Peking-Tsinghua Center for Life Sciences, Tsinghua University, Beijing 100084, China.
J Cell Biol. 2011 Dec 12;195(6):953-63. doi: 10.1083/jcb.201104142. Epub 2011 Dec 5.
Lipid droplets (LDs) are dynamic cellular organelles that control many biological processes. However, molecular components determining LD growth are poorly understood. Genetic analysis has indicated that Fsp27, an LD-associated protein, is important in controlling LD size and lipid storage in adipocytes. In this paper, we demonstrate that Fsp27 is focally enriched at the LD-LD contacting site (LDCS). Photobleaching revealed the occurrence of lipid exchange between contacted LDs in wild-type adipocytes and Fsp27-overexpressing cells but not Fsp27-deficient adipocytes. Furthermore, live-cell imaging revealed a unique Fsp27-mediated LD growth process involving a directional net lipid transfer from the smaller to larger LDs at LDCSs, which is in accordance with the biophysical analysis of the internal pressure difference between the contacting LD pair. Thus, we have uncovered a novel molecular mechanism of LD growth mediated by Fsp27.
脂滴 (LDs) 是控制许多生物学过程的动态细胞细胞器。然而，确定 LD 生长的分子成分知之甚少。遗传分析表明，LD 相关蛋白 Fsp27 对于控制脂肪细胞中 LD 的大小和脂质储存非常重要。在本文中，我们证明 Fsp27 集中富集在 LD-LD 接触部位 (LDCS)。光漂白显示在野生型脂肪细胞和过表达 Fsp27 的细胞中，接触的 LD 之间发生了脂质交换，但在缺乏 Fsp27 的脂肪细胞中没有发生脂质交换。此外，活细胞成像揭示了一种独特的 Fsp27 介导的 LD 生长过程，涉及在 LDCS 处从较小的 LD 到较大的 LD 的定向净脂质转移，这与接触 LD 对之间的内部压力差的生物物理分析一致。因此，我们揭示了 Fsp27 介导的 LD 生长的新分子机制。
