ZEB1 Links p63 and p73 in a Novel Neuronal Survival Pathway Rapidly Induced in Response to Cortical Ischemia

Istituto Dermopatico dell'Immacolata, Italy
PLoS ONE (Impact Factor: 3.23). 02/2009; 4(2):e4373. DOI: 10.1371/journal.pone.0004373
Source: PubMed


Acute hypoxic/ischemic insults to the forebrain, often resulting in significant cellular loss of the cortical parenchyma, are a major cause of debilitating injury in the industrialized world. A clearer understanding of the pro-death/pro-survival signaling pathways and their downstream targets is critical to the development of therapeutic interventions to mitigate permanent neurological damage.
We demonstrate here that the transcriptional repressor ZEB1, thought to be involved in regulating the timing and spatial boundaries of basic-Helix-Loop-Helix transactivator-mediated neurogenic determination/differentiation programs, functions to link a pro-survival transcriptional cascade rapidly induced in cortical neurons in response to experimentally induced ischemia. Employing histological, tissue culture, and molecular biological read-outs, we show that this novel pro-survival response, initiated through the rapid induction of p63, is mediated ultimately by the transcriptional repression of a pro-apoptotic isoform of p73 by ZEB1. We show further that this phylogenetically conserved pathway is induced as well in the human cortex subjected to episodes of clinically relevant stroke.
The data presented here provide the first evidence that ZEB1 induction is part of a protective response by neurons to ischemia. The stroke-induced increase in ZEB1 mRNA and protein levels in cortical neurons is both developmentally and phylogenetically conserved and may therefore be part of a fundamental cellular response to this insult. Beyond the context of stroke, the finding that ZEB1 is regulated by a member of the p53 family has implications for cell survival in other tissue and cellular environments subjected to ischemia, such as the myocardium and, in particular, tumor masses.

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    • "Furthermore it has been postulated that EMT enables tumors to escape from apoptosis and senescence signals by adopting embryonic signaling pathways36,37. Temporal changes in ZEB1 levels, that very closely reflect our findings were reported by Bui et al.38 in a hypoxia-induced stroke injury model. In that study ZEB1 was shown to induce a pro-survival response by the transcriptional repression of pro-apoptotic factors and upregulation of pro-survival factors. "
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    • "Zeb1 defi cient mice die perinatally but do not exert anomalies in the nervous system. Bui et al. ( 2009 ) have recently reported that Zeb1 mediates a pro-survival cascade in cortical neurons in response to experimentally induced ischemia and this cascade is initiated by p63, a member of the p53 family that regulates cell survival via its TA and D N isoforms. Opposite to Zeb1, Zeb2 defi cient mice exert numerous neural tube defects, such as an absence of neural tube closure as well as no sharp boundary between ectoderm and neural plate. "
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    • "The mechanisms involved in ZEB1-and ZEB2- mediated drug resistance are still being investigated. In different cell systems, ZEB1 has been shown to directly inhibit TAp73, which triggers apoptosis, but also Np73 and Np63, that function as anti-apoptotic factors [48] [126] [127]. The pro-survival effect of ZEB2 is independent of cell cycle arrest and intercellular adhesion and is mediated through inhibition of cleavage of PARP and pro-caspase 3 and phosphorylation of ATM/ATR substrates [98]. "
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