Quantitative transportomics identifies Kif5a as a major regulator of neurodegeneration.

Sahil H Shah,Evan G Cameron,Melissa Atkins,Lucio M Schiapparelli,Sarah Saturday,Satoshi Yokota,Yuanhui Ma,Jeffrey L Goldberg,Thanh Huang,Cara Knasel,Seth Blackshaw,Hollis T Cline,John R Yates Iii,Catalin B Sun,Xin Xia

doi:10.7554/elife.68148

Abstract

Many neurons in the adult central nervous system, including retinal ganglion cells (RGCs), degenerate and die after injury. Early axon protein and organelle trafficking failure is a key component in many neurodegenerative disorders yet changes to axoplasmic transport in disease models have not been quantified. We analyzed early changes in the protein 'transportome' from RGC somas to their axons after optic nerve injury and identified transport failure of an anterograde motor protein Kif5a early in RGC degeneration. We demonstrated that manipulating Kif5a expression affects anterograde mitochondrial trafficking in RGCs and characterized axon transport in Kif5a knockout mice to identify proteins whose axon localization was Kif5a-dependent. Finally, we found that knockout of Kif5a in RGCs resulted in progressive RGC degeneration in the absence of injury. Together with expression data localizing Kif5a to human RGCs, these data identify Kif5a transport failure as a cause of RGC neurodegeneration and point to a mechanism for future therapeutics.

Highlights

Adult mammalian central nervous system (CNS) neurons often undergo cell death and axon degeneration after injury and in disease
A variety of retinal proteins are labelled by intravitreal injection, dissection of the optic nerve isolates only proteins which have been transported from retinal ganglion cell (RGC) somas into RGC axons (Figure 1b)
There was no biotin signal distal to the crush, confirming the disruption of protein transport and lack of biotin transfer out of axons after injury. Together these data indicate that this protocol results in protein labeling within RGC axons in the optic nerves in both the control and injury conditions, allowing targeted isolation and investigation of changes in RGC proteins transported into the optic nerve after injury

Summary

INTRODUCTION

Adult mammalian central nervous system (CNS) neurons often undergo cell death and axon degeneration after injury and in disease. Neurodegenerative diseases such as glaucoma and acute injuries such as after optic nerve trauma may result in irreversible retinal ganglion cell (RGC) loss. Mechanisms underlying this degeneration include intracellular events such as acute calcium influx into the axon (Knoferle et al, 2010), loss of constitutive axon survival factors like. We previously developed a mass spectrometry-compatible technique for characterizing the axon transportome in the visual system (Schiapparelli et al, 2019) We adapt this technique to quantify changes in the axon transportome after optic nerve injury. Together this study adapts novel methods to identify Kif5a transport deficits as a contributor to RGC death after injury and offers new insights into kinesin motor cargo specificity

RESULTS

DISCUSSION

MATERIALS AND METHODS