Phosphoinositides (PIPs) are one kind of membrane components functioning in many intracellular processes, especially in signaling transduction and membrane transport. Phosphatidylinositide phosphatases (PIPases) are specifically important for the PIP homeostasis in cell. In our previous study, we have identified the actin-related protein CaSac1 in Candida albicans, while its functional mechanisms in regulating membrane homeostasis has not been identified. Here, we show that the PIPase CaSac1 is a main membrane-related protein and regulates hyphal polarization by governing phosphoinositide dynamic and plasma membrane (PM) electrostatic field. Deletion of CaSAC1 resulted in large-scale abnormal redistribution of phosphatidylinositide 4-phosphate (PI4P) from the endomembrane to the PM. This abnormality further led to disturbance of the PM's negative electrostatic field and abnormally spotted distribution of phosphatidylinositide 4,5-bisphosphate (PI(4,5)P₂). These changes led to a severe defect in polarized hyphal growth, which could be diminished with recovery of the PM's negative electrostatic field by the anionic polymer polyacrylic acid (PAA). This study revealed that the PIPase CaSac1 plays an essential role in regulating membrane homeostasis and membrane traffic, contributing to establishment of polarized hyphal growth.

磷脂酰肌醇（PIP）是在许多细胞内过程中起作用的一种膜成分，尤其是在信号转导和膜运输中。磷脂酰肌醇磷酸酶（PIPases）对于细胞内PIP稳态特别重要。在我们先前的研究中，我们已经在白色念珠菌中鉴定了肌动蛋白相关蛋白Ca Sac1 ，而其在调节膜稳态中的功能机制尚未确定。在这里，我们显示PIPase Ca Sac1是主要的膜相关蛋白，并通过控制磷酸肌醇动态和质膜（PM）静电场来调节菌丝极化。删除CaSAC1导致磷脂酰肌醇4磷酸酯（PI4P）从内膜到PM的大规模异常重新分布。这种异常进一步导致对PM负静电场的干扰，以及磷脂酰肌醇4,5-双磷酸酯（PI（4,5）P ₂）的斑点分布异常。这些变化导致极化菌丝生长的严重缺陷，可以通过阴离子聚合物聚丙烯酸（PAA）恢复PM的负静电场来减少。这项研究表明，PIPase Ca Sac1在调节膜稳态和膜运输中起重要作用，有助于建立极化的菌丝生长。