One of the major constituents of mitochondrial membranes is the phospholipids, which play a key role in maintaining the structure and the functions of the mitochondria. However, mitochondria do not synthesize most of the phospholipids , necessitating the presence of phospholipid import pathways. Even for the phospholipids, which are synthesized within the inner mitochondrial membrane (IMM), the phospholipid precursors must be imported from outside the mitochondria. Therefore, the mitochondria heavily rely on the phospholipid transport pathways for its proper functioning. Since, mitochondria are not part of a vesicular trafficking network, the molecular mechanisms of how mitochondria receive its phospholipids remain a relevant question. One of the major ways that hydrophobic phospholipids can cross the aqueous barrier of inter or intraorganellar spaces is by apposing membranes, thereby decreasing the distance of transport, or by being sequestered by lipid transport proteins (LTPs). Therefore, with the discovery of LTPs and membrane contact sites (MCSs), we are beginning to understand the molecular mechanisms of phospholipid transport pathways in the mitochondria. In this review, we will present a brief overview of the recent findings on the molecular architecture and the importance of the MCSs, both the intraorganellar and interorganellar contact sites, in facilitating the mitochondrial phospholipid transport. In addition, we will also discuss the role of LTPs for trafficking phospholipids through the intermembrane space (IMS) of the mitochondria. Mechanistic insights into different phospholipid transport pathways of mitochondria could be exploited to vary the composition of membrane phospholipids and gain a better understanding of their precise role in membrane homeostasis and mitochondrial bioenergetics.

中文翻译：

---

线粒体磷脂转运：接触位点和脂质转运蛋白的作用


线粒体膜的主要成分之一是磷脂，它在维持线粒体的结构和功能中发挥着关键作用。然而，线粒体不能合成大部分磷脂，因此需要存在磷脂输入途径。即使对于在线粒体内膜（IMM）内合成的磷脂，磷脂前体也必须从线粒体外部输入。因此，线粒体严重依赖磷脂转运途径来发挥其正常功能。由于线粒体不是囊泡运输网络的一部分，因此线粒体如何接收磷脂的分子机制仍然是一个相关问题。疏水性磷脂穿过细胞器间或细胞内空间水屏障的主要方式之一是通过并置膜，从而减少运输距离，或被脂质运输蛋白 (LTP) 隔离。因此，随着 LTP 和膜接触位点 (MCS) 的发现，我们开始了解线粒体中磷脂转运途径的分子机制。在这篇综述中，我们将简要概述分子结构的最新发现以及 MCS（细胞器内和细胞间接触位点）在促进线粒体磷脂转运中的重要性。此外，我们还将讨论 LTP 在通过线粒体膜间隙 (IMS) 运输磷脂方面的作用。 可以利用对线粒体不同磷脂转运途径的机制了解来改变膜磷脂的组成，并更好地了解它们在膜稳态和线粒体生物能学中的精确作用。