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Enhanced activity of multiple TRIC-B channels : an endoplasmic reticulum/sarcoplasmic reticulum mechanism to boost counterion currents

(2019) JOURNAL OF PHYSIOLOGY-LONDON. 597(10). p.2691-2705
Author
Organization
Abstract
The trimeric intracellular cation channels, TRIC-A and TRIC-B, represent two subtypes of sarcoplasmic reticulum (SR) K+-channel but their individual functional roles are unknown. We therefore compared the biophysical properties of SR K+-channels derived from the skeletal muscle of wild-type (WT) or Tric-a knockout (KO) mice. Because TRIC-A is the major TRIC-subtype in skeletal muscle, WT SR will predominantly contain TRIC-A channels, whereas Tric-a KO SR will only contain TRIC-B channels. When lone SR K+-channels were incorporated into bilayers, the open probability (Po) of channels from Tric-a KO mice was markedly lower than that of channels from WT mice; gating was characterized by shorter opening bursts and more frequent brief subconductance openings. However, unlike channels from WT mice, the Po of SR K+-channels from Tric-a KO mice increased as increasing channel numbers were present in the bilayer, driving the channels into long sojourns in the fully open state. When co-incorporated into bilayers, ryanodine receptor channels did not directly affect the gating of SR K+-channels, nor did the presence or absence of SR K+-channels influence ryanodine receptor activity. We suggest that because of high expression levels in striated muscle, TRIC-A produces most of the counterion flux required during excitation-contraction coupling. TRIC-B, in contrast, is sparsely expressed in most cells and, although lone TRIC-B channels exhibit low Po, the high Po levels reached by multiple TRIC-B channels may provide a compensatory mechanism to rapidly restore K+ gradients and charge differences across the SR of tissues containing few TRIC-A channels.
Keywords
Ca2+ release, TRIC channels, sarcoplasmic reticulum, Ryanodine receptor, FRAGMENTED SARCOPLASMIC-RETICULUM, CALCIUM-RELEASE CHANNELS, SELECTIVE CHANNEL, K+ CHANNELS, DELETION MUTATION, CONDUCTANCE, CA2+, VOLTAGE, MUSCLE, BLOCK

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MLA
O’Brien, Fiona, et al. “Enhanced Activity of Multiple TRIC-B Channels : An Endoplasmic Reticulum/Sarcoplasmic Reticulum Mechanism to Boost Counterion Currents.” JOURNAL OF PHYSIOLOGY-LONDON, vol. 597, no. 10, 2019, pp. 2691–705.
APA
O’Brien, F., Eberhardt, D., Witschas, K., El-Ajouz, S., Ida, T., Nishi, M., … Venturi, E. (2019). Enhanced activity of multiple TRIC-B channels : an endoplasmic reticulum/sarcoplasmic reticulum mechanism to boost counterion currents. JOURNAL OF PHYSIOLOGY-LONDON, 597(10), 2691–2705.
Chicago author-date
O’Brien, Fiona, David Eberhardt, Katja Witschas, Sam El-Ajouz, Tsunaki Ida, Miyuki Nishi, Hiroshi Takeshima, Rebecca Sitsapesan, and Elisa Venturi. 2019. “Enhanced Activity of Multiple TRIC-B Channels : An Endoplasmic Reticulum/Sarcoplasmic Reticulum Mechanism to Boost Counterion Currents.” JOURNAL OF PHYSIOLOGY-LONDON 597 (10): 2691–2705.
Chicago author-date (all authors)
O’Brien, Fiona, David Eberhardt, Katja Witschas, Sam El-Ajouz, Tsunaki Ida, Miyuki Nishi, Hiroshi Takeshima, Rebecca Sitsapesan, and Elisa Venturi. 2019. “Enhanced Activity of Multiple TRIC-B Channels : An Endoplasmic Reticulum/Sarcoplasmic Reticulum Mechanism to Boost Counterion Currents.” JOURNAL OF PHYSIOLOGY-LONDON 597 (10): 2691–2705.
Vancouver
1.
O’Brien F, Eberhardt D, Witschas K, El-Ajouz S, Ida T, Nishi M, et al. Enhanced activity of multiple TRIC-B channels : an endoplasmic reticulum/sarcoplasmic reticulum mechanism to boost counterion currents. JOURNAL OF PHYSIOLOGY-LONDON. 2019;597(10):2691–705.
IEEE
[1]
F. O’Brien et al., “Enhanced activity of multiple TRIC-B channels : an endoplasmic reticulum/sarcoplasmic reticulum mechanism to boost counterion currents,” JOURNAL OF PHYSIOLOGY-LONDON, vol. 597, no. 10, pp. 2691–2705, 2019.
@article{8609527,
  abstract     = {The trimeric intracellular cation channels, TRIC-A and TRIC-B, represent two subtypes of sarcoplasmic reticulum (SR) K+-channel but their individual functional roles are unknown. We therefore compared the biophysical properties of SR K+-channels derived from the skeletal muscle of wild-type (WT) or Tric-a knockout (KO) mice. Because TRIC-A is the major TRIC-subtype in skeletal muscle, WT SR will predominantly contain TRIC-A channels, whereas Tric-a KO SR will only contain TRIC-B channels. When lone SR K+-channels were incorporated into bilayers, the open probability (Po) of channels from Tric-a KO mice was markedly lower than that of channels from WT mice; gating was characterized by shorter opening bursts and more frequent brief subconductance openings. However, unlike channels from WT mice, the Po of SR K+-channels from Tric-a KO mice increased as increasing channel numbers were present in the bilayer, driving the channels into long sojourns in the fully open state. When co-incorporated into bilayers, ryanodine receptor channels did not directly affect the gating of SR K+-channels, nor did the presence or absence of SR K+-channels influence ryanodine receptor activity. We suggest that because of high expression levels in striated muscle, TRIC-A produces most of the counterion flux required during excitation-contraction coupling. TRIC-B, in contrast, is sparsely expressed in most cells and, although lone TRIC-B channels exhibit low Po, the high Po levels reached by multiple TRIC-B channels may provide a compensatory mechanism to rapidly restore K+ gradients and charge differences across the SR of tissues containing few TRIC-A channels.},
  author       = {O'Brien, Fiona and Eberhardt, David and Witschas, Katja and El-Ajouz, Sam and Ida, Tsunaki and Nishi, Miyuki and Takeshima, Hiroshi and Sitsapesan, Rebecca and Venturi, Elisa},
  issn         = {0022-3751},
  journal      = {JOURNAL OF PHYSIOLOGY-LONDON},
  keywords     = {Ca2+ release,TRIC channels,sarcoplasmic reticulum,Ryanodine receptor,FRAGMENTED SARCOPLASMIC-RETICULUM,CALCIUM-RELEASE CHANNELS,SELECTIVE CHANNEL,K+ CHANNELS,DELETION MUTATION,CONDUCTANCE,CA2+,VOLTAGE,MUSCLE,BLOCK},
  language     = {eng},
  number       = {10},
  pages        = {2691--2705},
  title        = {Enhanced activity of multiple TRIC-B channels : an endoplasmic reticulum/sarcoplasmic reticulum mechanism to boost counterion currents},
  url          = {http://dx.doi.org/10.1113/JP277241},
  volume       = {597},
  year         = {2019},
}

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