Endoplasmic reticulum stress affects the transport of phosphatidylethanolamine from mitochondria to the endoplasmic reticulum in S.cerevisiae.

Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are two of the most abundant phospholipids in cells. Although both lipids can be synthesized in the endoplasmic reticulum (ER), in S. cerevisiae PE can also be produced in mitochondria and endosomes; this PE can be transported back to the ER where it is converted to PC. In this study we found that dithiothreitol (DTT), which induces ER stress, decreases PE export from mitochondria to the ER. This results in decreased levels of total cellular PC and mitochondrial PC. These decreases were not caused by changes in levels of PC synthesizing or degrading enzymes. PE export from mitochondria to the ER during ER stress was further reduced in cells lacking Mdm10p, a component of an ER-mitochondrial tethering complex that may facilitated lipid exchange between these compartments. We also found that reducing mitochondrial PC levels induces mitophagy. In conclusion, we show that ER stress affected PE export from mitochondria to ER and the Mdm10p is important for this process.