Translocatable voltage-gated Ca2+ channel β subunits in α1-β complexes reveal competitive replacement yet no spontaneous dissociation.
Translocatable voltage-gated Ca2+ channel β subunits in α1-β complexes reveal competitive replacement yet no spontaneous dissociation.
复制标题
α1-β 复合物中的可易位电压门控 Ca2 通道 β 亚基揭示了竞争性替换，但没有自发解离。
DOI：
10.1073/pnas.1809762115
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发表时间：
2018
影响因子：
11.1
通讯作者：
Suh,Byung-Chang
中科院分区：
文献类型：
--
作者：
Yeon,Jun-Hee;Park,Cheon-Gyu;Hille,Bertil;Suh,Byung-Chang
β subunits of high voltage-gated Ca2+(CaV) channels promote cell-surface expression of pore-forming α1 subunits and regulate channel gating through binding to the α-interaction domain (AID) in the first intracellular loop. We addressed the stability of CaVα1B–β interactions by rapamycin-translocatable CaVβ subunits that allow drug-induced sequestration and uncoupling of the β subunit from CaV2.2 channel complexes in intact cells. Without CaVα1B/α2δ1, all modified β subunits, except membrane-tethered β2a and β2e, are in the cytosol and rapidly translocate upon rapamycin addition to anchors on target organelles: plasma membrane, mitochondria, or endoplasmic reticulum. In cells coexpressing CaVα1B/α2δ1 subunits, the translocatable β subunits colocalize at the plasma membrane with α1B and stay there after rapamycin application, indicating that interactions between α1B and bound β subunits are very stable. However, the interaction becomes dynamic when other competing β isoforms are coexpressed. Addition of rapamycin, then, switches channel gating and regulation by phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] lipid. Thus, expression of free β isoforms around the channel reveals a dynamic aspect to the α1B–β interaction. On the other hand, translocatable β subunits with AID-binding site mutations are easily dissociated from CaVα1B on the addition of rapamycin, decreasing current amplitude and PI(4,5)P2sensitivity. Furthermore, the mutations slow CaV2.2 current inactivation and shift the voltage dependence of activation to more positive potentials. Mutated translocatable β subunits work similarly in CaV2.3 channels. In sum, the strong interaction of CaVα1B–β subunits can be overcome by other free β isoforms, permitting dynamic changes in channel properties in intact cells.
