PDF(Pubmed)
Abstract：
Stramenopiles form a clade of diverse eukaryotic organisms, including multicellular algae, the fish and plant pathogenic oomycetes, such as the potato blight Phytophthora, and the human intestinal protozoan Blastocystis. In most eukaryotes, glycolysis is a strictly cytosolic metabolic pathway that converts glucose to pyruvate, resulting in the production of NADH and ATP (Adenosine triphosphate). In contrast, stramenopiles have a branched glycolysis in which the enzymes of the pay-off phase are located in both the cytosol and the mitochondrial matrix. Here, we identify a mitochondrial carrier in Blastocystis that can transport glycolytic intermediates, such as dihydroxyacetone phosphate and glyceraldehyde-3-phosphate, across the mitochondrial inner membrane, linking the cytosolic and mitochondrial branches of glycolysis. Comparative analyses with the phylogenetically related human mitochondrial oxoglutarate carrier (SLC25A11) and dicarboxylate carrier (SLC25A10) show that the glycolytic intermediate carrier has lost its ability to transport the canonical substrates malate and oxoglutarate. Blastocystis lacks several key components of oxidative phosphorylation required for the generation of mitochondrial ATP, such as complexes III and IV, ATP synthase, and ADP/ATP carriers. The presence of the glycolytic pay-off phase in the mitochondrial matrix generates ATP, which powers energy-requiring processes, such as macromolecular synthesis, as well as NADH, used by mitochondrial complex I to generate a proton motive force to drive the import of proteins and molecules. Given its unique substrate specificity and central role in carbon and energy metabolism, the carrier for glycolytic intermediates identified here represents a specific drug and pesticide target against stramenopile pathogens, which are of great economic importance.
All living organisms breakdown food molecules to generate energy for processes, such as growing, reproducing and movement. The series of chemical reactions that breakdown sugars into smaller molecules – known as glycolysis – is so important that it occurs in all life forms, from bacteria to humans. In higher organisms, such as fungi and animals, these reactions take place in the cytosol, the space surrounding the cell’s various compartments. A transport protein then shuttles the end-product of glycolysis – pyruvate – into specialised compartments, known as the mitochondria, where most energy is produced. However, recently it was discovered that a group of living organisms, called the stramenopiles, have a branched glycolysis in which the enzymes involved in the second half of this process are located in both the cytosol and mitochondrial matrix. But it was not known how the intermediate molecules produced after the first half of glycolysis enter the mitochondria. To answer this question, Pyrihová et al. searched for transport protein(s) that could link the two halves of the glycolysis pathway. Computational analyses, comparing the genetic sequences of many transport proteins from several different species, revealed a new group found only in stramenopiles. Pyrihová et al. then used microscopy to visualise these new transport proteins – called GIC-1 and GIC-2 – in the parasite Blastocystis, which infects the human gut, and observed that they localise to mitochondria. Further biochemical experiments showed that GIC-1 and GIC-2 can physically bind these intermediate molecules, but only GIC-2 can transport them across membranes. Taken together, these observations suggest that GIC-2 links the two halves of glycolysis in Blastocystis. Further analyses could reveal corresponding transport proteins in other stramenopiles, many of which have devastating effects on agriculture, such as Phytophthora, which causes potato blight, or Saprolegnia, which causes skin infections in farmed salmon. Since human cells do not have equivalent transporters, they could be new drug targets not only for Blastocystis, but for these harmful pathogens as well.
All living organisms breakdown food molecules to generate energy for processes, such as growing, reproducing and movement. The series of chemical reactions that breakdown sugars into smaller molecules – known as glycolysis – is so important that it occurs in all life forms, from bacteria to humans. In higher organisms, such as fungi and animals, these reactions take place in the cytosol, the space surrounding the cell’s various compartments. A transport protein then shuttles the end-product of glycolysis – pyruvate – into specialised compartments, known as the mitochondria, where most energy is produced. However, recently it was discovered that a group of living organisms, called the stramenopiles, have a branched glycolysis in which the enzymes involved in the second half of this process are located in both the cytosol and mitochondrial matrix. But it was not known how the intermediate molecules produced after the first half of glycolysis enter the mitochondria. To answer this question, Pyrihová et al. searched for transport protein(s) that could link the two halves of the glycolysis pathway. Computational analyses, comparing the genetic sequences of many transport proteins from several different species, revealed a new group found only in stramenopiles. Pyrihová et al. then used microscopy to visualise these new transport proteins – called GIC-1 and GIC-2 – in the parasite Blastocystis, which infects the human gut, and observed that they localise to mitochondria. Further biochemical experiments showed that GIC-1 and GIC-2 can physically bind these intermediate molecules, but only GIC-2 can transport them across membranes. Taken together, these observations suggest that GIC-2 links the two halves of glycolysis in Blastocystis. Further analyses could reveal corresponding transport proteins in other stramenopiles, many of which have devastating effects on agriculture, such as Phytophthora, which causes potato blight, or Saprolegnia, which causes skin infections in farmed salmon. Since human cells do not have equivalent transporters, they could be new drug targets not only for Blastocystis, but for these harmful pathogens as well.
摘要：
Stramenopiles形成了多种真核生物的进化枝，包括多细胞藻类，鱼类和植物致病卵菌，比如马铃薯疫病疫霉,和人类肠道原生动物囊胚。在大多数真核生物中，糖酵解是一种严格的细胞溶质代谢途径，将葡萄糖转化为丙酮酸，导致NADH和ATP（三磷酸腺苷）的产生。相比之下,stramenopiles具有分支的糖酵解，其中释放阶段的酶位于细胞质和线粒体基质中。这里,我们在囊胚中发现了一种线粒体载体，可以运输糖酵解中间体，如磷酸二羟基丙酮和3-磷酸甘油醛，穿过线粒体内膜，连接糖酵解的细胞溶质和线粒体分支。与系统发育相关的人线粒体酮戊二酸载体（SLC25A11）和二羧酸盐载体（SLC25A10）的比较分析表明，糖酵解中间载体已经失去了运输典型底物苹果酸和酮戊二酸的能力。囊胚缺乏线粒体ATP生成所需的氧化磷酸化的几个关键成分，如配合物III和IV，ATP合成酶,和ADP/ATP载体。线粒体基质中糖酵解释放阶段的存在会产生ATP，为需要能量的过程提供动力，如大分子合成，以及NADH，由线粒体复合物I用来产生质子动力来驱动蛋白质和分子的导入。鉴于其独特的底物特异性和在碳和能量代谢中的核心作用，这里确定的糖酵解中间体的载体代表了针对斯特拉门普菌病原体的特定药物和农药靶标，具有重要的经济意义。
所有生物体都会分解食物分子以产生能量，比如成长，复制和运动。将糖分解为较小分子的一系列化学反应-称为糖酵解-非常重要，以至于它发生在所有生命形式中，从细菌到人类在高等生物中，比如真菌和动物，这些反应发生在细胞质中，牢房各个隔间周围的空间。然后，运输蛋白将糖酵解的最终产物-丙酮酸盐-运送到专门的隔室中，称为线粒体，大部分能源都在那里生产。然而,最近发现一群生物，叫做stramenopiles，具有分支糖酵解，其中参与该过程后半段的酶位于细胞质和线粒体基质中。但是不知道糖酵解的前半部分后产生的中间分子如何进入线粒体。为了回答这个问题,Pyrihováetal.寻找可以连接糖酵解途径的两半的转运蛋白。计算分析，比较来自几个不同物种的许多运输蛋白的遗传序列，揭示了一个仅在stramenopiles发现的新群体。Pyrihováetal.然后用显微镜观察这些新的转运蛋白-称为GIC-1和GIC-2-在寄生虫胚泡中，感染人类肠道，并观察到它们定位于线粒体。进一步的生化实验表明，GIC-1和GIC-2可以物理结合这些中间分子，但只有GIC-2能将它们跨膜运输.一起来看,这些观察结果提示GIC-2将胚泡糖酵解的两半联系起来.进一步的分析可以揭示其他Stramenopiles中相应的转运蛋白，其中许多对农业产生破坏性影响，比如疫霉，导致马铃薯疫病，或者是断断续续,导致养殖鲑鱼皮肤感染。由于人类细胞没有等效的转运蛋白，它们不仅可以成为囊胚病的新药靶点，但对于这些有害的病原体也是如此。
所有生物体都会分解食物分子以产生能量，比如成长，复制和运动。将糖分解为较小分子的一系列化学反应-称为糖酵解-非常重要，以至于它发生在所有生命形式中，从细菌到人类在高等生物中，比如真菌和动物，这些反应发生在细胞质中，牢房各个隔间周围的空间。然后，运输蛋白将糖酵解的最终产物-丙酮酸盐-运送到专门的隔室中，称为线粒体，大部分能源都在那里生产。然而,最近发现一群生物，叫做stramenopiles，具有分支糖酵解，其中参与该过程后半段的酶位于细胞质和线粒体基质中。但是不知道糖酵解的前半部分后产生的中间分子如何进入线粒体。为了回答这个问题,Pyrihováetal.寻找可以连接糖酵解途径的两半的转运蛋白。计算分析，比较来自几个不同物种的许多运输蛋白的遗传序列，揭示了一个仅在stramenopiles发现的新群体。Pyrihováetal.然后用显微镜观察这些新的转运蛋白-称为GIC-1和GIC-2-在寄生虫胚泡中，感染人类肠道，并观察到它们定位于线粒体。进一步的生化实验表明，GIC-1和GIC-2可以物理结合这些中间分子，但只有GIC-2能将它们跨膜运输.一起来看,这些观察结果提示GIC-2将胚泡糖酵解的两半联系起来.进一步的分析可以揭示其他Stramenopiles中相应的转运蛋白，其中许多对农业产生破坏性影响，比如疫霉，导致马铃薯疫病，或者是断断续续,导致养殖鲑鱼皮肤感染。由于人类细胞没有等效的转运蛋白，它们不仅可以成为囊胚病的新药靶点，但对于这些有害的病原体也是如此。
