A type 2A phosphatase-sensitive phosphorylation site controls modal gating of L-type Ca2+ channels in human vascular smooth-muscle cells
A type 2A phosphatase-sensitive phosphorylation site controls modal gating of L-type Ca2+ channels in human vascular smooth-muscle cells
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DOI：
10.1042/bj3180513
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发表时间：
1996-09-01
影响因子：
4.1
通讯作者：
Romanin, C
中科院分区：
文献类型：
--
作者：
Groschner, K;Schuhmann, K;Romanin, C
应用膜片钳技术研究了人脐静脉平滑肌细胞L型钙通道的磷酸化/去磷酸化依赖性调节。冈田酸是磷蛋白磷酸酶1型（PP 1）和2A型（PP 2A）的抑制剂，它增加了完整细胞中通道处于开放状态（P-o）的概率。P-o的这种增加主要是由于促进了持久的通道开放，即促进了“模式2”门控行为。暴露于纯化的PP 2A催化亚基（PP 2A（c））的细胞质侧的切除补丁的膜导致相反的调制通道功能。PP 2A（c）（0.2U/ml）主要通过抑制“模式2”门控来降低Ca ~（2+）通道的P-o。PP 2A（c）的这种作用可被1 μ M冈田酸完全阻止。然而，PP 1的催化亚基（0.2单位/ml）几乎不影响通道活性。我们的研究结果提供了证据，PP 2A敏感的监管网站，控制平滑肌L型钙通道的模式门控。
The patch-clamp technique was employed to investigate phosphorylation/dephosphorylation-dependent modulation of L-type Ca2+ channels in smooth-muscle cells isolated from human umbilical vein. Okadaic acid, an inhibitor of phosphoprotein phosphatases type 1 (PP1) and 2A (PP2A), increased the probability of channels being in the open state (P-o) in intact cells. This increase in P-o was due mainly to promotion of long-lasting channel openings, i.e. promotion of 'mode 2' gating behaviour. Exposure of the cytoplasmic side of excised patches of membrane to the purified catalytic subunit of PP2A (PP2A(c)) resulted in the opposite modulation of channel function. PP2A(c) (0.2 unit/ml) reduced the P-o of Ca2+ channels mainly via suppression of 'mode 2' gating. This effect of PP2A(c) was completely prevented by 1 mu M okadaic acid. The catalytic subunit of PP1 (0.2 unit/ml), however, barely affected channel activity. Our results provide evidence for a PP2A-sensitive regulatory site that controls modal gating of L-type Ca2+ channels in smooth muscle.