) readmission (1.5 mM) to the medium increased Ca(2+) influx (twofold over basal), reflecting pre-activation of a CCE pathway. Cells pretreated with TG were unable to respond to ATP, thus indicating that the same Ca(2+) store is involved in their response. Moreover, IP(3)-dependent ATP-induced calcium mobilization and CCE were completely blocked using compound U-73122, an inhibitor of phospholipase C. Compound 2-APB (75 microM) and Gd(3+) (10 microM), antagonists of the CCE pathway, completely prevented ATP-stimulated capacitative Ca(2+) entry. CCE in MCF-7 cells was highly permeable to Mn(2+) and to the Ca(2+) surrogate Sr(2+). Mn(2+) entry sensitivity to Gd(3+) matched that of the Ca(2+) entry pathway. 17Beta-estradiol blocked ATP-induced CCE, but was without effect on TG-induced CCE. Besides, the estrogen blockade of the ATP-induced CCE was completely abolished by preincubation of the cells with an ER monoclonal antibody. ER alpha immunoreactivity could also be detected in a purified plasma membrane fraction of MCF-7 cells. These results represent the first evidence on the operation of a ATP-responsive CCE pathway in MCF-7 cells and also indicate that 17beta-estradiol interferes with this mechanism by acting at the cell surface level.
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Affiliation(s)
- Ana M Rossi
- Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, Bahia Blanca, Argentina
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