Elevating PI3P drives select downstream membrane trafficking pathways.
Elevating PI3P drives select downstream membrane trafficking pathways.
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DOI：
10.1091/mbc.e20-03-0191
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发表时间：
2021-01-15
影响因子：
3.3
通讯作者：
Weisman LS
中科院分区：
文献类型：
--
作者：
Steinfeld N;Lahiri V;Morrison A;Metur SP;Klionsky DJ;Weisman LS
磷酸肌肽信号脂质在几个细胞过程中是必不可少的。对磷酸肌肽的需求通常通过消耗相应的脂质激酶来研究。然而，很少有关于提高磷酸肌苷的影响的报道。磷酸肌苷在对刺激的反应中动态升高表明，磷酸肌苷除了是必需的外，还驱动下游途径。为了验证这一假设，我们通过产生酵母磷脂酰肌醇3-磷酸激酶（Vps34）的高活性等位基因，提高了磷脂酰肌醇3-磷酸（PI3P）水平。我们发现，过度活跃的Vps34驱动某些途径，包括磷脂酰肌醇-3,5-二磷酸合成和液泡的逆行运输。这表明PI3P在某些途径中是限速的。有趣的是，过度活跃的Vps34并不影响运输所需的内体分选复合物（ESCRT）功能。因此，升高PI3P并不总是增加PI3P依赖通路的速率。升高的PI3P也可以延迟一个通路。PI3P的升高减缓了自噬的后期阶段，部分原因是延迟了成熟自噬体中自噬蛋白的分解，以及延迟了自噬体与液泡的融合。后一种缺陷可能是由于液泡融合更普遍的缺陷，通过液泡形态的变化来评估。这些研究表明，刺激诱导的磷酸肌苷升高为这些刺激选择性调节下游过程提供了一种途径。
Phosphoinositide signaling lipids are essential for several cellular processes. The requirement for a phosphoinositide is conventionally studied by depleting the corresponding lipid kinase. However, there are very few reports on the impact of elevating phosphoinositides. That phosphoinositides are dynamically elevated in response to stimuli suggests that, in addition to being required, phosphoinositides drive downstream pathways. To test this hypothesis, we elevated the levels of phosphatidylinositol-3-phosphate (PI3P) by generating hyperactive alleles of the yeast phosphatidylinositol 3-kinase, Vps34. We find that hyperactive Vps34 drives certain pathways, including phosphatidylinositol-3,5-bisphosphate synthesis and retrograde transport from the vacuole. This demonstrates that PI3P is rate limiting in some pathways. Interestingly, hyperactive Vps34 does not affect endosomal sorting complexes required for transport (ESCRT) function. Thus, elevating PI3P does not always increase the rate of PI3P-dependent pathways. Elevating PI3P can also delay a pathway. Elevating PI3P slowed late steps in autophagy, in part by delaying the disassembly of autophagy proteins from mature autophagosomes as well as delaying fusion of autophagosomes with the vacuole. This latter defect is likely due to a more general defect in vacuole fusion, as assessed by changes in vacuole morphology. These studies suggest that stimulus-induced elevation of phosphoinositides provides a way for these stimuli to selectively regulate downstream processes.