Fig. 8: Overview of the molecular mechanisms underlying the effects of AAV.ULK1.DN-mediated ULK1 inhibition on axonal degeneration, neuronal survival, and axonal regeneration.

We have previously demonstrated that inhibition of ULK1 function via expression of dominant-negative ULK1 (ULK1.DN) attenuates axonal degeneration in different models of axonal injury in vitro and in vivo¹⁴. We connected these findings to reduced autophagy, increased mTOR-dependent translation, and differential splicing of the genes Kif1b and Ddit3, which we hypothesized to enhance axonal transport and reduce ER stress (previous results depicted in light blue). In this study, we additionally demonstrate that ULK1.DN-mediated ULK1 inhibition promotes neuronal survival and fosters axonal regeneration after axonal injury (results of this study depicted in dark blue). Mechanistically, we extend our previous findings by demonstrating elevated levels of p-ERK1 after transduction with AAV.ULK1.DN, which could promote survival and enhance the intrinsic axonal growth capacity via increased gene expression. Furthermore, we show reduced expression of the RhoA-ROCK2 pathway in ULK1.DN-transduced neurons, which counteracts the growth-inhibitory effect of glia-derived molecules such as CSPGs after lesion and could result in increased pro-regenerative actin dynamics after lesion. Correspondingly, ULK1.DN also mediates differential splicing of the CSPG receptor Ptprf¹⁴. Together, we propose that AAV.ULK1.DN-mediated ULK1 inhibition attenuates axonal degeneration, increases neuronal survival, and fosters axonal regeneration after axonal injury via a molecular switch to axon-protective, pro-survival, and growth-promoting pathways. Figure created with BioRender.com.