Vitasta Tiku

1 INTRODUCTION Mitochondria are double membrane-bound cell organelles that emerged by an endosymbiotic event two billion years ago. A eukaryotic ancestor cell incorporated a prokaryotic cell, which is similar to nowadays alpha-proteobacteria. Over the course of evolution most of the genetic information of the endosymbiont was either lost or transferred to the host genome. Only a small circular genome remains that encodes eight proteins in baker's yeast and 13 proteins in human mitochondria.

Abstract Mitochondria play central roles in the energetics and metabolism of eukaryotic cells. Their outer membrane is essential for protein transport, membrane dynamics, signalling and metabolic exchange with other cellular compartments. The mitochondrial import (MIM) complex functions as main translocase for importing the precursors of more than 90% of integral outer-membrane proteins. Here we report that the MIM complex performs a second major function in lipid-droplet homeostasis.

Abstract Mitochondria derive the majority of their lipids from other organelles through contact sites. These lipids, primarily phosphoglycerolipids, are the main components of mitochondrial membranes. In the cell, neutral lipids like triacylglycerides (TAGs) are stored in lipid droplets, playing an important role in maintaining cellular health. Enzymes like lipases mobilize these TAGs according to cellular needs.