Abd Emami Baharak, Shubbar Ahmed, Woods Hope, Moradi Mahmoud, Dastvan Reza
Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA.
Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA.
Res Sq. 2025 May 7:rs.3.rs-6575060. doi: 10.21203/rs.3.rs-6575060/v1.
Sphingosine kinase 1 (SK1) produces sphingosine-1-phosphate, a bioactive lipid implicated in cancer progression and other diseases. Despite its clinical relevance, the structural and dynamic basis of SK1 regulation and inhibition remains poorly understood. Using an integrated spectroscopic and computational approach, we uncover conformational transitions that govern substrate entry, catalysis, and inhibitor binding. Phosphorylation of Ser225 triggers regulatory loop rearrangements and salt bridge reshuffling, priming SK1 for membrane engagement and catalytic activity. We identify a previously uncharacterized catalytic intermediate featuring a distinct conformation with a highly dynamic lipid-binding loop 1 (LBL-1), sensitive to potent inhibitors such as PF-543. This inhibitor locks SK1 in an inactive state by restricting LBL-1 dynamics and globally stabilizing a non-catalytic conformation. Notably, SK1 forms functionally distinct dimers stabilized by ligand or membrane interactions, revealing a dynamic, multilayered regulatory mechanism governed by structural flexibility. These findings define a novel inhibitory mechanism and offer a structural framework for developing next-generation SK1-targeted therapeutics.
鞘氨醇激酶1（SK1）产生1-磷酸鞘氨醇，这是一种与癌症进展及其他疾病相关的生物活性脂质。尽管其具有临床相关性，但SK1调节和抑制的结构及动态基础仍知之甚少。我们采用综合光谱和计算方法，揭示了控制底物进入、催化及抑制剂结合的构象转变。Ser225的磷酸化触发调节环重排和盐桥重新排列，使SK1为膜结合和催化活性做好准备。我们鉴定出一种以前未被表征的催化中间体，其具有独特构象，脂质结合环1（LBL-1）高度动态，对PF-543等强效抑制剂敏感。这种抑制剂通过限制LBL-1的动态性并全局稳定非催化构象，将SK1锁定在无活性状态。值得注意的是，SK1通过配体或膜相互作用形成功能不同的二聚体，揭示了一种由结构灵活性控制的动态、多层调节机制。这些发现定义了一种新的抑制机制，并为开发下一代靶向SK1的治疗药物提供了结构框架。
