Structural Characterization of the Self-Association of the Death Domain of p75NTR

The neurotrophin receptor p75NTR conveys multiple signals via its intracellular death domain. However, how the death domain is activated and interacts with downstream adaptors remains unclear. Here, we report two crystal structures of the p75NTR death domain in the form of a non-covalent asymmetric dimer and a Cys379-Cys379 disulfide bond linked symmetric dimer, respectively. These two dimer arrangements have not previously been observed in other death domain-containing proteins. Further analysis shows that both the Cys379-Cys379 disulfide linked and non-covalent full-length p75NTR dimers are present on the cell surface. These observations suggest that various oligomers may exist simultaneously on the cell surface, and that p75NTR activation and signalling may be modulated by neurotrophins or other factors via inducing a shift of the equilibrium between different oligomeric states.