ABSTRACT
Adult mammalian central nervous system axons have intrinsically poor regenerative capacity, so axonal injury has permanent consequences. One approach to enhancing regeneration is to increase the axonal supply of growth molecules and organelles. We achieved this by expressing the adaptor molecule Protrudin which is normally found at low levels in non-regenerative neurons. Elevated Protrudin expression enabled robust central nervous system regeneration both in vitro in primary cortical neurons and in vivo in the injured adult optic nerve. Protrudin overexpression facilitated the accumulation of endoplasmic reticulum, integrins and Rab11 endosomes in the distal axon, whilst removing Protrudin's endoplasmic reticulum localization, kinesin-binding or phosphoinositide-binding properties abrogated the regenerative effects. These results demonstrate that Protrudin promotes regeneration by functioning as a scaffold to link axonal organelles, motors and membranes, establishing important roles for these cellular components in mediating regeneration in the adult central nervous system.
Subject(s)
Axons/physiology , Central Nervous System/physiology , Endoplasmic Reticulum/metabolism , Nerve Regeneration , Vesicular Transport Proteins/metabolism , Animals , Axons/metabolism , Cells, Cultured , Endoplasmic Reticulum/genetics , Endosomes/metabolism , Female , Humans , Integrins/metabolism , Mice , Mice, Inbred C57BL , Mutation , Nerve Regeneration/drug effects , Neurons/metabolism , Neurons/physiology , Neuroprotective Agents/administration & dosage , Optic Nerve Injuries/drug therapy , Optic Nerve Injuries/metabolism , Optic Nerve Injuries/pathology , Phosphorylation , Protein Domains , Rats , Rats, Sprague-Dawley , Retina/drug effects , Retina/physiology , Vesicular Transport Proteins/administration & dosage , Vesicular Transport Proteins/chemistry , Vesicular Transport Proteins/geneticsABSTRACT
The accumulation of chondroitin sulfate proteoglycans (CSPGs) in the glial scar following acute damage to the central nervous system (CNS) limits the regeneration of injured axons. Given the rich diversity of CSPG core proteins and patterns of GAG sulfation, identifying the composition of these CSPGs is essential for understanding their roles in injury and repair. Differential expression of core proteins and sulfation patterns have been characterized in the brain and spinal cord of mice and rats, but a comprehensive study of these changes following optic nerve injury has not yet been performed. Here, we show that the composition of CSPGs in the optic nerve and retina following optic nerve crush (ONC) in mice and rats exhibits an increase in aggrecan, brevican, phosphacan, neurocan and versican, similar to changes following spinal cord injury. We also observe an increase in inhibitory 4-sulfated (4S) GAG chains, which suggests that the persistence of CSPGs in the glial scar opposes the growth of CNS axons, thereby contributing to the failure of regeneration and recovery of function.
