AAV-mediated inhibition of ULK1 promotes axonal regeneration in the central nervous system in vitro and in vivo

Vinicius Toledo Ribas,Lars Tatenhorst,Raquel Alves Almeida,Paul Lingor,Hans Werner Müller,Veronica Estrada,Uwe Michel,Björn Friedhelm Vahsen,Mathias Bähr,Vivian Dambeck,Jan Christoph Koch

doi:10.1038/s41419-021-03503-3

Abstract

Axonal damage is an early step in traumatic and neurodegenerative disorders of the central nervous system (CNS). Damaged axons are not able to regenerate sufficiently in the adult mammalian CNS, leading to permanent neurological deficits. Recently, we showed that inhibition of the autophagic protein ULK1 promotes neuroprotection in different models of neurodegeneration. Moreover, we demonstrated previously that axonal protection improves regeneration of lesioned axons. However, whether axonal protection mediated by ULK1 inhibition could also improve axonal regeneration is unknown. Here, we used an adeno-associated viral (AAV) vector to express a dominant-negative form of ULK1 (AAV.ULK1.DN) and investigated its effects on axonal regeneration in the CNS. We show that AAV.ULK1.DN fosters axonal regeneration and enhances neurite outgrowth in vitro. In addition, AAV.ULK1.DN increases neuronal survival and enhances axonal regeneration after optic nerve lesion, and promotes long-term axonal protection after spinal cord injury (SCI) in vivo. Interestingly, AAV.ULK1.DN also increases serotonergic and dopaminergic axon sprouting after SCI. Mechanistically, AAV.ULK1.DN leads to increased ERK1 activation and reduced expression of RhoA and ROCK2. Our findings outline ULK1 as a key regulator of axonal degeneration and regeneration, and define ULK1 as a promising target to promote neuroprotection and regeneration in the CNS.

Highlights

Axonal damage is an early event in the course of traumatic injuries to the central nervous system (CNS) and is of major pathophysiological relevance in different chronic neurodegenerative diseases, including Parkinson’s disease, amyotrophic lateral sclerosis, Alzheimer’s disease, and glaucoma[1]
We showed that Unc-51 like autophagy activating kinase 1 (ULK1).DN-mediated ULK1 inhibition promoted axonal protection in different models of traumatic axonal lesion, in vitro and in vivo, and that application of the ULK1 inhibitor SBI-0206965 protected axons from degeneration induced by optic nerve crush (ONC) in vivo
For each time point (24–96 h), we counted the relative number of regenerating axons at defined distances (100–1000 μm) from the distal aperture of the microgrooves

Summary

Introduction

Axonal damage is an early event in the course of traumatic injuries to the central nervous system (CNS) and is of major pathophysiological relevance in different chronic neurodegenerative diseases, including Parkinson’s disease, amyotrophic lateral sclerosis, Alzheimer’s disease, and glaucoma[1]. Many of these disorders show a “dying back” degeneration pattern that frequently precedes somatic cell death[2]. Regeneration of damaged axons is severely hampered by extrinsic and intrinsic factors in the adult mammalian CNS3,4.

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Conclusion