51
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Transient receptor proteins illuminated: Current views on TRPs and disease. Vet J 2011; 187:153-64. [DOI: 10.1016/j.tvjl.2010.01.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 01/21/2010] [Accepted: 01/25/2010] [Indexed: 11/23/2022]
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52
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Abstract
Mast cells are multifunctional cells that initiate not only IgE-dependent allergic diseases but also play a fundamental role in innate and adaptive immune responses to microbial infection. They are also thought to play a role in angiogenesis, tissue remodeling, wound healing, and tumor repression or growth. The broad scope of these physiologic and pathologic roles illustrates the flexible nature of mast cells, which is enabled in part by their phenotypic adaptability to different tissue microenvironments and their ability to generate and release a diverse array of bioactive mediators in response to multiple types of cell-surface and cytosolic receptors. There is increasing evidence from studies in cell cultures that release of these mediators can be selectively modulated depending on the types or groups of receptors activated. The intent of this review is to foster interest in the interplay among mast cell receptors to help understand the underlying mechanisms for each of the immunological and non-immunological functions attributed to mast cells. The second intent of this review is to assess the pathophysiologic roles of mast cells and their products in health and disease. Although mast cells have a sufficient repertoire of bioactive mediators to mount effective innate and adaptive defense mechanisms against invading microorganisms, these same mediators can adversely affect surrounding tissues in the host, resulting in autoimmune disease as well as allergic disorders.
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Affiliation(s)
- Alasdair M Gilfillan
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-1881, USA.
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53
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Suzuki R, Liu X, Olivera A, Aguiniga L, Yamashita Y, Blank U, Ambudkar I, Rivera J. Loss of TRPC1-mediated Ca2+ influx contributes to impaired degranulation in Fyn-deficient mouse bone marrow-derived mast cells. J Leukoc Biol 2010; 88:863-75. [PMID: 20571036 DOI: 10.1189/jlb.0510253] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
MC degranulation requires the influx of calcium from the extracellular environment. Orai1/STIM1 is essential to MC SOCE, as shown in rat peritoneal MCs, the rat MC lines (RBL-2H3), or in Orai1 null embryo liver-derived, cultured MCs. However, minimal information exists about the role of other calcium channels expressed on these cells. Here, we demonstrate that the nonselective TRPC1 participates in FcεRI-mediated calcium entry in mouse BMMCs. We found that Fyn null MCs, which have an impaired degranulation response, expressed reduced levels of TRPC1, had normal depletion of intracellular calcium stores but an impaired calcium influx, and failed to depolymerize cortical F-actin (a key step for granule-plasma membrane fusion). Partial RNAi silencing of TRPC1 expression in WT MCs (to the level of Fyn null MCs) mimicked the Fyn null defect in calcium influx, cortical F-actin depolymerization, and MC degranulation. Ectopic expression of Fyn or TRPC1 in Fyn null MCs restored calcium responses and cortical F-actin depolymerization and increased MC degranulation. Together with our findings that expression of Orai1 is not altered in Fyn null MCs, our findings suggest that TRPC1 participates in calcium influx and other key events required for MC degranulation. This demonstrates that in addition to a role described previously for Orai1 in promoting MC degranulation, nonselective cation channels participate in promoting the exocytotic response.
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Affiliation(s)
- Ryo Suzuki
- National Institutes of Health, Bethesda, MD 20892-1930, USA
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54
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Sanchez-Miranda E, Ibarra-Sanchez A, Gonzalez-Espinosa C. Fyn kinase controls FcepsilonRI receptor-operated calcium entry necessary for full degranulation in mast cells. Biochem Biophys Res Commun 2009; 391:1714-20. [PMID: 20043875 DOI: 10.1016/j.bbrc.2009.12.139] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Accepted: 12/22/2009] [Indexed: 12/11/2022]
Abstract
IgE-antigen-dependent crosslinking of the high affinity IgE receptor (FcepsilonRI) on mast cells leads to degranulation, leukotriene synthesis and cytokine production. Calcium (Ca(2+)) mobilization is a sine qua non requisite for degranulation, allowing the rapid secretion of stored pro-inflammatory mediators responsible for allergy symptoms. Fyn is a Src-family kinase that positively controls FcepsilonRI-induced mast cell degranulation. However, our understanding of the mechanism connecting Fyn activation to secretion of pre-synthesized mediators is very limited. We analyzed FcepsilonRI-dependent Ca(2+) mobilization in bone marrow-derived mast cells (BMMCs) differentiated from WT and Fyn -/- knock out mice. Fyn -/- BMMCs showed a marked defect in extracellular Ca(2+) influx after FcepsilonRI crosslinking but not after thapsigargin addition. High concentrations of Gadolinium (Gd(3+)) partially blocked FcepsilonRI-induced Ca(2+) influx in WT cells but, in contrast, completely inhibited Ca(2+) mobilization in Fyn -/- cells. Low concentrations of an inhibitor of the canonical transient receptor potential (TRPC) Ca(2+) channels (2-aminoethoxyphenyl-borane, 2-APB) blocked FcepsilonRI-induced maximal Ca(2+) rise in WT but not in Fyn -/- cells. Ca(2+) entry through Fyn-controlled, 2-APB sensitive channels was found to be important for full degranulation and IL-2 mRNA accumulation in WT cells. Immunoprecipitation assays showed that Fyn kinase interacts with TRPC 3/6/7 channels after IgE-antigen stimulation, but its association is not related to protein tyrosine phosphorylation. Results indicate Fyn kinase mediates the receptor-dependent activation of TRPC channels that contribute to degranulation in FcepsilonRI-stimulated mast cells.
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Affiliation(s)
- Elizabeth Sanchez-Miranda
- Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados, Sede Sur, Calzada de los Tenorios 235, Col Granjas Coapa, CP 14330 Mexico City, Mexico
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55
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Mechanisms of mast cell signaling in anaphylaxis. J Allergy Clin Immunol 2009; 124:639-46; quiz 647-8. [PMID: 19815110 DOI: 10.1016/j.jaci.2009.08.035] [Citation(s) in RCA: 213] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 08/19/2009] [Accepted: 08/20/2009] [Indexed: 01/01/2023]
Abstract
The recent development of a consensus definition and proposed diagnostic criteria for anaphylaxis offers promise for research efforts and a better understanding of the epidemiology and pathogenesis of this enigmatic and life-threatening disease. This review examines basic principles and recent research advances in the mechanisms of mast cell signaling believed to underlie anaphylaxis. The unfolding complexity of mast cell signaling suggests that the system is sensitive to regulation by any of several individual signaling pathways and intermediates and that complementary pathways regulate mast cell activation by amplified signals. The signaling events underlying anaphylactic reactions have largely been identified through experiments in genetically modified mice and supported by biochemical studies of mast cells derived from these mice. These studies have revealed that signaling pathways exist to both upregulate and downregulate mast cell responses. In this review we will thus describe the key molecular players in these pathways in the context of anaphylaxis.
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56
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Baba Y, Kurosaki T. Physiological function and molecular basis of STIM1-mediated calcium entry in immune cells. Immunol Rev 2009; 231:174-88. [PMID: 19754897 DOI: 10.1111/j.1600-065x.2009.00813.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Calcium signals in immune cells regulate a variety of physiological responses such as cell activation, differentiation, gene transcription, and effector functions. Surface receptor stimulation induces an increase in the concentration of cytosolic calcium ions (Ca2+), which are derived mainly from two sources, intracellular endoplasmic reticulum (ER) Ca2+ stores and the extracellular space. The major cascade for Ca2+ entry in immune cells is through store-operated Ca2+ entry (SOCE) and Ca2+ release-activated Ca2+ (CRAC) channels. Activation of SOCE is triggered by depletion of intracellular ER Ca2+ stores, but the molecular mechanism was a long-standing issue. With the recent molecular identification of the ER Ca2+ sensor [stromal interacting molecule-1 (STIM1)] and a pore-forming subunit of the CRAC channel (Orai1), our understanding of the SOCE activation pathway has increased dramatically. These advances have now made it possible to shed some light on important questions: what is the physiological significance of SOCE, and what is its molecular basis? This review focuses on the recent progress in the field and the exciting opportunities for understanding how SOCE influences diverse immune functions.
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Affiliation(s)
- Yoshihiro Baba
- Laboratory for Lymphocyte Differentiation, WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan.
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57
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Cohen R, Torres A, Ma HT, Holowka D, Baird B. Ca2+ waves initiate antigen-stimulated Ca2+ responses in mast cells. THE JOURNAL OF IMMUNOLOGY 2009; 183:6478-88. [PMID: 19864608 DOI: 10.4049/jimmunol.0901615] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ca(2+) mobilization is central to many cellular processes, including stimulated exocytosis and cytokine production in mast cells. Using single cell stimulation by IgE-specific Ag and high-speed imaging of conventional or genetically encoded Ca(2+) sensors in rat basophilic leukemia and bone marrow-derived rat mast cells, we observe Ca(2+) waves that originate most frequently from the tips of extended cell protrusions, as well as Ca(2+) oscillations throughout the cell that usually follow the initiating Ca(2+) wave. In contrast, Ag conjugated to the tip of a micropipette stimulates local, repetitive Ca(2+) puffs at the region of cell contact. Initiating Ca(2+) waves are observed in most rat basophilic leukemia cells stimulated with soluble Ag and are sensitive to inhibitors of Ca(2+) release from endoplasmic reticulum stores and to extracellular Ca(2+), but they do not depend on store-operated Ca(2+) entry. Knockdown of transient receptor potential channel (TRPC)1 and TRPC3 channel proteins by short hairpin RNA reduces the sensitivity of these cells to Ag and shifts the wave initiation site from protrusions to the cell body. Our results reveal spatially encoded Ca(2+) signaling in response to immunoreceptor activation that utilizes TRPC channels to specify the initiation site of the Ca(2+) response.
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Affiliation(s)
- Roy Cohen
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14850, USA
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58
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Gross SA, Guzmán GA, Wissenbach U, Philipp SE, Zhu MX, Bruns D, Cavalié A. TRPC5 is a Ca2+-activated channel functionally coupled to Ca2+-selective ion channels. J Biol Chem 2009; 284:34423-32. [PMID: 19815560 DOI: 10.1074/jbc.m109.018192] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPC5 forms non-selective cation channels. Here we studied the role of internal Ca(2+) in the activation of murine TRPC5 heterologously expressed in human embryonic kidney cells. Cell dialysis with various Ca(2+) concentrations (Ca(2+)(i)) revealed a dose-dependent activation of TRPC5 channels by internal Ca(2+) with EC(50) of 635.1 and 358.2 nm at negative and positive membrane potentials, respectively. Stepwise increases of Ca(2+)(i) induced by photolysis of caged Ca(2+) showed that the Ca(2+) activation of TRPC5 channels follows a rapid exponential time course with a time constant of 8.6 +/- 0.2 ms at Ca(2+)(i) below 10 microM, suggesting that the action of internal Ca(2+) is a primary mechanism in the activation of TRPC5 channels. A second slow activation phase with a time to peak of 1.4 +/- 0.1 s was also observed at Ca(2+)(i) above 10 microM. In support of a Ca(2+)-activation mechanism, the thapsigargin-induced release of Ca(2+) from internal stores activated TRPC5 channels transiently, and the subsequent Ca(2+) entry produced a sustained TRPC5 activation, which in turn supported a long-lasting membrane depolarization. By co-expressing STIM1 plus ORAI1 or the alpha(1)C and beta(2) subunits of L-type Ca(2+) channels, we found that Ca(2+) entry through either calcium-release-activated-calcium or voltage-dependent Ca(2+) channels is sufficient for TRPC5 channel activation. The Ca(2+) entry activated TRPC5 channels under buffering of internal Ca(2+) with EGTA but not with BAPTA. Our data support the hypothesis that TRPC5 forms Ca(2+)-activated cation channels that are functionally coupled to Ca(2+)-selective ion channels through local Ca(2+) increases beneath the plasma membrane.
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Affiliation(s)
- Stefan Alfred Gross
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg/Saar, Germany
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59
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Abstract
Calcium signals mediate diverse cellular functions in immunological cells. Early studies with mast cells, then a preeminent model for studying Ca2+-dependent exocytosis, revealed several basic features of calcium signaling in non-electrically excitable cells. Subsequent studies in these and other cells further defined the basic processes such as inositol 1,4,5-trisphosphate-mediated release of Ca2+ from Ca2+ stores in the endoplasmic reticulum (ER); coupling of ER store depletion to influx of external Ca2+ through a calcium-release activated calcium (CRAC) channel now attributed to the interaction of the ER Ca2+ sensor, stromal interacting molecule-1 (STIM1), with a unique Ca2+-channel protein, Orai1/CRACM1, and subsequent uptake of excess Ca2+ into ER and mitochondria through ATP-dependent Ca2+ pumps. In addition, transient receptor potential channels and ion exchangers also contribute to the generation of calcium signals that may be global or have dynamic (e.g., waves and oscillations) and spatial resolution for specific functional readouts. This review discusses past and recent developments in this field of research, the pharmacologic agents that have assisted in these endeavors, and the mast cell as an exemplar for sorting out how calcium signals may regulate multiple outputs in a single cell.
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Affiliation(s)
- Hong-Tao Ma
- Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
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60
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Abstract
Calcium influx through plasma membrane store-operated Ca(2+) (SOC) channels is triggered when the endoplasmic reticulum (ER) Ca(2+) store is depleted - a homeostatic Ca(2+) signalling mechanism that remained enigmatic for more than two decades. RNA-interference (RNAi) screening and molecular and cellular physiological analysis recently identified STIM1 as the mechanistic 'missing link' between the ER and the plasma membrane. STIM proteins sense the depletion of Ca(2+) from the ER, oligomerize, translocate to junctions adjacent to the plasma membrane, organize Orai or TRPC (transient receptor potential cation) channels into clusters and open these channels to bring about SOC entry.
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Affiliation(s)
- Michael D Cahalan
- Department of Physiology and Biophysics and Institute for Immunology, University of California, Irvine, CA 92697-4561, USA.
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61
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Vasudevan L, Jeromin A, Volpicelli-Daley L, De Camilli P, Holowka D, Baird B. The beta- and gamma-isoforms of type I PIP5K regulate distinct stages of Ca2+ signaling in mast cells. J Cell Sci 2009; 122:2567-74. [PMID: 19549683 DOI: 10.1242/jcs.048124] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Crosslinking of IgE receptors by antigen initiates Ca2+ mobilization in mast cells by activating phospholipase-C gamma-mediated hydrolysis of phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2]. The resulting inositol 1,4,5-trisphosphate-mediated Ca2+ release from the endoplasmic reticulum (ER) activates store-operated Ca2+ entry, which is necessary for exocytotic release of inflammatory mediators. To investigate roles for PtdIns(4,5)P2-synthesizing isozymes of the type I phosphatidylinositol 4-phosphate 5-kinase family (PIP5K-I) in mast cell signaling, we compared the ectopic expression of wild-type and catalytically inactive PIP5K-I beta in RBL-2H3 mast cells. Surprisingly, both antigen and thapsigargin-stimulated Ca2+ influx were reduced by overexpression of active PIP5K-I beta, whereas antigen-stimulated Ca2+ release from ER stores was unaffected. Consistent with these results, Ca2+ entry stimulated by antigen or thapsigargin was enhanced by expression of a plasma-membrane-associated inositol polyphosphate 5'-phosphatase, whereas antigen-stimulated Ca2+ release from stores was reduced. To investigate the role of PIP5K-I gamma in antigen-stimulated Ca2+ mobilization, we used bone-marrow-derived mast cells from PIP5K-I gamma(-/-) mice. Antigen-stimulated Ca2+ release from ER stores was substantially reduced in the absence of PIP5K-I gamma, but thapsigargin-mediated Ca2+ entry was unaffected. In summary, PIP5K-I gamma positively regulates antigen-stimulated Ca2+ release from ER stores, whereas PIP5K-I beta negatively regulates store-operated Ca2+ entry, suggesting that these different PIP5K-I isoforms synthesize functionally distinct pools of PtdIns(4,5)P2 at the plasma membrane.
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Affiliation(s)
- Lavanya Vasudevan
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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62
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Chiu TY, Teng HC, Huang PC, Kao FJ, Yang DM. Dominant Role of Orai1 with STIM1 on the Cytosolic Entry and Cytotoxicity of Lead Ions. Toxicol Sci 2009; 110:353-62. [DOI: 10.1093/toxsci/kfp099] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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63
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Birnbaumer L. The TRPC class of ion channels: a critical review of their roles in slow, sustained increases in intracellular Ca(2+) concentrations. Annu Rev Pharmacol Toxicol 2009; 49:395-426. [PMID: 19281310 DOI: 10.1146/annurev.pharmtox.48.113006.094928] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The realization that there exists a multimembered family of cation channels with structural similarity to Drosophila's Trp channel emerged during the second half of the 1990s. In mammals, depending on the species, the TRP family counts 29 or 30 members which has been subdivided into 6 subfamilies on the basis of sequence similarity. TRP channels are nonselective monovalent cation channels, most of which also allow passage of Ca(2+). Many members of each of these families, but not all, are involved in sensory signal transduction. The C-type (for canonical or classical) subfamily, differs from the other TRP subfamilies in that it fulfills two different types of function: membrane depolarization, resembling sensory transduction TRPs, and mediation of sustained increases in intracellular Ca(2+). The mechanism(s) by which the C-class of TRP channels-the TRPCs-are activated is poorly understood and their role in mediating intracellular Ca(2+) increases is being questioned. Both of these questions-mechanism of activation and participation in Ca(2+) entry-are the topics of this review.
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Affiliation(s)
- Lutz Birnbaumer
- National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709, USA.
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64
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Abstract
Mast cell mediator release represents a pivotal event in the initiation of inflammatory reactions associated with allergic disorders. These responses follow antigen-mediated aggregation of immunoglobulin E (IgE)-occupied high-affinity receptors for IgE (Fc epsilon RI) on the mast cell surface, a response which can be further enhanced following stem cell factor-induced ligation of the mast cell growth factor receptor KIT (CD117). Activation of tyrosine kinases is central to the ability of both Fc epsilon RI and KIT to transmit downstream signaling events required for the regulation of mast cell activation. Whereas KIT possesses inherent tyrosine kinase activity, Fc epsilon RI requires the recruitment of Src family tyrosine kinases and Syk to control the early receptor-proximal signaling events. The signaling pathways propagated by these tyrosine kinases can be further upregulated by the Tec kinase Bruton's tyrosine kinase and downregulated by the actions of the tyrosine Src homology 2 domain-containing phosphatase 1 (SHP-1) and SHP-2. In this review, we discuss the regulation and role of specific members of this tyrosine kinase network in KIT and Fc epsilon RI-mediated mast cell activation.
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Affiliation(s)
- Alasdair M Gilfillan
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-1930, USA
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65
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DeHaven WI, Jones BF, Petranka JG, Smyth JT, Tomita T, Bird GS, Putney JW. TRPC channels function independently of STIM1 and Orai1. J Physiol 2009; 587:2275-98. [PMID: 19332491 DOI: 10.1113/jphysiol.2009.170431] [Citation(s) in RCA: 191] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Recent studies have defined roles for STIM1 and Orai1 as calcium sensor and calcium channel, respectively, for Ca(2+)-release activated Ca(2+) (CRAC) channels, channels underlying store-operated Ca(2+) entry (SOCE). In addition, these proteins have been suggested to function in signalling and constructing other channels with biophysical properties distinct from the CRAC channels. Using the human kidney cell line, HEK293, we examined the hypothesis that STIM1 can interact with and regulate members of a family of non-selective cation channels (TRPC) which have been suggested to also function in SOCE pathways under certain conditions. Our data reveal no role for either STIM1 or Orai1 in signalling of TRPC channels. Specifically, Ca(2+) entry seen after carbachol treatment in cells transiently expressing TRPC1, TRPC3, TRPC5 or TRPC6 was not enhanced by the co-expression of STIM1. Further, knockdown of STIM1 in cells expressing TRPC5 did not reduce TRPC5 activity, in contrast to one published report. We previously reported in stable TRPC7 cells a Ca(2+) entry which was dependent on TRPC7 and appeared store-operated. However, we show here that this TRPC7-mediated entry was also not dependent on either STIM1 or Orai1, as determined by RNA interference (RNAi) and expression of a constitutively active mutant of STIM1. Further, we determined that this entry was not actually store-operated, but instead TRPC7 activity which appears to be regulated by SERCA. Importantly, endogenous TRPC activity was also not regulated by STIM1. In vascular smooth muscle cells, arginine-vasopressin (AVP) activated non-selective cation currents associated with TRPC6 activity were not affected by RNAi knockdown of STIM1, while SOCE was largely inhibited. Finally, disruption of lipid rafts significantly attenuated TRPC3 activity, while having no effect on STIM1 localization or the development of I(CRAC). Also, STIM1 punctae were found to localize in regions distinct from lipid rafts. This suggests that TRPC signalling and STIM1/Orai1 signalling occur in distinct plasma membrane domains. Thus, TRPC channels appear to be activated by mechanisms dependent on phospholipase C which do not involve the Ca(2+) sensor, STIM1.
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Affiliation(s)
- Wayne I DeHaven
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences-NIH, Department of Health and Human Services, PO Box 12233, Research Triangle Park, NC 27709, USA
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66
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Kim MS, Zeng W, Yuan JP, Shin DM, Worley PF, Muallem S. Native Store-operated Ca2+ Influx Requires the Channel Function of Orai1 and TRPC1. J Biol Chem 2009; 284:9733-41. [PMID: 19228695 DOI: 10.1074/jbc.m808097200] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
With the discovery of STIM1 and Orai1 and gating of both TRPC and Orai1 channels by STIM1, a central question is the role of each of the channels in the native store-operated Ca(2+) influx (SOCs). Here, we used a strategy of knockdown of Orai1 and of TRPC1 alone and in combination and rescue by small interfering RNA-protected mutants (sm) of smOrai1 and smTRPC1 to demonstrate that in human embryonic kidney (HEK) cells, rescue of SOCs required co-transfection of low levels of both smOrai1 and smTRPC1. The pore mutant Orai1(E106Q) failed to rescue the SOCs in the presence or absence of TRPC1 and, surprisingly, the pore mutant TRPC1(F562A) failed to rescue the SOCs in the presence or absence of Orai1. TRPC1 is gated by electrostatic interaction between TRPC1(D639D,D640D) with STIM1(K684K, K685K). Strikingly, the channel-dead TRPC1(D639K,D640K) that can be rescued only by the STIM1(K684E,K685E) mutant could restore SOCs only when expressed with Orai1 and STIM1(K684E,K685E). Accordingly, we found a mutual requirement of Orai1 and TRPC1 for their interaction with the native STIM1 in HEK cells. By contrast, SOC and the CRAC current in Jurkat cells were inhibited by knockdown of Orai1 but were not influenced by knockdown on TRPC1 or TRPC3. These findings define the molecular makeup of the native SOCs in HEK cells and the role of a STIM1-Orai1-TRPC1 complex in SOC activity.
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Affiliation(s)
- Min Seuk Kim
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA
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67
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Abramowitz J, Birnbaumer L. Physiology and pathophysiology of canonical transient receptor potential channels. FASEB J 2009; 23:297-328. [PMID: 18940894 PMCID: PMC2630793 DOI: 10.1096/fj.08-119495] [Citation(s) in RCA: 244] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Accepted: 09/25/2008] [Indexed: 11/11/2022]
Abstract
The existence of a mammalian family of TRPC ion channels, direct homologues of TRP, the visual transduction channel of flies, was discovered during 1995-1996 as a consequence of research into the mechanism by which the stimulation of the receptor-Gq-phospholipase Cbeta signaling pathway leads to sustained increases in intracellular calcium. Mammalian TRPs, TRPCs, turned out to be nonselective, calcium-permeable cation channels, which cause both a collapse of the cell's membrane potential and entry of calcium. The family comprises 7 members and is widely expressed. Many cells and tissues express between 3 and 4 of the 7 TRPCs. Despite their recent discovery, a wealth of information has accumulated, showing that TRPCs have widespread roles in almost all cells studied, including cells from excitable and nonexcitable tissues, such as the nervous and cardiovascular systems, the kidney and the liver, and cells from endothelia, epithelia, and the bone marrow compartment. Disruption of TRPC function is at the root of some familial diseases. More often, TRPCs are contributing risk factors in complex diseases. The present article reviews what has been uncovered about physiological roles of mammalian TRPC channels since the time of their discovery. This analysis reveals TRPCs as major and unsuspected gates of Ca(2+) entry that contribute, depending on context, to activation of transcription factors, apoptosis, vascular contractility, platelet activation, and cardiac hypertrophy, as well as to normal and abnormal cell proliferation. TRPCs emerge as targets for a thus far nonexistent field of pharmacological intervention that may ameliorate complex diseases.
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Affiliation(s)
- Joel Abramowitz
- Transmembrane Signaling Group, Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
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68
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Martin ACL, Willoughby D, Ciruela A, Ayling LJ, Pagano M, Wachten S, Tengholm A, Cooper DMF. Capacitative Ca2+ entry via Orai1 and stromal interacting molecule 1 (STIM1) regulates adenylyl cyclase type 8. Mol Pharmacol 2009; 75:830-42. [PMID: 19171672 DOI: 10.1124/mol.108.051748] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Capacitative Ca(2+) entry (CCE), which occurs through the plasma membrane as a result of Ca(2+) store depletion, is mediated by stromal interacting molecule 1 (STIM1), a sensor of intracellular Ca(2+) store content, and the pore-forming component Orai1. However, additional factors, such as C-type transient receptor potential (TRPC) channels, may also participate in the CCE apparatus. To explore whether the store-dependent Ca(2+) entry reconstituted by coexpression of Orai1 and STIM1 has the functional properties of CCE, we used the Ca(2+)-calmodulin stimulated adenylyl cyclase type 8 (AC8), which responds selectively to CCE, whereas other modes of Ca(2+) entry, including those activated by arachidonate and the ionophore ionomycin, are ineffective. In addition, the Ca(2+) entry mediated by previous CCE candidates, diacylglycerol-activated TRPC channels, does not activate AC8. Here, we expressed Orai1 and STIM1 in HEK293 cells and saw a robust increment in CCE, and a proportional increase in CCE-stimulated AC8 activity. Inhibitors of the CCE assembly process ablated the effects on cyclase activity in both AC8-overexpressing HEK293 cells and insulin-secreting MIN6 cells endogenously expressing Ca(2+)-sensitive AC isoforms. AC8 is believed to be closely associated with the source of CCE; indeed, not only were AC8, Orai1, and STIM1 colocalized at the plasma membrane but also all three proteins occurred in lipid rafts. Together, our data indicate that Orai1 and STIM1 can be integral components of the cAMP and CCE microdomain associated with adenylyl cyclase type 8.
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Affiliation(s)
- Agnes C L Martin
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
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Abstract
Mast cells can function as effector and immunoregulatory cells in immunoglobulin E-associated allergic disorders, as well as in certain innate and adaptive immune responses. This review focuses on exciting new developments in the field of mast cell biology published in the past year. We highlight advances in the understanding of FcvarepsilonRI-mediated signaling and mast cell-activation events, as well as in the use of genetic models to study mast cell function in vivo. Finally, we discuss newly identified functions for mast cells or individual mast cell products, such as proteases and interleukin 10, in host defense, cardiovascular disease and tumor biology and in settings in which mast cells have anti-inflammatory or immunosuppressive functions.
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Affiliation(s)
- Janet Kalesnikoff
- Department of Pathology, Stanford University School of Medicine, Stanford, California 94305, USA.
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70
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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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71
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MacGlashan D. IgE receptor and signal transduction in mast cells and basophils. Curr Opin Immunol 2008; 20:717-23. [PMID: 18822373 DOI: 10.1016/j.coi.2008.08.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Revised: 08/27/2008] [Accepted: 08/28/2008] [Indexed: 12/11/2022]
Abstract
There are many aspects of mast cell and basophil biology that are being explored today. Notably, there is a wide variety of studies of the roles these two cell types play in the development of a multitude of diseases and the role they play in the general immune response. But the original reasons for studying these two cells types--because they are considered crucial to immediate hypersensitivity reactions--remain a driving force for research. These two cell types express the complete high affinity IgE receptor and aggregation of this receptor results in the secretion of multiple potent mediators that cause many of the signs and symptoms of an allergic reaction. Understanding more about the biology of the receptor and the signaling that it initiates remains important to the development of new therapeutic approaches to inhibit this reaction.
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Affiliation(s)
- Donald MacGlashan
- Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, United States.
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72
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Olivera A. Unraveling the complexities of sphingosine-1-phosphate function: the mast cell model. Prostaglandins Other Lipid Mediat 2008; 86:1-11. [PMID: 18403224 DOI: 10.1016/j.prostaglandins.2008.02.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Accepted: 02/26/2008] [Indexed: 11/16/2022]
Abstract
Sphingosine-1-phosphate (S1P) is a lipid mediator involved in diverse biological processes, from vascular and neural development to the regulation of lymphocyte trafficking. Many of its functions are regulated by five widely expressed S1P G-protein-coupled receptors (S1P(1-5)). S1P is produced mostly intracellularly, thus, much of its potential as an autocrine and paracrine mediator depends on how, when, and where it is generated or secreted out of the cells. However, S1P can also have intracellular activity independent of its receptors, adding to the complexity of S1P function. The mast cell, a major effector cell during an allergic response, has proven instrumental towards understanding the complex regulation and function of S1P. Antigen (Ag) engagement of the IgE receptor in mast cells stimulates sphingosine kinases, which generate S1P and are involved in the activation of calcium fluxes critical for mast cell responses. In addition, mast cells secrete considerable amounts of S1P upon activation, thus affecting the surrounding tissues and recruiting inflammatory cells. Export of S1P is also involved in the autocrine transactivation of S1P receptors present in mast cells. The in vivo response of mast cells, however, is not strictly dependent on their ability to generate S1P, but they are also affected by changes in S1P in the environment previous to Ag challenge. This review will discuss the recent advances towards understanding the intricacies of S1P generation, secretion and regulation in mast cells. In addition, how S1P receptors are activated and their involvement in mast cell functions will also be covered, including new insights on the role of S1P in the mast cell-mediated allergic response of systemic anaphylaxis.
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Affiliation(s)
- Ana Olivera
- Laboratory of Immune Cell Signaling, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, 9 Memorial Dr, Bldg 9, room# 1W122, Bethesda, MD 20892, USA.
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Rivera J, Fierro NA, Olivera A, Suzuki R. New insights on mast cell activation via the high affinity receptor for IgE. Adv Immunol 2008; 98:85-120. [PMID: 18772004 PMCID: PMC2761150 DOI: 10.1016/s0065-2776(08)00403-3] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Mast cells are innate immune cells that function as regulatory or effector cells and serve to amplify adaptive immunity. In adaptive immunity these cells function primarily through cell surface Fc receptors that bind immunoglobulin antibodies. The dysregulation of their adaptive role makes them central players in allergy and asthma. Upon encountering an allergen (antigen), which is recognized by immunoglobulin E (IgE) antibodies bound to the high affinity IgE receptor (FcepsilonRI) expressed on their cell surface, mast cells secrete both preformed and newly synthesized mediators of the allergic response. Blocking of these responses is an objective in therapeutic intervention of allergic diseases. Thus, understanding the mechanisms by which antigens elicit mast cell activation (via FcepsilonRI) holds promise toward identifying therapeutic targets. Here we review the most recent advances in understanding antigen-dependent mast cell activation. Specifically, we focus on the requirements for FcepsilonRI activation, the regulation of calcium responses, co-stimulatory signals in FcepsilonRI-mediated mast cell activation and function, and how genetics influences mast cell signaling and responses. These recent discoveries open new avenues of investigation with therapeutic potential.
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Affiliation(s)
- Juan Rivera
- Laboratory of Immune Cell Signaling, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland, USA
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