scholarly journals Singlet oxygen modification abolishes voltage-dependent inactivation of the sea urchin spHCN channel

2018 ◽  
Vol 150 (9) ◽  
pp. 1273-1286 ◽  
Author(s):  
Vinay Idikuda ◽  
Weihua Gao ◽  
Khade Grant ◽  
Zhuocheng Su ◽  
Qinglian Liu ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Molecular Level ◽  
Basic Research ◽  
Laser Pulses ◽  
Oxygen Species ◽  
Dependent Inactivation ◽  
Activation Gate ◽  
Voltage Dependent ◽  
Short Laser Pulses ◽  
Working Distance

Photochemically or metabolically generated singlet oxygen (1O2) reacts broadly with macromolecules in the cell. Because of its short lifetime and working distance, 1O2 holds potential as an effective and precise nanoscale tool for basic research and clinical practice. Here we investigate the modification of the spHCN channel that results from photochemically and chemically generated 1O2. The spHCN channel shows strong voltage-dependent inactivation in the absence of cAMP. In the presence of photosensitizers, short laser pulses transform the gating properties of spHCN by abolishing inactivation and increasing the macroscopic current amplitude. Alanine replacement of a histidine residue near the activation gate within the channel’s pore abolishes key modification effects. Application of a variety of chemicals including 1O2 scavengers and 1O2 generators supports the involvement of 1O2 and excludes other reactive oxygen species. This study provides new understanding about the photodynamic modification of ion channels by 1O2 at the molecular level.

scholarly journals State-dependent and site-directed photodynamic transformation of HCN2 channel by singlet oxygen

2014 ◽  
Vol 143 (5) ◽  
pp. 633-644 ◽  
Author(s):  
Weihua Gao ◽  
Zhuocheng Su ◽  
Qinglian Liu ◽  
Lei Zhou
Keyword(s):  
Singlet Oxygen ◽  
Basic Research ◽  
Laser Pulses ◽  
Inhibitory Effect ◽  
Biological Molecules ◽  
Hcn Channels ◽  
State Dependent ◽  
C Terminus ◽  
Instantaneous Current ◽  
Cardiac Pacemaking

Singlet oxygen (1O2), which is generated through metabolic reactions and oxidizes numerous biological molecules, has been a useful tool in basic research and clinical practice. However, its role as a signaling factor, as well as a mechanistic understanding of the oxidation process, remains poorly understood. Here, we show that hyperpolarization-activated, cAMP-gated (HCN) channels–which conduct the hyperpolarization-activated current (Ih) and the voltage-insensitive instantaneous current (Iinst), and contribute to diverse physiological functions including learning and memory, cardiac pacemaking, and the sensation of pain–are subject to modification by 1O2. To increase the site specificity of 1O2 generation, we used fluorescein-conjugated cAMP, which specifically binds to HCN channels, or a chimeric channel in which an in-frame 1O2 generator (SOG) protein was fused to the HCN C terminus. Millisecond laser pulses reduced Ih current amplitude, slowed channel deactivation, and enhanced Iinst current. The modification of HCN channel function is a photodynamic process that involves 1O2, as supported by the dependence on dissolved oxygen in solutions, the inhibitory effect by a 1O2 scavenger, and the results with the HCN2-SOG fusion protein. Intriguingly, 1O2 modification of the HCN2 channel is state dependent: laser pulses applied to open channels mainly slow down deactivation and increase Iinst, whereas for the closed channels, 1O2 modification mainly reduced Ih amplitude. We identified a histidine residue (H434 in S6) near the activation gate in the pore critical for 1O2 modulation of HCN function. Alanine replacement of H434 abolished the delay in channel deactivation and the generation of Iinst induced by photodynamic modification. Our study provides new insights into the instantaneous current conducted by HCN channels, showing that modifications to the region close to the intracellular gate underlie the expression of Iinst, and establishes a well-defined model for studying 1O2 modifications at the molecular level.

scholarly journals Molecular endpoints of Ca2+/calmodulin- and voltage-dependent inactivation of Cav1.3 channels

2010 ◽  
Vol 135 (3) ◽  
pp. 197-215 ◽  
Author(s):  
Michael R. Tadross ◽  
Manu Ben Johny ◽  
David T. Yue
Keyword(s):  
Selectivity Filter ◽  
Mutant Library ◽  
Allosteric Inhibition ◽  
Channel Activation ◽  
Channel Modulation ◽  
Dependent Inactivation ◽  
Activation Gate ◽  
Voltage Dependent ◽  
Novel Theory

Ca2+/calmodulin- and voltage-dependent inactivation (CDI and VDI) comprise vital prototypes of Ca2+ channel modulation, rich with biological consequences. Although the events initiating CDI and VDI are known, their downstream mechanisms have eluded consensus. Competing proposals include hinged-lid occlusion of channels, selectivity filter collapse, and allosteric inhibition of the activation gate. Here, novel theory predicts that perturbations of channel activation should alter inactivation in distinctive ways, depending on which hypothesis holds true. Thus, we systematically mutate the activation gate, formed by all S6 segments within CaV1.3. These channels feature robust baseline CDI, and the resulting mutant library exhibits significant diversity of activation, CDI, and VDI. For CDI, a clear and previously unreported pattern emerges: activation-enhancing mutations proportionately weaken inactivation. This outcome substantiates an allosteric CDI mechanism. For VDI, the data implicate a “hinged lid–shield” mechanism, similar to a hinged-lid process, with a previously unrecognized feature. Namely, we detect a “shield” in CaV1.3 channels that is specialized to repel lid closure. These findings reveal long-sought downstream mechanisms of inactivation and may furnish a framework for the understanding of Ca2+ channelopathies involving S6 mutations.

scholarly journals Production of ion beams in high-power laser–plasma interactions and their applications

2004 ◽  
Vol 22 (1) ◽  
pp. 19-24 ◽  
Author(s):  
F. PEGORARO ◽  
S. ATZENI ◽  
M. BORGHESI ◽  
S. BULANOV ◽  
T. ESIRKEPOV ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Medical Physics ◽  
Ion Beam ◽  
Laser Pulses ◽  
Ion Beams ◽  
Laser Plasma Interactions ◽  
Physical Mechanisms ◽  
Short Laser Pulses ◽  
Laser Pulse Intensity ◽  
Target Design

Energetic ion beams are produced during the interaction of ultrahigh-intensity, short laser pulses with plasmas. These laser-produced ion beams have important applications ranging from the fast ignition of thermonuclear targets to proton imaging, deep proton lithography, medical physics, and injectors for conventional accelerators. Although the basic physical mechanisms of ion beam generation in the plasma produced by the laser pulse interaction with the target are common to all these applications, each application requires a specific optimization of the ion beam properties, that is, an appropriate choice of the target design and of the laser pulse intensity, shape, and duration.

Mechanisms of nanoparticle formation by short laser pulses

2007 ◽  
Author(s):  
Tatiana E. Itina ◽  
Mikhail E. Povarnitsyn ◽  
Karine Gouriet ◽  
Sylvie Noël ◽  
Jörg Hermann
Keyword(s):  
Laser Pulses ◽  
Nanoparticle Formation ◽  
Short Laser Pulses

scholarly journals Activation-inactivation of potassium channels and development of the potassium-channel spike in internally perfused squid giant axons.

1981 ◽  
Vol 78 (1) ◽  
pp. 43-61 ◽  
Author(s):  
I Inoue
Keyword(s):  
Potassium Channels ◽  
Potassium Channel ◽  
Voltage Clamp ◽  
Time Constant ◽  
Equilibrium Potential ◽  
Giant Axons ◽  
Dependent Inactivation ◽  
Voltage Dependent ◽  
Time Courses ◽  
Calcium Permeability

A spike that is the result of calcium permeability through potassium channels was separated from the action potential is squid giant axons internally perfused with a 30 mM NaF solution and bathed in a 100 mM CaCl2 solution by blocking sodium channels with tetrodotoxin. Currents through potassium channels were studied under voltage clamp. The records showed a clear voltage-dependent inactivation of the currents. The inactivation was composed of at least two components; one relatively fast, having a time constant of 20--30 ms, and the other very slow, having a time constant of 5--10 s. Voltage clamp was carried out with a variety of salt compositions in both the internal and external solutions. A similar voltage-dependent inactivation, also composed of the two components, was recognized in all the current through potassium channels. Although the direction and intensity of current strongly depended on the salt composition of the solutions, the time-courses of these currents at corresponding voltages were very similar. These results strongly suggest that the inactivation of the currents in attributable to an essential, dynamic property of potassium channels themselves. Thus, the generation of a potassium-channel spike can be understood as an event that occurs when the equilibrium potential across the potassium channel becomes positive.

Multistate non-Hermitian Floquet dynamics in short laser pulses

2000 ◽  
Vol 61 (3) ◽  
Author(s):  
H. C. Day ◽  
Bernard Piraux ◽  
R. M. Potvliege
Keyword(s):  
Laser Pulses ◽  
Short Laser Pulses

Ultra-powerful compact amplifiers for short laser pulses

2000 ◽  
Vol 7 (5) ◽  
pp. 2232-2240 ◽  
Author(s):  
V. M. Malkin ◽  
G. Shvets ◽  
N. J. Fisch
Keyword(s):  
Laser Pulses ◽  
Short Laser Pulses
Sign in / Sign up

Export Citation Format

Share Document