Cytoplasmic Irradiation Induces Mitochondrial-Dependent 53BP1 Protein Relocalization in Irradiated and Bystander Cells

Abstract

The accepted paradigm for radiation effects is that direct DNA damage via energy deposition is required to trigger the downstream biological consequences. The radiation-induced bystander effect is the ability of directly irradiated cells to interact with their nonirradiated neighbors, which can then show responses similar to those of the targeted cells. p53 binding protein 1 (53BP1) forms foci at DNA double-strand break sites and is an important sensor of DNA damage. This study used an ionizing radiation microbeam approach that allowed us to irradiate specifically the nucleus or cytoplasm of a cell and quantify response in irradiated and bystander cells by studying ionizing radiation-induced foci (IRIF) formation of 53BP1 protein. Our results show that targeting only the cytoplasm of a cell is capable of eliciting 53BP1 foci in both hit and bystander cells, independently of the dose or the number of cells targeted. Therefore, direct DNA damage is not required to trigger 53BP1 IRIF. The use of common reactive oxygen species and reactive nitrogen species (RNS) inhibitors prevent the formation of 53BP1 foci in hit and bystander cells.

Mitochondrial dysfunction resulting from loss of cytochrome c impairs radiation-induced bystander effect

“…This study, together with several other studies (Lyng et al, 2000(Lyng et al, , 2002Limoli et al, 2003;Maguire et al, 2005;Murphy et al, 2005;Nugent et al, 2007;Tartier et al, 2007;Chen et al, 2008), suggested that mitochondria represent the sensor of radiationinduced ionisation events. In this study, we showed that Cyt c-null cells can respond to radiation normally in ROS/NO generations as Cyt c-normal cells (Figures 2B and 3B).…”

“…British Journal of Cancer (2009Cancer ( ) 100, 1912Cancer ( -1916 Mitochondria are pivotal cellular organelles for they not only generate the cellular ATP through oxidative phosphorylation but also initiate the intrinsic apoptosis (Li et al, 2000;Berg and Stryer, 2002). In recent years, emerging evidence indicated that mitochondria have also been implicated in radiation-induced bystander effect (RIBE) (Lyng et al, 2000(Lyng et al, , 2002Limoli et al, 2003;Maguire et al, 2005;Murphy et al, 2005;Nugent et al, 2007;Tartier et al, 2007). Earlier, we reported that cells deficient in mitochondrial DNA (mtDNA) showed a significant reduction of bystander signalling .…”

Exosomes Are Involved in Mediating Radiation Induced Bystander Signaling in Human Keratinocyte Cells

“…There have been many studies on membrane signaling in bystander cells (41,(50)(51)(52)(53). Rapid membrane signaling, calcium signaling and ROS induction has been reported previously in unirradiated cells after the addition of ICCM (41).…”

Role of connexin43 and ATP in long-range bystander radiation damage and oncogenesis in vivo

“…ATP can pass across gap junctions and hemichannels (Evans et al, 2006) and stress stimuli, including radiation, induce ATP release from cells (Tsukimoto et al, 2010). Thus, ATP released by irradiated cells, for example, through mitochondrial damage (Tartier et al, 2007), might be a candidate signaling molecule in the initiation of oncogenic bystander damage in vivo.…”