Fab1p is essential for PtdIns(3)P 5-kinase activity and the maintenance of vacuolar size and membrane homeostasis.
Fab1p is essential for PtdIns(3)P 5-kinase activity and the maintenance of vacuolar size and membrane homeostasis.
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DOI：
10.1083/jcb.143.1.65
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发表时间：
1998-10-05
期刊：
影响因子：
--
通讯作者：
Emr SD
中科院分区：
文献类型：
--
作者：
Gary JD;Wurmser AE;Bonangelino CJ;Weisman LS;Emr SD
酿酒酵母FAB1基因编码一个257-kD的蛋白，在其NH2末端含有一个富含半胱氨酸的环-FYVE结构域，在其COOH末端含有一个激动域。根据ITS序列，Fab1p最初被认为是一种磷脂酰肌醇4-磷酸(PtdIns(4)P)5-激酶。对Fab1p激动域的额外序列分析表明，Fab1p定义了一个可能的PtdInsP激酶亚家族，它不同于合成PtdIns(4，5)P2的激酶。与此一致，我们发现与野生型细胞不同，FAB1Δ、Fab1tsf和FAB1激酶域点突变体缺乏可检测到的PtdIns(3，5)P2水平，PtdIns(3，5)P2是一种最近在酵母和哺乳动物细胞中发现的磷酸肌醇。另一方面，PtdIns(4，5)P2的合成即使在FAB1Δ突变体中也只受到适度的影响。在FAB1突变体中存在PtdIns(3)P，结合以前的数据，表明PtdIns(3，5)P2的合成是一个两步过程，需要由Vps34P PtdIns 3-激酶产生PtdIns(3)P，然后依赖Fab1p对PtdIns(3)P进行磷酸化产生PtdIns(3，5)P2。尽管Vps34p介导的PtdIns(3)P的合成是从高尔基体到液泡的水解酶的正确分选所必需的，但Fab1p产生的PtdIns(3，5)P2并不直接影响高尔基体到液泡的运输，这表明PtdIns(3，5)P2具有独特的功能。Fab1p激酶失活的主要表型包括温度敏感型生长、空泡酸化缺陷和空泡大小急剧增加。根据我们的研究，我们假设Vps34p对于膜和蛋白质货物向液泡的顺行运输是必不可少的，而Fab1p可能在液泡沉积的膜的循环/周转中发挥重要的补偿作用。有趣的是，VAC7的缺失也会导致空泡形态扩大，没有检测到PtdIns(3，5)P2，这表明Vac7p作为上游调节因子，可能在与Fab1p的复合体中发挥作用。我们认为Fab1p和Vac7p是一个信号转导通路的组成部分，该通路通过调节PtdIns(3，5)P2的产生来调节液泡膜的外流或周转。
The Saccharomyces cerevisiae FAB1 gene encodes a 257-kD protein that contains a cysteine-rich RING-FYVE domain at its NH2-terminus and a kinase domain at its COOH terminus. Based on its sequence, Fab1p was initially proposed to function as a phosphatidylinositol 4-phosphate (PtdIns(4)P) 5-kinase. Additional sequence analysis of the Fab1p kinase domain, reveals that Fab1p defines a subfamily of putative PtdInsP kinases that is distinct from the kinases that synthesize PtdIns(4,5)P2. Consistent with this, we find that unlike wild-type cells, fab1Δ, fab1tsf, and fab1 kinase domain point mutants lack detectable levels of PtdIns(3,5)P2, a phosphoinositide recently identified both in yeast and mammalian cells. PtdIns(4,5)P2 synthesis, on the other hand, is only moderately affected even in fab1Δ mutants. The presence of PtdIns(3)P in fab1 mutants, combined with previous data, indicate that PtdIns(3,5)P2 synthesis is a two step process, requiring the production of PtdIns(3)P by the Vps34p PtdIns 3-kinase and the subsequent Fab1p- dependent phosphorylation of PtdIns(3)P yielding PtdIns(3,5)P2. Although Vps34p-mediated synthesis of PtdIns(3)P is required for the proper sorting of hydrolases from the Golgi to the vacuole, the production of PtdIns(3,5)P2 by Fab1p does not directly affect Golgi to vacuole trafficking, suggesting that PtdIns(3,5)P2 has a distinct function. The major phenotypes resulting from Fab1p kinase inactivation include temperature-sensitive growth, vacuolar acidification defects, and dramatic increases in vacuolar size. Based on our studies, we hypothesize that whereas Vps34p is essential for anterograde trafficking of membrane and protein cargoes to the vacuole, Fab1p may play an important compensatory role in the recycling/turnover of membranes deposited at the vacuole. Interestingly, deletion of VAC7 also results in an enlarged vacuole morphology and has no detectable PtdIns(3,5)P2, suggesting that Vac7p functions as an upstream regulator, perhaps in a complex with Fab1p. We propose that Fab1p and Vac7p are components of a signal transduction pathway which functions to regulate the efflux or turnover of vacuolar membranes through the regulated production of PtdIns(3,5)P2.
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影响因子：
7.8
作者：
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作者：
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通讯作者：
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影响因子：
3.3
作者：
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通讯作者：
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信号介导的膜蛋白从高尔基体中的膜蛋白回收到酵母中的ER。
DOI：
10.1083/jcb.127.3.653
发表时间：
1994-11
期刊：
The Journal of cell biology
影响因子：
--
作者：
Gaynor EC;te Heesen S;Graham TR;Aebi M;Emr SD
通讯作者：
Emr SD