Mitochondrial lipid trafficking

Mitochondria are dynamic organelles surrounded by two membranes with a defined lipid composition. The majority of lipids are synthesized in the endoplasmic reticulum (ER) and transported to the mitochondria, but the synthesis of cardiolipin and phosphatidylethanolamine in the inner membrane of mitochondria highlights their general importance for cellular lipid metabolism. Extensive exchange of lipids and their precursors occurs between the ER and mitochondria as well as between mitochondria! membranes. The recent identification of membrane-tethering complexes and lipid-transfer proteins in mitochondria now provides the first insight into the mechanisms of these transport processes, which are of fundamental importance for mitochondrial activities and cell homeostasis. Here, we summarize the current understanding of lipid trafficking at the mitochondria and discuss emerging models for the mechanisms of lipid transfer.