4D lipid phase · Reconstructing the 4D space of intracellular lipid phase separation and lipid droplet biogenesis

Reconstructing the 4D space of intracellular lipid phase separation and lipid droplet biogenesis

Tackling the growing obesity pandemic and its associated metabolic disorders requires detailed understanding of the molecular processes regulating how cells handle and store excess energy. Lipid droplets (LDs) are key organelles in these processes, consisting of a core of energy-dense neutral lipids (NLs) that is surrounded by a unique phospholipid monolayer. Their main function is to store excess energy, but they are also involved in a wide variety of other essential cellular processes. LD formation occurs in the endoplasmic reticulum (ER) bilayer via a concentrated action of specific, but only partly understood, molecular machinery. Importantly, our understanding of LD biogenesis through direct observations at molecular resolution is critically lacking. A major obstacle is that conventional electron microscopy techniques, lending the required resolving power, do not preserve the detailed membrane architecture of the ER and the fine structure of the macromolecular machinery driving LD biogenesis. In this project, my aim was to use cutting-edge microscopy techniques and computational analysis to shed light on LD formation and factors regulating LD growth in human cells. To this end, I have combined powerful light- and cryo-electron microscopy to observe LD dynamics at unprecedented detail. I found that the membrane architecture between the ER and the LDs is shaped by a protein called seipin, which is mutated in a congenital form of lipodystrophy in humans. The nanoscale architecture of this contact site is dynamically altered in response to the metabolic needs of the cell and appears to control the growth rate of LDs. These findings help us better understand how cells store and regulate their energy deposits and could lead to development of new therapeutics in the future. To be able to image LD formation inside cells using cryo-electron microscopy, I further co-developed new technologies allowing to localise specific molecules inside cells with high precision. We leveraged the fact that specific bacterial-derived protein assemblies have recognisable shapes, and by conditionally expressing and tethering such assemblies to our target proteins in human cells, we can thus localise these proteins inside cryo-electron tomograms with high precision. This technology has great potential in helping other researchers aiming to observe dynamic or rare events using cryo-electron tomography.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз