通常认为脂滴(LD)在ER中合成并在细胞质中利用。然而,在一些细胞的细胞核内观察到LD,尽管最近对核LDs的研究集中在培养的细胞系上。为了更好地理解体内发生的核LD,在此,我们检测了核包膜蛋白层相关多肽1(LAP1)耗竭后小鼠原代肝细胞中的LDs.显微图像分析表明,LAP1耗竭的肝细胞含有频繁的核LDs,它们的相关蛋白质不同于细胞质LD。我们发现了1型核质网,它们是内核膜的内陷,通常与这些肝细胞中的核LD相关。此外,小鼠肝细胞的核包膜蛋白laminA和C的体内消耗导致严重的核形态异常,但核LD明显少于LAP1耗尽时观察到的。此外,我们显示高脂饮食喂养和禁食小鼠增加了LAP1耗竭肝细胞的细胞质脂质,但减少了核LDs,证明LD形成与营养状态的关系。最后,微粒体甘油三酯转移蛋白的耗竭并没有改变LAP1耗竭肝细胞中核LDs的频率,这表明在这些细胞中核LD的生物发生是不需要的。一起,这些数据表明,LAP1耗尽的肝细胞代表了一个理想的哺乳动物系统,用于研究核LD的生物发生及其在细胞核和细胞质之间的分配,以响应体内营养状态和细胞代谢的变化。
Lipid droplets (LDs) are generally considered to be synthesized in the ER and utilized in the cytoplasm. However, LDs have been observed inside nuclei in some cells, although recent research on nuclear LDs has focused on cultured cell lines. To better understand nuclear LDs that occur in vivo, here we examined LDs in primary hepatocytes from mice following depletion of the nuclear envelope protein lamina-associated polypeptide 1 (LAP1). Microscopic image analysis showed that LAP1-depleted hepatocytes contain frequent nuclear LDs, which differ from cytoplasmic LDs in their associated proteins. We found type 1 nucleoplasmic reticula, which are invaginations of the inner nuclear membrane, are often associated with nuclear LDs in these hepatocytes. Furthermore, in vivo depletion of the nuclear envelope proteins lamin A and C from mouse hepatocytes led to severely abnormal nuclear morphology, but significantly fewer nuclear LDs than were observed upon depletion of LAP1. In addition, we show both high-fat diet feeding and fasting of mice increased cytoplasmic lipids in LAP1-depleted hepatocytes but reduced nuclear LDs, demonstrating a relationship of LD formation with nutritional state. Finally, depletion of microsomal triglyceride transfer protein did not change the frequency of nuclear LDs in LAP1-depleted hepatocytes, suggesting that it is not required for the biogenesis of nuclear LDs in these cells. Together, these data show that LAP1-depleted hepatocytes represent an ideal mammalian system to investigate the biogenesis of nuclear LDs and their partitioning between the nucleus and cytoplasm in response to changes in nutritional state and cellular metabolism in vivo.