Ser/Thr kinase Trc controls neurite outgrowth inDrosophilaby modulating microtubule-microtubule sliding

Correct neuronal development requires tailored neurite outgrowth. Neurite outgrowth is driven by microtubule sliding – the transport of microtubules along each other. We have recently demonstrated that a “mitotic” kinesin-6 (Pavarotti in Drosophila ) effectively inhibits microtubule-sliding and neurite outgrowth. However, mechanisms of Pavarotti regulation in interphase cells and specifically in neurite outgrowth are unknown. Here, we use a combination of live imaging and biochemical methods to show that the inhibition of microtubule sliding by Pavarotti is controlled by phosphorylation. We identify the Ser/Thr NDR kinase Tricornered (Trc) as a Pavarotti-dependent regulator of microtubule sliding in neurons. Further, we show that Trc-mediated phosphorylation of Pavarotti promotes its interaction with 14-3-3 proteins. 14-3-3 binding is necessary for Pavarotti to interact with microtubules and inhibit sliding. Thus, we propose a pathway by which microtubule sliding can be up or down regulated in neurons to control neurite outgrowth, and establish parallels between microtubule sliding in mitosis and post-mitotic neurons.