# Mechanisms of Lipid Droplet Formation

> **NIH NIH R01** · HARVARD UNIVERSITY D/B/A HARVARD SCHOOL OF PUBLIC HEALTH · 2020 · $315,984

## Abstract

PROJECT SUMMARY
Lipid droplets (LDs) are found in virtually all eukaryotic cells where they serve to store neutral
lipids, such as triglycerides (TGs), as reservoirs of energy and membrane lipids. Owing to their
roles in cellular metabolism, metabolic diseases, and industrial oil production, there has been a
huge increase in investigation of LD biology and progress is being made. However, the central
question of LD biology – how these monolayer-bound organelles are formed from the ER
bilayer – remains unanswered. In recent years, investigations by our laboratory and others
have revealed that LD formation occurs in distinct steps that are regulated by specific proteins.
We propose these steps are: a) TG synthesis in the ER membrane; b) collection of TG lenses
within the ER membrane; c) budding/separation of TG lenses from the ER to form “nascent”
LDs (less than 200 nm diameter); and d) growth and maturation of nascent LDs to mature iLDs
(400-600 nm diameter). The overarching goal of our proposal is to reveal the mechanistic
bases for the individual steps of LD formation. Proteins governing these steps appear to be
involved in determining the number of LD formation sites, whereas other proteins are involved
in promoting the budding/separation of LDs from the ER. Moreover, we recently showed that
the ER protein seipin promotes the maturation of budded nascent LDs to mature initial LDs,
although the precise mechanism is unclear. In this proposal, we will utilize cutting edge cell
biology tools (CRISPR engineering of cells; protein markers of LD formation; confocal, lattice
light-sheet and FIB-SEM microscopy) and in vitro assay systems to unravel specific steps in LD
formation. In Aim 1, we will study how LD formation sites are determined and test the
hypothesis that specific ER proteins that control ER shape, such as atlastin, regulate LD
formation in the ER. Aim 2 focuses on budding (i.e., complete separation) of LDs from the ER.
Here we will utilize an in vitro assay to identify cytoplasmic factors that promote LD formation
and budding/separation from the ER in an in vitro system. We will identify these factors and
determine how they promote LD formation in vitro and in cells. Aim 3 focuses on maturation of
budded nascent LDs to mature initial LDs, a process we showed recently that involves seipin.
We will determine the mechanism by which seipin causes growth of nascent LDs during LD
formation, and we will determine which proteins, in addition to seipin, maintain LD-ER contact
during LD formation. Successful completion of our aims will have a major impact on the field of
LD biology and reveal the basic biology that underlies numerous metabolic diseases of excess
lipid droplet accumulation, such as obesity and related diseases.

## Key facts

- **NIH application ID:** 9939587
- **Project number:** 5R01GM124348-04
- **Recipient organization:** HARVARD UNIVERSITY D/B/A HARVARD SCHOOL OF PUBLIC HEALTH
- **Principal Investigator:** ROBERT V FARESE
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $315,984
- **Award type:** 5
- **Project period:** 2017-09-01 → 2021-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9939587

## Citation

> US National Institutes of Health, RePORTER application 9939587, Mechanisms of Lipid Droplet Formation (5R01GM124348-04). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9939587. Licensed CC0.

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