MicroScale Thermophoresis (MST) is a powerful technology to investigate the affinity of various types of interactions, including protein-protein interactions. In this publication, MST was applied to determine the affinity of tubulin to intraflagellar transport factors. Based on these results, scientists from the research group “Intraflagellar Transport” at the MPI of Biochemistry in Martinsried headed by Esben Lorentzen suggest a model for tubulin transport and ciliary length control. The findings shed light onto cilium assembly and the crucial mechanism of intraflagellar transport thus leading to novel insights into the molecular level of numerous diseases.
Intraflagellar transport (IFT) of ciliary precursors such as tubulin from the cytoplasm to the ciliary tip is involved in the construction of the cilium, a hairlike organelle found on most eukaryotic cells. However, the molecular mechanisms of IFT are poorly understood. Here, we found that the two core IFT proteins IFT74 and IFT81 form a tubulin-binding module and mapped the interaction to a calponin homology domain of IFT81 and a highly basic domain in IFT74. Knockdown of IFT81 and rescue experiments with point mutants showed that tubulin binding by IFT81 was required for ciliogenesis in human cells.