Kinesin-3 KIF14 Regulates Intraflagellar Transport Dynamics in Primary Cilia

The primary cilium is an antenna-like organelle that plays a crucial role in development and homeostasis. Its growth and functions depend on the transport of cargo from the cilia base to the tip by intraflagellar transport (IFT) proteins and kinesin-2 motors. Primary cilia exhibit great variation in morphology and function across cell types and organisms. This diversity is thought to be conferred by the modulation of IFT by additional factors. However, examples of such non-canonical regulators, such as kinesin motors distinct from kinesin-2, are sparse. Thus, the involvement of non-canonical ciliary kinesins in intraciliary transport is unclear.

Here, we show that a poorly characterized member of the kinesin-3 family, KIF14, plays a prominent role in primary cilia trafficking in human cells. Using live cell imaging and expansion microscopy, we demonstrate that KIF14 depletion leads to impaired IFT. Furthermore, using TIRF microscopy we show that the motility of KIF14 and its effects on cilia trafficking rely on the motor domain of KIF14, which drives the processive runs along the ciliary axoneme in cells and in vitro , in co-operation with the C-terminal CC1 domain. Finally, we demonstrate that C-terminal truncations of KIF14, including patient mutation Q1380x, disrupt IFT by causing traffic jam-like accumulations of ciliary components in the distal part of the primary cilia, leading to bulged tips of cilia.

In summary, our data exemplify the role of a non-canonical ciliary kinesin in the regulation of ciliary trafficking and suggest a new paradigm for how kinesin-related trafficking defects may contribute to the pathology of disorder with a ciliary contribution.