Probing the mechanism and physiological roles of the bacterial DedA family of lipid transporters

Bacterial antibiotic resistance (AMR) is a rapidly growing global health concern that has the potential to render antibiotics obsolete and usher in a new era where previously innocuous infections become life-threatening. New antibiotics are essential, but antibiotic development is slow and resistance is inevitable. A promising alternative approach is to disrupt cellular functions that normally help bacteria adapt to environmental changes and antimicrobial attack, which would lead to sensitisation to current and future antibiotics. This approach could rejuvenate obsolete drugs and make new ones more effective. A crucial cellular structure for environmental adaptation and antibiotic resistance is the cell membrane, which forms a protective cellular shell. The membrane is a thin sheet composed of two layers (leaflets) forming a bilayer containing a complex mix of proteins and lipids. The rapid movement of lipids between the two membrane leaflets is essential to maintain normal cellular processes and adapt to environmental changes. Therefore, the proteins controlling lipid distribution are prime targets for inhibition in the quest for novel antimicrobials. Bacterial lipid transport mechanisms are extremely poorly understood limiting the development of inhibitors for this process. However, recently, the DedA family of proteins has emerged as key players in the transport of lipids between the membrane leaflets. In line with their central role, DedA proteins contribute substantially to AMR in bacterial pathogens; a DedA protein in the human pathogen Klebsiella pneumoniae is essential for resistance to colistin, a drug of last resort in the treatment of multidrug resistant bacterial infections, and disrupting the function of DedA proteins in Escherichia coli makes the bacterium extremely sensitive to a wide range of antimicrobial agents. Therefore, inhibiting the function of DedA proteins is a very promising route to reinvigorating and powering up antibiotics. However, we currently know very little about the structure of DedA proteins, how they work at the molecular level, and how their function is linked to antibiotic resistance, general physiology, and environmental adaptability, which limits our ability to develop molecules that will inhibit their function. Using an array of complementary experimental approaches, we will determine the architectural arrangement and lipid transport-related dynamics of DedA proteins. We will illuminate the mechanism of DedA lipid transport by defining how DedAs interact with lipids and how they power transport. Understanding what DedAs look like and how they work will arm us with the knowledge needed to inhibit their function. In addition, we will investigate the link between lipid transport and environmental adaptation to provide much needed insight into the physiological roles of these lipid transporters in bacteria. Completion of this project will provide insight into an essential physiological process of which we have virtually no understanding in bacteria and will lay the foundations for the development of future inhibitors targeting the DedA family. This project is frontier biosciences and is in complete alignment with the BBSRC’s Strategic Goals and areas for investment and support in developing an integrated understanding of health and the rules of life, antimicrobial resistance, and to ensure a healthy, prosperous and sustainable future.