Molecular Interactions at Lipid Droplet–Mitochondria Membrane Contact Sites in Mammalian Cells

Lipid droplets are the neutral lipid storage compartments of eukaryotic cells. Mitochondria are the main source for ATP, which is generated through oxidative phosphorylation. Thus, both organelles play essential roles in fatty acid metabolism and energy homeostasis. Therefore, functional and physical interaction of lipid droplets with mitochondria is of special importance as essential processes, such as lipolysis, triacylglycerol synthesis, thermogenesis or the protection against oxidative stress, and lipotoxicity, depend on cooperation of these two organelles. Physical interaction of LDs with mitochondria is mediated by specific molecular complexes at inter-organelle membrane contact sites. Substantial progress has been achieved during the last decade in understanding the formation and the structural components of lipid droplet–mitochondria contact sites. This review gives a brief overview of the different molecular complexes that have been identified in different mammalian cell types under different conditions and their regulation.