Hagiwara Daisuke, Kondo Atsushi, Fujioka Tomonori, Abe Keietsu
ABE-project, New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Japan.
Curr Genet. 2008 Dec;54(6):325-38. doi: 10.1007/s00294-008-0220-z. Epub 2008 Nov 11.
Calcium signaling systems are widely employed in eukaryotes and are implicated in the regulation of diverse biological processes. Calcineurin is an important signaling component, which mediates ion homeostasis and virulence in several fungi. Based on intensive studies conducted on budding yeast, transcription factor Crz1p is thought to be a target of calcineurin. To provide insight into calcium signaling, a Crz1p homolog (CrzA) in a filamentous fungus Aspergillus nidulans was identified and its function with special reference to calcium response was characterized. A crzA gene disruption mutant exhibited sensitivity to high concentrations of Mn(2+) and Ca(2+), and mediated the expression of P-type calcium-ATPase homologous genes. Comprehensive transcriptional analysis with DNA microarrays indicated that CrzA regulates the expression of a vacuolar Ca(2+)/H(+) exchanger gene in response to external calcium stimuli. It is suggested that the calcineurin-CrzA pathway is the mediator of Ca(2+) homeostasis in A. nidulans. Moreover, a crzA/hogA double mutant showed hypersensitivity to osmotic stress, indicating the importance of calcium homeostasis for adaptation to osmotic stress, a universal stress in filamentous fungi.
钙信号系统在真核生物中广泛应用，并参与多种生物过程的调控。钙调神经磷酸酶是一种重要的信号成分，在多种真菌中介导离子稳态和毒力。基于对芽殖酵母的深入研究，转录因子Crz1p被认为是钙调神经磷酸酶的一个靶点。为了深入了解钙信号，在丝状真菌构巢曲霉中鉴定出了Crz1p的同源物（CrzA），并对其在钙应答方面的功能进行了表征。一个crzA基因破坏突变体对高浓度的Mn(2+)和Ca(2+)表现出敏感性，并介导P型钙-ATP酶同源基因的表达。用DNA微阵列进行的全面转录分析表明，CrzA响应外部钙刺激调节液泡Ca(2+)/H(+)交换蛋白基因的表达。提示钙调神经磷酸酶-CrzA途径是构巢曲霉中Ca(2+)稳态的介导因子。此外，一个crzA/hogA双突变体对渗透胁迫表现出超敏感性，表明钙稳态对于适应渗透胁迫（丝状真菌中的一种普遍胁迫）的重要性。
