Subconductance Gating and Voltage Sensitivity of Sarcoplasmic Reticulum K+ Channels: A Modeling Approach

被引:8
作者
Matyjaszkiewicz, Antoni [1 ,2 ]
Venturi, Elisa [3 ]
O'Brien, Fiona [3 ]
Iida, Tsunaki [4 ]
Nishi, Miyuki [4 ]
Takeshima, Hiroshi [4 ]
Tsaneva-Atanasova, Krasimira [5 ]
Sitsapesan, Rebecca [3 ]
机构
[1] Univ Bristol, Bristol Ctr Complex Sci, Bristol, Avon, England
[2] Univ Bristol, Dept Engn Math, Bristol, Avon, England
[3] Univ Oxford, Dept Pharmacol, Oxford OX1 3QT, England
[4] Kyoto Univ, Grad Sch Pharmaceut Sci, Sakyo Ward, Kyoto, Japan
[5] Univ Exeter, Coll Engn Math & Phys Sci, Exeter, Devon, England
基金
英国工程与自然科学研究理事会; 日本学术振兴会;
关键词
RECESSIVE OSTEOGENESIS IMPERFECTA; CATION-SELECTIVE CHANNEL; TRIC-A CHANNELS; POTASSIUM CHANNEL; DELETION MUTATION; MISSED EVENTS; ION-CHANNELS; PATCH-CLAMP; MUSCLE; STATE;
D O I
10.1016/j.bpj.2015.06.020
中图分类号
Q6 [生物物理学];
学科分类号
071011 ;
摘要
Sarcoplasmic reticulum (SR) K+ channels are voltage-regulated channels that are thought to be actively gating when the membrane potential across the SR is close to zero as is expected physiologically. A characteristic of SR K+ channels is that they gate to subconductance open states but the relevance of the subconductance events and their contribution to the overall current flowing through the channels at physiological membrane potentials is not known. We have investigated the relationship between subconductance and full conductance openings and developed kinetic models to describe the voltage sensitivity of channel gating. Because there may be two subtypes of SR K+ channels (TRIC-A and TRIC-B) present in most tissues, to conduct our study on a homogeneous population of SR K+ channels, we incorporated SR vesicles derived from Tric-a knockout mice into artificial membranes to examine the remaining SR K+ channel (TRIC-B) function. The channels displayed very low open probability (Po) at negative potentials (<= 0 mV) and opened predominantly to subconductance open states. Positive holding potentials primarily increased the frequency of subconductance state openings and thereby increased the number of subsequent transitions into the full open state, although a slowing of transitions back to the sublevels was also important. We investigated whether the subconductance gating could arise as an artifact of incomplete resolution of rapid transitions between full open and closed states; however, we were not able to produce a model that could fit the data as well as one that included multiple distinct current amplitudes. Our results suggest that the apparent subconductance openings will provide most of the K+ flux when the SR membrane potential is close to zero. The relative contribution played by openings to the full open state would increase if negative charge developed within the SR thus increasing the capacity of the channel to compensate for ionic imbalances.
引用
收藏
页码:265 / 276
页数:12
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