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Zhang J, Yuan H, Yao X, Chen S. Endogenous ion channels expressed in human embryonic kidney (HEK-293) cells. Pflugers Arch 2022; 474:665-680. [PMID: 35567642 DOI: 10.1007/s00424-022-02700-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/25/2022] [Accepted: 04/30/2022] [Indexed: 12/21/2022]
Abstract
Mammalian expression systems, particularly the human embryonic kidney (HEK-293) cells, combined with electrophysiological studies, have greatly benefited our understanding of the function, characteristic, and regulation of various ion channels. It was previously assumed that the existence of endogenous ion channels in native HEK-293 cells could be negligible. Still, more and more ion channels are gradually reported in native HEK-293 cells, which should draw our attention. In this regard, we summarize the different ion channels that are endogenously expressed in HEK-293 cells, including voltage-gated Na+ channels, Ca2+ channels, K+ channels, Cl- channels, nonselective cation channels, TRP channels, acid-sensitive ion channels, and Piezo channels, which may complicate the recording of the heterogeneously expressed ion channels to a certain degree. We noted that the expression patterns and channel profiles varied with different studies, which may be due to the distinct originality of the cells, cell culture conditions, passage numbers, and different recording protocols. Therefore, a better knowledge of endogenous ion channels may help minimize potential problems in characterizing heterologously expressed ion channels. Based on this, it is recommended that HEK-293 cells from unknown sources should be examined before transfection for the characterization of their functional profile, especially when the expression level of exogenous ion channels does not overwhelm the endogenous ion channels largely, or the current amplitude is not significantly higher than the native currents.
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Affiliation(s)
- Jun Zhang
- School of Biomedical Sciences and Li Ka Shing Institute of Health Science, The Chinese University of Hong Kong, Hong Kong, China
| | - Huikai Yuan
- Department of General Surgery, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Xiaoqiang Yao
- School of Biomedical Sciences and Li Ka Shing Institute of Health Science, The Chinese University of Hong Kong, Hong Kong, China
| | - Shuo Chen
- Department of Biopharmaceutical Sciences, School of Pharmacy, Harbin Medical University at Daqing, No. 39 Xinyang Rd, High-tech District, Daqing, 163319, Heilongjiang Province, China.
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2
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Luo J, Chen L, Huang F, Gao P, Zhao H, Wang Y, Han S. Intraorganellar calcium imaging in Arabidopsis seedling roots using the GCaMP variants GCaMP6m and R-CEPIA1er. JOURNAL OF PLANT PHYSIOLOGY 2020; 246-247:153127. [PMID: 32007728 DOI: 10.1016/j.jplph.2020.153127] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 01/14/2020] [Accepted: 01/14/2020] [Indexed: 05/26/2023]
Abstract
Ca2+ acts as a universal second messenger in eukaryotes. In animals, a wide variety of environmental and developmental stimuli trigger Ca2+ dynamics in organelles, such as the cytoplasm, nucleus, and endoplasmic reticulum (ER). However, ER Ca2+ ([Ca2+]er) homeostasis and its contributions in cytosolic and/or nucleosolic Ca2+ dynamics in plants remain elusive. GCaMPs are comprised of a circularly permutated form of enhanced green fluorescent protein fused to calmodulin and myosin light-chain kinase M13 and used for monitoring Ca2+ dynamics in mammalian cells. Here, we targeted a high-affinity variant of GCaMP with nuclear export signal in the cytoplasm (NES-GCaMP6m), with a nuclear-localised signal in the nucleus (NLS-GCaMP6m), and a low-affinity variant of GCaMP, also known as calcium-measuring organelle-entrapped protein indicators (CEPIA), with a signal peptide sequence of the ER-localised protein Calreticulin 1a in the ER lumen (CRT1a-R-CEPIA1er) for intraorganellar Ca2+ imaging in Arabidopsis. We found that cytosolic Ca2+ ([Ca2+]cyt) increases induced by 250 mM sorbitol as an osmotic stress stimulus, 50 μM abscisic acid (ABA), or 1 mM carbachol (CCh) were mainly due to extracellular Ca2+ influx, whereas nucleosolic Ca2+ ([Ca2+]nuc) increases triggered by osmotic stress, ABA, or CCh were contributed by [Ca2+]er release. In addition, [Ca2+]er dynamics presented specific patterns in response to different stimuli such as osmotic stress, ABA, or CCh, indicating that Ca2+ signalling occurs in the ER in plants. These results provide valuable insights into subcellular Ca2+ dynamics in response to different stresses in Arabidopsis root cells and prove that GCaMP imaging is a useful tool for furthering our understanding of plant organelle functions.
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Affiliation(s)
- Jin Luo
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, China
| | - Lvli Chen
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, China
| | - Feifei Huang
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, China
| | - Ping Gao
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, China
| | - Heping Zhao
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, China
| | - Yingdian Wang
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, China
| | - Shengcheng Han
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, China.
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3
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Transient Receptor Potential Canonical 5-Scramblase Signaling Complex Mediates Neuronal Phosphatidylserine Externalization and Apoptosis. Cells 2020; 9:cells9030547. [PMID: 32110987 PMCID: PMC7140530 DOI: 10.3390/cells9030547] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 02/24/2020] [Accepted: 02/24/2020] [Indexed: 12/24/2022] Open
Abstract
Phospholipid scramblase 1 (PLSCR1), a lipid-binding and Ca2+-sensitive protein located on plasma membranes, is critically involved in phosphatidylserine (PS) externalization, an important process in cell apoptosis. Transient receptor potential canonical 5 (TRPC5), is a nonselective Ca2+ channel in neurons that interacts with many downstream molecules, participating in diverse physiological functions including temperature or mechanical sensation. The interaction between TRPC5 and PLSCR1 has never been reported. Here, we showed that PLSCR1 interacts with TRPC5 through their C-termini in HEK293 cells and mouse cortical neurons. Formation of TRPC5-PLSCR1 complex stimulates PS externalization and promotes cell apoptosis in HEK293 cells and mouse cerebral neurons. Furthermore, in vivo studies showed that PS externalization in cortical neurons induced by artificial cerebral ischemia-reperfusion was reduced in TRPC5 knockout mice compared to wild-type mice, and that the percentage of apoptotic neurons was also lower in TRPC5 knockout mice than in wild-type mice. Collectively, the present study suggested that TRPC5-PLSCR1 is a signaling complex mediating PS externalization and apoptosis in neurons and that TRPC5 plays a pathological role in cerebral-ischemia reperfusion injury.
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Youn DH, Weon H. Endogenous TRPC channels mediate Ca 2+ signals and trigeminal synaptic plasticity induced by mGluR5. Life Sci 2019; 231:116567. [PMID: 31202839 DOI: 10.1016/j.lfs.2019.116567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 06/11/2019] [Accepted: 06/12/2019] [Indexed: 11/30/2022]
Abstract
AIMS Metabotropic glutamate receptor 5 (mGluR5), a member of group I mGluR, exerts its effect via elevation of intracellular Ca2+ level. We here characterized Ca2+ signals in the tsA201 cells transfected with mGluR5 and investigated the role of passages for mGluR5-induced Ca2+ signals in synaptic plasticity. MAIN METHODS Using a genetically encoded Ca2+ indicator, GCamp2, Ca2+ signals were reliably induced by bath application of (S)-3,5-dihydroxyphenylglycine, the group I mGluR agonist, in the tsA201 cells transfected with mGluR5. Using whole-cell recordings in the substantia gelatinosa (SG) neurons of the spinal trigeminal subnucleus caudalis (Vc), excitatory postsynaptic currents were recorded by stimulating the trigeminal tract. KEY FINDINGS Ca2+ signals were mediated by "classical" or "canonical" transient receptor potential (TRPC) channels, particularly TRPC1/3/4/6, but not TRPC5, naturally existing in the tsA201 cells. Interestingly, the induction of Ca2+ signals was independent of the phospholipase C signaling pathway; instead, it critically involves the cyclic adenosine diphosphate ribose/ryanodine receptor-dependent signaling pathway and only partially protein kinase C. On the other hand, both TRPC3 and TRPC4 mediated mGluR1/5-induced long-lasting potentiation of excitatory synaptic transmission from the trigeminal primary afferents to the SG neurons of the Vc. SIGNIFICANCE This study demonstrates that endogenous TRPC channels contribute to mGluR5-induced Ca2+ signals in tsA201 cells and synaptic plasticity at excitatory synapses.
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Affiliation(s)
- Dong-Ho Youn
- Department of Oral Physiology, School of Dentistry, Kyungpook National University, 2177, Dalgubeol-daero, Jung-gu, Daegu, 41940, Republic of Korea.
| | - Haein Weon
- Department of Oral Physiology, School of Dentistry, Kyungpook National University, 2177, Dalgubeol-daero, Jung-gu, Daegu, 41940, Republic of Korea
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de la Peña E, Gomis A. Characterization of TRPC Channels in a Heterologous System Using Calcium Imaging and the Patch-Clamp Technique. Methods Mol Biol 2019; 1987:83-97. [PMID: 31028675 DOI: 10.1007/978-1-4939-9446-5_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The family of transient receptor potential (TRPs) channels contains 28 mammalian members, each a unique cellular sensor that responds to a wide variety of external and internal signals. TRP channels are expressed by most mammalian cells, where they are involved in many different physiological functions. Canonical TRP channels (TRPCs) form a family of nonselective cationic channels, although with greater selectivity for Ca2+. This family is made up of seven members (TRPC1-7), all of which contain a TRP box in the carboxyl terminal and 3-4 ankyrin repeats in the amino terminal. While these channels share some similar properties, they display diverse gating mechanisms and are involved in different signaling pathways (Gees M et al., Compr Physiol, 2012). The activation or inhibition of these channels has been studied using different approaches and techniques. Here, we characterize the activation of the TRPC5 channel expressed in a heterologous system, using calcium imaging and the patch-clamp technique in whole-cell configuration.
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Affiliation(s)
| | - Ana Gomis
- Instituto de Neurociencias, UMH-CSIC, Alicante, Spain.
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6
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May V, Clason TA, Buttolph TR, Girard BM, Parsons RL. Calcium influx, but not intracellular calcium release, supports PACAP-mediated ERK activation in HEK PAC1 receptor cells. J Mol Neurosci 2014; 54:342-50. [PMID: 24723666 PMCID: PMC4194181 DOI: 10.1007/s12031-014-0300-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 03/28/2014] [Indexed: 01/10/2023]
Abstract
In HEK cells expressing GFP-tagged PAC1Hop1 receptors, PACAP augments ERK phosphorylation through two parallel pathways: one through PACAP/PAC1 receptor internalization/endosome MEK/ERK signaling and the other through PLC/DAG/PKC activation. We examined whether elevation of intracellular calcium ([Ca(2+)]i) was required for either of the PACAP/PAC1 receptor-mediated ERK activation mechanisms. The PACAP (25 nM)-induced elevation of [Ca(2+)]i was greater with cells maintained in Ca(2+)-containing than in Ca(2+)-deficient solution, suggesting that both calcium release from internal stores and calcium influx contributed to the rise in [Ca(2+)]i. A thapsigargin-induced increase in [Ca(2+)]i also was greater with calcium in the external solution. OAG, the cell permeable analogue of DAG, increased [Ca(2+)]i, but only in Ca(2+)-containing solution. Decreasing external calcium or depleting internal calcium stores did not block PACAP-induced PAC1 receptor internalization. Omission of calcium from the external solution, but not thapsigargin pretreatment, significantly blunted PACAP-stimulated ERK phosphorylation. The PKC inhibitor BimI decreased PACAP-mediated ERK activation in both Ca(2+)-containing or Ca(2+)-deficient solutions. In contrast, following Pitstop 2 pretreatment to block endocytic mechanisms, PACAP activated ERK only when calcium was present in the external solution. We conclude that the endosome signaling pathway is largely calcium-independent whereas calcium influx appears necessary for the PLC/DAG/PKC component of PACAP-induced ERK activation.
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Affiliation(s)
- Victor May
- Department of Neurological Sciences, College of Medicine, University of Vermont, Burlington, VT, 05405, USA
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Sunryd JC, Cheon B, Graham JB, Giorda KM, Fissore RA, Hebert DN. TMTC1 and TMTC2 are novel endoplasmic reticulum tetratricopeptide repeat-containing adapter proteins involved in calcium homeostasis. J Biol Chem 2014; 289:16085-99. [PMID: 24764305 DOI: 10.1074/jbc.m114.554071] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The endoplasmic reticulum (ER) is organized in part by adapter proteins that nucleate the formation of large protein complexes. Tetratricopeptide repeats (TPR) are well studied protein structural motifs that support intermolecular protein-protein interactions. TMTC1 and TMTC2 were identified by an in silico search as TPR-containing proteins possessing N-terminal ER targeting signal sequences and multiple hydrophobic segments, suggestive of polytopic membrane proteins that are targeted to the secretory pathway. A variety of cell biological and biochemical assays was employed to demonstrate that TMTC1 and TMTC2 are both ER resident integral membrane proteins with multiple clusters of TPR domains oriented within the ER lumen. Proteomic analysis followed by co-immunoprecipitation verification found that both proteins associated with the ER calcium uptake pump SERCA2B, and TMTC2 also bound to the carbohydrate-binding chaperone calnexin. Live cell calcium measurements revealed that overexpression of either TMTC1 or TMTC2 caused a reduction of calcium released from the ER following stimulation, whereas the knockdown of TMTC1 or TMTC2 increased the stimulated calcium released. Together, these results implicate TMTC1 and TMTC2 as ER proteins involved in ER calcium homeostasis.
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Affiliation(s)
- Johan C Sunryd
- From the Departments of Biochemistry and Molecular Biology and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Banyoon Cheon
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003 Veterinary and Animal Sciences
| | - Jill B Graham
- From the Departments of Biochemistry and Molecular Biology and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Kristina M Giorda
- From the Departments of Biochemistry and Molecular Biology and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Rafael A Fissore
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003 Veterinary and Animal Sciences
| | - Daniel N Hebert
- From the Departments of Biochemistry and Molecular Biology and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003
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8
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Kadeba PI, Vasauskas AA, Chen H, Wu S, Scammell JG, Cioffi DL. Regulation of store-operated calcium entry by FK506-binding immunophilins. Cell Calcium 2013; 53:275-85. [PMID: 23375350 DOI: 10.1016/j.ceca.2012.12.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 12/21/2012] [Accepted: 12/24/2012] [Indexed: 02/06/2023]
Abstract
Calcium entry from the extracellular space into cells is an important signaling mechanism in both physiological and pathophysiological functions. In non-excitable cells, store-operated calcium (SOC) entry represents a principal mode of calcium entry. Activation of SOC entry in pulmonary artery endothelial cells leads to the formation of inter-endothelial cell gaps and subsequent endothelial barrier disruption. Regulation of endothelial SOC entry is poorly understood. In this work, we identify two large molecular weight immunophilins, FKBP51 and FKBP52, as novel regulators of SOC entry in endothelial cells. Using cell fractionation studies and immunocytochemistry we determined that a fraction of these largely cytosolic proteins localize to the plasma membrane where SOC entry channels are found. That FKBP51 and FKBP52 associate with SOC entry channel protein complexes was supported by co-precipitation of the immunophilins with TRPC4, a subunit of the calcium-selective, SOC entry channel ISOC. Dexamethasone-induced upregulation of FKBP51 expression in pulmonary artery endothelial cells reduced global SOC entry as well as ISOC. Similar results were observed when FKBP51 was over-expressed in an inducible HEK293 cell line. On the other hand, when FKBP52 was over-expressed SOC entry was enhanced. When expression of FKBP52 was inhibited, SOC entry was decreased. Collectively, our observations support regulatory roles for these large molecular weight immunophilins in which FKBP51 inhibits, whereas FKBP52 enhances, SOC entry in endothelial cells.
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Affiliation(s)
- Pierre I Kadeba
- Department of Biochemistry, University of South Alabama, Mobile, AL 36688, United States
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9
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Abstract
Transient receptor potential canonical (TRPC) channels are the canonical (C) subset of the TRP proteins, which are widely expressed in mammalian cells. They are thought to be primarily involved in determining calcium and sodium entry and have wide-ranging functions that include regulation of cell proliferation, motility and contraction. The channels are modulated by a multiplicity of factors, putatively existing as integrators in the plasma membrane. This review considers the sensitivities of TRPC channels to lipids that include diacylglycerols, phosphatidylinositol bisphosphate, lysophospholipids, oxidized phospholipids, arachidonic acid and its metabolites, sphingosine-1-phosphate, cholesterol and some steroidal derivatives and other lipid factors such as gangliosides. Promiscuous and selective lipid sensing have been detected. There appear to be close working relationships with lipids of the phospholipase C and A2 enzyme systems, which may enable integration with receptor signalling and membrane stretch. There are differences in the properties of each TRPC channel that are further complicated by TRPC heteromultimerization. The lipids modulate activity of the channels or insertion in the plasma membrane. Lipid microenvironments and intermediate sensing proteins have been described that include caveolae, G protein signalling, SEC14-like and spectrin-type domains 1 (SESTD1) and podocin. The data suggest that lipid sensing is an important aspect of TRPC channel biology enabling integration with other signalling systems.
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Affiliation(s)
- D. J. Beech
- Faculty of Biological Sciences, Institute of Membrane and Systems Biology, University of Leeds, Leeds, UK
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Kumar PG, Shoeb M. The Role of TRP Ion Channels in Testicular Function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:881-908. [DOI: 10.1007/978-94-007-0265-3_46] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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11
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Cvetkovic-Lopes V, Eggermann E, Uschakov A, Grivel J, Bayer L, Jones BE, Serafin M, Mühlethaler M. Rat hypocretin/orexin neurons are maintained in a depolarized state by TRPC channels. PLoS One 2010; 5:e15673. [PMID: 21179559 PMCID: PMC3002943 DOI: 10.1371/journal.pone.0015673] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Accepted: 11/19/2010] [Indexed: 12/14/2022] Open
Abstract
In a previous study we proposed that the depolarized state of the wake-promoting hypocretin/orexin (hcrt/orx) neurons was independent of synaptic inputs as it persisted in tetrodotoxin and low calcium/high magnesium solutions. Here we show first that these cells are hyperpolarized when external sodium is lowered, suggesting that non-selective cation channels (NSCCs) could be involved. As canonical transient receptor channels (TRPCs) are known to form NSCCs, we looked for TRPCs subunits using single-cell RT-PCR and found that TRPC6 mRNA was detectable in a small minority, TRPC1, TRPC3 and TRPC7 in a majority and TRPC4 and 5 in the vast majority (∼90%) of hcrt/orx neurons. Using intracellular applications of TRPC antibodies against subunits known to form NSCCs, we then found that only TRPC5 antibodies elicited an outward current, together with hyperpolarization and inhibition of the cells. These effects were blocked by co-application of a TRPC5 antigen peptide. Voltage-clamp ramps in the presence or absence of TRPC5 antibodies indicated the presence of a current with a reversal potential close to -15 mV. Application of the non-selective TRPC channel blocker, flufenamic acid, had a similar effect, which could be occluded in cells pre-loaded with TRPC5 antibodies. Finally, using the same TRPC5 antibodies we found that most hcrt/orx cells show immunostaining for the TRPC5 subunit. These results suggest that hcrt/orx neurons are endowed with a constitutively active non-selective cation current which depends on TRPC channels containing the TRPC5 subunit and which is responsible for the depolarized and active state of these cells.
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Affiliation(s)
- Vesna Cvetkovic-Lopes
- Département de Neurosciences Fondamentales, Centre Médical Universitaire, Genève, Switzerland
| | - Emmanuel Eggermann
- Département de Neurosciences Fondamentales, Centre Médical Universitaire, Genève, Switzerland
| | - Aaron Uschakov
- Département de Neurosciences Fondamentales, Centre Médical Universitaire, Genève, Switzerland
| | - Jeremy Grivel
- Département de Neurosciences Fondamentales, Centre Médical Universitaire, Genève, Switzerland
| | - Laurence Bayer
- Département de Neurosciences Fondamentales, Centre Médical Universitaire, Genève, Switzerland
| | - Barbara E. Jones
- Department of Neurology and Neurosurgery, McGill University, Montreal Neurological Institute, Montreal, Quebec, Canada
| | - Mauro Serafin
- Département de Neurosciences Fondamentales, Centre Médical Universitaire, Genève, Switzerland
| | - Michel Mühlethaler
- Département de Neurosciences Fondamentales, Centre Médical Universitaire, Genève, Switzerland
- * E-mail:
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12
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Association study of TRPC4 as a candidate gene for generalized epilepsy with photosensitivity. Neuromolecular Med 2010; 12:292-9. [PMID: 20574736 DOI: 10.1007/s12017-010-8122-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Accepted: 06/11/2010] [Indexed: 02/01/2023]
Abstract
Photoparoxysmal response (PPR) is characterized by abnormal visual sensitivity of the brain to photic stimulation. Frequently associated with idiopathic generalized epilepsies (IGEs), it might be an endophenotype for cortical excitability. Transient receptor potential cation (TRPC) channels are involved in the generation of epileptiform discharges, and TRPC4 constitutes the main TRPC channel in the central nervous system. The present study investigated an association of PPR with sequence variations of the TRPC4 gene. Thirty-five single nucleotide polymorphisms (SNP) within TRPC4 were genotyped in 273 PPR probands and 599 population controls. Association analyses were performed for the broad PPR endophenotype (PPR types I-IV; n = 273), a narrow model of affectedness (PPR types III and IV; n = 214) and PPR associated with IGE (PPR/IGE; n = 106) for each SNP and for corresponding haplotypes. Association was found between the intron 5 SNP rs10507456 and PPR/IGE both for single markers (P = 0.005) and haplotype level (P = 0.01). Three additional SNPs (rs1535775, rs10161932 and rs7338118) within the same haplotype block were associated with PPR/IGE at P < 0.05 (uncorrected) as well as two more markers (rs10507457, rs7329459) located in intron 3. Again, the corresponding haplotype also showed association with PPR/IGE. Results were not significant following correction for multiple comparisons by permutation analysis for single markers and Bonferroni-Holm for haplotypes. No association was found between variants in TRPC4 and other phenotypes. Our results showed a trend toward association of TRPC4 variants and PPR/IGE. Further studies including larger samples of photosensitive probands are required to clarify the relevance of TRPC4 for PPR and IGE.
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13
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Weick JP, Austin Johnson M, Zhang SC. Developmental regulation of human embryonic stem cell-derived neurons by calcium entry via transient receptor potential channels. Stem Cells 2010; 27:2906-16. [PMID: 19725137 DOI: 10.1002/stem.212] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Spontaneous calcium (Ca(2+)) transients in the developing nervous system can affect proliferation, migration, neuronal subtype specification, and neurite outgrowth. Here, we show that telencephalic human neuroepithelia (hNE) and postmitotic neurons (PMNs) generated from embryonic stem cells display robust Ca(2+) transients. Unlike previous reports in animal models, transients occurred by a Gd(3+)/La(3+)-sensitive, but thapsigargin- and Cd(2+)-insensitive, mechanism, strongly suggestive of a role for transient receptor potential (Trp) channels. Furthermore, Ca(2+) transients in PMNs exhibited an additional sensitivity to the canonical Trp (TrpC) antagonist SKF96365 and shRNA-mediated knockdown of the TrpC1 subunit. Functionally, inhibition of Ca(2+) transients in dividing hNE cells led to a significant reduction in proliferation, whereas either pharmacological inhibition or shRNA-mediated knockdown of the TrpC1 and TrpC4 subunits significantly reduced neurite extension in PMNs. Primary neurons cultured from fetal human cortex displayed nearly identical Ca(2+) transients and pharmacological sensitivities to Trp channel antagonists. Together these data suggest that Trp channels present a novel mechanism for controlling Ca(2+) transients in human neurons and may offer a target for regulating proliferation and neurite outgrowth when engineering cells for therapeutic transplantation.
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Affiliation(s)
- Jason P Weick
- Waisman Center, University of Wisconsin, Madison, Wisconsin 53705, USA
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14
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Wakabayashi I, Marumo M, Graziani A, Poteser M, Groschner K. TRPC4 expression determines sensitivity of the platelet-type capacitative Ca2+entry channel to intracellular alkalosis. Platelets 2009; 17:454-61. [PMID: 17074721 DOI: 10.1080/09537100600757489] [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] [Indexed: 10/24/2022]
Abstract
The present study was designed to analyze the molecular basis of the intracellular pH-dependent capacitative Ca2+ entry (CCE) of human platelets and megakaryocytic cells, specifically to test the hypothesis that members of the classical transient receptor potential (TRPC) protein family are involved in the CCE pathway that is promoted by intracellular alkalosis. Human platelets as well as the tested megakaryocytic cell lines (CMK cells, MEG-01 cells) and HEK293 cells displayed thapsigargin-induced CCE and responded to monensin with comparable elevation in intracellular pH. Promotion of CCE by monensin-induced intracellular alkalosis, however, was profound in mature platelets, moderate in CMK cells and lacking in MEG-01 cells as well as in HEK293 cells. Analysis of the TRPC expression pattern by immunoblotting revealed that mature platelets and CMK cells express TRPC4 along with TRPC1 and TRPC3, while TRPC4 is lacking in MEG-01 cells. HEK293 cells displayed CCE characteristics as well as lack of TRPC4 expression similar to MEG-01 cells. Over-expression of TRPC4 in HEK293 cells was found to result in a gain of pH-sensitivity of CCE with clearly detectable promotion of CCE in response to monensin. These results suggest that platelet CCE channel complexes contain TRPC4 as a molecular component that determines sensitivity of CCE to intracellular alkalosis.
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Affiliation(s)
- Ichiro Wakabayashi
- Department of Hygiene and Preventive Medicine, Yamagata University School of Medicine, Yamagata 990-9585, Japan.
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15
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Ulloa A, Gonzales AL, Zhong M, Kim YS, Cantlon J, Clay C, Ku CY, Earley S, Sanborn BM. Reduction in TRPC4 expression specifically attenuates G-protein coupled receptor-stimulated increases in intracellular calcium in human myometrial cells. Cell Calcium 2009; 46:73-84. [PMID: 19523685 DOI: 10.1016/j.ceca.2009.05.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Revised: 05/01/2009] [Accepted: 05/05/2009] [Indexed: 11/29/2022]
Abstract
Canonical transient receptor potential (TRPC) proteins may play a role in regulating changes in intracellular calcium ([Ca(2+)](i)). Human myometrium expresses TRPC4, TRPC1 and TRPC6 mRNAs in greatest relative abundance. Contributions of TRPC4 to increases in [Ca(2+)](i) were assessed in PHM1-41 and primary human uterine smooth muscle (UtSMC) cells using short hairpin RNAs (shRNAs). Based on a reporter assay screen, one shRNA was selected to construct an adenoviral expression vector (TC4sh1). TC4sh1 induced both mRNA and protein TRPC4 knockdown in PHM1-41 cells without affecting expression of other TRPCs. Signal-regulated Ca(2+) entry (SRCE), defined as a stimulus- and extracellular Ca(2+)-dependent increase in [Ca(2+)](i), was measured in PHM1-41 cells treated with oxytocin (G-protein coupled receptor (GPCR)-stimulated), thapsigargin (store depletion-stimulated), and OAG (diacylglycerol-stimulated), using Fura-2. Cells infected with TC4sh1 exhibited attenuated oxytocin-, ATP- and PGF2alpha-mediated SRCE, but no change in thapsigargin- or OAG-stimulated SRCE. Similar results were obtained in primary uterine smooth muscle cells. Additionally, cells expressing TC4sh1 exhibited a significantly smaller increase in channel activity in response to oxytocin administration than did cells infected with empty virus. These data show that, in human myometrial cells, knockdown of endogenous TRPC4 specifically attenuates GPCR-stimulated, but not thapsigargin- or OAG-stimulated extracellular calcium-dependent increases in [Ca(2+)](i). These data imply that, in this cellular context, the mechanisms regulating extracellular Ca(2+)-dependent increases in [Ca(2+)](i) are differentially affected by different signaling pathways.
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Affiliation(s)
- Aida Ulloa
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
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16
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Involvement of TRPC3 channels in calcium oscillations mediated by OX(1) orexin receptors. Biochem Biophys Res Commun 2009; 385:408-12. [PMID: 19464259 DOI: 10.1016/j.bbrc.2009.05.077] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Accepted: 05/19/2009] [Indexed: 11/20/2022]
Abstract
Oscillations of intracellular Ca2+ provide a novel mechanism for sustained activation of cellular processes. Receptor-activated oscillations are mainly thought to occur through rhythmic IP3-dependent store discharge. However, as shown here in HEK293 cells 1 nM orexin-A (Ox-A) acting at OX1 receptors (OX1R) triggered oscillatory Ca2+ responses, requiring external Ca2+. These responses were attenuated by interference with TRPC3 channel (but not TRPC1/4) function using dominant negative constructs, elevated Mg2+ (a blocker of many TRP channels) or inhibition of phospholipase A2. These treatments did not affect Ca2+ oscillations elicited by high concentrations of Ox-A (100 nM) in the absence of external Ca2+. OX1R are thus able to activate TRPC(3)-channel-dependent oscillatory responses independently of store discharge.
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17
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Koh S, Lee K, Wang C, Cabot RA, Machaty Z. STIM1 regulates store-operated Ca2+ entry in oocytes. Dev Biol 2009; 330:368-76. [PMID: 19362545 DOI: 10.1016/j.ydbio.2009.04.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Revised: 03/16/2009] [Accepted: 04/03/2009] [Indexed: 01/23/2023]
Abstract
The single transmembrane-spanning Ca(2+)-binding protein, STIM1, has been proposed to function as a Ca(2+) sensor that links the endoplasmic reticulum to the activation of store-operated Ca(2+) channels. In this study, the presence, subcellular localization and function of STIM1 in store-operated Ca(2+) entry in oocytes was investigated using the pig as a model. Cloning and sequence analysis revealed the presence of porcine STIM1 with a coding sequence of 2058 bp. In oocytes with full cytoplasmic Ca(2+) stores, STIM1 was localized predominantly in the inner cytoplasm as indicated by immunocytochemistry or overexpression of human STIM1 conjugated to the yellow fluorescent protein. Depletion of the Ca(2+) stores was associated with redistribution of STIM1 along the plasma membrane. Increasing STIM1 expression resulted in enhanced Ca(2+) influx after store depletion and subsequent Ca(2+) add-back; the influx was inhibited when the oocytes were pretreated with lanthanum, a specific inhibitor of store-operated Ca(2+) channels. When STIM1 expression was suppressed using siRNAs, there was no change in cytosolic free Ca(2+) levels in the store-depleted oocytes after Ca(2+) add-back. The findings suggest that in oocytes, STIM1 serves as a sensor of Ca(2+) store content that after store depletion moves to the plasma membrane to stimulate store-operated Ca(2+) entry.
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Affiliation(s)
- Sehwon Koh
- Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, USA
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18
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Beech DJ, Bahnasi YM, Dedman AM, Al-Shawaf E. TRPC channel lipid specificity and mechanisms of lipid regulation. Cell Calcium 2009; 45:583-8. [PMID: 19324410 PMCID: PMC3878645 DOI: 10.1016/j.ceca.2009.02.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 02/17/2009] [Accepted: 02/19/2009] [Indexed: 12/31/2022]
Abstract
TRPC channels are a subset of the transient receptor potential (TRP) proteins widely expressed in mammalian cells. They are thought to be primarily involved in determining calcium or sodium entry and have broad-ranging functions that include regulation of cell proliferation, motility and contraction. The channels do not respond to a single stimulator but rather are activated or modulated by a multiplicity of factors, potentially existing as integrators at the plasma membrane. This review considers the sensitivity of TRPCs to lipid factors, with focus on sensitivities to diacylglycerols, lysophospholipids, arachidonic acid and its metabolites, sphingosine-1-phosphate (S1P), cholesterol and derivatives, and other lipid factors such as gangliosides. Promiscuous and selective lipid-sensing are apparent. In many cases the lipids stimulate channel function or increase insertion of channels in the membrane. Both direct and indirect (receptor-dependent) lipid effects are evident. Although information is limited, the lipid profiles are consistent with TRPCs having close working relationships with phospholipase C and A2 enzymes. We need much more information about lipid-sensing by TRPCs if we are to fully appreciate its significance, but the available data suggest that lipid-sensing is a key, but not exclusive, aspect of TRPC biology.
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Affiliation(s)
- David J Beech
- Institute of Membrane & Systems Biology, Faculty of Biological Sciences, and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK.
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19
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Liu S, Qu MH, Ren W, Hu HZ, Gao N, Wang GD, Wang XY, Fei G, Zuo F, Xia Y, Wood JD. Differential expression of canonical (classical) transient receptor potential channels in guinea pig enteric nervous system. J Comp Neurol 2009; 511:847-62. [PMID: 18925632 DOI: 10.1002/cne.21874] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The canonical transient receptor potential (TRPC) family of ion channels is implicated in many neuronal processes including calcium homeostasis, membrane excitability, synaptic transmission, and axon guidance. TRPC channels are postulated to be important in the functional neurobiology of the enteric nervous system (ENS); nevertheless, details for expression in the ENS are lacking. Reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry were used to study the expression and localization of TRPC channels. We found mRNA transcripts, protein on Western blots, and immunoreactivity (IR) for TRPC1/3/4/6 expressed in the small intestinal ENS of adult guinea pigs. TRPC1/3/4/6-IR was localized to distinct subpopulations of enteric neurons and was differentially distributed between the myenteric and submucosal divisions of the ENS. TRPC1-IR was widely distributed and localized to neurons with cholinergic, calretinin, and nitrergic neuronal immunochemical codes in the myenteric plexus. It was localized to both cholinergic and noncholinergic secretomotor neurons in the submucosal plexus. TRPC3-IR was found only in the submucosal plexus and was expressed exclusively by neuropeptide Y-IR neurons. TRPC4/6-IR was expressed in only a small population of myenteric neurons, but was abundantly expressed in the submucosal plexus. TRPC4/6-IR was coexpressed with both cholinergic and nitrergic neurochemical codes in the myenteric plexus. In the submucosal plexus, TRPC4/6-IR was expressed exclusively in noncholinergic secretomotor neurons. No TRPC1/3/4/6-IR was found in calbindin-IR neurons. TRPC3/4/6-IR was widely expressed along varicose nerve fibers and colocalized with synaptophysin-IR at putative neurotransmitter release sites. Our results suggest important roles for TRPC channels in ENS physiology and neuronal regulation of gut function.
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Affiliation(s)
- Sumei Liu
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA.
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20
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Salido GM, Sage SO, Rosado JA. TRPC channels and store-operated Ca(2+) entry. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1793:223-30. [PMID: 19061922 DOI: 10.1016/j.bbamcr.2008.11.001] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Revised: 11/03/2008] [Accepted: 11/04/2008] [Indexed: 01/03/2023]
Abstract
Store-operated calcium entry (SOCE) is a major mechanism for Ca(2+) influx. Since SOCE was first proposed two decades ago many techniques have been used in attempting to identify the nature of store-operated Ca(2+) (SOC) channels. The first identified and best-characterised store-operated current is I(CRAC), but a number of other currents activated by Ca(2+) store depletion have also been described. TRPC proteins have long been proposed as SOC channel candidates; however, whether any of the TRPCs function as SOC channels remains controversial. This review attempts to provide an overview of the arguments in favour and against the role of TRPC proteins in the store-operated mechanisms of agonist-activated Ca(2+) entry.
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Affiliation(s)
- Ginés M Salido
- Department of Physiology (Cell Physiology Research Group), University of Extremadura, Cáceres 10071, Spain
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21
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Fiorio Pla A, Grange C, Antoniotti S, Tomatis C, Merlino A, Bussolati B, Munaron L. Arachidonic acid-induced Ca2+ entry is involved in early steps of tumor angiogenesis. Mol Cancer Res 2008; 6:535-45. [PMID: 18403634 DOI: 10.1158/1541-7786.mcr-07-0271] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Growth factor-induced intracellular calcium signals in endothelial cells regulate cytosolic and nuclear events involved in the angiogenic process. Among the intracellular messengers released after proangiogenic stimulation, arachidonic acid (AA) plays a key role and its effects are strictly related to calcium homeostasis and cell proliferation. Here, we studied AA-induced intracellular calcium signals in endothelial cells derived from human breast carcinomas (B-TEC). AA promotes B-TEC proliferation and organization of vessel-like structures in vitro. The effect is directly mediated by the fatty acid without a significant contribution of its metabolites. AA induces Ca(2+)(i) signals in the entire capillary-like structure during the early phases of tubulogenesis in vitro. No such responses are detectable in B-TECs organized in more structured tubules. In B-TECs growing in monolayer, AA induces two different signals: a Ca(2+)(i) increase due to Ca(2+) entry and an inhibition of store-dependent Ca(2+) entry induced by thapsigargin or ATP. An inhibitor of Ca(2+) entry and angiogenesis, carboxyamidotriazole, significantly and specifically decreases AA-induced B-TEC tubulogenesis, as well as AA-induced Ca(2+) signals in B-TECs. We conclude that (a) AA-activated Ca(2+) entry is associated with the progression through the early phases of angiogenesis, mainly involving proliferation and tubulogenesis, and it is down-regulated during the reorganization of tumor-derived endothelial cells in capillary-like structures; and (b) inhibition of AA-induced Ca(2+) entry may contribute to the antiangiogenic action of carboxyamidotriazole.
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Affiliation(s)
- Alessandra Fiorio Pla
- Department of Animal and Human Biology, University of Torino, Via Accademia Albertina 13, 10123 Turin, Italy.
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22
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Bréchard S, Tschirhart EJ. Regulation of superoxide production in neutrophils: role of calcium influx. J Leukoc Biol 2008; 84:1223-37. [PMID: 18519744 PMCID: PMC2567897 DOI: 10.1189/jlb.0807553] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Upon stimulation, activation of NADPH oxidase complexes in neutrophils produces a burst of superoxide anions contributing to oxidative stress and the development of inflammatory process. Store-operated calcium entry (SOCE), whereby the depletion of intracellular stores induces extracellular calcium influx, is known to be a crucial element of NADPH oxidase regulation. However, the mechanistic basis mediating SOCE is still only partially understood, as is the signal-coupling pathway leading to modulation of store-operated channels. This review emphasizes the role of calcium influx in the control of the NADPH oxidase and summarizes the current knowledge of pathways mediating this extracellular calcium entry in neutrophils. Such investigations into the cross-talk between NADPH oxidase and calcium might allow the identification of novel pharmacological targets with clinical use, particularly in inflammatory diseases.
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Affiliation(s)
- Sabrina Bréchard
- Life Sciences Research Unit, University of Luxembourg, Luxembourg.
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23
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Chen XF, Li CX, Wang PY, Li M, Wang WC. Dynamic simulation of the effect of calcium-release activated calcium channel on cytoplasmic Ca2+ oscillation. Biophys Chem 2008; 136:87-95. [PMID: 18538916 DOI: 10.1016/j.bpc.2008.04.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 04/28/2008] [Accepted: 04/28/2008] [Indexed: 11/26/2022]
Abstract
A mathematical model is proposed to illustrate the activation of STIM1 (stromal interaction molecule 1) protein, the assembly and activation of calcium-release activated calcium (CRAC) channels in T cells. In combination with De Young-Keizer-Li-Rinzel model, we successfully reproduce a sustained Ca(2+) oscillation in cytoplasm. Our results reveal that Ca(2+) oscillation dynamics in cytoplasm can be significantly affected by the way how the Orai1 CRAC channel are assembled and activated. A low sustained Ca(2+) influx is observed through the CRAC channels across the plasma membrane. In particular, our model shows that a tetrameric channel complex can effectively regulate the total quantity of the channels and the ratio of the active channels to the total channels, and a period of Ca(2+) oscillation about 29 s is in agreement with published experimental data. The bifurcation analyses illustrate the different dynamic properties between our mixed Ca(2+) feedback model and the single positive or negative feedback models.
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Affiliation(s)
- Xiao-fang Chen
- Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
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24
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Bréchard S, Melchior C, Plançon S, Schenten V, Tschirhart EJ. Store-operated Ca2+ channels formed by TRPC1, TRPC6 and Orai1 and non-store-operated channels formed by TRPC3 are involved in the regulation of NADPH oxidase in HL-60 granulocytes. Cell Calcium 2008; 44:492-506. [PMID: 18436303 DOI: 10.1016/j.ceca.2008.03.002] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Revised: 02/29/2008] [Accepted: 03/11/2008] [Indexed: 11/25/2022]
Abstract
Ca(2+) influx has been shown to be essential for NADPH oxidase activity which is involved in the inflammatory process. Ca(2+) conditions underlying the oxidative response are clearly delineated. Here, we show that store-operated Ca(2+) entry (SOCE) is required at the beginning of NADPH oxidase activation in response to fMLF (N-formyl-L-methionyl-L-leucyl-L-phenylalanine) in neutrophil-like HL-60 cells. When extracellular Ca(2+) is initially removed, early addition of Ca(2+) after stimulation causes a complete restoration of Ca(2+) entry and H(2)O(2) production. Both Ca(2+) entry and H(2)O(2) production are decreased by purported SOCE blockers, 2-aminoethoxydiphenyl borane (2-APB) and SK&F 96365. Endogenously expressed TRPC (transient receptor potential canonical) homologues and Orai1 were investigated for their role in supporting store-operated Ca(2+) channels activity. TRPC1, TRPC6 and Orai1 knock-out by siRNA resulted in the inhibition of Ca(2+) influx and H(2)O(2) production in response to fMLF and thapsigargin while suppression of TRPC3 had no effect on thapsigargin induced-SOCE. 2-APB and SK&F 96365 were able to amplify the reduction of fMLF-stimulated Ca(2+) entry and H(2)O(2) production observed in cells transfected by TRPC3 siRNA. In summary, Ca(2+) influx in HL-60 cells relies on different membrane TRPC channels and Orai1 for allowing NADPH oxidase activation. TRPC3 primarily mediates SOCE-independent pathways and TRPC1, TRPC6 and Orai1 exclusively contribute to SOCE.
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Affiliation(s)
- S Bréchard
- Life Sciences Research Unit, Université du Luxembourg, 162A, Avenue de la Faïencerie, L-1511 Luxembourg, Luxembourg
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25
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Woodard GE, Salido GM, Rosado JA. Enhanced exocytotic-like insertion of Orai1 into the plasma membrane upon intracellular Ca2+ store depletion. Am J Physiol Cell Physiol 2008; 294:C1323-31. [PMID: 18400989 DOI: 10.1152/ajpcell.00071.2008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Ca+ release-activated Ca2+ (CRAC) channels are activated when free Ca2+ concentration in the intracellular stores is substantially reduced and mediate sustained Ca2+ entry. Recent studies have identified Orai1 as a CRAC channel subunit. Here we demonstrate that passive Ca2+ store depletion using the inhibitor of the sarcoendoplasmic reticulum Ca2+-ATPase, thapsigargin (TG), enhances the surface expression of Orai1, a process that depends on rises in cytosolic free Ca2+ concentration, as demonstrated in cells loaded with dimethyl BAPTA, an intracellular Ca2+ chelator that prevented TG-evoked cytosolic free Ca2+ concentration elevation. Similar results were observed with a low concentration of carbachol. Cleavage of the soluble N-ethylmaleimide-sensitive-factor attachment protein receptor, synaptosomal-assiciated protein-25 (SNAP-25), with botulinum neurotoxin A impaired TG-induced increase in the surface expression of Orai1. In addition, SNAP-25 cleaving by botulinum neurotoxin A reduces the maintenance but not the initial stages of store-operated Ca2+ entry. In aggregate, these findings demonstrate that store depletion enhances Orai1 plasma membrane expression in an exocytotic manner that involves SNAP-25, a process that contributes to store-dependent Ca2+ entry.
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Affiliation(s)
- Geoffrey E Woodard
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
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26
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Odell AF, Van Helden DF, Scott JL. The spectrin cytoskeleton influences the surface expression and activation of human transient receptor potential channel 4 channels. J Biol Chem 2007; 283:4395-407. [PMID: 18048348 DOI: 10.1074/jbc.m709729200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Despite over a decade of research, only recently have the mechanisms governing transient receptor potential channel (TRPC) channel function begun to emerge, with an essential role for accessory proteins in this process. We previously identified a tyrosine phosphorylation event as critical in the plasma membrane translocation and activation of hTRPC4 channels following epidermal growth factor (EGF) receptor activation. To further characterize the signaling events underlying this process, a yeast-two hybrid screen was performed on the C terminus of hTRPC4. The intracellular C-terminal region from proline 686 to leucine 977 was used to screen a human brain cDNA library. Two members of the spectrin family, alphaII- and betaV-spectrin, were identified as binding partners. The interaction of hTRPC4 with alphaII-spectrin and betaV-spectrin was confirmed by glutathione S-transferase pulldown and co-immunoprecipitation experiments. Deletion analysis identified amino acids 730-758 of hTRPC4 as critical for the interaction with this region located within a coiled-coil domain, juxtaposing the Ca(2+)/calmodulin- and IP(3)R-binding region (CIRB domain). This region is deleted in the proposed deltahTRPC4 splice variant form, which failed to undergo both EGF-induced membrane insertion and activation, providing a genetic mechanism for regulating channel activity. We also demonstrate that the exocytotic insertion and activation of hTRPC4 following EGF application is accompanied by dissociation from alphaII-spectrin. Furthermore, depletion of alphaII-spectrin by small interference RNA reduces the basal surface expression of alphahTRPC4 and prevents the enhanced membrane insertion in response to EGF application. Importantly, depletion of alphaII-spectrin did not affect the expression of the delta variant. Taken together, these results demonstrate that a direct interaction between hTRPC4 and the spectrin cytoskeleton is involved in the regulation of hTRPC4 surface expression and activation.
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Affiliation(s)
- Adam F Odell
- School of Biomedical Sciences, Faculty of Health, University of Newcastle, Level 5, MSB, University Drive, New South Wales 2308, Australia.
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27
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Ambudkar IS, Ong HL, Liu X, Bandyopadhyay BC, Bandyopadhyay B, Cheng KT. TRPC1: The link between functionally distinct store-operated calcium channels. Cell Calcium 2007; 42:213-23. [PMID: 17350680 DOI: 10.1016/j.ceca.2007.01.013] [Citation(s) in RCA: 155] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 01/30/2007] [Accepted: 01/31/2007] [Indexed: 10/23/2022]
Abstract
Although store-operated calcium entry (SOCE) was identified more that two decades ago, understanding the molecular mechanisms that regulate and mediate this process continue to pose a major challenge to investigators in this field. Thus, there has been major focus on determining which of the models proposed for this mechanism is valid and conclusively establishing the components of the store-operated calcium (SOC) channel(s). The transient receptor potential canonical (TRPC) proteins have been suggested as candidate components of the elusive store-operated Ca(2+) entry channel. While all TRPCs are activated in response to agonist-stimulated phosphatidylinositol 4,5, bisphosphate (PIP(2)) hydrolysis, only some display store-dependent regulation. TRPC1 is currently the strongest candidate component of SOC and is shown to contribute to SOCE in many cell types. Heteromeric interactions of TRPC1 with other TRPCs generate diverse SOC channels. Recent studies have revealed novel components of SOCE, namely the stromal interacting molecule (STIM) and Orai proteins. While STIM1 has been suggested to be the ER-Ca(2+) sensor protein relaying the signal to the plasma membrane for activation of SOCE, Orai1 is reported to be the pore-forming component of CRAC channel that mediates SOCE in T-lymphocytes and other hematopoetic cells. Several studies now demonstrate that TRPC1 also associates with STIM1 suggesting that SOC and CRAC channels are regulated by similar molecular components. Interestingly, TRPC1 is also associated with Orai1 and a TRPC1-Orai1-STIM1 ternary complex contributes to SOC channel function. This review will focus on the diverse SOC channels formed by TRPC1 and the suggestion that TRPC1 might serve as a molecular link that determines their regulation by store-depletion.
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Affiliation(s)
- Indu S Ambudkar
- Secretory Physiology Section, GTTB, NIDCR, NIH, Bethesda, MD 20892, USA.
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28
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Abstract
This chapter reviews recent evidence indicating that canonical or classical transient receptor potential (TRPC) channels are directly or indirectly mechanosensitive (MS) and can therefore be designated as mechano-operated channels (MOCs). The MS functions of TRPCs may be mechanistically related to their better known functions as store-operated and receptor-operated channels (SOCs and ROCs). Mechanical forces may be conveyed to TRPC channels through the "conformational coupling" mechanism that transmits information regarding the status of internal Ca(2+) stores. All TRPCs are regulated by receptors coupled to phospholipases that are themselves MS and can regulate channels via lipidic second messengers. Accordingly, there may be several nonexclusive mechanisms by which mechanical forces may regulate TRPC channels, including direct sensitivity to bilayer mechanics, physical coupling to internal membranes and/or cytoskeletal proteins, and sensitivity to lipidic second messengers generated by MS enzymes. Various strategies that can be used for separating out different MS-gating mechanisms and their possible role in specific TRPCs are discussed.
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Affiliation(s)
- Owen P Hamill
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555
| | - Rosario Maroto
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555
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29
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Abstract
TRP channels, in particular the TRPC and TRPV subfamilies, have emerged as important constituents of the receptor-activated Ca2+ influx mechanism triggered by hormones, growth factors, and neurotransmitters through activation ofphospholipase C (PLC). Several TRPC channels are also activated by passive depletion of endoplasmic reticulum (ER) Ca2+. Although in several studies the native TRP channels faithfully reproduce the respective recombinant channels, more often the properties of Ca2+ entry and/or the store-operated current are strikingly different from that of the TRP channels expressed in the same cells. The present review aims to discuss this disparity in the context of interaction of TRPC channels with auxiliary proteins that may alter the permeation and regulation of TRPC channels.
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Affiliation(s)
- K Kiselyov
- Department of Biological Sciences University of Pittsburgh, Pittsburgh, PA 15260, USA
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30
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Trebak M, Lemonnier L, Smyth JT, Vazquez G, Putney JW. Phospholipase C-coupled receptors and activation of TRPC channels. Handb Exp Pharmacol 2007:593-614. [PMID: 17217081 DOI: 10.1007/978-3-540-34891-7_35] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The canonical transient receptor potential (TRPC) cation channels are mammalian homologs of the photoreceptor channel TRP in Drosophila melanogaster. All seven TRPCs (TRPC1 through TRPC7) can be activated through Gq/11 receptors or receptor tyrosine kinase (RTK) by mechanisms downstream of phospholipase C. The last decade saw a rapidly growing interest in understanding the role of TRPC channels in calcium entry pathways as well as in understanding the signal(s) responsible for TRPC activation. TRPC channels have been proposed to be activated by a variety of signals including store depletion, membrane lipids, and vesicular insertion into the plasma membrane. Here we discuss recent developments in the mode of activation as well as the pharmacological and electrophysiological properties of this important and ubiquitous family of cation channels.
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Affiliation(s)
- M Trebak
- Laboratory of Signal Transduction, Department of Health and Human Services, National Institute of Environmental Health Sciences-NIH, Research Triangle Park, PO Box 12233, NC 27709, USA
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31
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Holmes AM, Roderick HL, McDonald F, Bootman MD. Interaction between store-operated and arachidonate-activated calcium entry. Cell Calcium 2007; 41:1-12. [PMID: 16765441 DOI: 10.1016/j.ceca.2006.04.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 03/22/2006] [Accepted: 04/12/2006] [Indexed: 11/30/2022]
Abstract
A ubiquitous pathway for cellular Ca(2+) influx involves 'store-operated channels' that respond to depletion of intracellular Ca(2+) pools via an as yet unknown mechanism. Due to its wide-spread expression, store-operated Ca(2+) entry (SOCE) has been considered a principal route for Ca(2+) influx. However, recent evidence has suggested that alternative pathways, activated for example by lipid metabolites, are responsible for physiological Ca(2+) influx. It is not clear if these messenger-activated Ca(2+) entry routes exist in all cells and what interaction they have with SOCE. In the present study we demonstrate that HEK-293 cells and Saos-2 cells express an arachidonic acid (AA)-activated Ca(2+) influx pathway that is distinct from SOCE on the basis of sensitivity to pharmacological blockers and depletion of cellular cholesterol. We examined the functional interaction between SOCE and the arachidonate-triggered Ca(2+) influx (denoted non-SOCE). Both Ca(2+) entry routes could underlie substantial long-lasting Ca(2+) elevations. However, the two pathways could not operate simultaneously. With cells that had an on-going SOCE response, addition of arachidonate gave two profound effects. Firstly, it rapidly inhibited SOCE. Secondly, the mode of Ca(2+) influx switched to the non-SOCE mechanism. Addition of arachidonate to naïve cells resulted in rapid activation of the non-SOCE pathway. However, this Ca(2+) entry route was very slowly engaged if the SOCE pathway was already operative. These data indicate that the SOCE and arachidonate-activated non-SOCE pathways interact in an inhibitory manner. We probed the plausible mechanisms by which these two pathways may communicate.
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Affiliation(s)
- Anthony M Holmes
- The Babraham Institute, Laboratory of Molecular Signalling, Babraham, Cambridge CB2 4AT, UK
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Smyth JT, Dehaven WI, Jones BF, Mercer JC, Trebak M, Vazquez G, Putney JW. Emerging perspectives in store-operated Ca2+ entry: Roles of Orai, Stim and TRP. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:1147-60. [PMID: 17034882 DOI: 10.1016/j.bbamcr.2006.08.050] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Accepted: 08/30/2006] [Indexed: 11/28/2022]
Abstract
Depletion of intracellular Ca2+ stores induces Ca2+ influx across the plasma membrane through store-operated channels (SOCs). This store-operated Ca2+ influx is important for the replenishment of the Ca2+ stores, and is also involved in many signaling processes by virtue of the ability of intracellular Ca2+ to act as a second messenger. For many years, the molecular identities of particular SOCs, as well as the signaling mechanisms by which these channels are activated, have been elusive. Recently, however, the mammalian proteins STIM1 and Orai1 were shown to be necessary for the activation of store-operated Ca2+ entry in a variety of mammalian cells. Here we present molecular, pharmacological, and electrophysiological properties of SOCs, with particular focus on the roles that STIM1 and Orai1 may play in the signaling processes that regulate various pathways of store-operated entry.
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Affiliation(s)
- Jeremy T Smyth
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health/DHHS, Research Triangle Park, NC 27709, USA
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Abstract
Ca(2+) signaling regulates many important physiological events within a diverse set of living organisms. In particular, sustained Ca(2+) signals play an important role in controlling cell proliferation, cell differentiation and the activation of immune cells. Two key elements for the generation of sustained Ca(2+) signals are store-operated and receptor-operated Ca(2+) channels that are activated downstream of phospholipase C (PLC) stimulation, in response to G-protein-coupled receptor or growth factor receptor stimulation. One goal of this review is to help clarify the role of canonical transient receptor potential (TRPC) proteins in the formation of native store-operated and native receptor-operated channels. Toward that end, data from studies of endogenous TRPC proteins will be reviewed in detail to highlight the strong case for the involvement of certain TRPC proteins in the formation of one subtype of store-operated channel, which exhibits a low Ca(2+)-selectivity, in contrast to the high Ca(2+)-selectivity exhibited by the CRAC subtype of store-operated channel. A second goal of this review is to highlight the growing body of evidence indicating that native store-operated and native receptor-operated channels are formed by the heteromultimerization of TRPC subunits. Furthermore, evidence will be provided to argue that some TRPC proteins are able to form multiple channel types.
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Affiliation(s)
- Mitchel L Villereal
- Neurobiology, Pharmacology & Physiology, University of Chicago, 947 East 58th Street, Chicago, IL 60637, USA.
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Antoniotti S, Fiorio Pla A, Barral S, Scalabrino O, Munaron L, Lovisolo D. Interaction between TRPC channel subunits in endothelial cells. J Recept Signal Transduct Res 2006; 26:225-40. [PMID: 16818374 DOI: 10.1080/10799890600784050] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Transient Receptor Potential Canonical (TRPC) proteins have been identified in mammals as a family of plasma membrane calcium-permeable channels activated by different kinds of stimuli in several cell types. We have studied TRPC subunit expression in bovine aortic endothelial (BAE-1) cells, where stimulation with basic fibroblast growth factor (bFGF), a potent angiogenetic factor, induces calcium entry carried at least partially by TRPC1 channels. By means of a RT-PCR approach, we have found that, in addition to TRPC1, only TRPC4 is expressed, both at the mRNA and protein level, as confirmed by immunoblotting and immunocytochemical analysis. Because functional TRPC channels are formed by assembly of four subunits in either homo- or heterotetrameric structures, we have carried out immunoprecipitation experiments and showed that TRPC1 and TRPC4 interact to form heteromers in these cells, independently from culture conditions (high or low percent of fetal calf serum, stimulation with bFGF). Moreover, the data show that TRPC subunits are not tyrosine-phosphorylated after bFGF stimulation and they do not co-immunoprecipitate with the type 1 FGF receptor. These results suggest that BAE-1 cells are a suitable model to study function and regulation of endogenous TRPC1/TRPC4 heteromers.
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Affiliation(s)
- Susanna Antoniotti
- Department of Animal and Human Biology, University of Torino, Torino, Italy.
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Oike H, Wakamori M, Mori Y, Nakanishi H, Taguchi R, Misaka T, Matsumoto I, Abe K. Arachidonic acid can function as a signaling modulator by activating the TRPM5 cation channel in taste receptor cells. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1078-84. [PMID: 16935556 DOI: 10.1016/j.bbalip.2006.07.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Revised: 07/06/2006] [Accepted: 07/13/2006] [Indexed: 11/26/2022]
Abstract
Vertebrate sensory cells such as vomeronasal neurons and Drosophila photoreceptor cells use TRP channels to respond to exogenous stimuli. In mammalian taste cells, bitter and sweet substances as well as some amino acids are received by G protein-coupled receptors (T2Rs or T1Rs). As a result of activation of G protein and phospholipase Cbeta2, the TRPM5 channel is activated. Intracellular Ca(2+) is known to be a TRPM5 activator, but the participation of lipid activators remains unreported. To clarify the effect of arachidonic acid on TRPM5 in taste cells, we investigated the expression profile of a series of enzymes involved in controlling the intracellular free arachidonic acid level, with the result that in a subset of taste bud cells, monoglyceride lipase (MGL) and cyclooxygenase-2 (COX-2) are expressed as well as the previously reported group IIA phospholipase A(2) (PLA(2)-IIA). Double-labeling analysis revealed that MGL, COX-2 and PLA(2)-IIA are co-expressed in some cells that express TRPM5. We then investigated whether arachidonic acid activates TRPM5 via a heterologous expression system in HEK293 cells, and found that its activation occurred at 10 microM arachidonic acid. These results strongly suggest the possibility that arachidonic acid acts as a modulator of TRPM5 in taste signaling pathways.
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Affiliation(s)
- Hideaki Oike
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
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Jörs S, Kazanski V, Foik A, Krautwurst D, Harteneck C. Receptor-induced activation of Drosophila TRP gamma by polyunsaturated fatty acids. J Biol Chem 2006; 281:29693-702. [PMID: 16901908 DOI: 10.1074/jbc.m602215200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Cellular calcium homeostasis is regulated by hormones and neurotransmitters, resulting in the activation of a variety of proteins, in particular, channel proteins of the plasma membrane and of intracellular compartments. Such channels are, for example, TRP channels of the TRPC protein family that are activated by various mediators from receptor-stimulated signaling cascades. In Drosophila, two TRPC channels, TRP and TRPL, are involved in phototransduction. In addition, a third Drosophila TRPC channel, TRPgamma, has been identified and described as an auxiliary subunit of TRPL. Beyond it, our data show that heterologously expressed TRPgamma formed a receptor-activated, outwardly rectifying cation channel independent from TRPL co-expression. Analysis of the activation mechanism revealed that TRPgamma is activated by various polyunsaturated fatty acids generated in a phospholipase C- and phospholipase A(2)-dependent manner. The most potent activator of TRPgamma, the stable analogue of arachidonic acid, 5,8,11,14-eicosatetraynoic acid, induced currents in single channel recordings. Here we show that upon heterologous expression TRPgamma forms a homomeric channel complex that is activated by polyunsaturated fatty acids as mediators of receptor-dependent signaling pathways. Reverse transcription PCR analysis showed that TRPgamma is expressed in Drosophila heads and bodies. Its body-wide expression pattern and its activation mechanism suggest that TRPgamma forms a fly cation channel responsible for the regulation of intracellular calcium in a variety of hormonal signaling cascades.
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Affiliation(s)
- Simone Jörs
- Institut für Pharmakologie, Charité Campus Benjamin Franklin, Thielallee 69-73, 14195 Berlin, Germany
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Kim JY, Zeng W, Kiselyov K, Yuan JP, Dehoff MH, Mikoshiba K, Worley PF, Muallem S. Homer 1 mediates store- and inositol 1,4,5-trisphosphate receptor-dependent translocation and retrieval of TRPC3 to the plasma membrane. J Biol Chem 2006; 281:32540-9. [PMID: 16887806 DOI: 10.1074/jbc.m602496200] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Store-operated Ca(2+) channels (SOCs) mediate receptor-stimulated Ca(2+) influx. Accumulating evidence indicates that members of the transient receptor potential (TRP) channel family are components of SOCs in mammalian cells. Agonist stimulation activates SOCs and TRP channels directly and by inducing translocation of channels in intracellular vesicles to the plasma membrane (PM). The mechanism of TRP channel translocation in response to store depletion and agonist stimulation is not known. Here we use TRPC3 as a model to show that IP(3) and the scaffold Homer 1 (H1) regulate the rate of translocation and retrieval of TRPC3 from the PM. In resting cells, TRPC3 exists in TRPC3-H1b/c-IP(3)Rs complexes that are located in part at the PM and in part in intracellular vesicles. Binding of IP(3) to the IP(3)Rs dissociates the interaction between IP(3)Rs and H1 but not between H1 and TRPC3 to form IP(3)Rs-TRPC3-H1b/c. TIRFM and biotinylation assays show robust receptor- and store-dependent translocation of the TRPC3 to the PM and their retrieval upon termination of cell stimulation. The translocation requires depletion of stored Ca(2+) and is prevented by inhibition of the IP(3)Rs. In HEK293, dissociating the H1b/c-IP(3)R complex with H1a results in TRPC3 translocation to the PM, where it is spontaneously active. The TRPC3-H1b/c-IP(3)Rs complex is reconstituted by infusing H1c into these cells. Reconstitution is inhibited by IP(3). Deletion of H1 in mice markedly reduces the rates of translocation and retrieval of TRPC3. Conversely, infusion of H1c into H1(-/-) cells eliminates spontaneous channel activity and increases the rate of channel activation by agonist stimulation. The effects of H1c are inhibited by IP(3). These findings together with our earlier studies demonstrating gating of TRPC3 by IP(3)Rs were used to develop a model in which assembly of the TRPC3-H1b/c-IP(3)Rs complexes by H1b/c mediates both the translocation of TRPC3-containing vesicles to the PM and gating of TRPC3 by IP(3)Rs.
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Affiliation(s)
- Joo Young Kim
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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HU HONGZHEN, XIAO RUI, WANG CHUNBO, GAO NA, COLTON CRAIGK, WOOD JACKIED, ZHU MICHAELX. Potentiation of TRPV3 channel function by unsaturated fatty acids. J Cell Physiol 2006; 208:201-12. [PMID: 16557504 PMCID: PMC4458145 DOI: 10.1002/jcp.20648] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Transient receptor potential vanilloid (TRPV) channels are polymodal detectors of multiple environmental factors, including temperature, pH, and pressure. Inflammatory mediators enhance TRPV function through multiple signaling pathways. The lipoxygenase and epoxygenase products of arachidonic acid (AA) metabolism have been shown to directly activate TRPV1 and TRPV4, respectively. TRPV3 is a thermosensitive channel with an intermediate temperature threshold of 31-39 degrees C. We have previously shown that TRPV3 is activated by 2-aminoethoxydiphenyl borate (2APB). Here we show that AA and other unsaturated fatty acids directly potentiate 2APB-induced responses of TRPV3 expressed in HEK293 cells, Xenopus oocytes, and mouse keratinocytes. The AA-induced potentiation is observed in intracellular Ca2+ measurement, whole-cell and two-electrode voltage clamp studies, as well as single channel recordings of excised inside-out and outside-out patches. The fatty acid-induced potentiation is not blocked by inhibitors of protein kinase C and thus differs from that induced by the kinase. The potentiation does not require AA metabolism but is rather mimicked by non-metabolizable analogs of AA. These results suggest a novel mechanism regulating the TRPV3 response to inflammation, which differs from TRPV1 and TRPV4, and involves a direct action of free fatty acids on the channel.
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Affiliation(s)
- HONG-ZHEN HU
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio
| | - RUI XIAO
- Department of Neuroscience and Center for Molecular Neurobiology, The Ohio State University, Columbus, Ohio
| | - CHUNBO WANG
- Department of Neuroscience and Center for Molecular Neurobiology, The Ohio State University, Columbus, Ohio
| | - NA GAO
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio
| | - CRAIG K. COLTON
- Department of Neuroscience and Center for Molecular Neurobiology, The Ohio State University, Columbus, Ohio
| | - JACKIE D. WOOD
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio
- Correspondence to: Jackie D. Wood, Department of Physiology and Cell Biology, The Ohio State University, 304 Hamilton Hall, 1645 Neil Ave, Columbus, OH 43210.,
| | - MICHAEL X. ZHU
- Department of Neuroscience and Center for Molecular Neurobiology, The Ohio State University, Columbus, Ohio
- Correspondence to: Michael X. Zhu, Center for Molecular Neurobiology, The Ohio State University, 168 Rightmire Hall, 1060 Carmack Road, Columbus, OH 43210.,
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Abstract
Calcium sensing receptors (CaR) are unique among G-protein-coupled receptors (GPCRs) since both the first (extracellular) and second (intracellular) messengers are Ca(2+). CaR serves to translate small fluctuations in extracellular Ca(2+) into intracellular Ca(2+) oscillations. In many cells and tissues, CaR also acts as a coincidence detector, sensing both changes in extracellular Ca(2+) plus the presence of various allosteric activators including amino acids, polyamines, and/or peptides. CaR oscillations are uniquely shaped by the activating agonist, that is, Ca(2+) triggers sinusoidal oscillations while Ca(2+) plus phenylalanine trigger transient oscillations of lower frequency. The distinct oscillation patterns generated by Ca(2+)versus Ca(2+) plus phenylalanine are the results of activation of distinct signal transduction pathways. CaR is a member of Family C GPCRs, having a large extracellular agonist binding domain, and functioning as a disulfide-linked dimer. The CaR dimer likely can be driven to distinct active conformations by various Ca(2+) plus modulator combinations, which can drive preferential coupling to divergent signaling pathways. Such plasticity with respect to both agonist and signaling outcomes allows CaR to uniquely contribute to the physiology of organs and tissues where it is expressed. This chapter will examine the structural features of CaR, which contribute to its unique properties, the nature of CaR-induced intracellular Ca(2+) signals and the potential role(s) for CaR in development and differentiation.
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Affiliation(s)
- Gerda E Breitwieser
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822, USA
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40
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Kwan HY, Huang Y, Yao X. Protein kinase C can inhibit TRPC3 channels indirectly via stimulating protein kinase G. J Cell Physiol 2006; 207:315-21. [PMID: 16331690 DOI: 10.1002/jcp.20567] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
There are two known phosphorylation-mediated inactivation mechanisms for TRPC3 channels. Protein kinase G (PKG) inactivates TRPC3 by direct phosphorylation on Thr-11 and Ser-263 of the TRPC3 proteins, and protein kinase C (PKC) inactivates TRPC3 by phosphorylation on Ser-712. In the present study, we explored the relationship between these two inactivation mechanisms of TRPC3. HEK cells were first stably transfected with a PKG-expressing construct and then transiently transfected with a TRPC3-expressing construct. Addition of 1-oleoyl-2-acetyl-sn-glycerol (OAG), a membrane-permeant analog of diacylglycerol (DAG), elicited a TRPC3-mediated [Ca2+]i rise in these cells. This OAG-induced rise in [Ca2+]i could be inhibited by phorbol 12-myristate 13-acetate (PMA), an agonist for PKC, in a dose-dependent manner. Importantly, point mutations at two PKG phosphorylation sites (T11A-S263Q) of TRPC3 markedly reduced the PMA inhibition. Furthermore, inhibition of PKG activity by KT5823 (1 microM) or H8 (10 microM) greatly reduced the PMA inhibition of TRPC3. These data strongly suggest that the inhibitory action of PKC on TRPC3 is partly mediated through PKG in these PKG-overexpressing cells. The importance of this scheme was also tested in vascular endothelial cells, in which PKG plays a pivotal functional role. In these cells, OAG-induced [Ca2+]i rise was inhibited by PMA, which activates PKC, and by 8-BrcGMP and S-nitroso-N-acetylpenicillamine (SNAP), both of which activate PKG. Importantly, the PMA inhibition on OAG-induced [Ca2+]i rise was significantly reduced by PKG inhibitor KT5823 (1 microM) or DT-3 (500 nM), suggesting an important role of PKG in the PMA-induced inhibition of TRPC channels in native endothelial cells.
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Affiliation(s)
- Hiu-Yee Kwan
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, the Chinese University of Hong Kong, Hong Kong, China
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41
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Schreiber R. Ca2+ signaling, intracellular pH and cell volume in cell proliferation. J Membr Biol 2006; 205:129-37. [PMID: 16362501 DOI: 10.1007/s00232-005-0778-z] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2005] [Indexed: 01/06/2023]
Abstract
Mitogens control progression through the cell cycle in non-transformed cells by complex cascades of intracellular messengers, such as Ca2+ and protons, and by cell volume changes. Intracellular Ca2+ and proton concentrations are critical for linking external stimuli to proliferation, motility, apoptosis and differentiation. This review summarizes the role in cell proliferation of calcium release from intracellular stores and the Ca2+ entry through plasma membrane Ca2+ channels. In addition, the impact of intracellular pH and cell volume on cell proliferation is discussed.
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Affiliation(s)
- R Schreiber
- Institut für Physiologie, Universität Regensburg, Universitätsstr. 31, Regensburg, D-93053, Germany.
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42
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Pelucchi B, Aguiari G, Pignatelli A, Manzati E, Witzgall R, Del Senno L, Belluzzi O. Nonspecific cation current associated with native polycystin-2 in HEK-293 cells. J Am Soc Nephrol 2006; 17:388-97. [PMID: 16396967 DOI: 10.1681/asn.2004121146] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mutations in either PKD1 or PKD2 gene are associated with autosomal dominant polycystic kidney disease, the most common inherited kidney disorder. Polycystin-2 (PC2), the PKD2 gene product, and the related protein polycystin-L, function as Ca(2+)-permeable, nonselective cation channels in different expression systems. This work describes a nonspecific cation current (I(CC)) that is present in native HEK-293 cells and highly associated with a PC2-channel activity. The current is voltage dependent, activating for potentials that are positive to -50 mV and inactivating in a few milliseconds. It is sensitive to Cd(2+), Gd(3+), La(3+), SKF96365, and amiloride. After silencing of PC2 by RNA interfering, cells show a reduced current that is restored by transfection with normal but not truncated PC2. Consistently, I(CC) is abolished by perfusion with an anti-PC2 antibody. Furthermore, heterologous expression of the PC1 cytoplasmic tail significantly increases I(CC) peak amplitude compared with native cells. This is the first characterization of such a current in HEK-293 cells, a widely used expression system for ion channels. These cells, therefore, could be regarded as a suitable and readily accessible tool to study interactions between native PC2/PC1 complex and other membrane proteins, thus contributing to the understanding of autosomal dominant polycystic kidney disease pathogenesis.
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Affiliation(s)
- Bruna Pelucchi
- Department of Biology, University of Ferrara, Via L. Borsari 46, Ferrara I-44100, Italy.
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Cai S, Fatherazi S, Presland RB, Belton CM, Roberts FA, Goodwin PC, Schubert MM, Izutsu KT. Evidence that TRPC1 contributes to calcium-induced differentiation of human keratinocytes. Pflugers Arch 2005; 452:43-52. [PMID: 16283206 DOI: 10.1007/s00424-005-0001-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2005] [Revised: 03/31/2005] [Accepted: 06/10/2005] [Indexed: 11/29/2022]
Abstract
External calcium ion concentration is a major regulator of epidermal keratinocyte differentiation in vitro and probably also in vivo. Regulation of calcium-induced differentiation changes is proposed to occur via an external calcium-sensing, signaling pathway that utilizes increases in intracellular calcium ion concentration to activate differentiation-related gene expression. Calcium ion release from intracellular stores and calcium ion influx via store-operated calcium-permeable channels are key elements in this proposed signaling pathway; however, the channels involved have not yet been identified. The present report shows that human gingival keratinocytes (HGKs) also undergo calcium-induced differentiation in vitro as indicated by involucrin expression and morphological changes. Moreover, TRPC1, which functions as a store-operated calcium channel in a number of cell types, including epidermal keratinocytes, is expressed in both proliferating and differentiating HGKs. Transfection of HGKs with TRPC1 siRNA disrupted expression of TRPC1 mRNA and protein compared with transfection with scrambled TRPC1 siRNA. Cells with disrupted TRPC1 expression showed decreased calcium-induced differentiation as measured by involucrin expression or morphological changes, as well as decreased thapsigargin-induced calcium ion influx, and a decreased rate of store calcium release. These results indicate that TRPC1 is involved in calcium-induced differentiation of HGKs likely by supporting a store-operated calcium ion influx.
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Affiliation(s)
- Shiwei Cai
- Department of Oral Biology, University of Washington, Box 357132, Seattle, WA 98195, USA
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Odell AF, Scott JL, Van Helden DF. Epidermal Growth Factor Induces Tyrosine Phosphorylation, Membrane Insertion, and Activation of Transient Receptor Potential Channel 4. J Biol Chem 2005; 280:37974-87. [PMID: 16144838 DOI: 10.1074/jbc.m503646200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Various members of the canonical family of transient receptor potential channels (TRPCs) exhibit increased cation influx following receptor stimulation or Ca(2+) store depletion. Tyrosine phosphorylation of TRP family members also results in increased channel activity; however, the link between the two events is unclear. We report that two tyrosine residues in the C terminus of human TRPC4 (hTRPC4), Tyr-959 and Tyr-972, are phosphorylated following epidermal growth factor (EGF) receptor stimulation of COS-7 cells. This phosphorylation was mediated by Src family tyrosine kinases (STKs), with Fyn appearing to be the dominant kinase. In addition, EGF receptor stimulation induced the exocytotic insertion of hTRPC4 into the plasma membrane dependent on the activity of STKs and was accompanied by a phosphorylation-dependent increase in the association of hTRPC4 with Na(+)/H(+) exchanger regulatory factor. Furthermore, this translocation and association was defective upon mutation of Tyr-959 and Tyr-972 to phenylalanine. Significantly, inhibition of STKs was concomitant with a reduction in Ca(2+) influx in both native COS-7 cells and hTRPC4-expressing HEK293 cells, with cells expressing the Y959F/Y972F mutant exhibiting a reduced EGF response. These findings represent the first demonstration of a mechanism for phosphorylation to modulate TRPC channel function.
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Affiliation(s)
- Adam F Odell
- School of Biomedical Sciences, Level 5 MSB, University of Newcastle, Callaghan, New South Wales, Australia.
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45
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Xie Q, Zhang Y, Sun XC, Zhai C, Bonanno JA. Expression and functional evaluation of transient receptor potential channel 4 in bovine corneal endothelial cells. Exp Eye Res 2005; 81:5-14. [PMID: 15978249 PMCID: PMC4110920 DOI: 10.1016/j.exer.2005.01.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Revised: 01/06/2005] [Accepted: 01/07/2005] [Indexed: 10/25/2022]
Abstract
We previously found that activation of purinergic receptors mobilizes Ca2+ and enhances bicarbonate transport in bovine corneal endothelial cells (BCEC). Since transient receptor potential channel 4 (TRPC) has been reported to be a candidate for capacitative calcium entry (CCE) and receptor operated calcium entry (ROC), we examined the expression of TRPC4 and evaluated the potential involvement of TRPC4 in CCE or ROC in BCEC. The C-terminus of TRPC4 was fused into the glutathione S-transferase (GST) expression vector. The fusion protein GST-TRPC4c was induced in bacteria and purified by affinity chromatography. An antibody was raised in rabbit by using the purified GST-TRPC4c antigen. In Western blotting, the TRPC4 antibody recognized the fusion protein while the pre-immune IgG did not. The TRPC4 antibody recognized a band at around 80 kD for membrane proteins from both the fresh and cultured BCEC. The pre-immune IgG could not detect bands at the same size. Incubation with the TRPC4c antigen abolished the 80 kD band. Immunofluorescence using the TRPC4 antibody stained both fresh and cultured BCEC, while pre-immune IgG did not. RNAi knocked down the expression of TRPC4 in cultured BCEC. Ca2+ entry induced by the purinergic receptor agonist ATP, was increased in TRPC4-siRNA transfected cells compared with the scrambled siRNA control, while Ca2+ entry induced by store depletion through blocking the endoplasmic reticulum Ca2+ pump, did not differ between the siRNA and scrambled siRNA-treated cells. Taken together, these results show that TRPC4 protein is expressed in the bovine corneal endothelial cells and may be a negative regulator in ROC stimulated by purinergic activation, but not by store depletion itself.
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Affiliation(s)
| | | | | | | | - Joseph A. Bonanno
- Corresponding author. Dr Joseph A. Bonanno, School of Optometry, Indiana University, 800 E Atwater Avenue, Bloomington, IN 47405-3680, USA. (J.A. Bonanno)
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Li S, Gosling M, Poll C. Determining the functional role of TRPC channels in primary cells. Pflugers Arch 2005; 451:43-52. [PMID: 16078043 DOI: 10.1007/s00424-005-1465-8] [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] [Received: 05/01/2005] [Accepted: 05/04/2005] [Indexed: 10/25/2022]
Abstract
Although the TRPC members of the mammalian transient receptor potential TRP cation channel family were the first to be described in 1995, the depth of knowledge of TRPC channels has fallen behind that of their counterparts in the TRPV and TRPM subfamilies in the intervening years. The complexities and controversies of TRPC channel composition and regulation have hindered their progress as therapeutic targets in the drug discovery environment to date, however embracing these challenges as opportunities may bring TRPC channels to the forefront of the discovery of novel therapies for many diseases. These challenges and opportunities of exploring TRPC channels as therapeutic targets are highlighted and discussed in this review with respect to respiratory diseases.
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Affiliation(s)
- Su Li
- Novartis Institutes for Biomedical Research, Novartis Respiratory Research Centre, Wimblehurst Road, Horsham, West Sussex, RH12 5AB, UK.
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Zagranichnaya TK, Wu X, Villereal ML. Endogenous TRPC1, TRPC3, and TRPC7 Proteins Combine to Form Native Store-operated Channels in HEK-293 Cells. J Biol Chem 2005; 280:29559-69. [PMID: 15972814 DOI: 10.1074/jbc.m505842200] [Citation(s) in RCA: 173] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endogenously expressed canonical transient receptor potential (TRPC) homologs were investigated for their role in forming store-operated, 1-oleoyl-2-acetyl-sn-glycerol-stimulated, or carbachol (CCh)-stimulated calcium entry pathways in HEK-293 cells. Measurement of thapsigargin-stimulated Ba(2+) entry indicated that the individual suppression of TRPC1, TRPC3, or TRPC7 protein levels, by small interfering RNA (siRNA) techniques, dramatically inhibited (52-68%) store-operated calcium entry (SOCE), whereas suppression of TRPC4 or TRPC6 had no effect. Combined suppression of TRPC1-TRPC3, TRPC1-TRPC7, TRPC3-TRPC7, or TRPC1-TRPC3-TRPC7 gave only slightly more inhibition of SOCE (74-78%) than seen with suppression of TRPC1 alone (68%), suggesting that these three TRPC homologs work in tandem to mediate a large component of SOCE. Evidence from co-immunoprecipitation experiments indicates that a TRPC1-TRPC3-TRPC7 complex, predicted from siRNA results, does exist. The suppression of either TRPC3 or TRPC7, but not TRPC1, induced a high Ba(2+) leak flux that was inhibited by 2-APB and SKF96365, suggesting that the influx is via leaky store-operated channels. The high Ba(2+) leak flux is eliminated by co-suppression of TRPC1-TRPC3 or TRPC1-TRPC7. For 1-oleoyl-2-acetyl-sn-glycerol-stimulated cells, siRNA data indicate that TRPC1 plays no role in mediating Ba(2+) entry, which appears to be mediated by the participation of TRPC3, TRPC4, TRPC6, and TRPC7. CCh-stimulated Ba(2+) entry, on the other hand, could be inhibited by suppression of any of the five endogenously expressed TRPC homologs, with the degree of inhibition being consistent with CCh stimulation of both store-operated and receptor-operated channels. In summary, endogenous TRPC1, TRPC3, and TRPC7 participate in forming heteromeric store-operated channels, whereas TRPC3 and TRPC7 can also participate in forming heteromeric receptor-operated channels.
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Affiliation(s)
- Tatiana K Zagranichnaya
- Department of Neurobiology, Pharmacology and Physiology, University of Chicago, Illinois 60637, USA
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Kiselyov K, Kim JY, Zeng W, Muallem S. Protein-protein interaction and functionTRPC channels. Pflugers Arch 2005; 451:116-24. [PMID: 16044307 DOI: 10.1007/s00424-005-1442-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Accepted: 04/13/2005] [Indexed: 11/28/2022]
Abstract
Since their identification in the concluding years of the last century, the mammalian transient receptor potential (canonical) (TRPC) channels have remained in the limelight as the primary candidates for the Ca(2+) entry pathway activated by the hormones, growth factors, and neurotransmitters that exert their effect through activation of PLC. Although TRPC channels have been shown clearly to mediate, at least in part, receptor-activated Ca(2+) entry in literally all cell types, several of their central characteristics, as recorded in expression systems using recombinant channels, differ from those of the native receptor-dependent Ca(2+) influx channels. The present review attempts to highlight the interaction of TRPC channels with other proteins, which may explain the variability of TRPC channel activation and regulatory mechanisms observed with the native and recombinant channels. These include the homologous and heterotopous interactions of TRPC channel isoforms, the interaction of TRPC channels with calmodulin, PLCgamma, IP(3) receptors, and with scaffolding proteins like InaD, EBP50/NEHRF, caveolin, Janctate and Homers.
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Affiliation(s)
- Kirill Kiselyov
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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Estevez AY, Strange K. Calcium feedback mechanisms regulate oscillatory activity of a TRP-like Ca2+ conductance in C. elegans intestinal cells. J Physiol 2005; 567:239-51. [PMID: 15961418 PMCID: PMC1474156 DOI: 10.1113/jphysiol.2005.091900] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Inositol-1,4,5-trisphosphate (IP3)-dependent Ca2+ oscillations in Caenorhabditis elegans intestinal epithelial cells regulate the nematode defecation cycle. The role of plasma membrane ion channels in intestinal cell oscillatory Ca2+ signalling is unknown. We have shown previously that cultured intestinal cells express a Ca2+-selective conductance, I(ORCa), that is biophysically similar to TRPM7 currents. I(ORCa) activates slowly and stabilizes when cells are patch clamped with pipette solutions containing 10 mm BAPTA and free Ca2+ concentrations of approximately 17 nm. However, when BAPTA concentration is lowered to 1 mm, I(ORCa) oscillates. Oscillations in channel activity induced simultaneous oscillations in cytoplasmic Ca2+ levels. Removal of extracellular Ca2+ inhibited I(ORCa) oscillations, whereas readdition of Ca2+ to the bath caused a rapid and transient reactivation of the current. Experimental manoeuvres that elevated intracellular Ca2+ blocked current oscillations. Elevation of intracellular Ca2+ in the presence of 10 mm BAPTA to block I(ORCa) oscillations led to a dose-dependent increase in the rate of current activation. At intracellular Ca2+ concentrations of 250 nm, current activation was transient. Patch pipette solutions buffered with 1-4 mm of either BAPTA or EGTA gave rise to similar patterns of I(ORCa) oscillations. We conclude that changes in Ca2+ concentration close to the intracellular opening of the channel pore regulate channel activity. Low concentrations of Ca2+ activate the channel. As Ca2+ enters and accumulates near the pore mouth, channel activity is inhibited. Oscillating plasma membrane Ca2+ entry may play a role in generating intracellular Ca2+ oscillations that regulate the C. elegans defecation rhythm.
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Affiliation(s)
- Ana Y Estevez
- Vanderbilt University Medical Center, T-4202 Medical Center North, Nashville, TN 37232-2520, USA
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Brown A, Riddoch F, Robson A, Redfern C, Cheek T. Mechanistic and functional changes in Ca2+ entry after retinoic acid-induced differentiation of neuroblastoma cells. Biochem J 2005; 388:941-8. [PMID: 15673285 PMCID: PMC1183475 DOI: 10.1042/bj20042127] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Accepted: 01/27/2005] [Indexed: 11/17/2022]
Abstract
We have investigated effects of neuronal differentiation on hormone-induced Ca2+ entry. Fura-2 fluorescence measurements of undifferentiated SH-SY5Y neuroblastoma cells, stimulated with methacholine, revealed the presence of voltage-operated Ca2+-permeable, Mn2+-impermeable entry pathways, and at least two voltage-independent Ca2+- and Mn2+-permeable entry pathways, all of which apparently contribute to both peak and plateau phases of the Ca2+ signal. Similar experiments using 9-cis retinoic acid-differentiated cells, however, revealed voltage-operated Ca2+-permeable, Mn2+-impermeable channels, and, more significantly, the absence or down-regulation of the most predominant of the voltage-independent entry pathways. This down-regulated pathway is probably due to CCE (capacitative Ca2+ entry), since thapsigargin also stimulated Ca2+ and Mn2+ entry in undifferentiated but not differentiated cells. The Ca2+ entry components remaining in methacholine-stimulated differentiated cells contributed to only the plateau phase of the Ca2+ signal. We conclude that differentiation of SH-SY5Y cells results in a mechanistic and functional change in hormone-stimulated Ca2+ entry. In undifferentiated cells, voltage-operated Ca2+ channels, CCE and NCCE (non-CCE) pathways are present. Of the voltage-independent pathways, the predominant one appears to be CCE. These pathways contribute to both peak and plateau phases of the Ca2+ signal. In differentiated cells, CCE is either absent or down-regulated, whereas voltage-operated entry and NCCE remain active and contribute to only the plateau phase of the Ca2+ signal.
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Affiliation(s)
- Anna M. Brown
- *Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, U.K
| | - Fiona C. Riddoch
- *Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, U.K
| | - Andrew Robson
- *Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, U.K
| | - Christopher P. F. Redfern
- †Northern Institute for Cancer Research, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, U.K
| | - Timothy R. Cheek
- *Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, U.K
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