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Wang Q, Caraballo SG, Rychkov G, McGovern AE, Mazzone SB, Brierley SM, Harrington AM. Comparative localization of colorectal sensory afferent central projections in the mouse spinal cord dorsal horn and caudal medulla dorsal vagal complex. J Comp Neurol 2024; 532:e25546. [PMID: 37837642 DOI: 10.1002/cne.25546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 09/04/2023] [Accepted: 10/03/2023] [Indexed: 10/16/2023]
Abstract
The distal colon and rectum (colorectum) are innervated by spinal and vagal afferent pathways. The central circuits into which vagal and spinal afferents relay colorectal nociceptive information remain to be comparatively assessed. To address this, regional colorectal retrograde tracing and colorectal distension (CRD)-evoked neuronal activation were used to compare the circuits within the dorsal vagal complex (DVC) and dorsal horn (thoracolumbar [TL] and lumbosacral [LS] spinal levels) into which vagal and spinal colorectal afferents project. Vagal afferent projections were observed in the nucleus tractus solitarius (NTS), area postrema (AP), and dorsal motor nucleus of the vagus (DMV), labeled from the rostral colorectum. In the NTS, projections were opposed to catecholamine and pontine parabrachial nuclei (PbN)-projecting neurons. Spinal afferent projections were labeled from rostral through to caudal aspects of the colorectum. In the dorsal horn, the number of neurons activated by CRD was linked to pressure intensity, unlike in the DVC. In the NTS, 13% ± 0.6% of CRD-activated neurons projected to the PbN. In the dorsal horn, at the TL spinal level, afferent input was associated with PbN-projecting neurons in lamina I (LI), with 63% ± 3.15% of CRD-activated neurons in LI projecting to the PbN. On the other hand, at the LS spinal level, only 18% ± 0.6% of CRD-activated neurons in LI projected to the PbN. The collective data identify differences in the central neuroanatomy that support the disparate roles of vagal and spinal afferent signaling in the facilitation and modulation of colorectal nociceptive responses.
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Affiliation(s)
- QingQing Wang
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Sonia Garcia Caraballo
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Grigori Rychkov
- Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
- School of Biomedicine, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Alice E McGovern
- Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Stuart B Mazzone
- Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Stuart M Brierley
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
- School of Biomedicine, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Andrea M Harrington
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
- School of Biomedicine, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, South Australia, Australia
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Liu D, Rychkov G, Al-Hawwas M, Manaph NPA, Zhou F, Bobrovskaya L, Liao H, Zhou XF. Conversion of human urine-derived cells into neuron-like cells by small molecules. Mol Biol Rep 2020; 47:2713-2722. [PMID: 32185687 DOI: 10.1007/s11033-020-05370-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 03/04/2020] [Indexed: 01/04/2023]
Abstract
Neural cell transplantation is an effective way for treatment of neurological diseases. However, the absence of transplantable human neurons remains a barrier for clinical therapies. Human urine-derived cells, namely renal cells and urine stem cells, have become a good source of cells for reprogramming or trans-differentiation research. Here, we show that human urine-derived cells can be partially converted into neuron-like cells by applying a cocktail of small molecules. Gene expression analysis has shown that these induced cells expressed some neuron-specific genes, and a proportion of the cells are GABAergic neurons. Moreover, whole-cell patch clamping recording has shown that some induced cells have neuron-specific voltage gated Na+ and K+ currents but have failed to generate Ca2+ currents and action potentials. Taken together, these results suggest that induced neuronal cells from human urine-derived cells may be useful for neurological disease modelling, drug screening and cell therapies.
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Affiliation(s)
- Donghui Liu
- School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA, 5000, Australia
- Jiangsu Key Laboratory of Drug Screening, China Pharmaceutical University, 24 Tongjiaxiang Street, Nanjing, 210009, China
| | - Grigori Rychkov
- Discipline of Medicine, School of Medicine, University of Adelaide, Adelaide, SA, 5000, Australia
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, 5000, Australia
| | - Mohammed Al-Hawwas
- School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA, 5000, Australia
| | | | - Fiona Zhou
- School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA, 5000, Australia
- Discipline of Medicine, School of Medicine, University of Adelaide, Adelaide, SA, 5000, Australia
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, 5000, Australia
| | - Larisa Bobrovskaya
- School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA, 5000, Australia
| | - Hong Liao
- Jiangsu Key Laboratory of Drug Screening, China Pharmaceutical University, 24 Tongjiaxiang Street, Nanjing, 210009, China.
| | - Xin-Fu Zhou
- School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA, 5000, Australia.
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Grundy L, Caldwell A, Garcia-Caraballo S, Rychkov G, Brierley S. MP42-20 IDENTIFICATION OF NOVEL IRRITANT SENSING MECHANISMS IN THE BLADDER. J Urol 2017. [DOI: 10.1016/j.juro.2017.02.1309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Grundy L, Garcia-Caraballo S, Maddern J, Rychkov G, Ge P, Hannig G, Kurtz C, Silos-Santiago A, Brierley S. MP42-05 CHRONIC ORAL ADMINISTRATION OF THE GUANYLATE CYCLASE-C AGONIST LINACLOTIDE ATTENUATES COLITIS INDUCED BLADDER AFFERENT AND DORSAL ROOT GANGLION HYPERACTIVITY. J Urol 2017. [DOI: 10.1016/j.juro.2017.02.1294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Zhang W, Garg S, Eldi P, Zhou FHH, Johnson IR, Brooks DA, Lam F, Rychkov G, Hayball J, Albrecht H. Targeting prostate cancer cells with genetically engineered polypeptide-based micelles displaying gastrin-releasing peptide. Int J Pharm 2016; 513:270-279. [DOI: 10.1016/j.ijpharm.2016.09.039] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 08/12/2016] [Accepted: 09/10/2016] [Indexed: 01/15/2023]
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Grundy L, Garcia-Caraballo S, Maddern J, Rychkov G, Hannig G, Kurtz C, Silos-Santiago A, M. Brierley S. MP28-06 COLITIS INDUCES LONG-TERM BLADDER AFFERENT HYPERACTIVITY, WHICH IS ATTENUATED BY CHRONIC ORAL ADMINISTRATION OF THE GUANYLATE CYCLASE-C AGONIST LINACLOTIDE. J Urol 2016. [DOI: 10.1016/j.juro.2016.02.1056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Kilch T, Alansary D, Peglow M, Dörr K, Rychkov G, Rieger H, Peinelt C, Niemeyer BA. Mutations of the Ca2+-sensing stromal interaction molecule STIM1 regulate Ca2+ influx by altered oligomerization of STIM1 and by destabilization of the Ca2+ channel Orai1. J Biol Chem 2012; 288:1653-64. [PMID: 23212906 DOI: 10.1074/jbc.m112.417246] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A drop of endoplasmic reticulum Ca(2+) concentration triggers its Ca(2+) ssensor protein stromal interaction molecule 1 (STIM1) to oligomerize and accumulate within endoplasmic reticulum-plasma membrane junctions where it activates Orai1 channels, providing store-operated Ca(2+) entry. To elucidate the functional significance of N-glycosylation sites of STIM1, we created different mutations of asparagine-131 and asparagine-171. STIM1 NN/DQ resulted in a strong gain of function. Patch clamp, Total Internal Reflection Fluorescent (TIRF) microscopy, and fluorescence recovery after photobleaching (FRAP) analyses revealed that expression of STIM1 DQ mutants increases the number of active Orai1 channels and the rate of STIM1 translocation to endoplasmic reticulum-plasma membrane junctions with a decrease in current latency. Surprisingly, co-expression of STIM1 DQ decreased Orai1 protein, altering the STIM1:Orai1 stoichiometry. We describe a novel mathematical tool to delineate the effects of altered STIM1 or Orai1 diffusion parameters from stoichiometrical changes. The mutant uncovers a novel mechanism whereby "superactive" STIM1 DQ leads to altered oligomerization rate constants and to degradation of Orai1 with a change in stoichiometry of activator (STIM1) to effector (Orai1) ratio leading to altered Ca(2+) homeostasis.
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Affiliation(s)
- Tatiana Kilch
- Department of Biophysics, Saarland University, D-66421 Homburg, Germany
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Kilch T, Al-Ansary D, Rychkov G, Peinelt C, Niemeyer BA. STIM1 Mutants Modify CRAC by Altering Orai1 Protein Concentration. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.3700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
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Chan Y, Beltrame J, Rychkov G, Wilson D. Thromboxane A2-mediated L-type Calcium Channel Activation in the Vasculature. Heart Lung Circ 2012. [DOI: 10.1016/j.hlc.2012.05.068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Arthur A, Rychkov G, Shi S, Koblar SA, Gronthos S. Adult human dental pulp stem cells differentiate toward functionally active neurons under appropriate environmental cues. Stem Cells 2008; 26:1787-95. [PMID: 18499892 DOI: 10.1634/stemcells.2007-0979] [Citation(s) in RCA: 399] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Human adult dental pulp stem cells (DPSCs) reside within the perivascular niche of dental pulp and are thought to originate from migrating cranial neural crest (CNC) cells. During embryonic development, CNC cells differentiate into a wide variety of cell types, including neurons of the peripheral nervous system. Previously, we have demonstrated that DPSCs derived from adult human third molar teeth differentiate into cell types reminiscent of CNC embryonic ontology. We hypothesized that DPSCs exposed to the appropriate environmental cues would differentiate into functionally active neurons. The data demonstrated that ex vivo-expanded human adult DPSCs responded to neuronal inductive conditions both in vitro and in vivo. Human adult DPSCs, but not human foreskin fibroblasts (HFFs), acquired a neuronal morphology, and expressed neuronal-specific markers at both the gene and protein levels. Culture-expanded DPSCs also exhibited the capacity to produce a sodium current consistent with functional neuronal cells when exposed to neuronal inductive media. Furthermore, the response of human DPSCs and HFFs to endogenous neuronal environmental cues was determined in vivo using an avian xenotransplantation assay. DPSCs expressed neuronal markers and acquired a neuronal morphology following transplantation into the mesencephalon of embryonic day-2 chicken embryo, whereas HFFs maintained a thin spindle fibroblastic morphology. We propose that adult human DPSCs provide a readily accessible source of exogenous stem/precursor cells that have the potential for use in cell-therapeutic paradigms to treat neurological disease.
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Affiliation(s)
- Agnes Arthur
- The Australian Research Council, Centre for the Molecular Genetics of Development, University of Adelaide, Adelaide, Australia
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Abstract
The full-length transient receptor (TRPC)1 polypeptide is composed of about 790 amino acids, and several splice variants are known. The predicted structure and topology is of an integral membrane protein composed of six transmembrane domains, and a cytoplasmic C- and N-terminal domain. The N-terminal domain includes three ankyrin repeat motifs. Antibodies which recognise TRPC1 have been developed, but it has been difficult to obtain antibodies which have high affinity and specificity for TRPC1. This has made studies of the cellular functions of TRPC1 somewhat difficult. The TRPC1 protein is widely expressed in different types of animal cells, and within a given cell is found at the plasma membrane and at intracellular sites. TRPC1 interacts with calmodulin, caveolin-1, the InsP3 receptor, Homer, phospholipase C and several other proteins. Investigations of the biological roles and mechanisms of action of TRPC1 have employed ectopic (over-expression or heterologous expression) of the polypeptide in addition to studies of endogenous TRPC1. Both approaches have encountered difficulties. TRPC1 forms heterotetramers with other TRPC polypeptides resulting in cation channels which are non-selective. TRPC1 may be: a component of the pore of store-operated Ca2+ channels (SOCs); a subsidiary protein in the pathway of activation of SOCs; activated by interaction with InsP3R; and/or activated by stretch. Further experiments are required to resolve the exact roles and mechanisms of activation of TRPC1. Cation entry through the TRPC1 channel is feed-back inhibited by Ca2+ through interaction with calmodulin, and is inhibited by Gd3+, La3+, SKF96365 and 2-APB, and by antibodies targeted to the external mouth of the TRPC1 pore. Activation of TRPC1 leads to the entry to the cytoplasmic space of substantial amounts of Na+ as well as Ca2+. A requirement for TRPC1 is implicated in numerous downstream cellular pathways. The most clearly described roles are in the regulation of growth cone turning in neurons. It is concluded that TRPC1 is a most interesting protein because of the apparent wide variety of its roles and functions and the challenges posed to those attempting to elucidate its primary intracellular functions and mechanisms of action.
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Affiliation(s)
- G Rychkov
- School of Molecular and Biomedical Science, University of Adelaide, 5005 Adelaide, South Australia, Australia
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12
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13
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Abstract
ClC-1 is a dimeric, double-pored chloride channel that is present in skeletal muscle. Mutations of this channel can result in the condition myotonia, a muscle disorder involving increased muscle stiffness. It has been shown that the dominant form of myotonia often results from mutations that affect the so-called slow, or common, gating process of the ClC-1 channel. Mutations causing dominant myotonia are seen to cluster at the interface of the ClC-1 channel monomers. This study has investigated the role of the H, I, P, and Q helices, which lie on this interface, as well as the G helix, which is situated immediately behind the H and I helices, on ClC-1 gating. 11 mutant ClC-1 channels (T268M, C277S, C278S, S289A, T310M, S312A, V321S, T539A, S541A, M559T, and S572V) were produced using site-directed mutagenesis, and gating properties of these channels were investigated using electrophysiological techniques. Six of the seven mutations in G, H, and I, and two of the four mutations in P and Q, caused shifts of the ClC-1 open probability. In the majority of cases this was due to alterations in the common gating process, with only three of the mutants displaying any change in fast gating. Many of the mutant channels also showed alterations in the kinetics of the common gating process, particularly at positive potentials. The changes observed in common gating were caused by changes in the opening rate (e.g. T310M), the closing rate (e.g. C277S), or both rates. These results indicate that mutations in the helices forming the dimer interface are able to alter the ClC-1 common gating process by changing the energy of the open and/or closed channel states, and hence altering transition rates between these states.
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Affiliation(s)
- Michael Duffield
- Department of Physiology, University of Adelaide, Adelaide, South Australia 5005, Australia
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Brereton HM, Chen J, Rychkov G, Harland ML, Barritt GJ. Maitotoxin activates an endogenous non-selective cation channel and is an effective initiator of the activation of the heterologously expressed hTRPC-1 (transient receptor potential) non-selective cation channel in H4-IIE liver cells. Biochim Biophys Acta 2001; 1540:107-26. [PMID: 11513973 DOI: 10.1016/s0167-4889(01)00124-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The structures and mechanisms of activation of non-selective cation channels (NSCCs) are not well understood although NSCCs play important roles in the regulation of metabolism, ion transport, cell volume and cell shape. It has been proposed that TRP (transient receptor potential) proteins are the molecular correlates of some NSCCs. Using fura-2 and patch-clamp recording, it was shown that the maitotoxin-activated cation channels in the H4-IIE rat liver cell line admit Ca(2+), Mn(2+) and Na(+), have a high selectivity for Na(+) compared with Ca(2+), and are inhibited by Gd(3+) (half-maximal inhibition at 1 microM). Activation of the channels by maitotoxin was inhibited by increasing the extracellular Ca(2+) concentration or by inclusion of 10 mM EGTA in the patch pipette. mRNA encoding TRP proteins 1, 2 and 3 at levels comparable with those in brain was detected using reverse transcriptase-polymerase chain reaction in poly(A)(+) RNA prepared from H4-IIE cells and freshly-isolated rat hepatocytes. In H4-IIE cells transiently transfected with cDNA encoding hTRPC-1, the expressed hTRPC-1 protein was chiefly located at intracellular sites and at the plasma membrane. Cells expressing hTRPC-1 exhibited a substantial enhancement of maitotoxin-initiated Ca(2+) inflow and a modest enhancement of thapsigargin-initiated Ca(2+) inflow (measured using fura-2) and no enhancement of the highly Ca(2+)-selective store-operated Ca(2+) current (measured using patch-clamp recording). In cells expressing hTRPC-1, maitotoxin activated channels which were not found in untransfected cells, have an approximately equal selectivity for Na(+) and Ca(2+), and are inhibited by Gd(3+) (half-maximal inhibition at 3 microM). It is concluded that in liver cells (i) maitotoxin initiates the activation of endogenous NSCCs with a high selectivity for Na(+) compared with Ca(2+); (ii) TRP proteins 1, 2 and 3 are expressed; (iii) maitotoxin is an effective initiator of activation of heterologously expressed hTRPC-1 channels; and (iv) the endogenous TRP-1 protein is unlikely to be the molecular counterpart of the maitotoxin-activated NSCCs nor the highly Ca(2+)-selective store-operated Ca(2+) channels.
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Affiliation(s)
- H M Brereton
- Department of Medical Boichemistry, School of Medicine, Flinders University, Adelaide, SA, Australia
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Rychkov G, Brereton HM, Harland ML, Barritt GJ. Plasma membrane Ca2+ release-activated Ca2+ channels with a high selectivity for Ca2+ identified by patch-clamp recording in rat liver cells. Hepatology 2001; 33:938-47. [PMID: 11283858 DOI: 10.1053/jhep.2001.23051] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Repetitive waves of increased cytoplasmic Ca2+ concentration play a central role in the process by which hormones regulate liver function. Maintenance of these Ca2+ waves requires Ca2+ inflow through store-operated Ca2+ channels. The properties and mechanism(s) of activation of these channels are not well understood. Store-operated Ca2+ channels (SOCs) in the H4-IIE rat liver cell line were studied by whole-cell patch clamping. Depletion of Ca2+ in intracellular stores by intracellular perfusion with either inositol 1,4,5-trisphosphate (InsP(3)) or thapsigargin in the presence of 10 mmol/L ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid (EGTA), or with 10 mmol/L EGTA alone, activated an inward current that reversed at a membrane potential above +40 mV. In physiologic extracellular medium, this inward current was carried exclusively by Ca2+ and was blocked by a variety of di- and trivalent cations. In the absence of extracellular Ca2+ and Mg2+, the inward current was carried by monovalent cations. This current was 10 to 30 times larger than that observed in the presence of extracellular Ca2+, and permitted the detection of single-channel events that corresponded to a single-channel conductance of about 40 pS. Both the Ca2+ and Na+ inward currents were blocked by the calmodulin antagonist, N-(6-amino hexyl)-5-chloro-1-naphthalenesulphonamide (W7), but not by calmidazolium or calmodulin-dependent protein kinase II fragment 290-309. It is concluded that liver cells possess plasma membrane Ca2+ channels that have a high selectivity for Ca2+, are activated by a decrease in the concentration of Ca2+ in intracellular stores through a mechanism that is unlikely to involve calmodulin, and are involved in re-filling intracellular Ca2+ stores during Ca2+ signaling.
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Affiliation(s)
- G Rychkov
- Centre for Advanced Biomedical Studies, University of South Australia and Department of Physiology, University of Adelaide, South Australia
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Gregory RB, Rychkov G, Barritt GJ. Evidence that 2-aminoethyl diphenylborate is a novel inhibitor of store-operated Ca2+ channels in liver cells, and acts through a mechanism which does not involve inositol trisphosphate receptors. Biochem J 2001; 354:285-90. [PMID: 11171105 PMCID: PMC1221654 DOI: 10.1042/0264-6021:3540285] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The compound 2-aminoethyl diphenylborate (2-APB), an inhibitor of Ins(1,4,5)P(3) receptor action in some cell types, has been used to assess the role of Ins(1,4,5)P(3) receptors in the activation of store-operated Ca2+ channels (SOCs) [Ma, Patterson, van Rossum, Birnbaumer, Mikoshiba and Gill (2000) Science 287, 1647-1651]. In freshly-isolated rat hepatocytes, 2-APB inhibited thapsigargin- and vasopressin-stimulated Ca2+ inflow (measured using fura-2) with no detectable effect on the release of Ca2+ from intracellular stores. The concentration of 2-APB which gave half-maximal inhibition of Ca2+ inflow was approx. 10 microM. 2-APB also inhibited Ca2+ inflow initiated by a low concentration of adenophostin A but had no effect on maitotoxin-stimulated Ca2+ inflow through non-selective cation channels. The onset of the inhibitory effect of 2-APB on thapsigargin-stimulated Ca2+ inflow was rapid. When 2-APB was added to rat hepatocytes in the presence of extracellular Ca2+ after a vasopressin-induced plateau in the cytoplasmic free Ca2+ concentration ([Ca2+](cyt)) had been established, the kinetics of the decrease in [Ca2+](cyt) were identical with those induced by the addition of 50 microM Gd(3+) (gadolinium). 2-APB did not inhibit the release of Ca2+ from intracellular stores induced by the addition of Ins(1,4,5)P(3) to permeabilized hepatocytes. In the H4-IIE rat hepatoma cell line, 2-APB inhibited thapsigargin-stimulated Ca2+ inflow (measured using fura-2) and, in whole-cell patch-clamp experiments, the Ins(1,4,5)P(3)-induced inward current carried by Ca2+. It was concluded that, in liver cells, 2-APB inhibited SOCs through a mechanism which involved the binding of 2-APB to either the channel protein or an associated regulatory protein. 2-APB appeared to be a novel inhibitor of SOCs in liver cells with a mechanism of action which, in this cell type, is unlikely to involve an interaction of 2-APB with Ins(1,4,5)P(3) receptors. The need for caution in the use of 2-APB as a probe for the involvement of Ins(1,4,5)P(3) receptors in the activation of SOCs in other cell types is briefly discussed.
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Affiliation(s)
- R B Gregory
- Department of Medical Biochemistry, School of Medicine, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
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Astill DS, Rychkov G, Clarke JD, Hughes BP, Roberts ML, Bretag AH. Characteristics of skeletal muscle chloride channel C1C-1 and point mutant R304E expressed in Sf-9 insect cells. Biochim Biophys Acta 1996; 1280:178-86. [PMID: 8639692 DOI: 10.1016/0005-2736(95)00281-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Using the baculovirus system, the skeletal muscle chloride channel, CIC-1 (rat), and a point mutant replacing arginine 304 with glutamic acid were expressed at high levels in cultured Sf-9 insect cells. Whole-cell patch-clamping revealed large inwardly rectifying currents with maxima up to 15 nA inward and 2.5 nA outward. Saturation was evident at voltage steps positive to +40 mV whilst steps negative to -60 mV produced inactivating currents made up of a steady state component and two exponentially decaying components with tau 1 = 6.14+/- 0.92 ms, tau 2 = 36.5+/- 3.29 ms (S.D) n = 7 for steps to -120 mV. Currents recorded in the outside-out patch configuration were often unexpectedly large and up to 5% of whole-cell currents obtained in the same cell, suggesting an uneven channel distribution in the plasmalemma of Sf-9 cells. The pharmacology of a number of chloride channel blockers, including anthracene-9-carboxylate (A9C), niflumate, and perrhenate, was investigated and showed for the first time that perrhenate is an effective blocker of C1C-1 and that it has a complex mechanism of action. Further, the potency of A9C was found to be dependent on external chloride concentration. As in studies on muscle cells themselves, blockade was rapidly effective and easily reversible, except when applying the indanyloxyacetate derivative, IAA94/95, which took up to 10 min to act, and, consistent with an intracellular site of action, was difficult to reverse by washing. Mutation of the highly conserved arginine at position 304 to a glutamic acid did not significantly alter the behaviour of the channel.
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Affiliation(s)
- D S Astill
- Centre for Advanced Biomedical Studies, University of South Australia, North Terrace, Adelaide, Australia
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