Localized active transport shapes the nanoscopic features at the tip of mechanosensory cilia

Cilia, despite sharing a conserved axonemal structure, display diverse structural and molecular features, particularly at their tips. This study uncovers a mechanism that shapes the molecular features of fly mechanosensory cilia tips through localized active transport mediated by Kif19A, a kinesin-8 family member. Kif19A is predominantly expressed in peripheral neurons and is essential for enriching mechanosensory molecules at the ciliary tip, though it does not affect overall ciliary structure. In vitro studies show that Kif19A motors bind transiently to microtubules and exhibit non-processive movement individually, while multiple motors work together to drive plus end-directed movement of the cargoes, essential for precise localization and function of Kif19A in vivo. Building on the experimental observations, we propose a theoretical model in which nanoscale molecular polarity is established by local transport and binding sites that counteract rapid diffusion. This model highlights key principles by which molecular motors shape nanoscale cellular structures, thereby contributing to the diversity of cell architecture.