A SxIP motif interaction at the microtubule plus end is important for processive retrograde axonal transport.

The retrograde transport of endosomes within axons proceeds with remarkable uniformity despite having to navigate a discontinuous microtubule network. The mechanisms through which this navigation is achieved remain elusive. In this report, we demonstrate that access of SxIP motif proteins, such as BPAG1n4, to the microtubule plus end is important for the maintenance of processive and sustained retrograde transport along the axon. Disruption of this interaction at the microtubule plus end significantly increases endosome stalling. Our study thus provides strong insight into the role of plus-end-binding proteins in the processive navigation of cargo within the axon.