Importance of UDP-glucose biosynthesis for the protozoan parasite Leishmania major

UDP-葡萄糖(UDP-GLC)的生物合成对利什曼原虫的生长是必需的吗？最近，我们证明了利什曼原虫主要的UDP-葡萄糖焦磷酸化酶(UGP)的缺失并不会导致UDP-GLC缺陷的寄生虫，并描述了一种罕见的UDP-葡萄糖焦磷酸化酶(USP)可能补偿其丢失。我们试图产生一个两种酶都缺乏的突变体，但没有成功，这表明UDP-GLC对利什曼原虫是必不可少的。利用最近开发的系统，我们希望产生一个突变体，其中UDP-GLC的水平可以被调节并降低到可以忽略的水平，以明确地证明这种核苷酸糖对寄生虫生存的重要性，并研究它的作用。UDP-GLC可能参与脂多糖锚的生物合成，对糖杯的形成至关重要。更重要的是，就像在所有真核生物中一样，它是内质网(ER)中确保蛋白质正确折叠的钙网蛋白循环所必需的。在利什曼原虫中，这种内质网质量控制的重要性目前尚不清楚，但UDP-GLC转运体HUT1L以及UDP-葡萄糖向内质网的输送似乎是必不可少的。因此，该项目将特别讨论UDP-GLC在内质网中的作用及其与细胞生存能力的联系。我们希望为利什曼原虫的内质网质量控制提供重要的信息，可以移植到其他生物中。此外，通过这个项目获得的知识可能有助于确定如何对付利什曼原虫，利什曼原虫是世界上第二大寄生虫杀手。

Is UDP-Glucose (UDP-Glc) biosynthesis essential for the growth of Leishmania parasites? Recently, we demonstrated that deletion of Leishmania major UDP-glucose pyrophosphorylase (UGP) did not result in UDP-Glc deficient parasites and described an unusual UDP-sugar pyrophosphorylase (USP) likely compensating for its loss. Our attempts to generate a mutant deficient in both enzymes were unsuccessful suggesting that UDP-Glc is essential for Leishmania parasites. Using a recently developed system, we wish to generate a mutant in which the level of UDP-Glc can be tuned and reduced to negligible level to unequivocally demonstrate the essentiality of this nucleotide sugar for parasite viability and study its roles. UDP-Glc is likely involved in the biosynthesis of the lipophosphoglycan anchor and is crucial for glycocalix formation. More importantly, it is, as in every eukaryote, required in the endoplasmic reticulum (ER) for the calreticulin cycle that ensures proper protein folding. The importance of this ER quality control is currently unknown in Leishmania but the UDP-Glc transporter HUT1L and thus delivery of UDP-glucose to the ER seems essential. This project will thus particularly address the role of UDP-Glc in the ER and its link to cellular viability. We hope to provide important information about the ER quality control in Leishmania that could be translated to other organisms. Moreover, the knowledge gained with this project might help defining how to tackle Leishmania parasites, which are the second parasitic killer in the world.