Abstract
The regulation of lipid homeostasis is essential for normal cell physiology, and its disruption can lead to disease. Lipid droplets (LDs) are ubiquitous organelles dedicated to storing nonpolar lipids that are used for metabolic energy production or membrane biogenesis. LDs normally emerge from, and associate with, the endoplasmic reticulum and interact with other cytoplasmic organelles to deliver the stored lipids. Recently, LDs were found to reside also at the inner side of the nuclear envelope and inside the nucleus in yeast and mammalian cells. This unexpected finding raises fundamental questions about the nature of the inner nuclear membrane, its connection with the endoplasmic reticulum and the pathways of LD formation. In this viewpoint, we will highlight recent developments relating to these questions and discuss possible roles of LDs in nuclear physiology.
Highlights
Cells contain a myriad of lipids which perform key roles as structural components of membranes, energy storage molecules and signal transducers
lipid droplets (LDs) act as a lipid reservoir that provides fatty acids used for energy production during starvation, or other lipid precursors that are used for membrane biogenesis to support organelle or cell growth [1,2]
Whether phospholipids made at the outer nuclear membrane (ONM)/endoplasmic reticulum (ER) can diffuse via the pore membrane and freely equilibrate to the inner nuclear membrane (INM), or the INM can generate its own distinct lipid composition, for example by import of enzymes such as lipin, remains unknown
Summary
Cells contain a myriad of lipids which perform key roles as structural components of membranes, energy storage molecules and signal transducers. Recent studies led to the surprising identification of lipid droplets (LDs) inside the nuclei of both budding yeast and mammalian cells.
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