Desiphering the structural origins of functional multimodality in bacterial mechanosensitive ion channels

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Ion channels are central to life sciences due to direct involvement in signal transduction, aging, cancer and neurodegeneration. Despite progress in the fundamental understanding of the structure and function of specific membrane proteins (Nobel Prizes in Chemistry 1988, 1997, 2003 and 2012), this has only been the tip of the iceberg. There is now an immediate need for the development of novel triggers to control pores in the cell membrane of deadly pathogens and tackle antimicrobial resistance, the most common cause of death worldwide. We anticipate to achieve that by exploiting an ancient and ubiquitous mechanism of ion channel regulation named mechanosensation. The latter is the ability of membrane proteins to sense tension changes occurring within the lipid membrane and respond to these by altering their structure and function. This proposal aims to gain a fundamental understanding of mechanosensation and decipher the molecular basis of its co-existence with other forms of ion channel regulation. To this end, we will dissect the individual steps that form its molecular basis and identify the common, but essential structural elements responsible to transduce pressure-sensing abilities to channels. The fundamental aspect of the underlying impact of the lipid membrane in ion channel regulation along with the physiological role of the functional versatility of pressure sensitive channels will be elucidated. To this end, we will identify the unique structural features which allow functional multimodality of mechanosensitive channels and their ability to respond to other stimuli, such as ions, pH or specific molecules, in addition to mechanical triggers. Within the project we will develop and follow an integrated multidisciplinary approach in order to establish a link between mechanical-activation and ligand-gating. The proposed studies will involve using a suite of state-of-the-art structural (Cryo Electron Microscopy and X -Ray crystallography), biochemical (Protein Purification), biophysical (Electron Paramagnetic Resonance spectroscopy and Electrophysiology) and sophisticated computational methods (Molecular Dynamics) to address questions pertaining to the mechanism and regulation of distinct members of the bacterial mechanosensitive ion channel family at a molecular level.Collectively, we anticipate to translate forces within the membrane participating in the mechanical activation of channels into specific molecular stimuli, which would mimic mechanotransduction. Similar to optogenetics, a field which has massively evolved over the last years and is based on the interaction of proteins with the ancient physical property of light, pressure sensing, one of nature's most fundamental regulatory mechanisms, would enable a radically novel field to emerge.