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Lukas Traxler, Petr Rathner, Marc Fahrner, Michael Stadlbauer, Felix Faschinger, Tatsiana Charnavets, Norbert Müller, Christoph Romanin, Peter Hinterdorfer, Hermann J Gruber
Calmodulin (CaM) binds most of its targets by wrapping around an amphipathic α-helix. The N-terminus of Orai proteins contains a conserved CaM-binding segment but the binding mechanism is only partially characterized. Here, microscale thermophoresis (MST), surface plasmon resonance (SPR), and atomic force microscopy (AFM) were employed to study the binding equilibria, the kinetics, and the single-molecular interaction forces involved in the binding of CaM to the conserved helical segments of Orai1 and Orai3...
October 11, 2017: Angewandte Chemie
Aparna Gudlur, Patrick G Hogan
This chapter focuses on the Orai proteins, Orai1-Orai3, with special emphasis on Orai1, in humans and other mammals, and on the definitive evidence that Orai is the pore subunit of the CRAC channel. It begins by reviewing briefly the defining characteristics of the CRAC channel, then discusses the studies that implicated Orai as part of the store-operated Ca(2+) entry pathway and as the CRAC channel pore subunit, and finally examines ongoing work that is providing insights into CRAC channel structure and gating...
2017: Advances in Experimental Medicine and Biology
Jyoti Tanwar, Rajender K Motiani
Calcium (Ca(2+)) signaling plays a critical role in regulating plethora of cellular functions including cell survival, proliferation and migration. The perturbations in cellular Ca(2+) homeostasis can lead to cell death either by activating autophagic pathways or through induction of apoptosis. Endoplasmic reticulum (ER) is the major storehouse of Ca(2+) within cells and a number of physiological agonists mediate ER Ca(2+) release by activating IP3 receptors (IP3R). This decrease in ER Ca(2+) levels is sensed by STIM, which physically interacts and activates plasma membrane Ca(2+) selective Orai channels...
June 9, 2017: Cell Calcium
Jea Kwon, Heeyoung An, Moonsun Sa, Joungha Won, Jeong Im Shin, C Justin Lee
Astrocytes are non-excitable cells in the brain and their activity largely depends on the intracellular calcium (Ca(2+)) level. Therefore, maintaining the intracellular Ca(2+) homeostasis is critical for proper functioning of astrocytes. One of the key regulatory mechanisms of Ca(2+) homeostasis in astrocytes is the store-operated Ca(2+) entry (SOCE). This process is mediated by a combination of the Ca(2+)-store-depletion-sensor, Stim, and the store-operated Ca(2+)-channels, Orai and TrpC families. Despite the existence of all those families in astrocytes, previous studies have provided conflicting results on the molecular identification of astrocytic SOCE...
February 2017: Experimental Neurobiology
Daniel Leon-Aparicio, Jonathan Pacheco, Jesus Chavez-Reyes, Jose M Galindo, Jesus Valdes, Luis Vaca, Agustin Guerrero-Hernandez
We have studied in HeLa cells the molecular nature of the 2-APB induced ER Ca(2+) leak using synthetic Ca(2+) indicators that report changes in both the cytoplasmic ([Ca(2+)]i) and the luminal ER ([Ca(2+)]ER) Ca(2+) concentrations. We have tested the hypothesis that Orai channels participate in the 2-APB-induced ER Ca(2+) leak that was characterized in the companion paper. The expression of the dominant negative Orai1 E106A mutant, which has been reported to block the activity of all three types of Orai channels, inhibited the effect of 2-APB on the [Ca(2+)]ER but did not decrease the ER Ca(2+) leak after thapsigargin (TG)...
July 2017: Cell Calcium
Sylvain Chauvet, Louis Jarvis, Mireille Chevallet, Niroj Shrestha, Klaus Groschner, Alexandre Bouron
In the murine brain, the first post-mitotic cortical neurons formed during embryogenesis express store-operated channels (SOCs) sensitive to Pyr3, initially proposed as a blocker of the transient receptor potential channel of C type 3 (TRPC3 channel). However, Pyr3 does not discriminate between Orai and TRPC3 channels, questioning the contribution of TRPC3 in SOCs. This study was undertaken to clarify the molecular identity and the pharmacological profile of native SOCs from E13 cortical neurons. The mRNA expression of STIM1-2 and Orai1-3 was assessed by quantitative reverse transcription polymerase chain reaction...
2016: Frontiers in Pharmacology
Nazim Benzerdjeb, Henri Sevestre, Ahmed Ahidouch, Halima Ouadid-Ahidouch
Orai3 channel has emerged as important player in malignant transformation. Indeed, its expression is increased in cancer and favors cell proliferation and survival by permitting calcium influx. In this study, Orai3 was overexpressed in lung adenocarcinoma as compared to their matched non-tumour samples and was associated with tumoural aggressiveness. Moreover, its expression was associated with estrogen receptor alpha (ERα) expression and visceral pleural invasion in multivariate analysis. Furthermore, both the overall survival (OS) median and the metastasis free survival (MFS) median of tumors with high Orai3 expression were lower than in low Orai3 expression regardless of cancer stage (35...
December 6, 2016: Oncotarget
Susana Cubillos, Johannes Norgauer
Psoriasis is an inflammatory skin disease with or without joint involvement. In this disease, the thickened epidermis and impaired barrier are associated with altered calcium gradients. Calcium and vitamin D are known to play important roles in keratinocyte differentiation and bone metabolism. Intracellular calcium is regulated by calcium-sensing receptor (CASR), calcium release-activated calcium modulator (ORAI) and stromal interaction molecule (STIM). Other proteins modulated by vitamin D play important roles in calcium regulation e...
October 2016: International Journal of Molecular Medicine
Sumiko Denda, Kentaro Takei, Junichi Kumamoto, Makiko Goto, Mitsuhiro Denda
No abstract text is available yet for this article.
August 30, 2016: Experimental Dermatology
Letizia Albarrán, José J López, Luis J Gómez, Ginés M Salido, Juan A Rosado
Canonical transient receptor potential-1 (TRPC1) is an almost ubiquitously expressed channel that plays a relevant role in cell function. As other TRPC members, TRPC1 forms receptor-operated cation channels that exhibit both STIM1-dependent and store-independent behaviour. The STIM1 inhibitor SARAF (for store-operated Ca(2+) entry (SOCE)-associated regulatory factor) modulates SOCE by interaction with the STIM1 region responsible for Orai1 activation (SOAR). Furthermore, SARAF modulates Ca(2+) entry through the arachidonate-regulated Ca(2+) (ARC) channels, consisting of Orai1 and Orai3 heteropentamers and plasma membrane-resident STIM1...
October 15, 2016: Biochemical Journal
Francesco Moccia, Estella Zuccolo, Valentina Poletto, Ilaria Turin, Germano Guerra, Paolo Pedrazzoli, Vittorio Rosti, Camillo Porta, Daniela Montagna
An increase in intracellular Ca2+ concentration plays a key role in the establishment of many cancer hallmarks, including aberrant proliferation, migration, invasion, resistance to apoptosis and angiogenesis. The dysregulation of Ca2+ entry is one of the most subtle mechanisms by which cancer cells overwhelm their normal counterparts and gain the adaptive advantages that result in tumour growth, vascularisation and dissemination throughout the organism. Both constitutive and agonist-induced Ca2+ influx may be mediated by store-dependent as well as store-independent Ca2+ entry routes...
2016: Current Medicinal Chemistry
Rajesh Bhardwaj, Matthias A Hediger, Nicolas Demaurex
STIM1 and ORAI1 constitute the core machinery of the ubiquitous store-operated calcium entry pathway and loss of function in these proteins is associated with severe immune and muscular disorders. Other isoforms-STIM1L, STIM2, ORAI2 and ORAI3 exhibit varied expression levels in different cell types along with several other interaction partners and thereby play different roles to facilitate, regulate and fine-tune the calcium entry. STIM proteins convey the Ca(2+) store-depletion message to the PM and thereby participate in refilling of the ER by physically interacting with the Ca(2+)-selective ORAI channels at the PM...
August 2016: Cell Calcium
Stephanie Saul, Christine S Gibhardt, Barbara Schmidt, Annette Lis, Bastian Pasieka, David Conrad, Philipp Jung, Rosmarie Gaupp, Bodo Wonnenberg, Ebru Diler, Hedwig Stanisz, Thomas Vogt, Eva C Schwarz, Markus Bischoff, Mathias Herrmann, Thomas Tschernig, Reinhard Kappl, Heiko Rieger, Barbara A Niemeyer, Ivan Bogeski
In phagocytes, pathogen recognition is followed by Ca(2+) mobilization and NADPH oxidase 2 (NOX2)-mediated "oxidative burst," which involves the rapid production of large amounts of reactive oxygen species (ROS). We showed that ORAI Ca(2+) channels control store-operated Ca(2+) entry, ROS production, and bacterial killing in primary human monocytes. ROS inactivate ORAI channels that lack an ORAI3 subunit. Staphylococcal infection of mice reduced the expression of the gene encoding the redox-sensitive Orai1 and increased the expression of the gene encoding the redox-insensitive Orai3 in the lungs or in bronchoalveolar lavages...
March 8, 2016: Science Signaling
Meerim K Nurbaeva, Miriam Eckstein, Axel R Concepcion, Charles E Smith, Sonal Srikanth, Michael L Paine, Yousang Gwack, Michael J Hubbard, Stefan Feske, Rodrigo S Lacruz
Dental enamel formation requires large quantities of Ca(2+) yet the mechanisms mediating Ca(2+) dynamics in enamel cells are unclear. Store-operated Ca(2+) entry (SOCE) channels are important Ca(2+) influx mechanisms in many cells. SOCE involves release of Ca(2+) from intracellular pools followed by Ca(2+) entry. The best-characterized SOCE channels are the Ca(2+) release-activated Ca(2+) (CRAC) channels. As patients with mutations in the CRAC channel genes STIM1 and ORAI1 show abnormal enamel mineralization, we hypothesized that CRAC channels might be an important Ca(2+) uptake mechanism in enamel cells...
October 30, 2015: Scientific Reports
Christian Holzmann, Tatiana Kilch, Sven Kappel, Kathrin Dörr, Volker Jung, Michael Stöckle, Ivan Bogeski, Christine Peinelt
In prostate cancer, reactive oxygen species (ROS) are elevated and Ca(2+) signaling is impaired. Thus, several novel therapeutic strategies have been developed to target altered ROS and Ca(2+) signaling pathways in prostate cancer. Here, we investigate alterations of intracellular Ca(2+) and inhibition of cell viability caused by ROS in primary human prostate epithelial cells (hPECs) from healthy tissue and prostate cancer cell lines (LNCaP, DU145, and PC3). In hPECs, LNCaP and DU145 H2O2 induces an initial Ca(2+) increase, which in prostate cancer cells is blocked at high concentrations of H2O2...
October 6, 2015: Biophysical Journal
Pooja N Desai, Xuexin Zhang, Shilan Wu, Agnes Janoshazi, Sunitha Bolimuntha, James W Putney, Mohamed Trebak
In mammals exclusively, the pore-forming Ca(2+) release-activated Ca(2+) (CRAC) channel subunit Orai1 occurs in two forms because of alternative translation initiation. The longer, mammal-specific Orai1α contains an additional 63 amino acids upstream of the conserved start site for Orai1β, which occurs at methionine 64 in Orai1α. Orai1 participates in the generation of three distinct Ca(2+) currents, including two store-operated currents: Icrac, which involves activation of Orai1 channels by the Ca(2+)-sensing protein STIM1 (stromal interaction molecule 1), and Isoc, which involves an interaction among Orai1, the transient receptor potential (TRP) family member TRPC1 (TRP canonical 1), and STIM1...
July 28, 2015: Science Signaling
Robert Kraft
Stromal interaction molecules (STIM) 1 and 2 are sensors of the calcium concentration in the endoplasmic reticulum. Depletion of endoplasmic reticulum calcium stores activates STIM proteins which, in turn, bind and open calcium channels in the plasma membrane formed by the proteins ORAI1, ORAI2, and ORAI3. The resulting store-operated calcium entry (SOCE), mostly controlled by the principal components STIM1 and ORAI1, has been particularly characterized in immune cells. In the nervous system, all STIM and ORAI homologs are expressed...
2015: Channels
Jing Li, Alexander-Francisco Bruns, Bing Hou, Baptiste Rode, Peter J Webster, Marc A Bailey, Hollie L Appleby, Nicholas K Moss, Judith E Ritchie, Nadira Y Yuldasheva, Sarka Tumova, Matthew Quinney, Lynn McKeown, Hilary Taylor, K Raj Prasad, Dermot Burke, David O'Regan, Karen E Porter, Richard Foster, Mark T Kearney, David J Beech
OBJECTIVE: Vascular endothelial growth factor (VEGF) acts, in part, by triggering calcium ion (Ca(2+)) entry. Here, we sought understanding of a Synta66-resistant Ca(2+) entry pathway activated by VEGF. APPROACH AND RESULTS: Measurement of intracellular Ca(2+) in human umbilical vein endothelial cells detected a Synta66-resistant component of VEGF-activated Ca(2+) entry that occurred within 2 minutes after VEGF exposure. Knockdown of the channel-forming protein Orai3 suppressed this Ca(2+) entry...
September 2015: Arteriosclerosis, Thrombosis, and Vascular Biology
Ayushi Vashisht, Mohamed Trebak, Rajender K Motiani
Calcium (Ca(2+)) regulates a plethora of cellular functions including hallmarks of cancer development such as cell cycle progression and cellular migration. Receptor-regulated calcium rise in nonexcitable cells occurs through store-dependent as well as store-independent Ca(2+) entry pathways. Stromal interaction molecules (STIM) and Orai proteins have been identified as critical constituents of both these Ca(2+) influx pathways. STIMs and Orais have emerged as targets for cancer therapeutics as their altered expression and function have been shown to contribute to tumorigenesis...
October 1, 2015: American Journal of Physiology. Cell Physiology
Francesco Moccia, Estella Zuccolo, Teresa Soda, Franco Tanzi, Germano Guerra, Lisa Mapelli, Francesco Lodola, Egidio D'Angelo
Stim1 and Orai1 are ubiquitous proteins that have long been known to mediate Ca(2+) release-activated Ca(2+) (CRAC) current (ICRAC) and store-operated Ca(2+) entry (SOCE) only in non-excitable cells. SOCE is activated following the depletion of the endogenous Ca(2+) stores, which are mainly located within the endoplasmic reticulum (ER), to replete the intracellular Ca(2+) reservoir and engage specific Ca(2+)-dependent processes, such as proliferation, migration, cytoskeletal remodeling, and gene expression...
2015: Frontiers in Cellular Neuroscience
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