Mechanisms of lipid droplet biogenesis at the endoplasmic reticulum

Organisms and cells face a myriad of environmental changes with periods of nutrient surplus and shortage. It is therefore not surprising that in all kingdoms of life, cells have evolved the means to store energy and thereby minimize the effects of environmental fluctuations. While the capability for energy storage has obvious advantages, deregulated energy accumulation can also be detrimental. Indeed, excessive energy storage is the hallmark of some of the most common diseases in the Western world such as obesity, atherosclerosis or diabetes.

In most cells energy is stored as fat in a dedicated cellular compartment called lipid droplet (LD). LDs are found in virtually every eukaryotic cell and play a central role in cellular lipid and energy metabolism. Despite their ubiquitous presence and importance, the processes governing the formation of LDs are mysterious. This proposal is aimed at closing the gap in understanding LDs.

It is well accepted that another cellular compartment, the endoplasmic reticulum (ER) plays a key role in LD formation. Many of the ingredients present in LDs come from the ER and in cells, ER and LD are often seen in close proximity. Our previous work and preliminary results identified components stabilizing the connections between these two compartments and that play an essential function in proper LD formation and fat storage. We expect that our work will offer in-depth information on the process of LD formation. Ultimately the findings might contribute to a better understanding of human pathologies such as obesity and lipodystrophies.

Lipid droplets (LDs) are organelles present in virtually every cell, with central roles in lipid and energy metabolism. Importantly, LD deregulation is associated with metabolic disorders such as obesity, diabetes and lipodystrophy. At structural level, LDs are rather unique: they are composed of a hydrophobic core made of neutral lipids, mainly triglycerides (TAG) and sterol esters (SE), surrounded by a monolayer of phospholipids acting as surfactants and a specific set of proteins. Most LD components are derived from the endoplasmic reticulum (ER), an organelle that is often physically connected with LDs highlighting the key role of this organelle in LD biogenesis. However, the mechanisms involved in LD formation remain unknown. For example how are sites of LD biogenesis specified is mysterious. Moreover, functional understanding of machinery involved in LD is lacking. From the work of several laboratories, including ours, two conserved ER proteins, seipin and FIT, have emerged as central components of LD biogenesis. However, their molecular functions are elusive. Moreover, It is unclear whether these and potentially other unidentified factors work only during LD biogenesis or instead are required in controlling mature LD behavior. Here I propose a set of genetic, biochemical and imaging approaches to in a systematic manner address these fundamental question in cell biology. Our findings will provide comprehensive mechanistic insights into LD biogenesis and dynamics. Importantly, our results may shed light on disease processes and ultimately offer novel avenues for therapeutic intervention.

Who will benefit from this research?
This project is primarily aimed at increasing understanding on a basic biological process: How cells store energy and lipid precursors in the form of fat molecules? However answering this fundamental question will ultimately have long-term healthcare implications with the potential to benefit a wide range of patient groups,in particular patients suffering from metabolic diseases such as diabetes type 2 and lipodystrophy. Thus, the biomedical implications of this work fit within the BBSRC's Strategic Research Priority "Bioscience for health".

How will they benefit from this research?
Lipids droplets are widely conserved organelles among eukaryotes. Thus, we will take advantage of the facile genetics and of the model eukaryote Saccharomyces cerevisiae to address a fundamental question in cell biology: what are the mechanisms governing lipid droplet biogenesis? The proteins involved in lipid synthesis and lipid droplet biogenesis are extremely conserved between yeast and man. In fact, mutations in most of the yeast genes involved in the process can be rescued by expression of their mammalian counterparts. Thus, we anticipate that the main findings of this project will be relevant to understand the mechanism of lipid storage in humans.

What will be done to ensure that they have the opportunity to benefit from this research?
In addition to traditional routes of publication, the outcomes from this project will be communicated through our web pages, the University of Oxford's Communications and Marketing Unit, Oxford's Café Scientifique, and the BBSRC media office. Potential future health benefits will be exploited via colleagues within the Medical Sciences Division.

Professional development for staff working on the project

The multidisciplinary nature of the research will expose the postdotoral researcher to a broad range of approaches and techniques from molecular biology, genetics and biochemistry to light and electron microscopy with corresponding opportunities for skill development. As part of the project, the postdoc will also be involved in proteomics and lipidomics experiments. Even if performed collaboratively, he/she will haven the opportunity to analyze and interpret these datasets. Initially skill development will be fostered in house both within our lab, core facilities (EM and proteomics) and collaborator (lipidomics). Thus, the project will provide excellent opportunities for skill development within the project. Career development will be advanced via regular team meetings; in addition, the the trainee will meet at least annually with a senior academic mentor from outside of the department (but within the Medical Sciences faculty). Presentation skills will be internally developed through opportunities to present within the Dunn School (each post-doc presents at least once a year). Finally, the opportunity to attend a science communication workshop will also be offered.