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https://www.readbyqxmd.com/read/28202492/gating-ring-strengthens-marriage-of-bk-channel-voltage-sensing-to-pore-opening
#1
Caitlin Sedwick
A new JGP study shows that the gating ring helps the voltage-sensing domain open the BK channel's pore.
February 15, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/28196879/deletion-of-cytosolic-gating-ring-decreases-gate-and-voltage-sensor-coupling-in-bk-channels
#2
Guohui Zhang, Yanyan Geng, Yakang Jin, Jingyi Shi, Kelli McFarland, Karl L Magleby, Lawrence Salkoff, Jianmin Cui
Large conductance Ca(2+)-activated K(+) channels (BK channels) gate open in response to both membrane voltage and intracellular Ca(2+) The channel is formed by a central pore-gate domain (PGD), which spans the membrane, plus transmembrane voltage sensors and a cytoplasmic gating ring that acts as a Ca(2+) sensor. How these voltage and Ca(2+) sensors influence the common activation gate, and interact with each other, is unclear. A previous study showed that a BK channel core lacking the entire cytoplasmic gating ring (Core-MT) was devoid of Ca(2+) activation but retained voltage sensitivity (Budelli et al...
February 14, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/28195225/a-novel-bk-channel-targeted-peptide-suppresses-sound-evoked-activity-in-the-mouse-inferior-colliculus
#3
L L Scott, E J Brecht, A Philpo, S Iyer, N S Wu, S J Mihic, R W Aldrich, J Pierce, J P Walton
Large conductance calcium-activated (BK) channels are broadly expressed in neurons and muscle where they modulate cellular activity. Decades of research support an interest in pharmaceutical applications for modulating BK channel function. Here we report a novel BK channel-targeted peptide with functional activity in vitro and in vivo. This 9-amino acid peptide, LS3, has a unique action, suppressing channel gating rather than blocking the pore of heterologously expressed human BK channels. With an IC50 in the high picomolar range, the apparent affinity is higher than known high affinity BK channel toxins...
February 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28192090/optogenetic-control-of-ca-2-and-voltage-dependent-large-conductance-bk-potassium-channels
#4
Thomas Mager, Phillip G Wood, Ernst Bamberg
Ca(2+) concentration jumps for the activation of Ca(2+) dependent ion channels or transporters can be obtained either by fast solution exchange or the use of caged Ca(2+). Here we report on an alternate optogenetic method for activation of Ca(2+) and voltage dependent large conductance (BK) potassium channels. This was achieved through the use of the light-gated Ca(2+) permeable Channelrhodopsin 2 variant, CatCh, with enhanced Ca(2+) permeability, which produces locally [Ca(2+)] in the μM range on the inner side of the membrane, without significant [Ca(2+)] increase in the cytosol...
February 10, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28187982/the-renal-trpv4-channel-is-essential-for-adaptation-to-increased-dietary-potassium
#5
Mykola V Mamenko, Nabila Boukelmoune, Viktor N Tomilin, Oleg L Zaika, V Behrana Jensen, Roger G O'Neil, Oleh M Pochynyuk
To maintain potassium homeostasis, kidneys exert flow-dependent potassium secretion to facilitate kaliuresis in response to elevated dietary potassium intake. This process involves stimulation of calcium-activated large conductance maxi-K (BK) channels in the distal nephron, namely the connecting tubule and the collecting duct. Recent evidence suggests that the TRPV4 channel is a critical determinant of flow-dependent intracellular calcium elevations in these segments of the renal tubule. Here, we demonstrate that elevated dietary potassium intake (five percent potassium) increases renal TRPV4 mRNA and protein levels in an aldosterone-dependent manner and causes redistribution of the channel to the apical plasma membrane in native collecting duct cells...
February 7, 2017: Kidney International
https://www.readbyqxmd.com/read/28177804/entry-infection-replication-and-egress-of-human-polyomaviruses-an-update
#6
Soumen Bhattacharjee, Sutanuka Chattaraj
Polyomaviruses (PyVs), belonging to the family Polyomaviridae, are a group of small, nonenveloped, double-stranded, circular DNA viruses widely distributed in the vertebrates. PyVs cause no apparent disease in adult laboratory mice but cause a wide variety of tumors when artificially inoculated into neonates or semipermissive animals. A few human PyVs, such as BK, JC, and Merkel cell PyVs, have been unequivocally linked to pathogenesis under conditions of immunosuppression. Infection is thought to occur early in life and persists for the lifespan of the host...
October 29, 2016: Canadian Journal of Microbiology
https://www.readbyqxmd.com/read/28168949/erg-28-controls-bk-channel-trafficking-in-the-er-to-regulate-synaptic-function-and-alcohol-response-in-c-elegans
#7
Kelly H Oh, James J Haney, Xiaohong Wang, Chiou-Fen Chuang, Janet E Richmond, Hongkyun Kim
Voltage- and calcium-dependent BK channels regulate calcium-dependent cellular events such as neurotransmitter release by limiting calcium influx. Their plasma membrane abundance is an important factor in determining BK current and thus regulation of calcium-dependent events. In C. elegans, we show that ERG-28, an endoplasmic reticulum (ER) membrane protein, promotes the trafficking of SLO-1 BK channels from the ER to the plasma membrane by shielding them from premature degradation. In the absence of ERG-28, SLO-1 channels undergo aspartic protease DDI-1-dependent degradation, resulting in markedly reduced expression at presynaptic terminals...
February 7, 2017: ELife
https://www.readbyqxmd.com/read/28165042/relationship-between-auxiliary-gamma-subunits-and-mallotoxin-on-bk-channel-modulation
#8
Xin Guan, Qin Li, Jiusheng Yan
The large-conductance, calcium- and voltage-activated K(+)(BK) channel consists of the pore-forming α subunits (BKα) and auxiliary subunits. The auxiliary γ1-3 subunits potently modulate the BK channel by shifting its voltage-dependence of channel activation toward the hyperpolarizing direction by approximately 145 mV (γ1), 100 mV (γ2), and 50 mV (γ3). Mallotoxin is a potent small-molecule BK channel activator. We analyzed the relationship between mallotoxin and the γ subunits in their BK channel-activating effects in membrane patches excised from HEK-293 cells...
February 6, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28163105/nerve-growth-factor-derivative-ngf61-100-promotes-outgrowth-of-primary-sensory-neurons-with-reduced-signs-of-nociceptive-sensitization
#9
C Severini, P Petrocchi Passeri, M T Ciotti, F Florenzano, C Petrella, F Malerba, B Bruni, M D'Onofrio, I Arisi, R Brandi, R Possenti, P Calissano, A Cattaneo
Nerve Growth Factor (NGF) is being considered as a therapeutic candidate for Alzheimer's disease. However, the development of an NGF-based therapy is limited by its potent pain activity. We have developed a "painless" derivative form of human NGF (NGF61/100), characterized by identical neurotrophic properties but a reduced nociceptive sensitization activity in vivo. Here we characterized the response of rat dorsal root ganglia neurons (DRG) to the NGF derivative NGF61/100, in comparison to that of control NGF (NGF61), analyzing the expression of noxious pro-nociceptive mediators...
February 2, 2017: Neuropharmacology
https://www.readbyqxmd.com/read/28155571/the-augmentation-of-bk-channel-activity-by-nitric-oxide-signaling-in-rat-cerebral-arteries-involves-co-localized-regulatory-elements
#10
Barry D Kyle, Ramesh C Mishra, Andrew P Braun
Large conductance, Ca(2+)-activated K(+) (BK) channels control cerebrovascular tone; however, the regulatory processes influencing these channels remain poorly understood. Here, we investigate the cellular mechanisms underlying the enhancement of BK current in rat cerebral arteries by nitric oxide (NO) signaling. In isolated cerebral myocytes, BK current magnitude was reversibly increased by sodium nitroprusside (SNP, 100 μM) and sensitive to the BK channel inhibitor, penitrem-A (100 nM). Fostriecin (30 nM), a protein phosphatase type 2A (PP2A) inhibitor, significantly prolonged the SNP-induced augmentation of BK current and a similar effect was produced by sildenafil (30 nM), a phosphodiesterase 5 (PDE5) inhibitor...
January 1, 2017: Journal of Cerebral Blood Flow and Metabolism
https://www.readbyqxmd.com/read/28133948/maternal-high-salt-diet-altered-adenosine-mediated-vasodilatation-via-pka-bkchannel-pathway-in-offspring-rats
#11
Jue Wu, Na Li, Yanping Liu, Weisheng Li, Axin He, Di Zhu, Xueqin Feng, Bailin Liu, Ruixiu Shi, Yujuan Zhang, Juanxiu Lv, Zhice Xu
SCOPE: High salt (HS) diets are related to cardiovascular diseases, and prenatal HS was suggested to increase risks of coronary artery diseases in the offspring. This study tested the hypothesis that prenatal HS may influence Adenosine-induced vasodilatation via PKA pathway in coronary arteries. METHODS AND RESULTS: Sprague-Dawley rats were fed with 8% salt diet for gestation, the control was fed with 0.3% salt diet. Coronary arteries from male adult offspring were tested for K(+) channels and Adenosine signal pathways...
January 29, 2017: Molecular Nutrition & Food Research
https://www.readbyqxmd.com/read/28116849/a-pharmacological-approach-to-understanding-the-control-of-insulin-secretion-in-human-islets
#12
Jean-Claude Henquin, Denis Dufrane, Valery Gmyr, Julie Kerr-Conte, Myriam Nenquin
AIMS: To understand better the control of insulin secretion (IS) by human β-cells and identify similarities and differences with rodent models. METHODS: Dynamic IS was measured in perifused human islets treated with pharmacological agents of known modes of action. RESULTS: Glucokinase activation (Ro28-1675) lowered the glucose threshold for stimulation of IS to 1 mmol/l (G1), augmented the response to G3-G5 but not to G8-G15 whereas tolbutamide remained active in G20, which indicates that not all KATP -channels were closed by high glucose...
January 24, 2017: Diabetes, Obesity & Metabolism
https://www.readbyqxmd.com/read/28108028/comparison-of-ca-2-puffs-evoked-by-extracellular-agonists-and-photoreleased-ip3
#13
Jeffrey T Lock, Ian F Smith, Ian Parker
The inositol trisphosphate (IP3) signaling pathway evokes local Ca(2+) signals (Ca(2+) puffs) that arise from the concerted openings of clustered IP3 receptor/channels in the ER membrane. Physiological activation is triggered by binding of agonists to G-protein-coupled receptors (GPCRs) on the cell surface, leading to cleavage of phosphatidyl inositol bisphosphate and release of IP3 into the cytosol. Photorelease of IP3 from a caged precursor provides a convenient and widely employed means to study the final stage of IP3-mediated Ca(2+) liberation, bypassing upstream signaling events to enable more precise control of the timing and relative concentration of cytosolic IP3...
December 5, 2016: Cell Calcium
https://www.readbyqxmd.com/read/28090300/bk-channels-in-rat-and-human-pulmonary-smooth-muscle-cells-are-bk%C3%AE-%C3%AE-1-functional-complexes-lacking-the-oxygen-sensitive-stress-axis-regulated-exon-insert
#14
Neil D Detweiler, Li Song, Samantha J McClenahan, Rachel J Versluis, Sujay V Kharade, Richard C Kurten, Sung W Rhee, Nancy J Rusch
A loss of K(+) efflux in pulmonary arterial smooth muscle cells (PASMCs) contributes to abnormal vasoconstriction and PASMC proliferation during pulmonary hypertension (PH). Activation of high-conductance Ca(2+)-activated (BK) channels represents a therapeutic strategy to restore K(+) efflux to the affected PASMCs. However, the properties of BK channels in PASMCs-including sensitivity to BK channel openers (BKCOs)-are poorly defined. The goal of this study was to compare the properties of BK channels between PASMCs of normoxic (N) and chronic hypoxic (CH) rats and then explore key findings in human PASMCs...
December 2016: Pulmonary Circulation
https://www.readbyqxmd.com/read/28041976/moving-pieces-in-a-cryptomic-puzzle-cryptide-from-tityus-serrulatus-ts3-nav-toxin-as-potential-agonist-of-muscarinic-receptors
#15
Cibele Rocha-Resende, Nádia Miricéia Leão, Maria Elena de Lima, Robson Augusto Santos, Adriano Monteiro de Castro Pimenta, Thiago Verano-Braga
Cryptome is as a subset of a given proteome containing bioactive cryptides embedded in larger peptides or proteins. We pinpointed a striking sequence similarity between two peptides from the Tityus serrulatus venom: Ts10 (KKDGYPVEYDRAY) and the N-terminal of Ts3 (KKDGYPVEYDNCAY). Ts3 (former Tityustoxin or TsIV) is an α-neurotoxin acting on voltage-gated sodium channels while Ts10 (former Peptide T) is a bradykinin-potentiating peptide and was originally reported as inhibitor of the angiotensin-converting enzyme (ACEi)...
December 29, 2016: Peptides
https://www.readbyqxmd.com/read/28026020/low-pho-boosts-burst-firing-and-catecholamine-release-by-blocking-task-1-and-bk-channels-while-preserving-cav1-channels-in-mouse-chromaffin-cells
#16
Laura Guarina, David H F Vandael, Valentina Carabelli, Emilio Carbone
Mouse chromaffin cells (MCCs) generate action potential (AP) firing that regulates the Ca(2+) -dependent release of catecholamines (CAs). Recent findings indicate that MCCs possess a variety of spontaneous firing modes that span from the common "tonic-irregular" to the less frequent "burst" firing. This latter is evident in a small fraction of MCCs but occurs regularly when Nav1.3/1.7 channels are made less available or when the Slo1β2-subunit responsible for BK channel inactivation is deleted. Burst firing causes massive increases of Ca(2+) -entry and potentiates CA release ∼3...
December 27, 2016: Journal of Physiology
https://www.readbyqxmd.com/read/28025959/hypokalemia-associated-with-acute-colonic-pseudo-obstruction-in-an-esrd-patient
#17
Khaled Boobés, Robert M Rosa, Daniel Batlle
Ogilvie's syndrome, or acute colonic pseudo-obstruction, is characterized by massive dilation of the colon without mechanical obstruction. Water and electrolytes often can be sequestered in the dilated intestinal loops resulting in profuse and watery diarrhea as well as hypokalemia. We report an anuric, end-stage renal disease (ESRD) patient undergoing peritoneal dialysis (PD) who developed acute colonic pseudo-obstruction causing a prolonged hospitalization. He also developed severe hypokalemia with a serum potassium (K+) as low as 2...
December 27, 2016: Clinical Nephrology
https://www.readbyqxmd.com/read/28012000/differential-distribution-and-functional-impact-of-bk-channel-beta1-subunits-across-mesenteric-coronary-and-different-cerebral-arteries-of-the-rat
#18
Guruprasad Kuntamallappanavar, Shivantika Bisen, Anna N Bukiya, Alex M Dopico
Large conductance, Ca(2+)i- and voltage-gated K(+) (BK) channels regulate myogenic tone and, thus, arterial diameter. In smooth muscle (SM), BK channels include channel-forming α and auxiliary β1 subunits. BK β1 increases the channel's Ca(2+) sensitivity, allowing BK channels to negatively feedback on depolarization-induced Ca(2+) entry, oppose SM contraction and favor vasodilation. Thus, endothelial-independent vasodilation can be evoked though targeting of SM BK β1 by endogenous ligands, including lithocholate (LCA)...
December 24, 2016: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/27999123/early-alterations-of-hippocampal-neuronal-firing-induced-by-abeta42
#19
Daniela Gavello, Chiara Calorio, Claudio Franchino, Federico Cesano, Valentina Carabelli, Emilio Carbone, Andrea Marcantoni
We studied the effect of Amyloid β 1-42 oligomers (Abeta42) on Ca(2+) dependent excitability profile of hippocampal neurons. Abeta42 is one of the Amyloid beta peptides produced by the proteolytic processing of the amyloid precursor protein and participates in the initiating event triggering the progressive dismantling of synapses and neuronal circuits. Our experiments on cultured hippocampal network reveal that Abeta42 increases intracellular Ca(2+) concentration by 46% and inhibits firing discharge by 19%...
December 19, 2016: Cerebral Cortex
https://www.readbyqxmd.com/read/27989457/bk-channels-are-required-for-multisensory-plasticity-in-the-oculomotor-system
#20
Alexandra B Nelson, Michael Faulstich, Setareh Moghadam, Kimberly Onori, Andrea Meredith, Sascha du Lac
Neural circuits are endowed with several forms of intrinsic and synaptic plasticity that could contribute to adaptive changes in behavior, but circuit complexities have hindered linking specific cellular mechanisms with their behavioral consequences. Eye movements generated by simple brainstem circuits provide a means for relating cellular plasticity to behavioral gain control. Here we show that firing rate potentiation, a form of intrinsic plasticity mediated by reductions in BK-type calcium-activated potassium currents in spontaneously firing neurons, is engaged during optokinetic reflex compensation for inner ear dysfunction...
January 4, 2017: Neuron
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