The plus-end microtubule (MT) motor kinesin-1 is essential for normal development, with key roles in the nervous system. Kinesin-1 drives axonal transport of membrane cargoes to fulfill the metabolic needs of neurons and maintain synapses. We have previously demonstrated that kinesin-1, in addition to its well-established role in organelle transport, can drive MT-MT sliding by transporting "cargo" MTs along "track" MTs, resulting in dramatic cell shape changes. The mechanism and physiological relevance of this MT sliding are unclear. In addition to its motor domain, kinesin-1 contains a second MT-binding site, located at the C terminus of the heavy chain. Here, we mutated this C-terminal MT-binding site such that the ability of kinesin-1 to slide MTs is significantly compromised, whereas cargo transport is unaffected. We introduced this mutation into the genomic locus of kinesin-1 heavy chain (KHC), generating the Khc mutA allele. Khc mutA neurons displayed significant MT sliding defects while maintaining normal transport of many cargoes. Using this mutant, we demonstrated that MT sliding is required for axon and dendrite outgrowth in vivo. Consistent with these results, Khc mutA flies displayed severe locomotion and viability defects. To test the role of MT sliding further, we engineered a chimeric motor that actively slides MTs but cannot transport organelles. Activation of MT sliding in Khc mutA neurons using this chimeric motor rescued axon outgrowth in cultured neurons and in vivo, firmly establishing the role of sliding in axon outgrowth. These results demonstrate that MT sliding by kinesin-1 is an essential biological phenomenon required for neuronal morphogenesis and normal nervous system development.kinesin-1 | microtubules | Drosophila | axon outgrowth | dendrite outgrowth N eurons are the basic unit of the nervous system, forming vast networks throughout the body that communicate using receptorligand machinery located in long cellular projections called axons and dendrites. Learning how these processes form is key to understanding the early development and pathology of the nervous system. Microtubules (MTs) and actin microfilaments have been implicated in neurite outgrowth, with many studies focusing on the growth cone at the tip of the axon. Previous models suggest that the driving forces for neurite outgrowth are MT polymerization and the treadmilling of F-actin (1, 2). However, other studies demonstrate that F-actin is dispensable to outgrowth and neurites extend even in the absence of F-actin (3-5).Our group has found that the motor protein kinesin-1 can rearrange the MT network by sliding MTs against each other (6). We have shown that kinesin-1 is required for MT sliding in cultured neurons and kinesin-1 depletion inhibits both neurite outgrowth and regeneration (7,8). Additionally, we have observed MT sliding in axons as well as MTs pushing on the axon tip (9). Recent studies from other groups have also implicated MT translocation in axon extension and dendritic organization (10-12). Based on th...

Neuronal polarity relies on the axon- or dendrite-specific localization of cargo by molecular motors such as kinesin-1. This study shows how autoinhibition regulates both kinesin-1 activity and localization to keep dendritic Golgi outposts from entering axons.

Neurons are exquisitely polarized cells whose structure and function relies on microtubules. Microtubules in signal-receiving dendrites and signal-sending axons differ in their organization and microtubule-associated proteins. These differences, coupled with microtubule post-translational modifications, combine to locally regulate intracellular transport, morphology, and function. Recent discoveries provide new insight into the regulation of non-centrosomal microtubule arrays in neurons, the relationship between microtubule acetylation and mechanosensation, and the spatial patterning of microtubules that regulates motor activity and cargo delivery in axons and dendrites. Together, these new studies bring us closer to understanding how microtubule function is locally tuned to match the specialized tasks associated with signal reception and transmission.

Herein we describe a large capsule-like bis-calix[4]pyrrole 1, which is able to host concurrently two dihydrogen phosphate anions within a relatively large internal cavity. Evidence for the concurrent, dual recognition of the encapsulated anions came from 1H NMR and UV–vis spectroscopies and ITC titrations carried out in CD2Cl2/CD3OD (9/1, v/v) or dichloroethane (DCE), as well as single crystal X-ray diffraction analyses. Receptor 1 was also found to bind two dianionic sulfate anions bridged by two water molecules in the solid state. The resulting sulfate dimer was retained in DCE solution, as evidenced by spectroscopic analyses. Finally, receptor 1 was found capable of accommodating two trianionic pyrophosphate anions in the cavity. The present experimental findings are supported by DFT calculations along with 1H NMR and UV–vis spectroscopies, ITC studies, and single crystal X-ray diffraction analyses.

SummaryNeuronal polarity relies on the axon-or dendrite-specific localization of cargo by molecular motors such as kinesin-1. These studies show autoinhibition regulates both kinesin-1 activity and localization to keep dendritic cargo from entering axons. was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/275149 doi: bioRxiv preprint first posted online 1 AbstractNeuronal polarity relies on the selective localization of cargo to axons or dendrites. The molecular motor kinesin-1 moves cargo into axons but is also active in dendrites. This raises the question of how kinesin-1 activity is regulated to maintain the compartment-specific localization of cargo. Our in vivo structure-function analysis of endogenous Drosophila kinesin-1 reveals a novel role for autoinhibition in enabling the dendrite-specific localization of Golgi outposts.Mutations that disrupt kinesin-1 autoinhibition result in the axonal mislocalization of Golgi outposts. Autoinhibition also regulates kinesin-1 localization. Uninhibited kinesin-1 accumulates in axons and is depleted from dendrites, correlating with the change in outpost distribution and dendrite growth defects. Genetic interaction tests show that a balance of kinesin-1 inhibition and dynein activity is necessary to localize Golgi outposts to dendrites and keep them from entering axons. Our data indicate that kinesin-1 activity is precisely regulated by autoinhibition to achieve the selective localization of dendritic cargo.All rights reserved. No reuse allowed without permission.was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.