Role of amylopectin granules in chronic toxoplasmosis, an HIV-AIDS defining infection

项目摘要 像弓形虫一样形成尖端复合体的组织囊肿的一个显著特征是聚集 缓殖子内支链淀粉(淀粉)颗粒(AG)的分布及其在生长活跃的 速殖子的形式。作为葡萄糖的聚合物，AG的功能是作为电池，作为产生能量的储备 和生物合成功能。我们最近的工作证实，缓殖子保持着巨大的复制潜力。 体内的组织囊内。值得注意的是，大多数缓殖体在组织囊内的复制是与 成群的爆发式增长与非复制期交替出现。而触发这些信号的特定信号 爆发尚不清楚，但可以肯定的是，它们将需要大量的能量和代谢物输入来 执行。历史证据和我们的发现表明，包囊缓殖子内的AG水平很高 与寄生的成群的缺少AG的寄生生物相邻的另一些富含淀粉的寄生生物而变化。这表明 AG代谢既涉及合成又涉及周转，在组织囊内是活跃的，并可能在 在慢性弓形虫病进展中的作用。我们将直接解决动力学和生物学问题 在单个慢体水平上AGs在慢性感染进展中的作用 在我们最近出版的工作中开发的工具和概念。在包裹期内，AG的可变水平 缓殖子，表明AG的积累和消耗都受到监管控制。事实上， 淀粉合成和调节周转所需的酶机械编码在 弓形虫基因组。我们将直接测试AG在急性感染中的重要性，调节阶段 靶向承诺酶的慢性感染的转化和建立/进展 淀粉合成、UDP-葡萄糖焦磷酸化酶(TgUDP-GPP，TgME49_218200)和淀粉 合成酶(TGSS，TgME49_222800)。最近的证据表明，尽管在形态上(尽管不是 生物化学)可检测到的支链淀粉也可能在速殖子的中间代谢中发挥作用。在……里面 此外，AG对重新激活的贡献将是艾滋病毒-艾滋病症状性疾病的主要触发因素 在诱导免疫抑制的背景下解决。通过拟议的研究，我们的目标是剖析 AG在速殖子中的作用以前未被探索，作为速殖子向缓殖子转化的因素， 慢性感染的进展和临床危重的体内再激活。这些研究将确立 以AG代谢为靶点对慢性感染进行治疗干预的基础 在艾滋病毒/艾滋病的临床背景下，有效药物的使用仍然是一个重大问题。

Project Summary A distinguishing characteristic of tissue cyst forming Apicomplexa, like Toxoplasma gondii, is the accumulation of amylopectin (starch) granules (AG) within bradyzoites and their absence within the actively growing tachyzoite forms. As polymers of glucose, AG functions as a battery serving as a reserve for energy production and biosynthetic functions. Our recent work established that bradyzoites retain significant replicative potential within tissue cysts in vivo. Notably, most bradyzoite replication within tissue cysts occurs asynchronously with clustered bursts of growth interceded with non-replicative periods. While the specific signals triggering these bursts remain unknown, what is clear is that they would require substantial energy and metabolite inputs to execute. Historical evidence and our findings reveal that AG levels within encysted bradyzoites are highly variable with clusters of parasites lacking AGs adjacent to others that are loaded with starch. This suggests that AG metabolism involving both synthesis and turnover are active within tissue cysts and may play a central role in the progression of chronic toxoplasmosis. We will directly address the dynamics and biological contributions of AGs in the progression of the chronic infection at the level of individual bradyzoites using novel tools and concepts developed in our recently published work. The variable levels of AG, within encysted bradyzoites, suggest that both AG accumulation and depletion are under regulatory control. Indeed the enzymatic machinery required for both the synthesis and regulated turnover of starch are encoded in the Toxoplasma genome. We will directly test the importance of AG in the acute infection, the regulation of stage conversion and the establishment/ progression of the chronic infection by targeting the commitment enzyme for starch synthesis, the UDP-glucose pyrophosphorylase (TgUDP-GPP, TgME49_218200), and the starch synthase (TgSS, TgME49_222800). Recent evidence suggests that despite being morphologically (though not biochemically) detectable, amylopectin may play a role in tachyzoite intermediary metabolism as well. In addition, the contribution of AG's to reactivation, the primary trigger of symptomatic disease in HIV-AIDS will be addressed in the context of induced immune suppression. With the proposed studies we aim to dissect the previously unexplored role of AG in tachyzoites, as factors in tachyzoite to bradyzoite conversion, the progression of the chronic infection and clinically critical reactivation in vivo. These studies will establish the groundwork for targeting AG metabolism for therapeutic intervention in the chronic infection where the paucity of effective drugs remains a significant issue in the clinical context of HIV-AIDS.