Leucine Zipper-bearing Kinase promotes axon growth in mammalian central nervous system neurons.

Meifan Chen,Hetty N Wong,Yishi Jin,Mallorie T Nguyen,Cédric G Geoffroy,Lawrence B Holzman,Binhai Zheng,Oliver Tress

doi:10.1038/srep31482

Abstract

Leucine Zipper-bearing Kinase (LZK/MAP3K13) is a member of the mixed lineage kinase family with high sequence identity to Dual Leucine Zipper Kinase (DLK/MAP3K12). While DLK is established as a key regulator of axonal responses to injury, the role of LZK in mammalian neurons is poorly understood. By gain- and loss-of-function analyses in neuronal cultures, we identify LZK as a novel positive regulator of axon growth. LZK signals specifically through MKK4 and JNKs among MAP2Ks and MAPKs respectively in neuronal cells, with JNK activity positively regulating LZK protein levels. Neuronal maturation or activity deprivation activates the LZK-MKK4-JNK pathway. LZK and DLK share commonalities in signaling, regulation, and effects on axon extension. Furthermore, LZK-dependent regulation of DLK protein expression and the lack of additive effects on axon growth upon co-manipulation suggest complex functional interaction and cross-regulation between these two kinases. Together, our data support the possibility for two structurally related MAP3Ks to work in concert to mediate axonal responses to external insult or injury in mammalian CNS neurons.

Highlights

Cloned from the human cerebellum, Leucine Zipper-bearing Kinase (LZK, known as MAP3K13) is a Mitogen-Activated Protein Kinase Kinase Kinase (MAP3K) that signals through the MAPK cascade known to orchestrate cellular responses to extracellular stimuli[1]
We demonstrate that LZK promotes axon growth in mouse neuroblastoma cells and primary central nervous system (CNS) neurons by both gain- and loss-of-function analyses through a combination of transient overexpression, RNA interference (RNAi) and gene deletion
LZK and DLK are both mammalian homologues of invertebrate DLK-1/Wallenda, which has been established as a key regulator of various aspects of nervous system development and physiology ranging from synapse formation to neuronal and axonal responses to insult or injury[4,5,7,8,9,16]

Summary

Introduction

Cloned from the human cerebellum, Leucine Zipper-bearing Kinase (LZK, known as MAP3K13) is a Mitogen-Activated Protein Kinase Kinase Kinase (MAP3K) that signals through the MAPK cascade known to orchestrate cellular responses to extracellular stimuli[1]. Invertebrate DLK-1 and Wallenda/DLK are known to play multiple roles in the developing and mature nervous systems, such as synaptic development and growth, regeneration of the proximal axonal segment and Wallerian degeneration of the distal segment following axonal injury[4,5,6,7,8,9,10]. Interaction in the adult mouse brain as detected by mass spectrometry[18], suggests related biochemical and functional properties between these two proteins in the nervous system. In this context, all previous biochemical characterization of LZK signaling resorted to the use of exogenously expressed substrates in non-neuronal cell lines[1,22,23], raising the question on the biological relevance of the role of LZK in neurons. Co-manipulation of LZK and DLK reveal functional interaction and cross-regulation at the protein level implicating coordinate regulation of axonal responses to injury by this pair of kinases

Methods

Results

Conclusion