Intracellular calcium (Ca²⁺) is crucial for signal transduction in Cryptococcus neoformans, the major cause of fatal fungal meningitis. The calcineurin pathway is the only Ca²⁺-requiring signaling cascade implicated in cryptococcal stress adaptation and virulence, with Ca²⁺ binding mediated by the EF-hand domains of the Ca²⁺ sensor protein calmodulin. In this study, we identified the cryptococcal ortholog of neuronal calcium sensor 1 (Ncs1) as a member of the EF-hand superfamily. We demonstrated that Ncs1 has a role in Ca²⁺ homeostasis under stress and nonstress conditions, as the ncs1Δ mutant is sensitive to a high Ca²⁺ concentration and has an elevated basal Ca²⁺ level. Furthermore, NCS1 expression is induced by Ca²⁺, with the Ncs1 protein adopting a punctate subcellular distribution. We also demonstrate that, in contrast to the case with Saccharomyces cerevisiae, NCS1 expression in C. neoformans is regulated by the calcineurin pathway via the transcription factor Crz1, as NCS1 expression is reduced by FK506 treatment and CRZ1 deletion. Moreover, the ncs1Δ mutant shares a high temperature and high Ca²⁺ sensitivity phenotype with the calcineurin and calmodulin mutants (cna1Δ and cam1Δ), and the NCS1 promoter contains two calcineurin/Crz1-dependent response elements (CDRE1). Ncs1 deficiency coincided with reduced growth, characterized by delayed bud emergence and aberrant cell division, and hypovirulence in a mouse infection model. In summary, our data show that Ncs1 has a significant role as a Ca²⁺ sensor in C. neoformans, working with calcineurin to regulate Ca²⁺ homeostasis and, consequently, promote fungal growth and virulence.

中文翻译：

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钙结合蛋白 Ncs1 是新型隐球菌中调节的钙调神经磷酸酶，对细胞分裂和毒力至关重要。


细胞内钙 (Ca ²⁺ ) 对于新生隐球菌的信号转导至关重要，而新生隐球菌是致命性真菌性脑膜炎的主要原因。钙调磷酸酶途径是与隐球菌应激适应和毒力相关的唯一需要Ca ²⁺的信号级联，其中Ca ²⁺结合由Ca ²⁺传感器蛋白钙调蛋白的EF-hand 结构域介导。在这项研究中，我们将神经元钙传感器 1 (Ncs1) 的隐球菌直系同源物鉴定为 EF-hand 超家族的成员。我们证明了 Ncs1 在应激和非应激条件下在 Ca ²⁺稳态中发挥作用，因为ncs1Δ突变体对高 Ca ²⁺浓度敏感并且具有升高的基础 Ca ²⁺水平。此外， NCS1表达由Ca ²⁺诱导，Ncs1蛋白呈点状亚细胞分布。我们还证明，与酿酒酵母的情况相反，新型隐球菌中的NCS1表达受到钙调神经磷酸酶途径通过转录因子Crz1的调节，因为FK506处理和CRZ1缺失会降低NCS1表达。此外， ncs1Δ突变体与钙调神经磷酸酶和钙调蛋白突变体（ cna1Δ和cam1Δ ）共享高温和高Ca ²⁺敏感性表型，并且NCS1启动子包含两个钙调神经磷酸酶/Crz1依赖性反应元件（CDRE1）。 Ncs1 缺陷与生长减慢同时发生，其特征是芽出现延迟和细胞分裂异常，以及小鼠感染模型中的低毒力。 总之，我们的数据表明，Ncs1 作为 Ca ²⁺传感器在新型隐球菌中具有重要作用，与钙调神经磷酸酶一起调节 Ca ²⁺稳态，从而促进真菌生长和毒力。