Membrane bridges and nanodomain partitioning govern membrane protein targeting to lipid droplets
8 affiliations
- 1Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- 2Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- 3Department of Chemistry and Nanoscience Center, University of Copenhagen, Copenhagen, Denmark
- 4Abberior Instruments America, Bethesda, MD, USA
- 5Novo Nordisk Center for Optimized Oligo Escape and Control of Disease, University of Copenhagen, Copenhagen, Denmark
- 6Cell Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA. [email protected]
- 7Cell Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA. [email protected]
- 8Howard Hughes Medical Institute, New York, NY, USA. [email protected]
Abstract
Numerous metabolic enzymes translocate from the endoplasmic reticulum (ER) membrane bilayer to the lipid droplet (LD) monolayer, where they perform essential functions. Mislocalization of certain LD-targeted membrane proteins, including HSD17B13 and PNPLA3, is implicated in metabolic dysfunction-associated steatotic liver disease. However, the mechanisms governing the trafficking and accumulation of ER proteins on LDs remain poorly understood. Here using minimal fluorescence photon fluxes nanoscopy and highly inclined and laminated optical single-molecule tracking combined with machine learning, we show that HSD17B13, GPAT4 and the model cargo 'LiveDrop' diffuse at comparable speeds in the ER and on LDs, but become nano-confined upon reaching the LD surface. Mechanistic dissection of LiveDrop targeting revealed that this confinement, along with protein accumulation on LDs, depends on specific residues within its targeting motif. These residues mediate preferential interactions with nanoscale membrane domains, suggesting that LD-targeted proteins selectively partition into distinct lipid-protein environments that transiently alter local motion and concentrate them at the LD surface. Single-molecule trajectories further revealed bidirectional trafficking of LiveDrop across seipin-containing ER-LD bridges, providing direct evidence for lateral protein transfer across membrane contact sites. These findings establish nanodomain-based confinement as a key mechanism driving selective protein accumulation on LDs and reveal how membrane bridges between organelles facilitate protein sorting.
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BibTeX
@article{mizrak2026membrane,
title = {{Membrane bridges and nanodomain partitioning govern membrane protein targeting to lipid droplets}},
author = {Arda Mizrak and Jacob Kæstel‐Hansen and Jessica Matthias and J. Wade Harper and Nikos S. Hatzakis and Robert V. Farese and Tobias C. Walther},
journal = {Nature Cell Biology},
year = {2026},
month = may,
doi = {10.1038/s41556-026-01963-3},
url = {https://doi.org/10.1038/s41556-026-01963-3},
note = {CC BY},
}
RIS
TY - JOUR
TI - Membrane bridges and nanodomain partitioning govern membrane protein targeting to lipid droplets
AU - Arda Mizrak
AU - Jacob Kæstel‐Hansen
AU - Jessica Matthias
AU - J. Wade Harper
AU - Nikos S. Hatzakis
AU - Robert V. Farese
AU - Tobias C. Walther
PY - 2026
DA - 2026/05/26
JO - Nature Cell Biology
DO - 10.1038/s41556-026-01963-3
UR - https://doi.org/10.1038/s41556-026-01963-3
AB - Numerous metabolic enzymes translocate from the endoplasmic reticulum (ER) membrane bilayer to the lipid droplet (LD) monolayer, where they perform essential functions. Mislocalization of certain LD-targeted membrane proteins, including HSD17B13 and PNPLA3, is implicated in metabolic dysfunction-associated steatotic liver disease. However, the mechanisms governing the trafficking and accumulation of ER proteins on LDs remain poorly understood. Here using minimal fluorescence photon fluxes nanoscopy and highly inclined and laminated optical single-molecule tracking combined with machine learning, we show that HSD17B13, GPAT4 and the model cargo 'LiveDrop' diffuse at comparable speeds in the ER and on LDs, but become nano-confined upon reaching the LD surface. Mechanistic dissection of LiveDrop targeting revealed that this confinement, along with protein accumulation on LDs, depends on specific residues within its targeting motif. These residues mediate preferential interactions with nanoscale membrane domains, suggesting that LD-targeted proteins selectively partition into distinct lipid-protein environments that transiently alter local motion and concentrate them at the LD surface. Single-molecule trajectories further revealed bidirectional trafficking of LiveDrop across seipin-containing ER-LD bridges, providing direct evidence for lateral protein transfer across membrane contact sites. These findings establish nanodomain-based confinement as a key mechanism driving selective protein accumulation on LDs and reveal how membrane bridges between organelles facilitate protein sorting.
SN - 1465-7392
SN - 1476-4679
ER -