The distribution of phosphatidylinositol 4,5-bisphosphate in the budding yeast plasma membrane.
The distribution of phosphatidylinositol 4,5-bisphosphate in the budding yeast plasma membrane.
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磷脂酰肌醇 4,5-二磷酸在芽殖酵母质膜中的分布。
DOI：
10.1007/s00418-021-01989-8
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
A.
中科院分区：
文献类型：
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作者：
Kurokawa;Y.;Konishi;R.;Yoshida;A.;Tomioku;K.;Tanabe;K.;Fujita;A.
磷脂酰肌醇4，5-二磷酸（PtdIns（4，5）P2）通过Mss 4p（酵母细胞中唯一的PtdIns磷酸5-激酶）磷酸化磷脂酰肌醇4-磷酸（PtdIns（4）P）而产生。PtdIns（4，5）P2参与酵母的多种功能。PtdIns（4）P不仅是PtdIns（4，5）P2的直接前体，也是质膜、高尔基体和内体系统中的重要信号分子。为了在纳米水平上分析PtdIns（4，5）P2和PtdIns（4）P在酵母质膜中的分布，我们采用了冷冻断裂电子显微镜（EM）方法，该方法原位物理固定脂质分子。据报道，芽殖酵母的质膜可分为三个不同的区域：沟，六角形，和未分化的平坦。以前，使用冷冻断裂EM方法，我们确定PtdIns（4）P定位在未分化的平坦区域，避免质膜的沟槽和六边形区域。在本研究中，我们发现PtdIns（4，5）P2定位于质膜的胞质小叶，并集中在沟区。有三种类型的PtdIns 4-激酶，其由ystt 4、pik 1和lsb 6编码。细胞膜上PtdIns（4）P标记密度在pik 1 ts和stt 4 ts突变体中均显著降低。而pik 1 ts和stt 4 ts突变体质膜上PtdIns（4，5）P2的标记密度与野生型酵母相当。这些结果表明，PtdIns（4）P产生的Pik 1 p或Stt 4p立即被Mss 4p磷酸化，并转化为PtdIns（4，5）P2在质膜上。
Phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) is generated through phosphorylation of phosphatidylinositol 4-phosphate (PtdIns(4)P) by Mss4p, the only PtdIns phosphate 5-kinase in yeast cells. PtdIns(4,5)P2is involved in various kinds of yeast functions. PtdIns(4)P is not only the immediate precursor of PtdIns(4,5)P2, but also an essential signaling molecule in the plasma membrane, Golgi, and endosomal system. To analyze the distribution of PtdIns(4,5)P2and PtdIns(4)P in the yeast plasma membrane at a nanoscale level, we employed a freeze–fracture electron microscopy (EM) method that physically immobilizes lipid molecules in situ. It has been reported that the plasma membrane of budding yeast can be divided into three distinct areas: furrowed, hexagonal, and undifferentiated flat. Previously, using the freeze–fracture EM method, we determined that PtdIns(4)P is localized in the undifferentiated flat area, avoiding the furrowed and hexagonal areas of the plasma membrane. In the present study, we found that PtdIns(4,5)P2was localized in the cytoplasmic leaflet of the plasma membrane, and concentrated in the furrowed area. There are three types of PtdIns 4-kinases which are encoded bystt4,pik1, andlsb6. The labeling density of PtdIns(4)P in the plasma membrane significantly decreased in bothpik1tsandstt4tsmutants. However, the labeling densities of PtdIns(4,5)P2in the plasma membrane of both thepik1tsandstt4tsmutants were comparable to that of the wild type yeast. These results suggest that PtdIns(4)P produced by either Pik1p or Stt4p is immediately phosphorylated by Mss4p and converted to PtdIns(4,5)P2at the plasma membrane.