Polarized growth is required in eukaryotic cells for processes such as cell division, morphogenesis and motility, which involve conserved and interconnected signalling pathways controlling cell cycle progression, cytoskeleton reorganization and secretory pathway functioning. While many of the factors involved in polarized growth are known, it is not yet clear how they are coordinated both spatially and temporally. Several lines of evidence point to the important role of lipid flippases in polarized growth events. Lipid flippases, which mainly belong to the P4 subfamily of P-type ATPases, are active transporters that move different lipids to the cytosolic side of biological membranes at the expense of ATP. The involvement of the Saccharomyces cerevisiae plasma membrane P4 ATPases Dnf1p and Dnf2p in polarized growth and their activation by kinase phosphorylation were established some years ago. However, these two proteins do not seem to be responsible for the phosphatidylserine internalization required for early recruitment of proteins to the plasma membrane during yeast mating and budding. In a recent publication, we demonstrated that the Golgi-localized P4 ATPase Dnf3p has a preference for PS as a substrate, can reach the plasma membrane in a cell cycle-dependent manner, and is regulated by the same kinases that activate Dnf1p and Dnf2p. This finding solves a long-lasting enigma in the field of lipid flippases and suggests that tight and heavily coordinated spatiotemporal control of lipid translocation at the plasma membrane is important for proper polarized growth.

在真核细胞中，细胞分裂、形态发生和运动等过程需要极化生长，这些过程涉及控制细胞周期进程、细胞骨架重组和分泌途径功能的保守和相互关联的信号通路。虽然涉及极化增长的许多因素是已知的，但尚不清楚它们是如何在空间和时间上协调的。几条证据表明脂质翻转酶在极化生长事件中的重要作用。脂质翻转酶主要属于 P 型 ATP 酶的 P4 亚家族，是一种主动转运蛋白，以消耗 ATP 为代价将不同的脂质移动到生物膜的胞质侧。酿酒酵母的参与几年前建立了极化生长中的质膜 P4 ATPases Dnf1p 和 Dnf2p 以及它们通过激酶磷酸化的激活。然而，这两种蛋白质似乎并不负责在酵母交配和出芽期间早期募集蛋白质到质膜所需的磷脂酰丝氨酸内化。在最近的一篇文章中，我们证明了高尔基体定位的 P4 ATPase Dnf3p 偏好 PS 作为底物，可以以细胞周期依赖的方式到达质膜，并且受激活 Dnf1p 和 Dnf2p 的相同激酶的调节。这一发现解决了脂质翻转酶领域的一个长期谜团，并表明质膜脂质易位的紧密和高度协调的时空控制对于适当的极化生长很重要。