Bacterial chemosensory arrays are protein assemblies that are the key structural and functional component for motile bacteria to sense their internal or environmental chemical signals. Cryo... Show moreBacterial chemosensory arrays are protein assemblies that are the key structural and functional component for motile bacteria to sense their internal or environmental chemical signals. Cryo electron tomography is a technique of transmission electron microscopy that allows the visualization of protein complexes in their near-native cellular context. This thesis includes a general introduction of the basics of bacterial chemosensory and the structural diversity of chemosensory arrays, as well as a description of the workflow of using cryo electron tomography to image bacterial chemosensory arrays in situ. This thesis presents the discovery of a different stoichiometry of chemotaxis proteins and a direct visualization of the kinase distribution within the chemosensory arrays in Vibrio cholerae. This highlight that a structural diversity of chemoreceptor arrays does exist, and that is the norm and not an exception. This thesis also includes studies illustrating the conformational dynamics of the Escherichia coli chemoreceptors correlated to its signaling states, which gives crucial insights on how the receptors function in a trimers-of-dimers packing arrangement. In short, studies present here broaden the appreciation of the structural diversity of chemosensory arrays and deepen our understanding of how arrays dynamically functions during chemosensory signal transduction. Show less
This thesis focuses on the role of chemokine receptors CXCR3 and CCR2 in the inflammatory process and infection control using the zebrafish model. It describes the regulatory interplay between an... Show moreThis thesis focuses on the role of chemokine receptors CXCR3 and CCR2 in the inflammatory process and infection control using the zebrafish model. It describes the regulatory interplay between an atypical and a conventional chemokine receptor during chemotaxis in macrophages, the role of chemotactic signaling in cell polarization and explores an in vivo screening workflow for human anti-inflammatory drugs using zebrafish. Show less
The behavior of single G-protein coupled receptor molecules were studied with single-molecule microscopy in the plasmamembrane during Dictyostelium discoideum chemotaxis. The mobility of the... Show moreThe behavior of single G-protein coupled receptor molecules were studied with single-molecule microscopy in the plasmamembrane during Dictyostelium discoideum chemotaxis. The mobility of the receptor was different in the anterior and posterior regions of living cells migrating towards the source of chemoattractant. This difference of mobility can account for an amplification of the extracellular signal, necessary for chemotaxis. It was also found that the receptor molecules are internalized. Show less
