Proteomics analysis of lipid droplets indicates involvement of membrane trafficking proteins in lipid droplet breakdown in the oleaginous diatom Fistulifera solaris
Proteomics analysis of lipid droplets indicates involvement of membrane trafficking proteins in lipid droplet breakdown in the oleaginous diatom Fistulifera solaris
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DOI：
10.1016/j.algal.2019.101660
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发表时间：
2019-12-01
影响因子：
5.1
通讯作者：
Tanaka, Tsuyoshi
中科院分区：
文献类型：
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作者：
Nonoyama, Tomomi;Nojima, Daisuke;Tanaka, Tsuyoshi
微藻将甘油三酯（TAG）储存在称为脂滴的细胞内特殊的隔室中。尽管对微藻脂滴相关蛋白的研究仍然有限，但其动力学被认为是由各种脂滴相关蛋白控制的。本研究通过蛋白质组学分析，在产油的海洋硅藻fisstulifera solaris JPCC DA0580中鉴定了新的脂滴相关蛋白候选物。从硅藻细胞中提取脂滴，然后用尿素溶液洗涤以减少污染物。随后，从经尿素处理的脂滴部分中鉴定出蛋白质。本研究与以往其他微藻的蛋白质组学研究对比发现，从不同微藻中提取的脂滴组分普遍含有与膜转运相关的蛋白，如囊泡外壳蛋白和热休克蛋白，其中一些蛋白可能参与自噬。已知自噬可以降解其他生物（如哺乳动物细胞和酵母）中的脂滴，这一过程被称为脂噬。因此，本研究中从蛋白质组中检测到的膜运输相关蛋白可能在TAG的脂噬水解中起作用。为了证实这一假设，我们利用了膜运输相关蛋白和脂噬的抑制剂。在脂滴分解过程中加入抑制剂抑制了脂肪酸水解，支持脂噬可能参与脂肪酸水解的观点。这一现象也在另一种模式三角角藻（Phaeodactylum tricornutum）中观察到，这意味着食脂介导的脂滴分解可能是一种共同特征，至少在pennate硅藻中是如此。这些发现揭示了微藻脂质代谢的新方面，这可以应用于未来利用微藻提高生物燃料生产的油脂产量的新方法。
Microalgae store triacylglycerol (TAG) in a specialized intracellular compartment called the lipid droplet. Its dynamics are believed to be controlled by various lipid droplet-associated proteins, although studies of micro-algal lipid droplet-associated proteins are still limited. In the present study, proteomics analysis was carried out to identify novel lipid droplet-associated protein candidates in the oleaginous marine diatom Fistulifera solaris JPCC DA0580. Lipid droplets were extracted from diatom cells, followed by washing with urea solution to decrease contaminants. Subsequently, proteins were identified from the urea-treated lipid droplet fraction. Comparisons between the present study and previous proteomic research on other microalgae revealed that the lipid droplet fraction extracted from diverse microalgae commonly contained membrane trafficking-related proteins such as vesicle coat proteins and heat shock proteins, some of which could potentially be involved in autophagy. Autophagy is known to degrade lipid droplets in other organisms (i.e. mammalian cells and yeasts), and this process is termed lipophagy. Thus, the membrane trafficking-related proteins which were detected from the proteome in this study might play a role in TAG hydrolysis via lipophagy. In order to confirm this hypothesis, we utilized inhibitors of membrane trafficking-related proteins and lipophagy. The addition of the inhibitors to F. solaris during lipid droplet breakdown suppressed TAG hydrolysis, supporting the idea that lipophagy may participate in TAG hydrolysis in F. solaris. The phenomenon was also observed in another model pennate diatom, Phaeodactylum tricornutum, implying that lipophagy-mediated lipid droplet breakdown could be a common feature, at least in pennate diatoms. These findings shed light on novel aspects of lipid metabolism in microalgae, and this can be applied to new approaches for increasing the oil productivity of biofuel production using microalgae in the future.