Krieger Andreas, Radhakrishnan Kayalvizhi, Pereverzev Alexey, Siapich Siarhei A, Banat Mohammed, Kamp Marcel A, Leroy Jérome, Klöckner Udo, Hescheler Jürgen, Weiergräber Marco, Schneider Toni
Institute for Neurophysiology, University of Cologne, Germany.
Cell Physiol Biochem. 2006;17(3-4):97-110. doi: 10.1159/000092071. Epub 2006 Mar 14.
Multiple types of voltage-activated Ca2+ channels (T, L, N, P, Q, R type) coexist in excitable cells and participate in synaptic differentiation, secretion, transmitter release, and neuronal plasticity. Ca2+ ions entering cells trigger these events through their interaction with the ion channel itself or through Ca2+ binding to target proteins initiating signalling cascades at cytosolic loops of the ion conducting subunit (Cava1). These loops interact with target proteins in a Ca2+-dependent or independent manner. In Cav2.3-containing channels the cytosolic linker between domains II and III confers a novel Ca2+ sensitivity to E-type Ca2+ channels including phorbol ester sensitive signalling via protein kinase C (PKC) in Cav2.3 transfected HEK-293 cells. To understand Ca2+ and phorbol ester mediated activation of Cav2.3 Ca2+ channels, protein interaction partners of the II-III loop were identified. FLAG-tagged II-III - loop of human Cav2.3 was over-expressed in HEK 293 cells, and the molecular chaperone hsp70, which is known to interact with PKC, was identified as a novel functional interaction partner. Immunopurified II-III loop-protein of neuronal and endocrine Cav2.3 splice variants stimulate autophosphorylation of PKCa, leading to the suggestion that hsp70--binding to the II-III loop--may act as an adaptor for Ca2+ dependent targeting of PKC to E-type Ca2+ channels.
多种类型的电压激活钙通道（T型、L型、N型、P型、Q型、R型）共存于可兴奋细胞中，并参与突触分化、分泌、递质释放和神经元可塑性。进入细胞的钙离子通过与离子通道本身相互作用或通过钙离子与靶蛋白结合，在离子传导亚基（Cava1）的胞质环处启动信号级联反应，从而引发这些事件。这些环以钙依赖或非依赖的方式与靶蛋白相互作用。在含有Cav2.3的通道中，结构域II和III之间的胞质连接子赋予E型钙通道一种新的钙敏感性，包括在转染Cav2.3的HEK-293细胞中通过蛋白激酶C（PKC）介导的佛波酯敏感信号传导。为了了解钙离子和佛波酯介导的Cav2.3钙通道激活机制，我们鉴定了II-III环的蛋白相互作用伙伴。人Cav2.3的FLAG标签II-III环在HEK 293细胞中过表达，已知与PKC相互作用的分子伴侣hsp70被鉴定为一种新的功能相互作用伙伴。免疫纯化的神经元和内分泌Cav2.3剪接变体的II-III环蛋白刺激PKCa的自磷酸化，这表明hsp70与II-III环的结合可能作为PKC钙依赖性靶向E型钙通道的衔接子。
