scholarly journals Elimination of the Actin-Binding Domain in Kelch-Like 1 Protein Induces T-Type Calcium Channel Modulation Only in the Presence of Action Potential Waveforms

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Kelly A. Aromolaran ◽  
Kelly A. Benzow ◽  
Leanne L. Cribbs ◽  
Michael D. Koob ◽  
Erika S. Piedras-Rentería
Keyword(s):  
Action Potential ◽  
Calcium Channel ◽  
Conformational Changes ◽  
Current Density ◽  
Calcium Influx ◽  
Direct Interaction ◽  
Recovery Phase ◽  
Actin Binding ◽  
Kinetic Properties ◽  
Action Potential Waveform

The Kelch-like 1 protein (KLHL1) is a neuronal actin-binding protein that modulates calcium channel function. It increases the current density of Cav3.2 (α1H) calcium channels via direct interaction with α1H and actin-F, resulting in biophysical changes in Cav3.2 currents and an increase in recycling endosomal activity with subsequent increased α1H channel number at the plasma membrane. Interestingly, removal of the actin-binding Kelch motif (ΔKelch) prevents the increase in Cav3.2 current density seen with wild-type KLHL1 when tested with normal square pulse protocols but does not preclude the effect when tested using action potential waveforms (AP). Here, we dissected the kinetic properties of the AP waveform that confer the mutant Kelch the ability to interact with Cav3.2 and induce an increase in calcium influx. We modified the action potential waveform by altering the slopes of repolarization and/or recovery from hyperpolarization or by changing the duration of the depolarization plateau or the hyperpolarization phase and tested the modulation of Cav3.2 by the mutant ΔKelch. Our results show that the recovery phase from hyperpolarization phase determines the conformational changes that allow the α1H subunit to properly interact with mutant KLHL1 lacking its actin-binding Kelch domains, leading to increased Ca influx.

scholarly journals Homeostatic synaptic depression is achieved through a regulated decrease in presynaptic calcium channel abundance

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Michael A Gaviño ◽  
Kevin J Ford ◽  
Santiago Archila ◽  
Graeme W Davis
Keyword(s):  
Synaptic Plasticity ◽  
Neuromuscular Junction ◽  
Action Potential ◽  
Calcium Channel ◽  
Neurotransmitter Release ◽  
Calcium Influx ◽  
Homeostatic Synaptic Plasticity ◽  
Action Potential Waveform ◽  
Presynaptic Calcium ◽  
Potential Waveform

Homeostatic signaling stabilizes synaptic transmission at the neuromuscular junction (NMJ) of Drosophila, mice, and human. It is believed that homeostatic signaling at the NMJ is bi-directional and considerable progress has been made identifying mechanisms underlying the homeostatic potentiation of neurotransmitter release. However, very little is understood mechanistically about the opposing process, homeostatic depression, and how bi-directional plasticity is achieved. Here, we show that homeostatic potentiation and depression can be simultaneously induced, demonstrating true bi-directional plasticity. Next, we show that mutations that block homeostatic potentiation do not alter homeostatic depression, demonstrating that these are genetically separable processes. Finally, we show that homeostatic depression is achieved by decreased presynaptic calcium channel abundance and calcium influx, changes that are independent of the presynaptic action potential waveform. Thus, we identify a novel mechanism of homeostatic synaptic plasticity and propose a model that can account for the observed bi-directional, homeostatic control of presynaptic neurotransmitter release.

Nifedipine, A Promising Drug for Prevention of Heart Changes During Weightlessness

1988 ◽  
Vol 46 ◽  
pp. 130-131
Author(s):  
D.E. Philpott ◽  
K. Kato ◽  
J. Stevenson ◽  
J. Miguel ◽  
W. Sapp
Keyword(s):  
Calcium Channel ◽  
Structural Changes ◽  
Channel Blocker ◽  
Calcium Influx ◽  
Space Station ◽  
Recovery Phase ◽  
Channel Blockers ◽  
Simulated Weightlessness ◽  
Heart Attacks ◽  
Limited Success

NASA plans to have a space station operating in 1994 and is considering a 30 month Mars flight. These plans call for exposure to microgravity for longer periods of time than space travelers have endured to date. Vascular deconditioning is known to occur during space flight and during simulated weightlessness. The degree of deconditioning for these extended flights and the amount of possible reversibility is unknown. If a sudden demanding burden should be placed on the astronaut after prolonged deconditioning, there could be serious consequences. Exercise has been tried with limited success. What is needed is a counter measure to deconditioning. Calcium channel blockers are known to protect the heart during the recovery phase after heart attacks by regulating the calcium influx, thus protecting the cell and mitochondria from calcium overload. Sudden demands also increase blood flow, mimicking the post attack reperfusion, and could be serious for a deconditioned heart. We have found nifedipine, a calcium channel blocker, to be a promising drug for prevention of structural changes during simulated weightlessness.

scholarly journals The active-zone protein Munc13 controls the use-dependence of presynaptic voltage-gated calcium channels

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Nathaniel Calloway ◽  
Géraldine Gouzer ◽  
Mingyu Xue ◽  
Timothy A Ryan
Keyword(s):  
Action Potential ◽  
Calcium Channel ◽  
Active Zone ◽  
Information Transfer ◽  
Calcium Influx ◽  
Single Action ◽  
Synaptic Modulation ◽  
Voltage Gated ◽  
Presynaptic Calcium

Presynaptic calcium channel function is critical for converting electrical information into chemical communication but the molecules in the active zone that sculpt this function are poorly understood. We show that Munc13, an active-zone protein essential for exocytosis, also controls presynaptic voltage-gated calcium channel (VGCC) function dictating their behavior during various forms of activity. We demonstrate that in vitro Munc13 interacts with voltage-VGCCs via a pair of basic residues in Munc13's C2B domain. We show that elimination of this interaction by either removal of Munc13 or replacement of Munc13 with a Munc13 C2B mutant alters synaptic VGCC's response to and recovery from high-frequency action potential bursts and alters calcium influx from single action potential stimuli. These studies illustrate a novel form of synaptic modulation and show that Munc13 is poised to profoundly impact information transfer at nerve terminals by controlling both vesicle priming and the trigger for exocytosis.

scholarly journals KCNQ channels enable reliable presynaptic spiking and synaptic transmission at high-frequency

2019 ◽  
Author(s):  
Yihui Zhang ◽  
Dainan Li ◽  
Youad Darwish ◽  
Laurence O. Trussell ◽  
Hai Huang
Keyword(s):  
Action Potential ◽  
Synaptic Transmission ◽  
High Frequency ◽  
Calcium Influx ◽  
List Type ◽  
Kcnq Channels ◽  
Axon Terminals ◽  
Presynaptic Action ◽  
Action Potential Waveform ◽  
Potential Waveform

SUMMARYThe presynaptic action potential (AP) results in calcium influx which triggers neurotransmitter release. For this reason, the AP waveform is crucial in determining the timing and strength of synaptic transmission. The calyx of Held nerve terminals of rat show minimum changes in AP waveform during high-frequency AP firing. We found that the stability of the calyceal AP waveform requires KCNQ K+ channel activated during high-frequency spiking activity. High-frequency presynaptic spikes gradually led to accumulation of KCNQ channels in open states which kept interspike membrane potential sufficiently negative to maintain Na+ channel availability. Accordingly, blocking KCNQ channels during stimulus trains led to inactivation of presynaptic Na+, and to a lesser extent KV1 channels, thereby reducing the AP height and broadening AP duration. Thus, while KCNQ channels are generally thought to prevent hyperactivity of neurons, we find that in axon terminals these channels function to facilitate high-frequency firing needed for sensory coding.HIGHLIGHTSKCNQ channels are activated during high-frequency firingThe activity of KCNQ channels helps the recovery of Na+ and KV1 channels from inactivation and maintains action potential waveformReliable presynaptic action potential waveform preserves stable Ca2+ influx and reliable synaptic signaling

Polarization and interaction of adhesion molecules P-selectin glycoprotein ligand 1 and intercellular adhesion molecule 3 with moesin and ezrin in myeloid cells

Blood ◽  
2000 ◽  
Vol 95 (7) ◽  
pp. 2413-2419 ◽  
Author(s):  
José L. Alonso-Lebrero ◽  
Juan M. Serrador ◽  
Carmen Domı́nguez-Jiménez ◽  
Olga Barreiro ◽  
Alfonso Luque ◽  
...  
Keyword(s):  
Adhesion Molecules ◽  
Adhesion Molecule ◽  
Direct Interaction ◽  
Intercellular Adhesion ◽  
Actin Binding ◽  
Intercellular Adhesion Molecule ◽  
Human Neutrophils ◽  
Binding Assays ◽  
Glutathione S Transferase ◽  
Amino Terminal

Abstract In response to the chemoattractants interleukin 8, C5a,N-formyl-methionyl-leucyl-phenylalanine, and interleukin 15, adhesion molecules P-selectin glycoprotein ligand 1 (PSGL-1), intercellular adhesion molecule 3 (ICAM-3), CD43, and CD44 are redistributed to a newly formed uropod in human neutrophils. The adhesion molecules PSGL-1 and ICAM-3 were found to colocalize with the cytoskeletal protein moesin in the uropod of stimulated neutrophils. Interaction of PSGL-1 with moesin was shown in HL-60 cell lysates by isolating a complex with glutathione S-transferase fusions of the cytoplasmic domain of PSGL-1. Bands of 78- and 81-kd were identified as moesin and ezrin by Western blot analysis. ICAM-3 and moesin also coeluted from neutrophil lysates with an anti-ICAM-3 immunoaffinity assay. Direct interaction of the cytoplasmic domains of ICAM-3 and PSGL-1 with the amino-terminal domain of recombinant moesin was demonstrated by protein-protein binding assays. These results suggest that the redistribution of PSGL-1 and its association with intracellular molecules, including the ezrin-radixin-moesin actin-binding proteins, regulate functions mediated by PSGL-1 in leukocytes stimulated by chemoattractants.

scholarly journals Inhibition of acanthamoeba actomyosin-II ATPase activity and mechanochemical function by specific monoclonal antibodies.

1984 ◽  
Vol 99 (3) ◽  
pp. 1024-1033 ◽  
Author(s):  
D P Kiehart ◽  
T D Pollard
Keyword(s):  
Monoclonal Antibodies ◽  
Atpase Activity ◽  
Conformational Changes ◽  
Binding Sites ◽  
Polyclonal Antibodies ◽  
Myosin Ii ◽  
Antigenic Site ◽  
Actin Binding ◽  
Filamentous Form ◽  
Antibody Effects

Monoclonal and polyclonal antibodies that bind to myosin-II were tested for their ability to inhibit myosin ATPase activity, actomyosin ATPase activity, and contraction of cytoplasmic extracts. Numerous antibodies specifically inhibit the actin activated Mg++-ATPase activity of myosin-II in a dose-dependent fashion, but none blocked the ATPase activity of myosin alone. Control antibodies that do not bind to myosin-II and several specific antibodies that do bind have no effect on the actomyosin-II ATPase activity. In most cases, the saturation of a single antigenic site on the myosin-II heavy chain is sufficient for maximal inhibition of function. Numerous monoclonal antibodies also block the contraction of gelled extracts of Acanthamoeba cytoplasm. No polyclonal antibodies tested inhibited ATPase activity or gel contraction. As expected, most antibodies that block actin-activated ATPase activity also block gel contraction. Exceptions were three antibodies M2.2, -15, and -17, that appear to uncouple the ATPase activity from gel contraction: they block gel contraction without influencing ATPase activity. The mechanisms of inhibition of myosin function depends on the location of the antibody-binding sites. Those inhibitory antibodies that bind to the myosin-II heads presumably block actin binding or essential conformational changes in the myosin heads. A subset of the antibodies that bind to the proximal end of the myosin-II tail inhibit actomyosin-II ATPase activity and gel contraction. Although this part of the molecule is presumably some distance from the ATP and actin-binding sites, these antibody effects suggest that structural domains in this region are directly involved with or coupled to catalysis and energy transduction. A subset of the antibodies that bind to the tip of the myosin-II tail appear to inhibit ATPase activity and contraction through their inhibition of filament formation. They provide strong evidence for a substantial enhancement of the ATPase activity of myosin molecules in filamentous form and suggest that the myosin filaments may be required for cell motility.

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