Schäfer Jan-Hannes, Körner Carolin, Esch Bianca M, Limar Sergej, Parey Kristian, Walter Stefan, Januliene Dovile, Moeller Arne, Fröhlich Florian
Osnabrück University Department of Biology/Chemistry Structural Biology section, 49076, Osnabrück, Germany.
Osnabrück University Department of Biology/Chemistry Bioanalytical Chemistry section, 49076, Osnabrück, Germany.
Nat Commun. 2023 Oct 4;14(1):6196. doi: 10.1038/s41467-023-41747-z.
Sphingolipids are structural membrane components that also function in cellular stress responses. The serine palmitoyltransferase (SPT) catalyzes the rate-limiting step in sphingolipid biogenesis. Its activity is tightly regulated through multiple binding partners, including Tsc3, Orm proteins, ceramides, and the phosphatidylinositol-4-phosphate (PI4P) phosphatase Sac1. The structural organization and regulatory mechanisms of this complex are not yet understood. Here, we report the high-resolution cryo-EM structures of the yeast SPT in complex with Tsc3 and Orm1 (SPOT) as dimers and monomers and a monomeric complex further carrying Sac1 (SPOTS). In all complexes, the tight interaction of the downstream metabolite ceramide and Orm1 reveals the ceramide-dependent inhibition. Additionally, observation of ceramide and ergosterol binding suggests a co-regulation of sphingolipid biogenesis and sterol metabolism within the SPOTS complex.
鞘脂是结构性膜成分，也在细胞应激反应中发挥作用。丝氨酸棕榈酰转移酶（SPT）催化鞘脂生物合成中的限速步骤。其活性通过多种结合伙伴受到严格调控，包括Tsc3、Orm蛋白、神经酰胺和磷脂酰肌醇-4-磷酸（PI4P）磷酸酶Sac1。该复合物的结构组织和调控机制尚不清楚。在这里，我们报告了酵母SPT与Tsc3和Orm1形成的复合物（SPOT）作为二聚体和单体以及进一步携带Sac1的单体复合物（SPOTS）的高分辨率冷冻电镜结构。在所有复合物中，下游代谢物神经酰胺与Orm1的紧密相互作用揭示了神经酰胺依赖性抑制作用。此外，对神经酰胺和麦角固醇结合的观察表明，SPOTS复合物内鞘脂生物合成和固醇代谢存在共同调节。
