Localized calcineurin confers Ca2+-dependent inactivation on neuronal L-type Ca2+ channels.
Localized calcineurin confers Ca2+-dependent inactivation on neuronal L-type Ca2+ channels.
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DOI：
10.1523/jneurosci.2302-12.2012
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发表时间：
2012-10-31
期刊：
影响因子：
--
通讯作者：
Sather WA
中科院分区：
文献类型：
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作者：
Oliveria SF;Dittmer PJ;Youn DH;Dell'Acqua ML;Sather WA
通过L型电压门控Ca 2+通道的兴奋驱动的Ca 2+进入控制神经元中的基因表达和其他种类的可兴奋细胞中的各种基本活动。CaV1.2 L型通道开放的可能性受到cAMP依赖性蛋白激酶（PKA）的显著增强，PKA通过A-激酶锚定蛋白（AKAP）支架化到CaV1.2通道。CaV1.2通道也通过Ca 2+依赖性失活（CDI）进行负性自身调节，这强烈限制了Ca 2+的进入。大量的证据表明，CDI依赖于Ca 2 +/钙调蛋白（CaM）的CaV1.2 L-型通道的羧基尾部的IQ基序的结合，似乎无关的磷酸化介导的通道增强的分子机制。但我们的工作表明，在培养的海马神经元和异源表达系统中，Ca 2 +/CaM激活的磷酸酶钙调神经磷酸酶（CaN）通过神经元锚定蛋白AKAP 79/150支架化到CaV 1.2通道，并且不能结合CaN的AKAP 79/150突变体（ΔPIX）的过度表达阻碍了CDI。抑制CaN活性的干预措施--其催化位点的突变、环孢霉素A或FK 506的拮抗作用或用模拟磷酸酶自身抑制结构域序列的肽进行细胞内灌注--干扰正常的CDI。在来自ΔPIX敲入小鼠的培养的海马神经元中，不存在CDI。腺苷酸环化酶刺激剂forskolin和PKA抑制剂PKI的实验结果表明，Ca 2 +/CaM激活的CaN通过逆转由激酶如PKA实现的通道增强来促进CDI。因此，我们对AKAP 79/150锚定的CaN的研究调和了基于CaM的CDI模型与基于去磷酸化信号传导的早期似乎矛盾的模型。
Excitation-driven entry of Ca2+ through L-type voltage-gated Ca2+ channels controls gene expression in neurons and a variety of fundamental activities in other kinds of excitable cells. The probability of opening of CaV1.2 L-type channels is subject to pronounced enhancement by cAMP-dependent protein kinase (PKA), which is scaffolded to CaV1.2 channels by A-kinase anchoring proteins (AKAPs). CaV1.2 channels also undergo negative autoregulation via Ca2+-dependent inactivation (CDI), which strongly limits Ca2+ entry. An abundance of evidence indicates that CDI relies upon binding of Ca2+/calmodulin (CaM) to an IQ motif in the carboxy tail of CaV1.2 L-type channels, a molecular mechanism seemingly unrelated to phosphorylation-mediated channel enhancement. But our work reveals, in cultured hippocampal neurons and a heterologous expression system, that the Ca2+/CaM-activated phosphatase calcineurin (CaN) is scaffolded to CaV1.2 channels by the neuronal anchoring protein AKAP79/150 and that over-expression of an AKAP79/150 mutant incapable of binding CaN (ΔPIX) impedes CDI. Interventions that suppress CaN activity—mutation in its catalytic site, antagonism with cyclosporine A or FK506, or intracellular perfusion with a peptide mimicking the sequence of the phosphatase’s autoinhibitory domain—interfere with normal CDI. In cultured hippocampal neurons from a ΔPIX knock-in mouse, CDI is absent. Results of experiments with the adenylyl cyclase stimulator forskolin and with the PKA inhibitor PKI suggest that Ca2+/CaM-activated CaN promotes CDI by reversing channel enhancement effectuated by kinases such as PKA. Hence our investigation of AKAP79/150-anchored CaN reconciles the CaM-based model of CDI with an earlier, seemingly contradictory model based on dephosphorylation signaling.