Structural and Functional Studies of Human Serine Palmitoyltransferase Complexes

项目摘要 鞘脂不仅是真核生物膜的重要结构成分， 信号分子和介导许多生物过程。鞘脂代谢缺陷通常是 与癌症和神经退行性疾病有关。尽管生物活性鞘脂很重要， 它们的生物发生和体内平衡的分子机制仍然知之甚少。在人类中，第一个和 鞘脂生物合成的限速步骤由丝氨酸棕榈酰转移酶复合物催化， 由催化组分SPTLC和调节组分ssSPT和ORMDL组成。这种关键酶 复合物还能感知细胞鞘脂水平，从而相应地调节鞘脂的产生，使其成为一种 在维持鞘脂体内平衡的关键反馈调节剂。人类基因突变导致 遗传性感觉神经病和早发性肌萎缩侧索硬化症。然而，该机制和 复杂的规则尚不清楚。我们建议阐明1）底物识别和催化 复合物的反应，2）调节成分的作用，以及3）鞘脂传感和反馈 机制为了实现这些目标，我们将联合收割机结合高分辨率的结构生物学，生物化学， 生物物理学提供结构和机制的见解鞘脂生物合成和稳态 由丝氨酸棕榈酰转移酶复合物控制。我们提出的研究将大大促进我们的 通过揭示鞘脂中一个重要步骤的分子基础来了解鞘脂生物学 生物发生和鞘脂体内平衡的机制。

PROJECT SUMMARY Sphingolipids not only are essential structural components of eukaryotic membranes, but also function as signaling molecules and mediate many biological processes. Defects in sphingolipid metabolism are often associated with cancers and neurodegenerative diseases. Despite the importance of bioactive sphingolipids, molecular mechanisms of their biogenesis and homeostasis remain poorly understood. In humans, the first and rate-limiting step of sphingolipid biosynthesis is catalyzed by the serine palmitoyltransferase complex, which consists of catalytic component SPTLCs and regulatory components ssSPT and ORMDL. This key enzyme complex also senses cellular sphingolipid levels to adjust sphingolipid production accordingly, making it a critical feedback regulator in maintaining sphingolipid homeostasis. Human mutations in the complex lead to hereditary sensory neuropathy and early-onset amyotrophic lateral sclerosis. However, the mechanism and regulation of the complex are unclear. We propose to elucidate 1) the substrate recognition and catalytic reaction of the complex, 2) the role of regulatory components, and 3) the sphingolipid-sensing and feedback mechanism. To accomplish these aims, we will combine high-resolution structural biology, biochemistry, and biophysics to provide structural and mechanistic insights into sphingolipid biogenesis and homeostasis governed by the serine palmitoyltransferase complex. Our proposed studies will greatly advance our understanding of sphingolipid biology by uncovering the molecular basis of an essential step in sphingolipid biogenesis and a mechanism of sphingolipid homeostasis.