Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Republic of Korea.
Elife. 2022 Nov 14;11:e69500. doi: 10.7554/eLife.69500.
High-voltage-activated Ca (Ca) channels that adjust Ca influx upon membrane depolarization are differentially regulated by phosphatidylinositol 4,5-bisphosphate (PIP) in an auxiliary Ca β subunit-dependent manner. However, the molecular mechanism by which the β subunits control the PIP sensitivity of Ca channels remains unclear. By engineering various α1B and β constructs in tsA-201 cells, we reported that at least two PIP-binding sites, including the polybasic residues at the C-terminal end of I-II loop and the binding pocket in S4 domain, exist in the Ca2.2 channels. Moreover, they were distinctly engaged in the regulation of channel gating depending on the coupled Ca β2 subunits. The membrane-anchored β subunit abolished the PIP interaction of the phospholipid-binding site in the I-II loop, leading to lower PIP sensitivity of Ca2.2 channels. By contrast, PIP interacted with the basic residues in the S4 domain of Ca2.2 channels regardless of β2 isotype. Our data demonstrated that the anchoring properties of Ca β2 subunits to the plasma membrane determine the biophysical states of Ca2.2 channels by regulating PIP coupling to the nonspecific phospholipid-binding site in the I-II loop.
高电压激活钙 (Ca) 通道在膜去极化时调节 Ca 内流，其受磷脂酰肌醇 4,5-二磷酸 (PIP) 的调节具有辅助 Caβ 亚基依赖性。然而，β 亚基控制 Ca 通道对 PIP 敏感性的分子机制仍不清楚。通过在 tsA-201 细胞中构建各种α1B 和β 构建体，我们报道了至少存在两个 PIP 结合位点，包括 I-II 环末端的多碱性残基和 S4 结构域中的结合口袋，存在于 Ca2.2 通道中。此外，它们根据偶联的 Caβ2 亚基明显参与了通道门控的调节。膜锚定的β亚基消除了 I-II 环中磷脂结合位点与 PIP 的相互作用，导致 Ca2.2 通道对 PIP 的敏感性降低。相比之下，PIP 与 Ca2.2 通道 S4 结构域中的碱性残基相互作用，而与β2 同工型无关。我们的数据表明，Caβ2 亚基与质膜的锚定特性通过调节 PIP 与 I-II 环中非特异性磷脂结合位点的偶联，决定 Ca2.2 通道的生物物理状态。
