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Journal of General Physiology

Anne C Wolfes, Saheeb Ahmed, Ankit Awasthi, Markus A Stahlberg, Ashish Rajput, Daniel S Magruder, Stefan Bonn, Camin Dean
Interactions between astrocytes and neurons rely on the release and uptake of glial and neuronal molecules. But whether astrocytic vesicles exist and exocytose in a regulated or constitutive fashion is under debate. The majority of studies have relied on indirect methods or on astrocyte cultures that do not resemble stellate astrocytes found in vivo. Here, to investigate vesicle-associated proteins and exocytosis in stellate astrocytes specifically, we developed a simple, fast, and economical method for growing stellate astrocyte monocultures...
December 1, 2016: Journal of General Physiology
Daniel R Miranda, Monica Wong, Shannon H Romer, Cynthia McKee, Gabriela Garza-Vasquez, Alyssa C Medina, Volker Bahn, Andrew D Steele, Robert J Talmadge, Andrew A Voss
Huntington's disease (HD) patients suffer from progressive and debilitating motor dysfunction. Previously, we discovered reduced skeletal muscle chloride channel (ClC-1) currents, inwardly rectifying potassium (Kir) channel currents, and membrane capacitance in R6/2 transgenic HD mice. The ClC-1 loss-of-function correlated with increased aberrant mRNA processing and decreased levels of full-length ClC-1 mRNA (Clcn1 gene). Physiologically, the resulting muscle hyperexcitability may help explain involuntary contractions of HD...
November 29, 2016: Journal of General Physiology
Srboljub M Mijailovich, Oliver Kayser-Herold, Boban Stojanovic, Djordje Nedic, Thomas C Irving, Michael A Geeves
The effect of molecule tethering in three-dimensional (3-D) space on bimolecular binding kinetics is rarely addressed and only occasionally incorporated into models of cell motility. The simplest system that can quantitatively determine this effect is the 3-D sarcomere lattice of the striated muscle, where tethered myosin in thick filaments can only bind to a relatively small number of available sites on the actin filament, positioned within a limited range of thermal movement of the myosin head. Here we implement spatially explicit actomyosin interactions into the multiscale Monte Carlo platform MUSICO, specifically defining how geometrical constraints on tethered myosins can modulate state transition rates in the actomyosin cycle...
December 2016: Journal of General Physiology
Byung-Ju Jin, Alex J Smith, Alan S Verkman
A "glymphatic system," which involves convective fluid transport from para-arterial to paravenous cerebrospinal fluid through brain extracellular space (ECS), has been proposed to account for solute clearance in brain, and aquaporin-4 water channels in astrocyte endfeet may have a role in this process. Here, we investigate the major predictions of the glymphatic mechanism by modeling diffusive and convective transport in brain ECS and by solving the Navier-Stokes and convection-diffusion equations, using realistic ECS geometry for short-range transport between para-arterial and paravenous spaces...
December 2016: Journal of General Physiology
Vanessa Leone, José D Faraldo-Gómez
Two subunits within the transmembrane domain of the ATP synthase-the c-ring and subunit a-energize the production of 90% of cellular ATP by transducing an electrochemical gradient of H(+) or Na(+) into rotational motion. The nature of this turbine-like energy conversion mechanism has been elusive for decades, owing to the lack of definitive structural information on subunit a or its c-ring interface. In a recent breakthrough, several structures of this complex were resolved by cryo-electron microscopy (cryo-EM), but the modest resolution of the data has led to divergent interpretations...
December 2016: Journal of General Physiology
Guruprasad Kuntamallappanavar, Alex M Dopico
In most mammalian tissues, Ca(2+)i/voltage-gated, large conductance K(+) (BK) channels consist of channel-forming slo1 and auxiliary (β1-β4) subunits. When Ca(2+)i (3-20 µM) reaches the vicinity of BK channels and increases their activity at physiological voltages, β1- and β4-containing BK channels are, respectively, inhibited and potentiated by intoxicating levels of ethanol (50 mM). Previous studies using different slo1s, lipid environments, and Ca(2+)i concentrations-all determinants of the BK response to ethanol-made it impossible to determine the specific contribution of β subunits to ethanol action on BK activity...
November 2016: Journal of General Physiology
Medha M Pathak, Truc Tran, Liang Hong, Béla Joós, Catherine E Morris, Francesco Tombola
The voltage-gated proton channel, Hv1, is expressed in tissues throughout the body and plays important roles in pH homeostasis and regulation of NADPH oxidase. Hv1 operates in membrane compartments that experience strong mechanical forces under physiological or pathological conditions. In microglia, for example, Hv1 activity is potentiated by cell swelling and causes an increase in brain damage after stroke. The channel complex consists of two proton-permeable voltage-sensing domains (VSDs) linked by a cytoplasmic coiled-coil domain...
November 2016: Journal of General Physiology
Grace Jeng, Muskaan Aggarwal, Wei-Ping Yu, Tsung-Yu Chen
The TMEM16 family encompasses Ca(2+)-activated Cl(-) channels (CaCCs) and lipid scramblases. These proteins are formed by two identical subunits, as confirmed by the recently solved crystal structure of a TMEM16 lipid scramblase. However, the high-resolution structure did not provide definitive information regarding the pore architecture of the TMEM16 channels. In this study, we express TMEM16A channels constituting two covalently linked subunits with different Ca(2+) affinities. The dose-response curve of the heterodimer appears to be a weighted sum of two dose-response curves-one corresponding to the high-affinity subunit and the other to the low-affinity subunit...
November 2016: Journal of General Physiology
Novandy K Lim, Andy K M Lam, Raimund Dutzler
The TMEM16 proteins constitute a family of membrane proteins with unusual functional breadth, including lipid scramblases and Cl(-) channels. Members of both these branches are activated by Ca(2+), acting from the intracellular side, and probably share a common architecture, which was defined in the recent structure of the lipid scramblase nhTMEM16. The structural features of subunits and the arrangement of Ca(2+)-binding sites in nhTMEM16 suggest that the dimeric protein harbors two locations for catalysis that are independent with respect to both activation and lipid conduction...
November 2016: Journal of General Physiology
H Criss Hartzell, Jarred M Whitlock
No abstract text is available yet for this article.
November 2016: Journal of General Physiology
Bernhard E Flucher
No abstract text is available yet for this article.
October 2016: Journal of General Physiology
Seiichi Tsukamoto, Teruyuki Fujii, Kotaro Oyama, Seine A Shintani, Togo Shimozawa, Fuyu Kobirumaki-Shimozawa, Shin'ichi Ishiwata, Norio Fukuda
In cardiac muscle, contraction is triggered by sarcolemmal depolarization, resulting in an intracellular Ca(2+) transient, binding of Ca(2+) to troponin, and subsequent cross-bridge formation (excitation-contraction [EC] coupling). Here, we develop a novel experimental system for simultaneous nano-imaging of intracellular Ca(2+) dynamics and single sarcomere length (SL) in rat neonatal cardiomyocytes. We achieve this by expressing a fluorescence resonance energy transfer (FRET)-based Ca(2+) sensor yellow Cameleon-Nano (YC-Nano) fused to α-actinin in order to localize to the Z disks...
October 2016: Journal of General Physiology
Nawreen Rahman, Lavoisier Ramos-Espiritu, Teresa A Milner, Jochen Buck, Lonny R Levin
Lysosomes, the degradative organelles of the endocytic and autophagic pathways, function at an acidic pH. Lysosomes are acidified by the proton-pumping vacuolar ATPase (V-ATPase), but the molecular processes that set the organelle's pH are not completely understood. In particular, pH-sensitive signaling enzymes that can regulate lysosomal acidification in steady-state physiological conditions have yet to be identified. Soluble adenylyl cyclase (sAC) is a widely expressed source of cAMP that serves as a physiological pH sensor in cells...
October 2016: Journal of General Physiology
Lucien Fabre, Eugenio Santelli, Driss Mountassif, Annemarie Donoghue, Aviroop Biswas, Rikard Blunck, Dorit Hanein, Niels Volkmann, Robert Liddington, Isabelle Rouiller
Anthrax toxin comprises three soluble proteins: protective antigen (PA), lethal factor (LF), and edema factor (EF). PA must be cleaved by host proteases before it oligomerizes and forms a prepore, to which LF and EF bind. After endocytosis of this tripartite complex, the prepore transforms into a narrow transmembrane pore that delivers unfolded LF and EF into the host cytosol. Here, we find that translocation of multiple 90-kD LF molecules is rapid and efficient. To probe the molecular basis of this translocation, we calculated a three-dimensional map of the fully loaded (PA63)7-(LF)3 prepore complex by cryo-electron microscopy (cryo-EM)...
October 2016: Journal of General Physiology
Bryan A Krantz
No abstract text is available yet for this article.
October 2016: Journal of General Physiology
Gianluca Pietra, Michele Dibattista, Anna Menini, Johannes Reisert, Anna Boccaccio
The Ca(2+)-activated Cl(-) channel TMEM16B is highly expressed in the cilia of olfactory sensory neurons (OSNs). Although a large portion of the odor-evoked transduction current is carried by Ca(2+)-activated Cl(-) channels, their role in olfaction is still controversial. A previous report (Billig et al. 2011. Nat. Neurosci. showed that disruption of the TMEM16b/Ano2 gene in mice abolished Ca(2+)-activated Cl(-) currents in OSNs but did not produce any major change in olfactory behavior...
October 2016: Journal of General Physiology
David Naranjo, Hans Moldenhauer, Matías Pincuntureo, Ignacio Díaz-Franulic
Ion channels are membrane proteins that mediate efficient ion transport across the hydrophobic core of cell membranes, an unlikely process in their absence. K(+) channels discriminate K(+) over cations with similar radii with extraordinary selectivity and display a wide diversity of ion transport rates, covering differences of two orders of magnitude in unitary conductance. The pore domains of large- and small-conductance K(+) channels share a general architectural design comprising a conserved narrow selectivity filter, which forms intimate interactions with permeant ions, flanked by two wider vestibules toward the internal and external openings...
October 2016: Journal of General Physiology
David Fleck, Nadine Mundt, Felicitas Bruentgens, Petra Geilenkirchen, Patricia A Machado, Thomas Veitinger, Sophie Veitinger, Susanne M Lipartowski, Corinna H Engelhardt, Marco Oldiges, Jennifer Spehr, Marc Spehr
Spermatogenesis ranks among the most complex, yet least understood, developmental processes. The physiological principles that control male germ cell development in mammals are notoriously difficult to unravel, given the intricate anatomy and complex endo- and paracrinology of the testis. Accordingly, we lack a conceptual understanding of the basic signaling mechanisms within the testis, which control the seminiferous epithelial cycle and thus govern spermatogenesis. Here, we address paracrine signal transduction in undifferentiated male germ cells from an electrophysiological perspective...
September 2016: Journal of General Physiology
Laurent Pinelli, Antoine Nissant, Aurélie Edwards, Stéphane Lourdel, Jacques Teulon, Marc Paulais
ClC-K2, a member of the ClC family of Cl(-) channels and transporters, forms the major basolateral Cl(-) conductance in distal nephron epithelial cells and therefore plays a central role in renal Cl(-) absorption. However, its regulation remains largely unknown because of the fact that recombinant ClC-K2 has not yet been studied at the single-channel level. In the present study, we investigate the effects of voltage, pH, Cl(-), and Ca(2+) on native ClC-K2 in the basolateral membrane of intercalated cells from the mouse connecting tubule...
September 2016: Journal of General Physiology
Ida Björkgren, Polina V Lishko
No abstract text is available yet for this article.
September 2016: Journal of General Physiology
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