OBJECTIVE: To address these gaps, this study investigated the systemic control mechanisms of MAM on neutral lipids synthesis by recruiting seipin, focusing on the role of the inositol trisphosphate receptor-1,4,5(Ip3r)-75 kDa glucose-regulated protein (Grp75)-voltage-dependent anion channel (Vdac) complex and their relevant Ca2+ signaling in this process.
METHODS: To this end, a model animal for lipid metabolism, yellow catfish (Pelteobagrus fulvidraco), were fed 6 different diets containing a range of palmitic acid (PA) concentrations from 0-150 g/kg in vivo for 10 wk. In vitro, experiments were also conducted to intercept the MAM-mediated Ca2+ signaling in isolated hepatocytes by transfecting them with si-mitochondrial calcium uniporter (mcu). Because mcu was placed in the inner mitochondrial membrane (IMM), si-mcu cannot disrupt MAM\'s structural integrity.
RESULTS: 1. Hepatocellular MAM subproteome analysis indicated excessive dietary PA intake enhanced hepatic MAM structure joined by activating Ip3r-Grp75-Vdac complexes. 2. Dietary PA intake induced hepatic neutral lipid accumulation through MAM recruiting Seipin, which activated lipid droplet biogenesis. Our findings also revealed a previously unidentified mechanism whereby MAM-recruited seipin and controlled hepatic lipid homeostasis, depending on Ip3r-Grp75-Vdac-controlled Ca2+ signaling and not only MAM\'s structural integrity.
CONCLUSIONS: These results offer a novel insight into the MAM-recruited seipin in controlling hepatic lipid synthesis in a MAM structural integrity-dependent and Ca2+ signaling-dependent manner, highlighting the critical contribution of MAM in maintaining hepatic neutral lipid homeostasis.
目标:为了解决这些差距,本研究通过招募Seipin研究了MAM在中性脂质合成中的系统控制机制,重点介绍Ip3r-Grp75-Vdac复合物及其相关Ca2+信号在此过程中的作用。
方法:为此,脂质代谢的模型动物,黄鲶鱼(黄鲈鱼),在体内饲喂六种不同的饮食,其中包含0g/kg至150g/kg的棕榈酸(PA)浓度范围,持续10周。还进行了体外实验,通过用线粒体钙单向转运蛋白(mcu)转染分离的肝细胞来拦截MAM介导的Ca2信号传导。由于mcu位于线粒体内膜(IMM),si-mcu不能破坏MAM的结构完整性。
结果:1.肝细胞MAM亚蛋白质组分析表明,过量的饮食PA摄入通过激活Ip3r-Grp75电压依赖性阴离子通道(Vdac)复合物来增强肝MAM结构连接。2.膳食PA摄入通过MAM招募Seipin诱导肝中性脂质积累,激活了脂滴生物合成。我们的发现还揭示了以前未知的机制,即MAM招募了Seipin并控制了肝脏脂质稳态,取决于Ip3r-Grp75-Vdac控制的Ca2+信号,而不仅仅是MAM的结构完整性。
结论:这些结果为MAM招募的Seipin以MAM结构完整性依赖性和Ca2信号依赖性方式控制肝脂质合成提供了新的见解,强调MAM在维持肝脏中性脂质稳态方面的关键贡献。