title: Death Domain Signaling by Disulfide-Linked Dimers of the p75 Neurotrophin Receptor Mediates Neuronal Death in the CNS.
abstract: The p75 neurotrophin receptor (p75(NTR)) mediates neuronal death in response to neural insults by activating a caspase apoptotic pathway. The oligomeric state and activation mechanism that enable p75(NTR) to mediate these effects have recently been called into question. Here, we have investigated mutant mice lacking the p75(NTR) death domain (DD) or a highly conserved transmembrane (TM) cysteine residue (Cys(259)) implicated in receptor dimerization and activation. Neuronal death induced by proneurotrophins or epileptic seizures was assessed and compared with responses in p75(NTR) knock-out mice and wild-type animals. Proneurotrophins induced apoptosis of cultured hippocampal and cortical neurons from wild-type mice, but mutant neurons lacking p75(NTR), only the p75(NTR) DD, or just Cys(259) were all equally resistant to proneurotrophin-induced neuronal death. Homo-FRET anisotropy experiments demonstrated that both NGF and proNGF induce conformational changes in p75(NTR) that are dependent on the TM cysteine. In vivo, neuronal death induced by pilocarpine-mediated seizures was significantly reduced in the hippocampus and somatosensory, piriform, and entorhinal cortices of all three strains of p75(NTR) mutant mice. Interestingly, the levels of protection observed in mice lacking the DD or only Cys(259) were identical to those of p75(NTR) knock-out mice even though the Cys(259) mutant differed from the wild-type receptor in only one amino acid residue. We conclude that, both in vitro and in vivo, neuronal death induced by p75(NTR) requires the DD and TM Cys(259), supporting the physiological relevance of DD signaling by disulfide-linked dimers of p75(NTR) in the CNS.
  
  
  
  A detailed understanding of the physiological significance of distinct structural determinants in the p75 neurotrophin receptor (p75(NTR)) is crucial for the identification of suitable drug targets in this receptor. We have tested the relevance of the p75(NTR) death domain (DD) and the highly conserved transmembrane residue Cys(259) for the ability of p75(NTR) to induce apoptosis in neurons of the CNS using gene-targeted mutant mice. The physiological importance of these determinants had been contested in some recent in vitro studies. Our results indicate a requirement for DD signaling by disulfide-linked dimers of p75(NTR) for neuronal death induced by proneurotrophins and epileptic seizures. These new mouse models will be useful for clarifying different aspects of p75(NTR) physiology.
authors.affiliation: Department of Physiology, National University of Singapore, Singapore 117597, Singapore, Life Sciences Institute, National University of Singapore, Singapore 117456, Singapore.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: Department of Neuroscience, Karolinska Institute, Stockholm S-17177, Sweden, and.
authors.forename: Claire E
authors.initials: CE
authors.lastname: Kelly
authors.affiliation: Department of Physiology, National University of Singapore, Singapore 117597, Singapore, Life Sciences Institute, National University of Singapore, Singapore 117456, Singapore.
authors.forename: Ket Yin
authors.identifier: 0000-0003-4264-558X
authors.initials: KY
authors.lastname: Goh
authors.affiliation: Department of Physiology, National University of Singapore, Singapore 117597, Singapore, Life Sciences Institute, National University of Singapore, Singapore 117456, Singapore.
authors.forename: Kim Buay
authors.initials: KB
authors.lastname: Lim
authors.affiliation: Department of Physiology, National University of Singapore, Singapore 117597, Singapore, Life Sciences Institute, National University of Singapore, Singapore 117456, Singapore, Department of Neuroscience, Karolinska Institute, Stockholm S-17177, Sweden, and Stellenbosch Institute for Advanced Study, Wallenberg Research Centre at Stellenbosch University, Stellenbosch 7600, South Africa phscfi@nus.edu.sg.
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Ibáñez
mesh_terms: D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D002522:Chlorocebus aethiops; D003545:Cysteine / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D009474:Neurons / Q000378:metabolism / Q000502:physiology; D010862:Pilocarpine / Q000633:toxicity; D000072417:Protein Domains; D055503:Protein Multimerization; D017475:Receptors, Nerve Growth Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012640:Seizures / Q000209:etiology / Q000235:genetics; D015398:Signal Transduction
chemical_list: D017475:Receptors, Nerve Growth Factor; C517634:Ngfr protein, mouse; D010862:Pilocarpine; D003545:Cysteine
keywords: apoptosis; disulfide bond; epilepsy; neurotrophins; seizures