The interaction of Uncoupling Protein 1 with regulatory ligands - new metabolite players in controlling brown fat thermogenic energy expenditure

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Mammals gain energy to live through the breakdown of nutrients in food. The bulk of the energy harnessed occurs though biochemical processes that occur in mitochondria, the 'energy factories' present in just about all cells of the body. These energy hubs work to breakdown food molecules to generate ATP, a universal 'fuel' molecule that powers the many processes in cells. While conventional 'white' fat is used to store excess food nutrients, mammals can also produce specialised brown fat, or "good fat", which is packed with mitochondria containing Uncoupling protein 1 (UCP1), a unique protein that allows nutrient calories to be 'burned' off as heat instead of making ATP. Activity of the protein is used to protect animals including livestock (e.g. sheep), especially new-borns, from cold temperatures, but also occurs in human adults where it confers health benefits. Brown fat with UCP1 is found more in leaner people, and when stimulated expends calories, removing glucose and fat from the blood, combating diabetes and obesity. These conditions are a major national and international issue, urgently requiring improved therapies. Obesity and related conditions are estimated to cost the UK alone ~£27 billion per year.Researchers worldwide are looking into ways to encourage brown fat development as a promising strategy for improved health. However, a key issue is that, even when present, UCP1 is inactive in brown fat cells unless specifically 'switched on' in response to particular physiological stimulation such as cold temperatures, which occurs through interactions with key activator and inhibitor molecules that control activity. Methods to artificially activate the protein have potential to greatly increase the calorie turnover capacity of the tissue and its associated health benefits. UCP1 is not present in other major tissues and is an attractive therapeutic target. The protein has been studied for over 40 years, though, until recently, little was understood on how it works. UCP1 is a membrane protein, which are insoluble and often unstable when isolated, making them particularly difficult to study. However, we have been able to develop specialised methods to produce, isolate and study intact UCP1. Our work has clarified the protein's composition, core mechanism and how key activator molecules interact to induce activity, allowing us to identify new molecules that can also activate the protein, e.g. particular drugs.We have now identified novel features in UCP1 that provide a credible model of how inhibitor molecules interact to control the protein. Additionally, we have discovered a completely new class of regulator molecule, important in brown fat metabolism, that interacts with UCP1, and may indicate a major new function. This project aims to determine the molecular details of how these molecules interact to influence UCP1 activity and function. Isolated UCP1 will be investigated using biophysical and biochemical methods, including specialised assays to monitor membrane protein interactions and protein state changes through specific changes in the protein's stability. The protein will be studied in artificial membranes, using radiolabelling methods to tract molecules, and determine how they influence the protein. Molecular biology methods to change specific features of UCP1 will be used to identify where and how molecules interact. Advanced cryogenic electron microscopy methods will also be carried out to gain a detailed 'snap shot' of the protein's 3D molecular structure, to provide a framework for rationalising the molecular processes of UCP1 regulation. The work will provide molecular details on how UCP1 is regulated in fat tissue, advancing our fundamental understanding on membrane protein function, energy metabolism and fat biology. The work also has potential to define new biochemical pathways, which help downstream avenues to therapeutically target energy expenditure to combat obesity and metabolic disease.