Klimecka Maria, Muszyńska Grazyna
Plant Biochemistry Department, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warszawa, Poland.
Acta Biochim Pol. 2007;54(2):219-33. Epub 2007 Apr 19.
Calcium ions as second messengers play an essential role in many important cellular processes. In plants, transient changes in calcium content in the cytosol (calcium signatures) have been observed during growth, development and under stress conditions. Such diverse functions require many different calcium sensors. One of the largest and most differentiated group of calcium sensors are protein kinases, among them calcium-dependent protein kinases (CDPKs) which were identified only in plants and protists. CDPKs have a regulatory domain which is able to bind calcium ions. For regulation of CDPKs activities not only calcium ions but also specific phospholipids and autophosphorylation are responsible. CDPKs have many different substrates, which reflects the diversity of their functions. Potential protein substrates of CDPK are involved in carbon and nitrogen metabolism, phospholipid synthesis, defense responses, ion and water transport, cytoskeleton organization, transcription and hormone responses. Presently, participation of CDPKs in stress signal transduction pathways (e.g., cold, drought, high salinity, wounding) is intensively studied in many laboratories. An intriguing, but still not fully clarified problem is the cross-talk via CDPKs among different signaling pathways that enables signal integration at different levels and ensure appropriate downstream responses.
钙离子作为第二信使在许多重要的细胞过程中发挥着至关重要的作用。在植物中，已观察到在生长、发育以及胁迫条件下，细胞质中钙含量会发生瞬时变化（钙信号）。如此多样的功能需要许多不同的钙传感器。最大且分化程度最高的钙传感器组之一是蛋白激酶，其中钙依赖蛋白激酶（CDPKs）仅在植物和原生生物中被发现。CDPKs具有一个能够结合钙离子的调节结构域。不仅钙离子，特定的磷脂和自身磷酸化也参与CDPKs活性的调节。CDPKs有许多不同的底物，这反映了它们功能的多样性。CDPK的潜在蛋白质底物参与碳和氮代谢、磷脂合成、防御反应、离子和水运输、细胞骨架组织、转录以及激素反应。目前，许多实验室正在深入研究CDPKs在胁迫信号转导途径（如寒冷、干旱、高盐度、创伤）中的参与情况。一个有趣但仍未完全阐明的问题是，不同信号通路之间通过CDPKs进行的相互作用，这种相互作用能够在不同水平上实现信号整合，并确保适当的下游反应。
