1
|
Petersen OH. The 2022 George E Palade Medal Lecture: Toxic Ca 2+ signals in acinar, stellate and endogenous immune cells are important drivers of acute pancreatitis. Pancreatology 2023; 23:1-8. [PMID: 36539315 PMCID: PMC10809214 DOI: 10.1016/j.pan.2022.12.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 12/13/2022] [Accepted: 12/14/2022] [Indexed: 01/11/2023]
Abstract
In this account of the 2022 Palade Medal Lecture, an attempt is made to explain, as simply as possible, the most essential features of normal physiological control of pancreatic enzyme secretion, as they have emerged from more than 50 years of experimental work. On that basis, further studies on the mechanism by which acute pancreatitis is initiated are then described. Calcium ion signaling is crucially important for both the normal physiology of secretion control as well as for the development of acute pancreatitis. Although acinar cell processes have, rightly, been central to our understanding of pancreatic physiology and pathophysiology, attention is here drawn to the additional critical influence of calcium signaling events in stellate and immune cells in the acinar environment. These signals contribute significantly to the crucially important inflammatory response in acute pancreatitis.
Collapse
Affiliation(s)
- Ole H Petersen
- School of Biosciences, Sir Martin Evans Building, Cardiff University, Wales, CF10 3AX, UK.
| |
Collapse
|
2
|
An J, Zhang Y, Ying Z, Li H, Liu W, Wang J, Liu X. The Formation, Structural Characteristics, Absorption Pathways and Bioavailability of Calcium–Peptide Chelates. Foods 2022; 11:foods11182762. [PMID: 36140890 PMCID: PMC9497609 DOI: 10.3390/foods11182762] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 09/04/2022] [Accepted: 09/06/2022] [Indexed: 12/04/2022] Open
Abstract
Calcium is one of the most important mineral elements in the human body and is closely related to the maintenance of human health. To prevent calcium deficiency, various calcium supplements have been developed, but their application tends to be limited by low calcium content and highly irritating effects on the stomach, among other side effects. Recently, calcium–peptide chelates, which have excellent stability and are easily absorbed, have received attention as an alternative emerging calcium supplement. Calcium-binding peptides (CaBP) are usually obtained via the hydrolysis of animal or plant proteins, and calcium-binding capacity (CaBC) can be further improved through chromatographic purification techniques. In calcium ions, the phosphate group, carboxylic group and nitrogen atom in the peptide are the main binding sites, and the four modes of combination are the unidentate mode, bidentate mode, bridging mode and α mode. The stability and safety of calcium–peptide chelates are discussed in this paper, the intestinal absorption pathways of calcium elements and peptides are described, and the bioavailability of calcium–peptide chelates, both in vitro and in vivo, is also introduced. This review of the research status of calcium–peptide chelates aims to provide a reasonable theoretical basis for their application as calcium supplementation products.
Collapse
Affiliation(s)
- Jiulong An
- National Soybean Processing Industry Technology Innovation Center, Beijing Technology and Business University (BTBU), Beijing 100048, China
| | - Yinxiao Zhang
- National Soybean Processing Industry Technology Innovation Center, Beijing Technology and Business University (BTBU), Beijing 100048, China
| | - Zhiwei Ying
- National Soybean Processing Industry Technology Innovation Center, Beijing Technology and Business University (BTBU), Beijing 100048, China
| | - He Li
- National Soybean Processing Industry Technology Innovation Center, Beijing Technology and Business University (BTBU), Beijing 100048, China
- Correspondence: (H.L.); (X.L.); Tel.: +86-10-68984481 (H.L.)
| | - Wanlu Liu
- National Soybean Processing Industry Technology Innovation Center, Beijing Technology and Business University (BTBU), Beijing 100048, China
| | - Junru Wang
- National Soybean Processing Industry Technology Innovation Center, Beijing Technology and Business University (BTBU), Beijing 100048, China
| | - Xinqi Liu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology and Business University (BTBU), Beijing 100048, China
- Correspondence: (H.L.); (X.L.); Tel.: +86-10-68984481 (H.L.)
| |
Collapse
|
3
|
Wongdee K, Chanpaisaeng K, Teerapornpuntakit J, Charoenphandhu N. Intestinal Calcium Absorption. Compr Physiol 2021; 11:2047-2073. [PMID: 34058017 DOI: 10.1002/cphy.c200014] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In this article, we focus on mammalian calcium absorption across the intestinal epithelium in normal physiology. Intestinal calcium transport is essential for supplying calcium for metabolism and bone mineralization. Dietary calcium is transported across the mucosal epithelia via saturable transcellular and nonsaturable paracellular pathways, both of which are under the regulation of 1,25-dihydroxyvitamin D3 and several other endocrine and paracrine factors, such as parathyroid hormone, prolactin, 17β-estradiol, calcitonin, and fibroblast growth factor-23. Calcium absorption occurs in several segments of the small and large intestine with varying rates and capacities. Segmental heterogeneity also includes differential expression of calcium transporters/carriers (e.g., transient receptor potential cation channel and calbindin-D9k ) and the presence of favorable factors (e.g., pH, luminal contents, and gut motility). Other proteins and transporters (e.g., plasma membrane vitamin D receptor and voltage-dependent calcium channels), as well as vesicular calcium transport that probably contributes to intestinal calcium absorption, are also discussed. © 2021 American Physiological Society. Compr Physiol 11:1-27, 2021.
Collapse
Affiliation(s)
- Kannikar Wongdee
- Faculty of Allied Health Sciences, Burapha University, Chonburi, Thailand.,Center of Calcium and Bone Research (COCAB), Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Krittikan Chanpaisaeng
- Center of Calcium and Bone Research (COCAB), Faculty of Science, Mahidol University, Bangkok, Thailand.,Functional Ingredients and Food Innovation Research Group, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani, Thailand
| | - Jarinthorn Teerapornpuntakit
- Center of Calcium and Bone Research (COCAB), Faculty of Science, Mahidol University, Bangkok, Thailand.,Department of Physiology, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand
| | - Narattaphol Charoenphandhu
- Center of Calcium and Bone Research (COCAB), Faculty of Science, Mahidol University, Bangkok, Thailand.,Department of Physiology, Faculty of Science, Mahidol University, Bangkok, Thailand.,Institute of Molecular Biosciences, Mahidol University, Nakhon Pathom, Thailand.,The Academy of Science, The Royal Society of Thailand, Bangkok, Thailand
| |
Collapse
|
4
|
Sun N, Wu H, Du M, Tang Y, Liu H, Fu Y, Zhu B. Food protein-derived calcium chelating peptides: A review. Trends Food Sci Technol 2016. [DOI: 10.1016/j.tifs.2016.10.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
5
|
Kellett GL. Alternative perspective on intestinal calcium absorption: proposed complementary actions of Ca(v)1.3 and TRPV6. Nutr Rev 2011; 69:347-70. [PMID: 21729089 DOI: 10.1111/j.1753-4887.2011.00395.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Transcellular models of dietary Ca(2+) absorption by the intestine assign essential roles to TRPV6 and calbindin-D(9K) . However, studies with gene-knockout mice challenge this view. Something fundamental is missing. The L-type channel Ca(v) 1.3 is located in the apical membrane from the duodenum to the ileum. In perfused rat jejunum in vivo and in Caco-2 cells, Ca(v) 1.3 mediates sodium glucose transporter 1 (SGLT1)-dependent and prolactin-induced active, transcellular Ca(2+) absorption, respectively. TRPV6 is activated by hyperpolarization and is vitamin D dependent; in contrast, Ca(v) 1.3 is activated by depolarization and is independent of calbindin-D(9K) and vitamin D. This review considers evidence supporting the idea that Ca(v) 1.3 and TRPV6 have complementary roles in the regulation of intestinal Ca(2+) absorption as depolarization and repolarization of the apical membrane occur during and between digestive periods, respectively, and as chyme moves from one intestinal segment to another and food transit times increase. Reassessment of current arguments for paracellular flow reveals that key phenomena have alternative explanations within the integrated Ca(v) 1.3/TRPV6 view of transcellular Ca(2+) absorption.
Collapse
Affiliation(s)
- George L Kellett
- Department of Biology, University of York, Heslington, United Kingdom.
| |
Collapse
|
6
|
Hu H, O'Mullane LM, Cummins MM, Campbell CR, Hosoda Y, Poronnik P, Dinudom A, Cook DI. Negative regulation of Ca(2+) influx during P2Y(2) purinergic receptor activation is mediated by Gbetagamma-subunits. Cell Calcium 2010; 47:55-64. [PMID: 20056275 DOI: 10.1016/j.ceca.2009.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 11/03/2009] [Accepted: 11/11/2009] [Indexed: 12/01/2022]
Abstract
We have previously reported that P2Y(2) purinoceptors and muscarinic M(3) receptors trigger Ca(2+) responses in HT-29 cells that differ in their timecourse, the Ca(2+) response to P2Y(2) receptor activation being marked by a more rapid decline of intracellular Ca(2+) concentration ([Ca(2+)](i)) after the peak response and that this rapid decline of [Ca(2+)](i) was slowed in cells expressing heterologous beta-adrenergic receptor kinase (betaARK). In the present study, we demonstrate that, during P2Y(2) receptor activation, betaARK expression increases the rate of Gd(3+)-sensitive Mn(2+) influx, a measure of the rate of store-operated Ca(2+) entry from the extracellular space, during P2Y(2) activation and that this effect of betaARK is mimicked by exogenous alpha-subunits of G(q), G(11) and G(i2). The effect of betaARK on the rate of Mn(2+) influx is thus attributable to its ability to scavenge G protein betagamma-subunits released during activation of P2Y(2) receptor. We further find that the effect of betaARK on the rate of Mn(2+) influx during P2Y(2) receptor activation can be overcome by arachidonic acid. In addition, the UTP-induced Mn(2+) influx rate was significantly increased by inhibitors of phospholipase A(2) (PLA(2)) and an siRNA directed against PLA(2)beta, but not by an siRNA directed against PLA(2)alpha or by inhibitors of arachidonic acid metabolism. These findings provide evidence for the existence of a P2Y(2) receptor-activated signalling system that acts in parallel with depletion of intracellular Ca(2+) stores to inhibit Ca(2+) influx across the cell membrane. This signalling process is mediated via Gbetagamma and involves PLA(2)beta and arachidonic acid.
Collapse
Affiliation(s)
- Haibi Hu
- The University of Sydney, New South Wales, Australia
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Abstract
1. Calcium (re)absorption occurs in epithelia, including the intestine, kidney, mammary glands, placenta and gills (in the case of fish). 2. Calcium is transported across epithelia by two transport mechanisms, paracellular and transcellular, and the movement is regulated by a complex array of transport processes that are mediated by hormonal, developmental and physiological factors involving the gastrointestinal tract, bone, kidney and the parathyroids. 3. Clear understanding of the calcium transport pathways and their endocrine regulation is critical for minimizing various metabolic and health disorders at different physiological stages. Here, we first briefly review the calcium transport mechanisms before discussing in detail the endocrine factors that regulate calcium transport in the epithelia.
Collapse
Affiliation(s)
- Ramesh C Khanal
- Department of Food Science, University of Arkansas, Fayetteville, Arizona, Utah State University, Logan, Utah, USA
| | | |
Collapse
|
8
|
Affiliation(s)
- Ramesh C. Khanal
- Department of Nutrition and Food Sciences and the Center for Integrated BioSystems, Utah State University, Logan, Utah 84322;
| | - Ilka Nemere
- Department of Nutrition and Food Sciences and the Center for Integrated BioSystems, Utah State University, Logan, Utah 84322;
| |
Collapse
|
9
|
Petersen OH. Ca2+ signalling and Ca2+-activated ion channels in exocrine acinar cells. Cell Calcium 2008; 38:171-200. [PMID: 16107275 DOI: 10.1016/j.ceca.2005.06.024] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 06/28/2005] [Indexed: 01/11/2023]
Abstract
The development of the calcium signalling field, from its early beginnings some 40 years ago to the present, is described. Calcium signalling in exocrine gland acinar cells and the effects of neurotransmitter- or hormone-elicited rises in the cytosolic calcium ion concentration on ion channel gating are reviewed. The highly polarized arrangement of the organelle systems in living acinar cells is described as well as its importance for the physiologically relevant local and polarized calcium signalling events.
Collapse
Affiliation(s)
- Ole H Petersen
- MRC Group, The Physiological Laboratory, University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
| |
Collapse
|
10
|
Homann V, Kinne-Saffran E, Arnold WH, Gaengler P, Kinne RKH. Calcium transport in human salivary glands: a proposed model of calcium secretion into saliva. Histochem Cell Biol 2005; 125:583-91. [PMID: 16270201 DOI: 10.1007/s00418-005-0100-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/05/2005] [Indexed: 10/25/2022]
Abstract
Salivary calcium plays a vital role in bio-mineralization of dental enamel and exposed dentin. In order to elucidate the yet unknown cellular and molecular mechanisms of calcium secretion in human salivary glands the presence of various relevant plasma membrane transport systems for calcium were investigated. Using an RT-PCR approach, expression of the epithelial calcium channel (CaT-Like), the calcium binding protein (calbindin-2), the endoplasmic reticulum pumps (SERCA-2 and -3), and the plasma membrane calcium ATPases (PMCA-1, -2, and -4), were found in parotid and submandibular glands. Immunohistochemistry revealed that CaT-Like is located in the basolateral plasma membrane of acinar cells; while calbindin-2, SERCA-2 and SERCA-3 were found inside the acinar cells; and PMCA-2 was found in the apical membrane and in the secretory canaliculi between the cells. Based on these findings, we propose the following model of calcium secretion in human salivary glands: (1) calcium enters the acinar cell at the basolateral side via calcium channel CaT-Like (calcium influx); (2) intracellular calcium is taken up into the endoplasmic reticulum by SERCA-2 and possibly SERCA3 or bound to calbindin-2 (intracellular calcium pool); and (3) calcium is secreted by PMCAs at the apical plasma membrane (calcium efflux).
Collapse
Affiliation(s)
- Veronika Homann
- Abteilung Epithelphysiologie, Max-Planck-Institut für molekulare Physiologie, 44139, Dortmund, Germany
| | | | | | | | | |
Collapse
|
11
|
Nilius B, Prenen J, Tang J, Wang C, Owsianik G, Janssens A, Voets T, Zhu MX. Regulation of the Ca2+ sensitivity of the nonselective cation channel TRPM4. J Biol Chem 2004; 280:6423-33. [PMID: 15590641 DOI: 10.1074/jbc.m411089200] [Citation(s) in RCA: 219] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPM4, a Ca(2+)-activated cation channel of the transient receptor potential superfamily, undergoes a fast desensitization to Ca(2+). The mechanisms underlying the alterations in Ca(2+) sensitivity are unknown. Here we show that cytoplasmic ATP reversed Ca(2+) sensitivity after desensitization, whereas mutations to putative ATP binding sites resulted in faster and more complete desensitization. Phorbol ester-induced activation of protein kinase C (PKC) increased the Ca(2+) sensitivity of wild-type TRPM4 but not of two mutants mutated at putative PKC phosphorylation sites. Overexpression of a calmodulin mutant unable to bind Ca(2+) dramatically reduced TRPM4 activation. We identified five Ca(2+)-calmodulin binding sites in TRPM4 and showed that deletion of any of the three C-terminal sites strongly impaired current activation by reducing Ca(2+) sensitivity and shifting the voltage dependence of activation to very positive potentials. Thus, the Ca(2+) sensitivity of TRPM4 is regulated by ATP, PKC-dependent phosphorylation, and calmodulin binding at the C terminus.
Collapse
Affiliation(s)
- Bernd Nilius
- Department of Physiology, Campus Gasthuisberg, KU Leuven, B-3000 Leuven, Belgium.
| | | | | | | | | | | | | | | |
Collapse
|
12
|
Baryshnikov SG, Rogachevskaja OA, Kolesnikov SS. Calcium signaling mediated by P2Y receptors in mouse taste cells. J Neurophysiol 2003; 90:3283-94. [PMID: 12878712 DOI: 10.1152/jn.00312.2003] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Evidence implicates a number of neuroactive substances and their receptors in mediating complex cell-to-cell communications in the taste bud. Recently, we found that ATP, a ubiquitous neurotransmitter/neuromodulator, mobilizes intracellular Ca2+ in taste cells by activating P2Y receptors. Here, P2Y receptor-cellular response coupling was characterized in detail using single cell ratio photometry and the inhibitory analysis. The sequence of underlying events was shown to include ATP-dependent activation of PLC, IP3 production, and IP3 receptor-mediated Ca2+ release followed by Ca2+ influx. Data obtained favor SOC channels rather than receptor-operated channels as a pathway for Ca2+ influx that accompanies Ca2+ release. Intracellular Ca2+ mobilized by ATP is apparently extruded by the plasma membrane Ca2+-ATPase, while a contribution of the Na+/Ca2+ exchange and other mechanisms of Ca2+ clearance is negligible. Cyclic AMP-dependent phosphorylation is likely to control a gain of the phosphoinositide cascade involved in ATP transduction. ATP-responsive taste cells are abundant in circumvallate, foliate, and fungiform papillae. Taken together, our observations point to a putative role for ATP as a neurotransmitter operative in the taste bud.
Collapse
Affiliation(s)
- Sergey G Baryshnikov
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | | | | |
Collapse
|
13
|
Abstract
A calcium signal is a sudden increase in concentration of calcium ions (Ca2+) in the cytosol. Such signals are crucial for the control of many important functions of the body. In the brain, for example, Ca2+ signals are responsible for memory, in muscle cells they switch on contraction, whereas in gland cells they are responsible for regulation of secretion. In many cases Ca2+ signals can control several different processes in the same cell. As an example, we shall deal with one particular cell type, namely the pancreatic acinar cell, which is responsible for the secretion of the enzymes essential for the digestion of food. In this cell, Ca2+ signals do not only control the normal enzyme secretion, but also regulate growth (cell division) and programmed cell death (apoptosis). Until recently, it was a mystery how the same type of signal could regulate such diverse functions in one and the same cell. Recent technical advances have shown that different patterns of Ca2+ signals can be created, in space and time, which allow specific cellular responses to be elicited.
Collapse
Affiliation(s)
- O H Petersen
- MRC Secretory Control Research Group, The Physiological Laboratory, University of Liverpool, Liverpool, UK
| | | |
Collapse
|
14
|
|
15
|
Mogami H, Zhang H, Suzuki Y, Urano T, Saito N, Kojima I, Petersen OH. Decoding of short-lived Ca2+ influx signals into long term substrate phosphorylation through activation of two distinct classes of protein kinase C. J Biol Chem 2003; 278:9896-904. [PMID: 12514176 DOI: 10.1074/jbc.m210653200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In electrically excitable cells, membrane depolarization opens voltage-dependent Ca(2+) channels eliciting Ca(2+) influx, which plays an important role for the activation of protein kinase C (PKC). However, we do not know whether Ca(2+) influx alone can activate PKC. The present study was conducted to investigate the Ca(2+) influx-induced activation mechanisms for two classes of PKC, conventional PKC (cPKC; PKCalpha) and novel PKC (nPKC; PKCtheta), in insulin-secreting cells. We have demonstrated simultaneous translocation of both DsRed-tagged PKCalpha to the plasma membrane and green fluorescent protein (GFP)-tagged myristoylated alanine-rich C kinase substrate to the cytosol as a dual marker of PKC activity in response to depolarization-evoked Ca(2+) influx in the DsRed-tagged PKCalpha and GFP-tagged myristoylated alanine-rich C kinase substrate co-expressing cells. The result indicates that Ca(2+) influx can generate diacylglycerol (DAG), because cPKC is activated by Ca(2+) and DAG. We showed this in three different ways by demonstrating: 1) Ca(2+) influx-induced translocation of GFP-tagged C1 domain of PKCgamma, 2) Ca(2+) influx-induced translocation of GFP-tagged pleckstrin homology domain, and 3) Ca(2+) influx-induced translocation of GFP-tagged PKCtheta, as a marker of DAG production and/or nPKC activity. Thus, Ca(2+) influx alone via voltage-dependent Ca(2+) channels can generate DAG, thereby activating cPKC and nPKC, whose activation is structurally independent of Ca(2+).
Collapse
Affiliation(s)
- Hideo Mogami
- Department of Physiology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan.
| | | | | | | | | | | | | |
Collapse
|
16
|
Bakowski D, Parekh AB. Permeation through store-operated CRAC channels in divalent-free solution: potential problems and implications for putative CRAC channel genes. Cell Calcium 2002; 32:379-91. [PMID: 12543097 DOI: 10.1016/s0143416002001914] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
CRAC channels are key calcium conduits in both physiological and pathological states. Understanding how these channels are controlled is important as this will not only provide insight into a novel signal transduction pathway coupling intracellular stores to the channels in the plasma membrane, but might also be of clinical relevance. Determining the molecular identity of the CRAC channels will certainly be a major step forward. Like all Ca(2+)-selective channels, CRAC channels lose their selectivity in divalent-free external solution to support large monovalent Na(+) currents. This approach has provided new insight into channel permeation and selectivity, and identifies some interesting differences between CRAC channels and voltage-operated calcium channels (VOCCs). Studies in divalent-free solution are a double-edged sword, however. Electrophysiologists need to be wary because some of the conditions used to study I(CRAC) in divalent-free external solution, notably omission of Mg(2+)/Mg-ATP from the recording pipette solution, activates an additional current permeating through Mg(2+)-nucleotide-regulated metal ion current (MagNuM; TRPM7) channels. This channel underlies the large single-channel events that have been attributed to CRAC channels in the past and which have been used to as a tool to identify store-operated channels in native cells and recombinant expression systems.Are we any closer to identifying the elusive CRAC channel gene(s)? TRPV6 seemed a very attractive candidate, but one of the main arguments supporting it was a single-channel conductance in divalent-free solution similar to that for CRAC reported under conditions where MagNuM is active. We now know that the conductance of TRPV6 is approximately 200-fold larger than that of CRAC in native tissue. Moreover, it is unclear if TRPV6 is store-operated. Further work on TRPV6, particularly whether its single-channel conductance is still high under conditions where it apparently forms multimers with endogenous store-operated channels, and whether it is activated by a variety of store depletion protocols, will be helpful in finally resolving this issue.
Collapse
Affiliation(s)
- D Bakowski
- Department of Physiology, University of Oxford, Parks Road, OX1 3PT, Oxford, UK
| | | |
Collapse
|
17
|
Schindl R, Kahr H, Graz I, Groschner K, Romanin C. Store depletion-activated CaT1 currents in rat basophilic leukemia mast cells are inhibited by 2-aminoethoxydiphenyl borate. Evidence for a regulatory component that controls activation of both CaT1 and CRAC (Ca(2+) release-activated Ca(2+) channel) channels. J Biol Chem 2002; 277:26950-8. [PMID: 12011062 DOI: 10.1074/jbc.m203700200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The intestinal Ca(2+) transport protein CaT1 encoded by TRPV6 has been reported (Yue, L., Peng, J. B., Hediger, M. A., and Clapham, D. E. (2001) Nature 410, 705-709) to be all or a part of the Ca(2+) release-activated Ca(2+) channel (CRAC). The major characteristic of CRAC is its activation following store depletion. We expressed CaT1 in HEK293 cells and rat basophilic leukemia (RBL) mast cells and measured whole-cell currents by the patch clamp technique. In HEK293 cells, the expression of CaT1 consistently yielded a constitutively active current, the size of which was strongly dependent on the holding potential and duration of voltage ramps. In CaT1-expressing RBL cells, the current was either activated by store depletion or was constitutively active at a higher current density. CaT1 currents could be clearly distinguished from endogenous CRAC by their typical current-voltage relationship in divalent free solution. 2-aminoethoxydiphenyl borate (2-APB), which is considered a blocker of CRAC, was tested for its inhibitory effect on both cell types expressing CaT1. Endogenous CRAC as well as store-dependent CaT1-derived currents of RBL cells were largely blocked by 75 microm 2-APB, whereas constitutively active CaT1 currents in both RBL and HEK293 cells were slightly potentiated. These results indicate that despite the difference in the permeation properties of CRAC and CaT1 channels, the latter are similarly able to form store depletion-activated conductances in RBL mast cells that are inhibited by 2-APB.
Collapse
Affiliation(s)
- Rainer Schindl
- Institute for Biophysics, University of Linz, A-4040 Linz, Austria
| | | | | | | | | |
Collapse
|
18
|
Larsson D, Nemere I. Vectorial Transcellular Calcium Transport in Intestine: Integration of Current Models. J Biomed Biotechnol 2002; 2:117-119. [PMID: 12488574 PMCID: PMC161364 DOI: 10.1155/s1110724302205045] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In spite of decades of research, the exact subcellular pathway for calcium transport in intestine has not been elucidated. In this mini-review, we present three models for vectorial movement of calcium across the cell: facilitated (cytoplasmic) diffusion, vesicular/lysosomal transport, and tunneling through the endoplasmic reticulum compartment. We conclude by offering one way to integrate elements of these three models.
Collapse
Affiliation(s)
- Dennis Larsson
- Department of Nutrition and Food Sciences and the Biotechnology Center, Utah State University, Logan, UT 85322-8700, USA
- Fish Endocrinology Laboratory, Department of Zoology/Zoophysiology, Göteborg University, Box 463, SE-405 30 Göteborg, Sweden
| | - Ilka Nemere
- Department of Nutrition and Food Sciences and the Biotechnology Center, Utah State University, Logan, UT 85322-8700, USA
| |
Collapse
|
19
|
Voets T, Prenen J, Fleig A, Vennekens R, Watanabe H, Hoenderop JG, Bindels RJ, Droogmans G, Penner R, Nilius B. CaT1 and the calcium release-activated calcium channel manifest distinct pore properties. J Biol Chem 2001; 276:47767-70. [PMID: 11687570 DOI: 10.1074/jbc.c100607200] [Citation(s) in RCA: 185] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The calcium release-activated calcium channel (CRAC) is a highly Ca(2+)-selective ion channel that is activated on depletion of inositol triphosphate (IP(3))-sensitive intracellular Ca(2+) stores. It was recently reported that CaT1, a member of the TRP family of cation channels, exhibits the unique biophysical properties of CRAC, which led to the conclusion that CaT1 comprises all or part of the CRAC pore (Yue, L., Peng, J. B., Hediger, M. A., and Clapham, D. E. (2001) Nature 410, 705-709). Here, we directly compare endogenous CRAC with heterologously expressed CaT1 and show that they manifest several clearly distinct properties. CaT1 can be distinguished from CRAC in the following features: sensitivity to store-depleting agents; inward rectification in the absence of divalent cations; relative permeability to Na(+) and Cs(+); effect of 2-aminoethoxydiphenyl borate (2-APB). Moreover, CaT1 displays a mode of voltage-dependent gating that is fully absent in CRAC and originates from the voltage-dependent binding/unbinding of Mg(2+) inside the channel pore. Our results imply that the pores of CaT1 and CRAC are not identical and indicate that CaT1 is a Mg(2+)-gated channel not directly related to CRAC.
Collapse
Affiliation(s)
- T Voets
- Laboratory of Physiology, Catholic University of Leuven, B-3000 Leuven, Belgium.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Caroppo R, Gerbino A, Debellis L, Kifor O, Soybel DI, Brown EM, Hofer AM, Curci S. Asymmetrical, agonist-induced fluctuations in local extracellular [Ca(2+)] in intact polarized epithelia. EMBO J 2001; 20:6316-26. [PMID: 11707403 PMCID: PMC125728 DOI: 10.1093/emboj/20.22.6316] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We recently proposed that extracellular Ca(2+) ions participate in a novel form of intercellular communication involving the extracellular Ca(2+)-sensing receptor (CaR). Here, using Ca(2+)-selective microelectrodes, we directly measured the profile of agonist-induced [Ca(2+)]ext changes in restricted domains near the basolateral or luminal membranes of polarized gastric acid-secreting cells. The Ca(2+)-mobilizing agonist carbachol elicited a transient, La(3+)-sensitive decrease in basolateral [Ca(2+)] (average approximately 250 microM, but as large as 530 microM). Conversely, carbachol evoked an HgCl2-sensitive increase in [Ca(2+)] (average approximately 400 microM, but as large as 520 microM) in the lumen of single gastric glands. Both responses were significantly reduced by pre-treatment with sarco-endoplasmic reticulum Ca(2+) ATPase (SERCA) pump inhibitors or with the intracellular Ca(2+) chelator BAPTA-AM. Immunofluorescence experiments demonstrated an asymmetric localization of plasma membrane Ca(2+) ATPase (PMCA), which appeared to be partially co-localized with CaR and the gastric H(+)/K(+)-ATPase in the apical membrane of the acid-secreting cells. Our data indicate that agonist stimulation results in local fluctuations in [Ca(2+)]ext that would be sufficient to modulate the activity of the CaR on neighboring cells.
Collapse
Affiliation(s)
| | | | | | - Olga Kifor
- Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy,
Endocrine Hypertension Division, Membrane Biology Program, Department of Medicine and Department of Surgery, Brigham and Women’s Hospital and Boston VA Healthcare System, Harvard Medical School, Boston and West Roxbury, 1400 VFW Parkway, West Roxbury, MA 02132, USA Corresponding author e-mail:
| | - David I. Soybel
- Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy,
Endocrine Hypertension Division, Membrane Biology Program, Department of Medicine and Department of Surgery, Brigham and Women’s Hospital and Boston VA Healthcare System, Harvard Medical School, Boston and West Roxbury, 1400 VFW Parkway, West Roxbury, MA 02132, USA Corresponding author e-mail:
| | - Edward M. Brown
- Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy,
Endocrine Hypertension Division, Membrane Biology Program, Department of Medicine and Department of Surgery, Brigham and Women’s Hospital and Boston VA Healthcare System, Harvard Medical School, Boston and West Roxbury, 1400 VFW Parkway, West Roxbury, MA 02132, USA Corresponding author e-mail:
| | - Aldebaran M. Hofer
- Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy,
Endocrine Hypertension Division, Membrane Biology Program, Department of Medicine and Department of Surgery, Brigham and Women’s Hospital and Boston VA Healthcare System, Harvard Medical School, Boston and West Roxbury, 1400 VFW Parkway, West Roxbury, MA 02132, USA Corresponding author e-mail:
| | - Silvana Curci
- Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy,
Endocrine Hypertension Division, Membrane Biology Program, Department of Medicine and Department of Surgery, Brigham and Women’s Hospital and Boston VA Healthcare System, Harvard Medical School, Boston and West Roxbury, 1400 VFW Parkway, West Roxbury, MA 02132, USA Corresponding author e-mail:
| |
Collapse
|