Interdependence of Bad and Puma during Ionizing-Radiation-Induced Apoptosis

Abstract

Ionizing radiation (IR)-induced DNA double-strand breaks trigger an extensive cellular signaling response that involves the coordination of hundreds of proteins to regulate DNA repair, cell cycle arrest and apoptotic pathways. The cellular outcome often depends on the level of DNA damage as well as the particular cell type. Proliferating zebrafish embryonic neurons are highly sensitive to IR-induced apoptosis, and both p53 and its transcriptional target puma are essential mediators of the response. The BH3-only protein Puma has previously been reported to activate mitochondrial apoptosis through direct interaction with the pro-apoptotic Bcl-2 family proteins Bax and Bak, thus constituting the role of an “activator” BH3-only protein. This distinguishes it from BH3-only proteins like Bad that are thought to indirectly promote apoptosis through binding to anti-apoptotic Bcl-2 family members, thereby preventing the sequestration of activator BH3-only proteins and allowing them to directly interact with and activate Bax and Bak. We have shown previously that overexpression of the BH3-only protein Bad in zebrafish embryos supports normal embryonic development but greatly sensitizes developing neurons to IR-induced apoptosis. While Bad has previously been shown to play only a minor role in promoting IR-induced apoptosis of T cells in mice, we demonstrate that Bad is essential for robust IR-induced apoptosis in zebrafish embryonic neural tissue. Moreover, we found that both p53 and Puma are required for Bad-mediated radiosensitization in vivo. Our findings show the existence of a hierarchical interdependence between Bad and Puma whereby Bad functions as an essential sensitizer and Puma as an essential activator of IR-induced mitochondrial apoptosis specifically in embryonic neural tissue.

Variations in sister chromatid cohesion dysfunction in esco2 mutant zebrafish reflects the phenotypic diversity of Roberts Syndrome

“…We observed that the genomic-instability-induced apoptosis occurs predominantly in the neural tube. These results are consistent with other published data on DNA-damage-induced genomic instability in mouse and zebrafish ( Lang et al, 2004 ; Berghmans et al, 2005 ; Sidi et al, 2008 ; Parant et al, 2010 ; Toruno et al, 2014 ). These tissue-specific effects might explain the many neural-related RBS phenotypes such as microcephaly, craniofacial defects and mental retardation.…”

“…During tumorigenesis, p53 is activated following cellular stress, resulting in sequestration or termination of the stressed cell ( Junttila and Evan, 2009 ; Meek, 2009 ). Through our previous studies, we observed that, either following loss of mdm2 , the negative regulator of p53, or following ionizing radiation (IR) treatment, zebrafish embryos displayed a darkening of the head region, referred to as head necrosis at 24 hpf (hours post-fertilization), which results from an increase in apoptosis in the neural tube ( Berghmans et al, 2005 ; Sidi et al, 2008 ; Parant et al, 2010 ; Toruno et al, 2014 ). To better understand (1) which cellular stresses activate p53, (2) what birth defects result from p53 activation and (3) the mechanisms of p53 activation following the cellular stress, we devised a genetic screen to identify p53-dependent embryonic-lethal zebrafish mutants.…”

Novel 3-(3, 5-difluoro-4-hydroxyphenyl)-1-(naphthalen-2-yl) prop-2-en-1-one as a potent inhibitor of MAP-kinase in HeLa cell lines and anti-angiogenic activity is mediated by HIF-1α in EAC animal model

“…At the molecular level, apoptosis is firmly controlled by the activation of cysteine-dependent aspartate directed protease (Caspase) cascade [ 11 ]. The mitochondrial pathway is managed by initiating favourable to apoptotic proteins BAX and Bcl2 inhibition [ 12 , 13 ]. Cell stress incites supportive of apoptotic protein BAX to move to the outside of the mitochondria, where it multiplies pores in the mitochondrial membrane and grant the arrival of cytochrome C into the cytoplasm.…”

Non-induction of radioadaptive response in zebrafish embryos by neutrons

“…The number of apoptotic signals within the whole embryos was adopted as the biological endpoint in the present study (‘apoptosis signals’ referring to the observed numbers of cells that were undergoing apoptosis). The number of apoptotic signals has been commonly employed as the biological endpoint to assess the effects of radiation in zebrafish embryos [ 32 , 50 – 52 ].…”