Perilipin membrane association determines Lipid Droplet heterogeneity in differentiating adipocytes
The storage of fat within lipid droplets (LDs) of adipocytes is critical for whole-body health. Acute fatty acid (FA) uptake by differentiating adipocytes leads to the formation of at least two LD-classes marked by distinct perilipins (PLINs). How this LD-heterogeneity arises is an important yet unresolved cell biological problem. Here, we show that an unconventional integral membrane-segment (iMS) targets the adipocyte specific LD-surface factor PLIN1 to the endoplasmic reticulum (ER) and facilitates high affinity binding to the first LD-class. The other PLINs remain largely excluded from these LDs until FA-influx recruits them to a second LD-population. Preventing ER-targeting turns PLIN1 into a soluble, cytoplasmic LD-protein, reduces its LD-affinity and switches its LD-class specificity. Conversely, moving the iMS to PLIN2 leads to ER-insertion and formation of a separate LD-class. Our results shed light on how differences in organelle targeting and disparities in lipid-affinity of LD-surface factors contribute to formation of LD-heterogeneity. HighlightsO_LIPLIN1 is an integral membrane protein behaving as a class I LD protein. C_LIO_LIAn unconventional integral membrane segment (iMS) mediates ER insertion. C_LIO_LIThe iMS is required for LD-heterogeneity in differentiating adipocytes. C_LIO_LIHigh affinity LD-targeting from the ER is likely a gated process. C_LI eTOC blurbMajchrzak et al. use biochemistry, imaging and in vitro experiments to identify molecular features in PLIN1 that determine ER insertion and high lipid droplet affinity which are both important in the generation of LD-heterogeneity within differentiating adipocytes.