Subcellular mechanisms coupling lipid synthesis and methionine metabolism

项目总结 细胞器间膜接触部位(Mcs)正在成为调节代谢途径的关键枢纽。 这使细胞能够适应外界的扰动和环境压力。因为他们在 细胞代谢，MCSs的调节失调与许多代谢和神经退行性变有关 疾病和衰老。到目前为止，许多研究都将MCSs与非囊泡性脂质转移和 脂代谢的空间组织。使用酵母作为模型系统，我们发现接触点之间 内质网(ER)和溶酶体招募脂酶来在空间上组织脂类合成 和储存，作为对脂毒应激的反应。脂质的生物合成与蛋氨酸代谢密切相关。 具体地说，S-腺苷蛋氨酸是蛋氨酸的直接产物，是必不可少的甲基供体。 是膜脂生物合成所必需的。然而，MCS如何监管非 SAM等脂类代谢物目前尚不清楚。令人惊讶的是，我们发现ER-溶酶体的缺失 酵母中的栓系显著改变SAM水平，并使酵母对蛋氨酸缺乏敏感。除了……之外 SAM为磷脂甲基化提供甲基，参与其他细胞功能，如 营养信号、表观遗传调节和维持氧化还原平衡。因此，通过以下方式降低SAM水平 干扰ER-溶酶体接触部位将对这些重要的细胞通路产生直接影响。 基于这些结果，我们认为内质网-溶酶体接触部位的脂质合成调节SAM 可用性，这是调节下游细胞通路的重要驱动因素。中心目标 这一建议的目的是通过1)阐明内质网溶酶体拴系的机制来检验这一假说 调节磷脂合成；2)确定改变的区划的功能后果 3)确定内质网结合和转运脂质的分子和结构基础。 4)确定内质网-溶酶体接触部位调节SAM的保守机制。 总而言之，我们的研究结果将提供对SAM监管的组织方面的洞察， 这如何改变脂体，以及它与衰老和代谢性疾病的关系。

PROJECT SUMMARY Inter-organelle membrane contact sites (MCSs) are emerging as critical hubs that regulate metabolic pathways which enables cellular adaptation to external perturbations and environmental stress. Because of their roles in cellular metabolism, dysregulation of MCSs has been linked to numerous metabolic and neurodegenerative disorders as well as aging. Numerous studies to date have linked MCSs to non-vesicular lipid transfer and spatial organization of lipid metabolism. Using yeast as a model system, we found that contact sites between the Endoplasmic reticulum (ER) and the lysosome recruit lipid enzymes to spatially organize lipid synthesis and storage as a response to lipotoxic stress. Lipid biosynthesis is intimately linked to methionine metabolism. Specifically, S-adenosyl methionine (SAM) which is a direct product of methionine, is an essential methyl donor required for membrane lipid biosynthesis. However, how MCSs regulate the availability and utilization of non- lipidic metabolites such as SAM is currently unknown. Surprisingly, we found that deletion of ER-lysosome tethers in yeast significantly alters SAM levels and sensitizes yeast to methionine-deprivation. In addition to providing methyl groups for phospholipid methylation, SAM is involved in other cellular functions such as nutrient signaling, epigenetic regulation, and maintaining redox balance. Therefore, lowering SAM levels by perturbing ER-lysosome contact sites will have direct consequences on these essential cellular pathways. Based on these results, we propose that lipid synthesis at ER-lysosome contact sites regulates SAM availability, which serves as an important driver for regulating downstream cellular pathways. The central goal of this proposal is to test this hypothesis by 1) elucidating the mechanisms by which ER-lysosome tethers regulate phospholipid synthesis; 2) determining the functional consequences for altered compartmentalization of phospholipid methylation; 3) defining molecular and structural basis for lipid binding and transport by ER- lysosome tethers; and 4) identifying conserved mechanisms for SAM regulation by ER-lysosome contact sites. Collectively, the results of our studies will provide insight into the organizational aspects of SAM regulation, how this alters the lipidome, and its relationship to aging and metabolic diseases.