Project Summary Pore-forming membrane channels are central mediators of many complex biological phenomena; such as synchronizing the contraction of our heart and electro-chemical signals in our brain, and detecting light, sound, touch, taste and smells of the world around us. This ability is dependent upon dynamic mechanism used to spatially and temporally modulate their cellular activity. Our research group is focused on understanding how these types of phenomena are choreographed by remarkably complex strategies of cell-to-cell communication, through the gap junctions. We aim to develop a molecular and atomic-level of mechanistic understanding of how gap junctions coordinate inter-cellular communication. To achieve this level of detail, we are combining the unique power of electron cryo-microscopy (CryoEM), together with computational modeling and targeted biophysical and functional studies to address several fundamental questions, such as: i) How do the gap junctions selectively control the flow of chemical information between cells? ii) How are their activities allosterically modulated by physiological signals and pharmacological agents? iii) How gap junction assembly, structure and function is coupled with the local lipid/cellular environment? Despite their physiological and medical relevance, membrane proteins still only represent ~4% of the protein structure database. However, recent advances in the field of high-resolution CryoEM, coupled with advancements in membrane protein biochemistry and in situ imaging technologies, are beginning to revolutionize the way we structurally characterize these proteins. With these tools in hand, we are addressing several key questions about gap junction assembly, selectivity and regulation. The results of our investigations are expected to provide an architectural framework and the mechanistic knowledge required for the rational development of targeted therapies against a range of gap junction related diseases, such as blindness, deafness, arrhythmia, stroke and cancers.