KIF13A and KIF13B tails bind transferrin receptor vesicles. (A) A schematic showing the three constructs expressed in this assay before and after assembly of the split kinesin. (B) Kymographs showing the transport of TfR vesicles in dendrites before assembly of the split kinesin in two different dendrites. (C) Kymographs showing the transport of TfR vesicles in the axon before and at varying times after adding the linker drug (AP 21967, 1 µM) in a cell expressing the FRB-KIF13B tail. Before adding the linker drug there was far less vesicle transport in the axon than the dendrites (compare with B). After drug-induced assembly of the split kinesin there was a pronounced increase in long-range anterograde vesicle transport in the axon. Time and distance calibration are the same for kymographs in B and C. (D) Images showing the cell body and proximal axon of the neuron imaged immediately before (0 min) and after 16 min of treatment with linker drug. Note the increase in intensity of TfR-GFP in the axon after 16 min. Bar, 20 µm. (E–L) Kymographs illustrating axonal transport of TfR-GFP vesicles in hippocampal neurons expressing different split kinesin tail constructs. The kymographs show the transport of TfR vesicles in the axon before (0 min) and 14–28 min after addition of the linker drug. There was no change in the overall transport of TfR vesicles when KIF1A, KIF1Bα, KIF1Bβ, KIF5C, KIF17, or KIF21B tails were expressed. In contrast, there was a large increase in the long-range anterograde transport events of TfR vesicles when KIF13A (H) or KIF13B (I) tails were used. See also Video 2. Time and distance calibrations are the same for kymographs in E–L.