Phosphatidylinositol-4-phosphate 5-kinase regulates fission yeast cell integrity through a phospholipase C-mediated protein kinase C-independent pathway
Phosphatidylinositol-4-phosphate 5-kinase regulates fission yeast cell integrity through a phospholipase C-mediated protein kinase C-independent pathway
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DOI：
10.1074/jbc.m502660200
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发表时间：
2005-07-29
影响因子：
4.8
通讯作者：
Kuno, T
中科院分区：
文献类型：
--
作者：
Deng, L;Sugiura, R;Kuno, T
裂殖酵母its3-1突变体是必需基因its3(+)的等位基因，编码磷脂酰肌醇-4-磷酸5-激酶(PIP5K)，产生磷脂酰肌醇4,5-二磷酸。我们发现its3-1突变体对米卡芬净（一种（1,3）-β-D-葡聚糖合酶抑制剂）敏感，表明细胞壁完整性缺陷。一致地，its3-1 突变引起 (1,3)-β-D-葡聚糖合酶突变体 bgs1-i2 的合成致死，并且its3-1 突变细胞显示绿色荧光蛋白-Bgs1 的异常定位。绿色荧光蛋白标记的 Rgf1（一种假定的 Rho 蛋白磷脂酰肌醇 4,5-二磷酸结合鸟嘌呤核苷酸交换因子）在其 3-1 突变体中也观察到类似的异常定位，表明 Rgf1/Rho 途径有缺陷。为了阐明分子机制，分析了 PIP5K 信号传导的假定下游组件。出乎意料的是，磷脂酶 C (Plc1) 的过表达（而非蛋白激酶 C（PKC；Pck1 和 Pck2））抑制了 it3-1 突变体的表型。这些发现表明 PKC 不参与抑制，并且进一步分析表明 PKC 不是裂殖酵母中 Plc1 的下游。此外，Plc1 的酶活性对于表型的抑制和 it3-1 突变体的生存能力至关重要。这些发现表明，除了 Rho/PKC 途径外，Its3 PIP5K 通过 Plc1 介导的 PKC 独立途径调节细胞完整性。
Fission yeast its3-1 mutant is an allele of the essential gene its3(+) that encodes a phosphatidylinositol-4-phosphate 5-kinase (PIP5K) that produces phosphatidylinositol 4,5-bisphosphate. We found that the its3-1 mutant is sensitive to micafungin, a (1,3)-beta-D-glucan synthase inhibitor, suggesting a cell wall integrity defect. Consistently, its3-1 mutation caused synthetic lethality with a (1,3)-beta-D-glucan synthase mutant, bgs1-i2, and its3-1 mutant cells showed aberrant localization of green fluorescent protein-Bgs1. Similar aberrant localization of green fluorescent protein-tagged Rgf1, a putative phosphatidylinositol 4,5-bisphosphate-binding guanine nucleotide exchange factor for Rho protein, in its3-1 mutants was observed, suggesting a defective Rgf1/Rho pathway. To unravel the molecular mechanism(s), putative downstream components of PIP5K signaling were analyzed. Unexpectedly, overexpression of phospholipase C (Plc1), but not that of protein kinase C (PKC; Pck1 and Pck2), suppressed the phenotypes of the its3-1 mutant. These findings indicate that PKCs are not involved in the suppression, and further analysis revealed that PKCs are not downstream of Plc1 in fission yeast. Also, the enzymatic activity of Plc1 is essential for the suppression of the phenotypes and for the viability of the its3-1 mutant. These findings suggest that Its3 PIP5K regulates cell integrity through a Plc1-mediated PKC-independent pathway, in addition to the Rho/PKC pathway.