Three-Step Model for Polarized Sorting of KIF17 into Dendrites

Abstract

Kinesin and dynein motors drive bidirectional cargo transport along microtubules and have a critical role in polarized cargo trafficking in neurons [1, 2]. The kinesin-2 family protein KIF17 is a dendrite-specific motor protein and has been shown to interact with several dendritic cargoes [3-7]. However, the mechanism underlying the dendritic targeting of KIF17 remains poorly understood [8-11]. Using live-cell imaging combined with inducible trafficking assays to directly probe KIF17 motor activity in living neurons, we found that the polarized sorting of KIF17 to dendrites is regulated in multiple steps. First, cargo binding of KIF17 relieves autoinhibition and initiates microtubule-based cargo transport. Second, KIF17 does not autonomously target dendrites, but enters the axon where the actin cytoskeleton at the axon initial segment (AIS) prevents KIF17 vesicles from moving further into the axon. Third, dynein-based motor activity is able to redirect KIF17-coupled cargoes into dendrites. We propose a three-step model for polarized targeting of KIF17, in which the collective function of multiple motor teams is required for proper dendritic sorting.

Differentiation of ciliated human midbrain-derived LUHMES neurons

“…LUHMES differentiation into functional neurons has been described elsewhere and our work faithfully replicated the findings, including the overall time frame (Scholz et al, 2011; Shah et al, 2016; Harischandra et al, 2020). Accordingly, we observed that, in addition to the ciliary marker ARL13B ( Figure 5A ), differentiating LUHMES neurons expressed the general neurite marker tubulin beta 3 (TUBB3) and the synaptic marker post-synaptic density protein 95 (PSD95) ( Figure 5B ), the neuronal transport marker kinesin 17 (KIF17) ( Figure 5C ) as well as tyrosine hydroxylase (TH), the terminal differentiation marker for dopaminergic neurons ( Figure 5D ) (Wulle and Schnitzler, 1989; Lee et al, 1990; Hunt et al, 1996; Franker et al, 2016). The expression of various markers for neuronal differentiation, maturation and function, suggested that our culture conditions successfully induced neuronal differentiation, in accordance with previous findings.…”

Structure and Function of an Actin-Based Filter in the Proximal Axon

“…In particular, experiments examining the trafficking of full-length Kif-17 identified distinct roles for the two motor proteins (Franker et al, 2016). Actin appears to be involved in halting Kif-17-mediated movement of peroxisomes following entry into the proximal axon, in a manner similar to halting that was observed for vesicles carrying dendritic proteins (Al-Bassam et al, 2012).…”

“…Conversely, vesicles carrying nonspecifically localized proteins that are induced to interact with Myosin Va halt and reverse. Finally, full length Kif17 localizes to dendrites in part as a result of interaction with the actin cytoskeleton in the proximal axon, which stops its movement into the distal axon (Franker et al, 2016). …”

TRIM46 Organizes Microtubule Fasciculation in the Axon Initial Segment

“…The AIS recruits cell adhesion molecules to create a dense membrane protein region to prevent plasma membrane mixing. And the AIS controls entry of axonal cargoes and prevents erroneous entry of somatodendritic vesicles and redirects them back to the cell body (Lewis et al, 2009;Watanabe et al, 2012;Franker et al, 2016;Kuijpers et al, 2016).…”