title: Apoptotic actions of p53 require transcriptional activation of PUMA and do not involve a direct mitochondrial/cytoplasmic site of action in postnatal cortical neurons.
abstract: Recent studies in non-neuronal cells have shown that the tumor suppressor p53 can promote cell death through a transcription-independent mechanism involving its direct action with a subset of Bcl-2 family member proteins in the cytosol and at the mitochondria. In cultured cortical neurons, however, we could not find evidence supporting a significant contribution of the cytosolic/mitochondrial p53 pathway, and available evidence instead corroborated the requirement for the transcriptional activity of p53. When directly targeted to the cytosol/mitochondria, wild-type p53 lost its apoptosis-inducing activity in neurons but not in non-neuronal cells. The N-terminal p53 fragment (transactivation and proline-rich domains), which induces apoptosis in non-neuronal cells via the cytosolic/mitochondrial pathway, displayed no apoptogenic activity in neurons. In neuronal apoptosis induced by camptothecin or an MDM2 (murine double minute 2) inhibitor, nutlin-3, endogenous p53 protein did not accumulate in the cytosol/mitochondria, and transcriptional inhibition after p53 induction effectively blocked cell death. In addition, overexpression of a dominant-negative form of p53 (R273H) completely suppressed induction of proapoptotic p53 target genes and cell death. PUMA (p53-upregulated modulator of apoptosis) was one such gene induced by camptothecin, and its overexpression was sufficient to induce Bax (Bcl-2-associated X protein)-dependent neuronal death, whereas Noxa was not apoptogenic. These results collectively demonstrate that, in contrast to non-neuronal cells, the apoptotic activity of p53 in postnatal cortical neurons does not rely on its direct action at the cytosol/mitochondria but is exclusively mediated through its transcription-dependent functions. The uniqueness of p53-mediated apoptotic signaling in postnatal cortical neurons was further illustrated by the dispensable function of the proline-rich domain of p53.
authors.affiliation: Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington 98195-6470, USA.
authors.forename: Takuma
authors.initials: T
authors.lastname: Uo
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Kinoshita
authors.forename: Richard S
authors.initials: RS
authors.lastname: Morrison
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D002166:Camptothecin / Q000494:pharmacology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D041681:NIH 3T3 Cells; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis* / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D051017:Apoptosis Regulatory Proteins; C488588:PUMA protein, mouse; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D002166:Camptothecin