Cilia and flagella are organelles that protrude from the surfaces of most eukaryotic cells and serve important functions in motility, sensory reception and signalling. Motile cilia are for example found on sperm cells and on epethilial cells lining the trachea where they remove dust and particles from the lungs. In addition to motile cilia, a primary cilium is found on almost all vertebrate cells where it functions in signalling and sensory reception. 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 of the eye where cilia play an important role in vision. In addition, cilia are found on olfactory cells responsible for smell. Genetic disorders that lead to cilia with compromised function result in a number of diseases with phenotypes including sterility, blindness and kidney failure (collectively known as ciliopathies). To assemble and maintain a functional cilium, the cell relies on active transport of cilium components, a process termed intraflagellar transport (IFT). IFT is the bi-directional movement of large particles along the microtubule-based axoneme of the cilium and is powered by kinesin and dynein molecular motors. The IFT process in turn depends on a large protein complex (the IFT complex) that presumably mediates the contact between ciliary cargo and molecular motors. 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 poorly understood. To this end our laboratory aims at determining the molecular basis for IFT using a combination of structural biology 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 states of IFT proteins and (sub)-complexes. These include in vitro pull downs, ultracentrifugation, isothermal titration calorimetry (ITC), microscale thermophoresis and light scattering.