Cilia (also called flagella) are large macromolecular structures that protrude from the cell surface and serve important functions in both motility and sensing. Motile cilia serve as the motor driving the movement of certain cell types (such as sperm cells). Immotile cilia (also called primary cilia) are found in most animal cells as sensory organelles that allow cells to correctly respond to their outer environment. Cilia are in particular important during development but are also required for normal physiology. A specialized case of the sensory cilium is found in photoreceptor cells in the eye where cilia play an important role in vision. In addition, cilia are found in the inner ear as well as on olfactory cells responsible for smell. Genetic disorders that lead to non-functional cilia result in a number of diseases including sterility, blindness and kidney failure. To assemble and maintain a functional cilium, the cell relies on active transport of cilium components, a process termed intraflagellar transport (IFT). This process depends on a large protein complex (the IFT complex) that binds cilia proteins and transports them along microtubule filaments to reach the tip of the cilium. Although the protein components of the IFT complex have been identified and to some extent characterized, the overall composition of the complex as well as the molecular basis for cargo interaction remain undiscovered. To this end our laboratory aims at determining the molecular basis for IFT using a combination of structural and biochemical techniques in order to shed light on the underlying processes of cilia assembly, function and its pathological conditions
To understand the mechanisms behind intraflagellar transport we aim at establishing the architecture of the IFT complex and the molecular basis for motor and cargo association. To this end we are developing purification and reconstitution protocols for IFT complexes in order to study their detailed 3D structure using the methods of X-ray crystallography and electron microscopy. In addition to the structural techniques we employ a number of biophysical and biochemical methods to shed light on individual interactions and oligomeric state of IFT proteins and (sub)-complexes. These include in vitro pull downs, ultracentrifugation, isothermal titration calorimetry (ITC), Biacore and light scattering. It is the hope that this will ultimately lead to a better mechanistic understanding of cilia assembly as well as the associated diseases.
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