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Sher Ali, Tao Xu, Xiaolan Xu
Ca(2+) release-activated Ca(2+) (CRAC) channels play an essential role in the immune system. The pore-forming subunit, Orai1, is an important pharmacological target. Here, we summarize the recent discoveries on the structure-function relationship of Orai1, as well as its interaction with the native channel opener STIM1 and chemical modulator 2-aminoethoxydiphenyl borate (2-APB). We first introduce the critical structural elements of Orai1, which include a Ca(2+) accumulating region (CAR), ion selectivity filter, hydrophobic centre, basic region, extended transmembrane orai1 N-terminal (ETON), transmembrane (TM) regions 2 and 3, P245 bend, (263) SHK(265) hinge linker and L273-L276 hydrophobic patch...
October 18, 2016: Journal of Physiology
Axel R Concepcion, Martin Vaeth, Larry E Wagner, Miriam Eckstein, Lee Hecht, Jun Yang, David Crottes, Maximilian Seidl, Hyosup P Shin, Carl Weidinger, Scott Cameron, Stuart E Turvey, Thomas Issekutz, Isabelle Meyts, Rodrigo S Lacruz, Mario Cuk, David I Yule, Stefan Feske
Eccrine sweat glands are essential for sweating and thermoregulation in humans. Loss-of-function mutations in the Ca2+ release-activated Ca2+ (CRAC) channel genes ORAI1 and STIM1 abolish store-operated Ca2+ entry (SOCE), and patients with these CRAC channel mutations suffer from anhidrosis and hyperthermia at high ambient temperatures. Here we have shown that CRAC channel-deficient patients and mice with ectodermal tissue-specific deletion of Orai1 (Orai1K14Cre) or Stim1 and Stim2 (Stim1/2K14Cre) failed to sweat despite normal sweat gland development...
October 10, 2016: Journal of Clinical Investigation
Amit Jairaman, Chelsea H Maguire, Robert P Schleimer, Murali Prakriya
Aberrant immune responses to environmental allergens including insect allergens from house dust mites and cockroaches contribute to allergic inflammatory diseases such as asthma in susceptible individuals. Airway epithelial cells (AECs) play a critical role in this process by sensing the proteolytic activity of allergens via protease-activated receptors (PAR2) to initiate inflammatory and immune responses in the airway. Elevation of cytosolic Ca(2+) is an important signaling event in this process, yet the fundamental mechanism by which allergens induce Ca(2+) elevations in AECs remains poorly understood...
2016: Scientific Reports
Bin Jia, Yanzi Song, Min Wu, Baicheng Lin, Kang Xiao, Zhangli Hu, Ying Huang
BACKGROUND: Microalgae biofuel has become the most promising renewable energy over the past few years. But limitations still exist because of its high cost. Although, efforts have been made in enhancement of lipid productivity, the major cost problem in harvesting and oil extraction is still intractable. Thus, the idea of fatty acids (FAs) secretion which can massively facilitate algae harvesting and oil extraction was investigated here. RESULTS: The cDNAs of two long-chain acyl-CoA synthetases (LACSs) genes were cloned from Chlamydomonas reinhardtii and named as cracs1 and cracs2...
2016: Biotechnology for Biofuels
Catherine A Rivet, Ariel S Kniss-James, Margaret A Gran, Anish Potnis, Abby Hill, Hang Lu, Melissa L Kemp
T cells reach a state of replicative senescence characterized by a decreased ability to proliferate and respond to foreign antigens. Calcium release associated with TCR engagement is widely used as a surrogate measure of T cell response. Using an ex vivo culture model that partially replicates features of organismal aging, we observe that while the amplitude of Ca2+ signaling does not change with time in culture, older T cells exhibit faster Ca2+ rise and a faster decay. Gene expression analysis of Ca2+ channels and pumps expressed in T cells by RT-qPCR identified overexpression of the plasma membrane CRAC channel subunit ORAI1 and PMCA in older T cells...
2016: PloS One
Evan Koufos, En Hyung Chang, Elnaz S Rasti, Eric Krueger, Angela C Brown
Recognition of and binding to cholesterol on the host cell membrane is an initial step in the mechanism of numerous pathogens, including viruses, bacteria, and bacterial toxins; however, a viable method of inhibiting this interaction has not yet been uncovered. Here, we describe the mechanism by which a cholesterol recognition amino acid consensus peptide interacts with cholesterol and inhibits the activity of a cholesterol-binding bacterial leukotoxin (LtxA). Using a series of biophysical techniques, we have shown that the peptide recognizes the hydroxyl group of cholesterol with nanomolar affinity and does not disrupt membrane packing, suggesting that it sits primarily near the membrane surface...
August 30, 2016: Biochemistry
Masato Mashimo, Yukako Yurie, Koichiro Kawashima, Takeshi Fujii
AIMS: T lymphocytes express muscarinic acetylcholine receptors (mAChRs) involved in regulating their proliferation, differentiation and cytokine release. Activation of M1, M3 or M5 mAChRs increases the intracellular Ca(2+) concentration ([Ca(2+)]i) through inositol-1,4,5-phosphate (IP3)-mediated Ca(2+) release from endoplasmic reticulum Ca(2+) stores. In addition, T lymphocytes express Ca(2+)-release activated Ca(2+) (CRAC) channels to induce Ca(2+) influx and to regulate diverse immune functions...
September 15, 2016: Life Sciences
Ilaria Maccari, Renping Zhao, Martin Peglow, Karsten Schwarz, Ivan Hornak, Mathias Pasche, Ariel Quintana, Markus Hoth, Bin Qu, Heiko Rieger
Ca(2+) microdomains and spatially resolved Ca(2+) signals are highly relevant for cell function. In T cells, local Ca(2+) signaling at the immunological synapse (IS) is required for downstream effector functions. We present experimental evidence that the relocation of the MTOC towards the IS during polarization drags mitochondria along with the microtubule network. From time-lapse fluorescence microscopy we conclude that mitochondria rotate together with the cytoskeleton towards the IS. We hypothesize that this movement of mitochondria towards the IS together with their functionality of absorption and spatial redistribution of Ca(2+) is sufficient to significantly increase the cytosolic Ca(2+) concentration...
July 7, 2016: Cell Calcium
Ahmad Almilaji, Jing Yan, Zohreh Hosseinzadeh, Evi Schmid, Meinrad Gawaz, Florian Lang
BACKGROUND: Blood platelets are activated by increase of cytosolic Ca2+ activity ([Ca2+]i). Ca2+ entry is accomplished in part by store operated Ca2+ entry (SOCE) involving Ca2+ release activated Ca2+-channel (CRAC) moiety Orai1 and its regulator STIM1, which are stimulated by depletion of intracellular Ca2+ stores. An increase of [Ca2+]i is terminated by Na+/Ca2+-exchange. The expression of both, Orai1 and STIM1 in megakaryocytes is up-regulated by tumor growth factor TGFβ1, a powerful regulator of megakaryocyte differentiation...
2016: Cellular Physiology and Biochemistry
Catherine A Hartzell, Katarzyna I Jankowska, Janis K Burkhardt, Richard S Lewis
T cell receptor (TCR) engagement opens Ca(2+) release-activated Ca(2+) (CRAC) channels and triggers formation of an immune synapse between T cells and antigen-presenting cells. At the synapse, actin reorganizes into a concentric lamellipod and lamella with retrograde actin flow that helps regulate the intensity and duration of TCR signaling. We find that Ca(2+) influx is required to drive actin organization and dynamics at the synapse. Calcium acts by promoting actin depolymerization and localizing actin polymerization and the actin nucleation promotion factor WAVE2 to the periphery of the lamellipod while suppressing polymerization elsewhere...
2016: ELife
Renshan Sun, Yongqiang Yang, Xinze Ran, Tao Yang
Using the systematic evolution of ligands by exponential enrichment (SELEX) method, we identified oligonucleotides that bind to the first extracellular domain of the Orai1 protein with high affinities and high specificities. These ligands were isolated from a random single-strand DNA (ssDNA) library with 40 randomized sequence positions, using synthesized peptides with amino acid sequences identical to the first extracellular domain of the Orai1 protein as the targets for SELEX selection. Seven aptamers were obtained after 12 rounds of SELEX...
2016: PloS One
Xiaolan Xu, Sher Ali, Yufeng Li, Haijie Yu, Mingshu Zhang, Jingze Lu, Tao Xu
2-Aminoethoxydiphenyl borate (2-APB) elicits potentiation current (Ip) on Ca(2+) release-activated Ca(2+) (CRAC) channels. An accurate investigation into this modulation mechanism would reveal how STIM1-dependent channel gating is enhanced, and benefit the future immune enhancer development. Here, we directly probed the pore diameter of CRAC channels and found that 2-APB enlarged the pore size of STIM1-activated Orai1 from 3.8 to 4.6 Å. We demonstrated that ions with small sizes, i.e., Ca(2+) and Na(+), mediated prominent 2-APB-induced Ip on the wildtype (WT) Orai1 channels of narrow pore sizes, while conducted decreased or no Ip on Orai1-V102C/A/G mutant channels with enlarged pore diameters...
2016: Scientific Reports
M Joskova, M Sutovska, P Durdik, D Koniar, L Hargas, P Banovcin, M Hrianka, V Khazaei, L Pappova, S Franova
Overproduction of mucus is a hallmark of asthma. The aim of this study was to identify potentially effective therapies for removing excess mucus. The role of voltage-gated (Kir 6.1, KCa 1.1) and store-operated ion channels (SOC, CRAC) in respiratory cilia, relating to the tracheal ciliary beat frequency (CBF), was compared under the physiological and allergic airway conditions. Ex vivo experiments were designed to test the local effects of Kir 6.1, KCa 1.1 and CRAC ion channel modulators in a concentration-dependent manner on the CBF...
2016: Advances in Experimental Medicine and Biology
Gene A Morrill, Adele B Kostellow, Raj K Gupta
The steroid hormone, vitamin D3, regulates gene transcription via at least two receptors and initiates putative rapid response systems at the plasma membrane. The vitamin D receptor (VDR) binds vitamin D3 and a second receptor, importin-4, imports the VDR-vitamin D3 complex into the nucleus via nuclear pores. Here we present evidence that the Homo sapiens VDR homodimer contains two transmembrane (TM) helices ((327)E - D(342)), two TM "half-helix" ((264)K N(276)), one or more large channels, and 16 cholesterol binding (CRAC/CARC) domains...
September 2, 2016: Biochemical and Biophysical Research Communications
Namrata Singh, Debasish Bhattacharyya
Microorganisms express a variety of proteases that degrade many proteins of the host body and subvert host immune response. While elucidating the mechanism/s of an immune stimulatory drug that contains bile lipid, regulation of proteolytic activity was investigated. The drug and bile lipids both stabilize Proteinase K, an aggressive protease of fungal origin against auto-digestion. Among the components of bile lipids, only cholesterol and its derivatives stabilize the enzyme. Biophysical evidences such as scattering of light, intrinsic and extrinsic fluorescence emission spectra, circular dichroism spectra, atomic force microscopy and transmission electron microscopy images indicated that cholesterol and its derivatives interact with Proteinase K...
June 15, 2016: Journal of Cellular Physiology
Shuang Liu, Muhammad Novrizal Abdi Sahid, Erika Takemasa, Takeshi Kiyoi, Miyuki Kuno, Yusuke Oshima, Kazutaka Maeyama
Ca(2+) release-activated calcium channel 3 (CRACM3) is a unique member of the CRAC family of Ca(2+)-selective channels. In a non-excitable exocytosis model, we found that the extracellular L3 domain and the cytoplasmic C-terminus of CRACM3 interacted in an activity-dependent manner with the N-peptide of syntaxin4, a soluble N-ethylmaleimide-sensitive factor attachment receptor protein. Our biochemical, electrophysiological and single-vesicle studies showed that knockdown of CRACM3 suppressed functional exocytosis by decreasing the open time of the vesicle fusion pore without affecting Ca(2+) influx, the activity-dependent membrane capacitance (Cm) change, and the total number of fusion events...
2016: Scientific Reports
Martin Vaeth, Miriam Eckstein, Patrick J Shaw, Lina Kozhaya, Jun Yang, Friederike Berberich-Siebelt, Robert Clancy, Derya Unutmaz, Stefan Feske
T follicular helper (Tfh) cells promote affinity maturation of B cells in germinal centers (GCs), whereas T follicular regulatory (Tfr) cells limit the GC reaction. Store-operated Ca(2+) entry (SOCE) through Ca(2+) release-activated Ca(2+) (CRAC) channels mediated by STIM and ORAI proteins is a fundamental signaling pathway in T lymphocytes. Conditional deletion of Stim1 and Stim2 genes in T cells abolished SOCE and strongly reduced antibody-mediated immune responses following viral infection caused by impaired differentiation and function of Tfh cells...
June 21, 2016: Immunity
Marek K Korzeniowski, Barbara Baird, David Holowka
Oligomerization of the Ca(2+) sensor, STIM1, in the endoplasmic reticulum (ER) membrane, caused by depletion of ER Ca(2+) stores, results in STIM1 coupling to the plasma membrane Ca(2+) channel protein, Orai1, to activate Ca(2+) influx in a process known as store-operated Ca(2+) entry. We use fluorimetry-based fluorescence resonance energy transfer (FRET) to monitor changes in STIM1 oligomerization in COS7 cells transfected with STIM1 constructs containing selected truncations, deletions, and point mutations, and labeled with donor and acceptor fluorescent proteins at either the luminal (N-terminal) or the cytoplasmic (C-terminal) ends...
2016: AIMS Biophysics
Sonal Srikanth, Jin Seok Woo, Yousang Gwack
More than 60 Rab GTPases exist in the human genome to regulate vesicle trafficking between organelles. Rab GTPases are members of the Ras GTPase superfamily that broadly control budding, uncoating, motility and fusion of vesicles in most cell types. Rab proteins interconvert between active, GTP-bound form and inactive, GDP-bound form. In their active conformation, they interact with various effector molecules to carry out diverse functions. Rab GTPases are usually small containing only a GTPase domain with a C-terminal prenylation site for membrane anchoring...
May 24, 2016: Small GTPases
Qiao-Chu Wang, Qiaoxia Zheng, Haiyan Tan, Bing Zhang, Xiaoling Li, Yuxiu Yang, Jie Yu, Yang Liu, Hao Chai, Xi Wang, Zhongshuai Sun, Jiu-Qiang Wang, Shu Zhu, Fengli Wang, Maojun Yang, Caixia Guo, Heng Wang, Qingyin Zheng, Yang Li, Quan Chen, Aimin Zhou, Tie-Shan Tang
Maintaining homeostasis of Ca(2+) stores in the endoplasmic reticulum (ER) is crucial for proper Ca(2+) signaling and key cellular functions. The Ca(2+)-release-activated Ca(2+) (CRAC) channel is responsible for Ca(2+) influx and refilling after store depletion, but how cells cope with excess Ca(2+) when ER stores are overloaded is unclear. We show that TMCO1 is an ER transmembrane protein that actively prevents Ca(2+) stores from overfilling, acting as what we term a "Ca(2+) load-activated Ca(2+) channel" or "CLAC" channel...
June 2, 2016: Cell
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