Protein Kinase A Activity Controls the Regulation of T-type CaV3.2 Channels by Gβγ Dimers
Protein Kinase A Activity Controls the Regulation of T-type CaV3.2 Channels by Gβγ Dimers
复制标题
DOI：
10.1074/jbc.m808049200
复制
发表时间：
2009-03-20
影响因子：
4.8
通讯作者：
Barrett, Paula Q.
中科院分区：
文献类型：
--
作者：
Hu, Changlong;Depuy, Seth D.;Barrett, Paula Q.
低电压激活（LVA）， t型，钙通道介导多种生物功能，并被G β - γ二聚体抑制，但通道抑制所需的分子事件尚不清楚。在这里，我们发现蛋白激酶A （PKA）是一个分子开关，允许G β (2) γ x二聚体对Ca(v)3.2通道进行电压无关的抑制。抑制需要磷酸化丝氨酸（1107），这是通道孔蛋白II-III环上的一个关键丝氨酸残基。S1107A可以阻止重组G β (2) γ x二聚体对单一电流的抑制，但不会破坏二聚体的结合，也不会改变其特异性。受体激活后释放的G β -二聚体也需要PKA活性才能发挥抑制作用。因此，多巴胺对Cav3.2全细胞电流的抑制作用被G β - γ清道夫蛋白或阻断PKA催化活性的肽所排除。当受体选择性浓度下单独使用时，D-1或D-2激动剂不会引起通道抑制，而是协同抑制Cav3.2通道电流。我们认为多巴胺通过双受体调节机制来控制Cav3.2通道的活性。例如，这种机制在醛固酮产生的肾上腺肾小球细胞中很重要，因为通道失调会导致醛固酮过量产生，从而导致心脏、肾脏和脑靶器官损伤。
Low voltage-activated (LVA), T-type, calcium channels mediate diverse biological functions and are inhibited by G beta gamma dimers, yet the molecular events required for channel inhibition remain unknown. Here, we identify protein kinase A (PKA) as a molecular switch that allows G beta(2)gamma x dimers to effect voltage-independent inhibition of Ca(v)3.2 channels. Inhibition requires phosphorylation of Ser(1107), a critical serine residue on the II-III loop of the channel pore protein. S1107A prevents inhibition of unitary currents by recombinant G beta(2)gamma x dimers but does not disrupt dimer binding nor change its specificity. G beta gamma dimers released upon receptor activation also require PKA activity for their inhibitory actions. Hence, dopamine inhibition of Cav3.2 whole cell current is precluded by G beta gamma-scavenger proteins or a peptide that blocks PKA catalytic activity. Fittingly, when used alone at receptor-selective concentrations, D-1 or D-2 agonists do not elicit channel inhibition yet together synergize to inhibit Cav3.2 channel currents. We propose that a dual-receptor regulatory mechanism is used by dopamine to control Cav3.2 channel activity. This mechanism, for example, would be important in aldosterone producing adrenal glomerulosa cells where channel dysregulation would lead to overproduction of aldosterone and consequent cardiac, renal, and brain target organ damage.