AraC interacts with p75NTR transmembrane domain to induce cell death of mature neurons

Cytosine arabinoside (AraC) is one of the main therapeutic treatments for several types of cancer, including acute myeloid leukaemia. However, after a high-dose AraC chemotherapy regime, patients develop severe neurotoxicity and cell death 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 hypothesise that the upregulation of the death receptor p75(NTR) is responsible for AraC-mediated neurodegeneration and cell death in leukaemia patients undergoing AraC treatment. To determine the role of AraC-p75(NTR) signalling in the cell death of mature neurons, we used mature cerebellar granule neurons' primary cultures from p75(NTR) knockout and p75(NTRCys259) mice. Evaluation of neurite degeneration, cell death and p75(NTR) signalling was done by immunohistochemistry and immunoblotting. To assess the interaction between AraC and p75(NTR), we performed cellular thermal shift and AraTM assays as well as Homo-FRET anisotropy imaging. We show that AraC induces neurite degeneration and programmed cell death of mature cerebellar granule neurons in a p75(NTR)-dependent manner. Mechanistically, Proline 252 and Cysteine 256 residues facilitate AraC interaction with the transmembrane domain of p75(NTR) resulting in uncoupling of p75(NTR) from the NF & kappa;B survival pathway. This, in turn, exacerbates the activation of the cell death/JNK pathway by recruitment of TRAF6 to p75(NTR). Our findings identify p75(NTR) as a novel molecular target to develop treatments for counteract AraC-mediated cell death of mature neurons.