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Journal of General Physiology

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https://www.readbyqxmd.com/read/29343502/taking-deterministic-control-of-membrane-protein-monomer-dimer-measurements
#1
REVIEW
Karen G Fleming
No abstract text is available yet for this article.
January 17, 2018: Journal of General Physiology
https://www.readbyqxmd.com/read/29339379/correction-lipid-signaling-to-membrane-proteins-from-second-messengers-to-membrane-domains-and-adapter-free-endocytosis
#2
Donald W Hilgemann, Gucan Dai, Anthony Collins, Vincenzo Lariccia, Simona Magi, Christine Deisl, Michael Fine
No abstract text is available yet for this article.
January 16, 2018: Journal of General Physiology
https://www.readbyqxmd.com/read/29326133/lipid-signaling-to-membrane-proteins-from-second-messengers-to-membrane-domains-and-adapter-free-endocytosis
#3
REVIEW
Donald W Hilgemann, Gucan Dai, Anthony Collins, Vincenzo Lariccia, Simona Magi, Christine Deisl, Michael Fine
Lipids influence powerfully the function of ion channels and transporters in two well-documented ways. A few lipids act as bona fide second messengers by binding to specific sites that control channel and transporter gating. Other lipids act nonspecifically by modifying the physical environment of channels and transporters, in particular the protein-membrane interface. In this short review, we first consider lipid signaling from this traditional viewpoint, highlighting innumerable Journal of General Physiology publications that have contributed to our present understanding...
January 11, 2018: Journal of General Physiology
https://www.readbyqxmd.com/read/29321264/estimating-kinetic-mechanisms-with-prior-knowledge-i-linear-parameter-constraints
#4
Autoosa Salari, Marco A Navarro, Mirela Milescu, Lorin S Milescu
To understand how ion channels and other proteins function at the molecular and cellular levels, one must decrypt their kinetic mechanisms. Sophisticated algorithms have been developed that can be used to extract kinetic parameters from a variety of experimental data types. However, formulating models that not only explain new data, but are also consistent with existing knowledge, remains a challenge. Here, we present a two-part study describing a mathematical and computational formalism that can be used to enforce prior knowledge into the model using constraints...
January 10, 2018: Journal of General Physiology
https://www.readbyqxmd.com/read/29321263/estimating-kinetic-mechanisms-with-prior-knowledge-ii-behavioral-constraints-and-numerical-tests
#5
Marco A Navarro, Autoosa Salari, Mirela Milescu, Lorin S Milescu
Kinetic mechanisms predict how ion channels and other proteins function at the molecular and cellular levels. Ideally, a kinetic model should explain new data but also be consistent with existing knowledge. In this two-part study, we present a mathematical and computational formalism that can be used to enforce prior knowledge into kinetic models using constraints. Here, we focus on constraints that quantify the behavior of the model under certain conditions, and on constraints that enforce arbitrary parameter relationships...
January 10, 2018: Journal of General Physiology
https://www.readbyqxmd.com/read/29321262/nonsensing-residues-in-s3-s4-linker-s-c-terminus-affect-the-voltage-sensor-set-point-in-k-channels
#6
Joao L Carvalho-de-Souza, Francisco Bezanilla
Voltage sensitivity in ion channels is a function of highly conserved arginine residues in their voltage-sensing domains (VSDs), but this conservation does not explain the diversity in voltage dependence among different K+ channels. Here we study the non-voltage-sensing residues 353 to 361 in Shaker K+ channels and find that residues 358 and 361 strongly modulate the voltage dependence of the channel. We mutate these two residues into all possible remaining amino acids (AAs) and obtain Q-V and G-V curves. We introduced the nonconducting W434F mutation to record sensing currents in all mutants except L361R, which requires K+ depletion because it is affected by W434F...
January 10, 2018: Journal of General Physiology
https://www.readbyqxmd.com/read/29321261/a-model-free-method-for-measuring-dimerization-free-energies-of-clc-ec1-in-lipid-bilayers
#7
Rahul Chadda, Lucy Cliff, Marley Brimberry, Janice L Robertson
The thermodynamic reasons why membrane proteins form stable complexes inside the hydrophobic lipid bilayer remain poorly understood. This is largely because of a lack of membrane-protein systems amenable for equilibrium studies and a limited number of methods for measuring these reactions. Recently, we reported the equilibrium dimerization of the CLC-ec1 Cl-/H+ transporter in lipid bilayers (Chadda et al. 2016. eLife https://doi.org/10.7554/eLife.17438), which provided a new type of model system for studying protein association in membranes...
January 10, 2018: Journal of General Physiology
https://www.readbyqxmd.com/read/29317466/the-relationship-between-form-and-function-throughout-the-history-of-excitation-contraction-coupling
#8
REVIEW
Clara Franzini-Armstrong
The concept of excitation-contraction coupling is almost as old as Journal of General Physiology It was understood as early as the 1940s that a series of stereotyped events is responsible for the rapid contraction response of muscle fibers to an initial electrical event at the surface. These early developments, now lost in what seems to be the far past for most young investigators, have provided an endless source of experimental approaches. In this Milestone in Physiology, I describe in detail the experiments and concepts that introduced and established the field of excitation-contraction coupling in skeletal muscle...
January 9, 2018: Journal of General Physiology
https://www.readbyqxmd.com/read/29301861/molecular-determinants-of-ph-regulation-in-the-cardiac-na-ca2-exchanger
#9
Scott John, Brian Kim, Riccardo Olcese, Joshua I Goldhaber, Michela Ottolia
The cardiac Na+-Ca2+ exchanger (NCX) plays a critical role in the heart by extruding Ca2+ after each contraction and thus regulates cardiac contractility. The activity of NCX is strongly inhibited by cytosolic protons, which suggests that intracellular acidification will have important effects on heart contractility. However, the mechanisms underlying this inhibition remain elusive. It has been suggested that pH regulation originates from the competitive binding of protons to two Ca2+-binding domains within the large cytoplasmic loop of NCX and requires inactivation by intracellular Na+ to fully develop...
January 4, 2018: Journal of General Physiology
https://www.readbyqxmd.com/read/29284662/junctional-trafficking-and-restoration-of-retrograde-signaling-by-the-cytoplasmic-ryr1-domain
#10
Alexander Polster, Stefano Perni, Dilyana Filipova, Ong Moua, Joshua D Ohrtman, Hicham Bichraoui, Kurt G Beam, Symeon Papadopoulos
The type 1 ryanodine receptor (RyR1) in skeletal muscle is a homotetrameric protein that releases Ca2+ from the sarcoplasmic reticulum (SR) in response to an "orthograde" signal from the dihydropyridine receptor (DHPR) in the plasma membrane (PM). Additionally, a "retrograde" signal from RyR1 increases the amplitude of the Ca2+ current produced by CaV1.1, the principle subunit of the DHPR. This bidirectional signaling is thought to depend on physical links, of unknown identity, between the DHPR and RyR1. Here, we investigate whether the isolated cytoplasmic domain of RyR1 can interact structurally or functionally with CaV1...
December 28, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29282210/atp-is-stored-in-lamellar-bodies-to-activate-vesicular-p2x4-in-an-autocrine-fashion-upon-exocytosis
#11
Giorgio Fois, Veronika Eva Winkelmann, Lara Bareis, Laura Staudenmaier, Elena Hecht, Charlotte Ziller, Konstantin Ehinger, Jürgen Schymeinsky, Christine Kranz, Manfred Frick
Vesicular P2X4 receptors are known to facilitate secretion and activation of pulmonary surfactant in the alveoli of the lungs. P2X4 receptors are expressed in the membrane of lamellar bodies (LBs), large secretory lysosomes that store lung surfactant in alveolar type II epithelial cells, and become inserted into the plasma membrane after exocytosis. Subsequent activation of P2X4 receptors by adenosine triphosphate (ATP) results in local fusion-activated cation entry (FACE), facilitating fusion pore dilation, surfactant secretion, and surfactant activation...
December 27, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29259040/small-ca2-releases-enable-hour-long-high-frequency-contractions-in-midshipman-swimbladder-muscle
#12
Frank E Nelson, Stephen Hollingworth, James O Marx, Stephen M Baylor, Lawrence C Rome
Type I males of the Pacific midshipman fish (Porichthys notatus) vibrate their swimbladder to generate mating calls, or "hums," that attract females to their nests. In contrast to the intermittent calls produced by male Atlantic toadfish (Opsanus tau), which occur with a duty cycle (calling time divided by total time) of only 3-8%, midshipman can call continuously for up to an hour. With 100% duty cycles and frequencies of 50-100 Hz (15°C), the superfast muscle fibers that surround the midshipman swimbladder may contract and relax as many as 360,000 times in 1 h...
December 19, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29247050/voltage-modulates-halothane-triggered-ca2-release-in-malignant-hyperthermia-susceptible-muscle
#13
Alberto Zullo, Martin Textor, Philipp Elischer, Stefan Mall, Andreas Alt, Werner Klingler, Werner Melzer
Malignant hyperthermia (MH) is a fatal hypermetabolic state that may occur during general anesthesia in susceptible individuals. It is often caused by mutations in the ryanodine receptor RyR1 that favor drug-induced release of Ca2+ from the sarcoplasmic reticulum. Here, knowing that membrane depolarization triggers Ca2+ release in normal muscle function, we study the cross-influence of membrane potential and anesthetic drugs on Ca2+ release. We used short single muscle fibers of knock-in mice heterozygous for the RyR1 mutation Y524S combined with microfluorimetry to measure intracellular Ca2+ signals...
December 15, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29237756/the-prokaryotic-na-ca2-exchanger-ncx_mj-transports-na-and-ca2-in-a-3-1-stoichiometry
#14
Irina Shlosman, Fabrizio Marinelli, José D Faraldo-Gómez, Joseph A Mindell
Intracellular Ca2+ signals control a wide array of cellular processes. These signals require spatial and temporal regulation of the intracellular Ca2+ concentration, which is achieved in part by a class of ubiquitous membrane proteins known as sodium-calcium exchangers (NCXs). NCXs are secondary-active antiporters that power the translocation of Ca2+ across the cell membrane by coupling it to the flux of Na+ in the opposite direction, down an electrochemical gradient. Na+ and Ca2+ are translocated in separate steps of the antiport cycle, each of which is thought to entail a mechanism whereby ion-binding sites within the protein become alternately exposed to either side of the membrane...
December 13, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29237755/differential-contribution-of-ca2-sources-to-day-and-night-bk-current-activation-in-the-circadian-clock
#15
Joshua P Whitt, Beth A McNally, Andrea L Meredith
Large conductance K+ (BK) channels are expressed widely in neurons, where their activation is regulated by membrane depolarization and intracellular Ca2+ (Ca2+i). To enable this regulation, BK channels functionally couple to both voltage-gated Ca2+ channels (VGCCs) and channels mediating Ca2+ release from intracellular stores. However, the relationship between BK channels and their specific Ca2+ source for particular patterns of excitability is not well understood. In neurons within the suprachiasmatic nucleus (SCN)-the brain's circadian clock-BK current, VGCC current, and Ca2+i are diurnally regulated, but paradoxically, BK current is greatest at night when VGCC current and Ca2+i are reduced...
December 13, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29237754/the-ins-and-outs-of-acid-base-transport-in-skeletal-muscle
#16
Christian Aalkjær, Ole Bækgaard Nielsen
No abstract text is available yet for this article.
December 13, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29233886/structural-insights-into-the-mechanisms-of-cnbd-channel-function
#17
REVIEW
Zachary M James, William N Zagotta
Cyclic nucleotide-binding domain (CNBD) channels are a family of ion channels in the voltage-gated K+ channel superfamily that play crucial roles in many physiological processes. CNBD channels are structurally similar but functionally very diverse. This family includes three subfamilies: (1) the cyclic nucleotide-gated (CNG) channels, which are cation-nonselective, voltage-independent, and cyclic nucleotide-gated; (2) the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which are weakly K+ selective, hyperpolarization-activated, and cyclic nucleotide-gated; and (3) the ether-à-go-go-type (KCNH) channels, which are strongly K+ selective, depolarization-activated, and cyclic nucleotide-independent...
December 12, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29233885/a-perspective-on-na-and-k-channel-inactivation
#18
REVIEW
Clay M Armstrong, Stephen Hollingworth
We are wired with conducting cables called axons that rapidly transmit electrical signals (e.g., "Ouch!") from, for example, the toe to the spinal cord. Because of the high internal resistance of axons (salt water rather than copper), a signal must be reinforced after traveling a short distance. Reinforcement is accomplished by ion channels, Na channels for detecting the signal and reinforcing it by driving it further positive (to near 50 mV) and K channels for then restoring it to the resting level (near -70 mV)...
December 12, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29233884/revisiting-multimodal-activation-and-channel-properties-of-pannexin-1
#19
REVIEW
Yu-Hsin Chiu, Michael S Schappe, Bimal N Desai, Douglas A Bayliss
Pannexin 1 (Panx1) forms plasma membrane ion channels that are widely expressed throughout the body. Panx1 activation results in the release of nucleotides such as adenosine triphosphate and uridine triphosphate. Thus, these channels have been implicated in diverse physiological and pathological functions associated with purinergic signaling, such as apoptotic cell clearance, blood pressure regulation, neuropathic pain, and excitotoxicity. In light of this, substantial attention has been directed to understanding the mechanisms that regulate Panx1 channel expression and activation...
December 12, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29233883/uncorking-ampa-receptors
#20
Caitlin Sedwick
New JGP study explains how auxiliary proteins relieve polyamine block of AMPARs.
December 12, 2017: Journal of General Physiology
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