AraC binds the p75^NTR transmembrane domain to induce neurodegeneration in mature neurons

Background Cytosine arabinoside (AraC) is one of the main therapeutic treatments for several types of cancer including acute myeloid leukaemia. However, after high dose AraC chemotherapy regime, patients develop severe neurotoxicity and neurodegeneration in the central nervous system leading to cerebellar ataxia, dysarthria, nystagmus, somnolence and drowsiness. AraC induces apoptosis in dividing cells, however, the mechanism by which it leads to neurite degeneration and cell death in mature neurons remains unclear. We hypothesized that the upregulation of the death receptor p75^NTR is responsible for AraC-mediated neurodegeneration and cell death in leukemia patients undergoing AraC treatment.

Methods To determine the role of AraC-p75^NTR signalling in degeneration of mature cerebellar granule neurons, we used primary cultures from p75^NTR knockout and p75^NTRCys259 mice. Evaluation of neurodegeneration, cell death and p75^NTR signalling was done by immunohistochemistry and immunoblotting. To assess the direct interaction between AraC and p75^NTR, we performed isothermal dose response-cellular thermal shift and AraTM assays as well as Homo-FRET anisotropy imaging.

Results We show that AraC induces neurite degeneration and programmed cell death of mature cerebellar granule neurons in a p75^NTR-dependent manner. Mechanistically, AraC binds to Proline 252 and Cysteine 256 of the p75^NTR transmembrane domain and selectively uncouples p75^NTR from the NFκB survival pathway. This in turn, exacerbates the activation of the cell death/JNK pathway by recruitment of TRAF6 to p75^NTR.

Conclusion Our findings identify p75^NTR as a novel molecular target to develop treatments to counteract AraC-mediated neurodegeneration.