An Arabidopsis Hydrophilic Ca2-Binding Protein with a PEVK-Rich Domain, PCaP2, is Associated with the Plasma Membrane and Interacts with Calmodulin and Phosphatidylinositol Phosphates
An Arabidopsis Hydrophilic Ca2-Binding Protein with a PEVK-Rich Domain, PCaP2, is Associated with the Plasma Membrane and Interacts with Calmodulin and Phosphatidylinositol Phosphates
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DOI：
10.1093/pcp/pcq003
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发表时间：
2010-03-01
影响因子：
4.9
通讯作者：
Maeshima, Masayoshi
中科院分区：
文献类型：
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作者：
Kato, Mariko;Nagasaki-Takeuchi, Nahoko;Maeshima, Masayoshi
我们在拟南芥中发现了一种新的亲水性蛋白。实时荧光定量聚合酶链式反应证实该蛋白在根中表达。启动子-葡萄糖苷酸酶融合的组织化学分析表明，它在根毛中广泛表达。该蛋白富含脯氨酸、谷氨酸、缬氨酸和赖氨酸残基(富含PEVK结构域)，即使在镁-2和钾的存在下也能结合钙-2，通过钙-45覆盖试验检测。K、Mn-2、Zn-2、Na、ABA和赤霉酸处理以及低温和干旱胁迫提高了转录水平。与绿色荧光蛋白连锁的蛋白在拟南芥中的表达表明，该蛋白在细胞膜上定位，并在包括根毛和伸长的花粉管在内的表皮细胞中特异表达。因此，我们将该蛋白命名为PCaP2(质膜相关钙结合蛋白-2)。2位甘氨酸被丙氨酸取代导致PCaP2的胞质定位。这些结果和N-末端的特征基序表明PCaP2在Gly2处是N-肉豆蔻酰化的。我们检测了PCaP2与磷脂酰肌醇磷酸(PtdInsPs)的结合能力，发现PCaP2与PtdIns(3，5)P-2、PtdIns(4，5)P-2和PtdIns(3，4，5)P-3有很强的相互作用，而与PtdIns(3，4)P-2作用较弱。此外，钙调蛋白与PCaP2以钙依赖的方式结合，它的结合削弱了PCaP2与PtdInsps的相互作用。这些结果表明，在生长的根毛中，PCaP2通过与PtdInsps和钙调蛋白的相互作用参与细胞内信号转导。PCaP2此前被报道为微管相关蛋白-18。我们讨论了PCaP2与细胞内微管相关的生理作用。
We found a new hydrophilic protein in Arabidopsis thaliana. Real-time PCR demonstrated that the protein was expressed in roots. Histochemical analysis of promoter-glucuronidase fusions demonstrated its extensive expression in root hairs. The protein is rich in proline, glutamate, valine and lysine residues (PEVK-rich domain), and bound Ca-2 even in the presence of Mg-2 and K when examined by the Ca-45 overlay assay. Treatment of seedlings with K, Mn-2, Zn-2, Na, ABA and gibberellic acid, and cold and drought stresses enhanced the transcription. Expression of the protein linked to green fluorescent protein in A. thaliana showed its plasma membrane localization and cell-specific expression in the epidermal cells including root hairs and the elongating pollen tubes. Therefore, we named the protein PCaP2 (plasma membrane-associated Ca-2-binding protein-2). The substitution of glycine at position 2 with alanine resulted in cytoplasmic localization of PCaP2. These results and the N-terminal characteristic motif suggest that PCaP2 is N-myristoylated at Gly2. We examined the capacity for binding to phosphatidylinositol phosphates (PtdInsPs), and found that PCaP2 interacts strongly with PtdIns(3,5)P-2, PtdIns(4,5)P-2 and PtdIns(3,4,5)P-3, and weakly with PtdIns(3,4)P-2. Furthermore, calmodulin was associated with PCaP2 in a Ca-2-dependent manner, and its association weakened the interaction of PCaP2 with PtdInsPs. These results indicate that PCaP2 is involved in intracellular signaling through interaction with PtdInsPs and calmodulin in growing root hairs. PCaP2 was previously reported as microtubule-associated protein-18. We discuss the physiological roles of PCaP2 in relation to microtubules in cells.