Triacylglycerols sequester monotopic membrane proteins to lipid droplets

August 21, 2020

Title

Triacylglycerols sequester monotopic membrane proteins to lipid droplets

Author

Lucie Caillon, Vincent Nieto, Pauline Gehan, Mohyeddine Omrane, Nicolas Rodriguez, Luca Monticelli & Abdou Rachid Thiam

Year

2020

Journal

Nature Communications volume 11, Article number: 3944 (2020)

Abstract

Triacylglycerols (TG) are synthesized at the endoplasmic reticulum (ER) bilayer and packaged into organelles called lipid droplets (LDs). LDs are covered by a single phospholipid monolayer contiguous with the ER bilayer. This connection is used by several monotopic integral membrane proteins, with hydrophobic membrane association domains (HDs), to diffuse between the organelles. However, how proteins partition between ER and LDs is not understood. Here, we employed synthetic model systems and found that HD-containing proteins strongly prefer monolayers and returning to the bilayer is unfavorable. This preference for monolayers is due to a higher affinity of HDs for TG over membrane phospholipids. Protein distribution is regulated by PC/PE ratio via alterations in monolayer packing and HD-TG interaction. Thus, HD-containing proteins appear to non-specifically accumulate to the LD surface. In cells, protein editing mechanisms at the ER membrane would be necessary to prevent unspecific relocation of HD-containing proteins to LDs.

Instrument

J-815

Keywords

Circular dichroism, HPLC, proteins, endoplasmic reticulum, triacylglycerols, lipid droplets