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Activation Time Constant

The Experts below are selected from a list of 204 Experts worldwide ranked by ideXlab platform

X Shawn Z Xu – 1st expert on this subject based on the ideXlab platform

  • c elegans trp family protein trp 4 is a pore forming subunit of a native mechanotransduction channel
    Neuron, 2010
    Co-Authors: Lijun Kang, William R Schafer, X Shawn Z Xu

    Abstract:

    Summary Mechanotransduction channels mediate several common sensory modalities such as hearing, touch, and proprioception; however, very little is known about the molecular identities of these channels. Many TRP family channels have been implicated in mechanosensation, but none have been demonstrated to form a mechanotransduction channel, raising the question of whether TRP proteins simply play indirect roles in mechanosensation. Using Caenorhabditis elegans as a model, here we have recorded a mechanosensitive conductance in a ciliated mechanosensory neuron in vivo. This conductance develops very rapidly upon mechanical stimulation with its latency and Activation Time Constant reaching the range of microseconds, consistent with mechanical gating of the conductance. TRP-4, a TRPN (NOMPC) subfamily channel, is required for this conductance. Importantly, point mutations in the predicted pore region of TRP-4 alter the ion selectivity of the conductance. These results indicate that TRP-4 functions as an essential pore-forming subunit of a native mechanotransduction channel.

Lijun Kang – 2nd expert on this subject based on the ideXlab platform

  • c elegans trp family protein trp 4 is a pore forming subunit of a native mechanotransduction channel
    Neuron, 2010
    Co-Authors: Lijun Kang, William R Schafer, X Shawn Z Xu

    Abstract:

    Summary Mechanotransduction channels mediate several common sensory modalities such as hearing, touch, and proprioception; however, very little is known about the molecular identities of these channels. Many TRP family channels have been implicated in mechanosensation, but none have been demonstrated to form a mechanotransduction channel, raising the question of whether TRP proteins simply play indirect roles in mechanosensation. Using Caenorhabditis elegans as a model, here we have recorded a mechanosensitive conductance in a ciliated mechanosensory neuron in vivo. This conductance develops very rapidly upon mechanical stimulation with its latency and Activation Time Constant reaching the range of microseconds, consistent with mechanical gating of the conductance. TRP-4, a TRPN (NOMPC) subfamily channel, is required for this conductance. Importantly, point mutations in the predicted pore region of TRP-4 alter the ion selectivity of the conductance. These results indicate that TRP-4 functions as an essential pore-forming subunit of a native mechanotransduction channel.

G. Gueret – 3rd expert on this subject based on the ideXlab platform

  • Sodium Channel Na_V1.5 Expression is Enhanced in Cultured Adult Rat Skeletal Muscle Fibers
    Journal of Membrane Biology, 2010
    Co-Authors: J. Morel, F. Rannou, H. Talarmin, M. A. Giroux-metges, J. P. Pennec, G. Dorange, G. Gueret

    Abstract:

    This study analyzes changes in the distribution, electrophysiological properties, and proteic composition of voltage-gated sodium channels (Na_V) in cultured adult rat skeletal muscle fibers. Patch clamp and molecular biology techniques were carried out in flexor digitorum brevis (FDB) adult rat skeletal muscle fibers maintained in vitro after cell dissociation with collagenase. After 4 days of culture, an increase of the Na_V1.5 channel type was observed. This was confirmed by an increase in TTX-resistant channels and by Western blot test. These channels exhibited increased Activation Time Constant (τ_m) and reduced conductance, similar to what has been observed in denervated muscles in vivo, where the density of Na_V1.5 was increasing progressively after denervation. By real-Time polymerase chain reaction, we found that the expression of β subunits was also modified, but only after 7 days of culture: increase in β_1 without β_4 modifications. β_1 subunit is known to induce a negative shift of the inActivation curve, thus reducing current amplitude and duration. At day 7, τ_h was back to normal and τ_m still increased, in agreement with a decrease in sodium current and conductance at day 4 and normalization at day 7. Our model is a useful tool to study the effects of denervation in adult muscle fibers in vitro and the expression of sodium channels. Our data evidenced an increase in Na_V1.5 channels and the involvement of β subunits in the regulation of sodium current and fiber excitability.