Farnesylated RhoB inhibits radiation-induced mitotic cell death and controls radiation-induced centrosome overduplication

Abstract

Our previous results demonstrated that expressing the GTPase ras homolog gene family, member B (RhoB) in radiosensitive NIH3T3 cells increases their survival following 2 Gy irradiation (SF2). We have first demonstrated here that RhoB expression inhibits radiation-induced mitotic cell death. RhoB is present in both a farnesylated and a geranylgeranylated form in vivo. By expressing RhoB mutants encoding for farnesylated (RhoB-F cells), geranylgeranylated or the CAAX deleted form of RhoB, we have then shown that only RhoB-F expression was able to increase the SF2 value by reducing the sensitivity of these cells to radiation-induced mitotic cell death. Moreover, RhoB-F cells showed an increased G2 arrest and an inhibition of centrosome overduplication following irradiation mediated by the Rhokinase, strongly suggesting that RhoB-F may control centrosome overduplication during the G2 arrest after irradiation. Overall, our results for the first time clearly implicate farnesylated RhoB as a crucial protein in mediating cellular resistance to radiation-induced nonapoptotic cell death.

Modulation of cell cycle and gene expression in pancreatic tumor cell lines by methionine deprivation (methionine stress): implications to the therapy of pancreatic adenocarcinoma

“…Enhancement of the efficacy of 5-fluorouracil against pancreatic tumors by methionine stress is supported by the observed down-regulation of TYMS, DTYMK, and UP, which are involved in 5-fluorouracil metabolism, and FEN1, FANCG, and RAD23B, which are involved in the repair of 5-fluorouracil-induced DNA damage (45). Enhancement of the efficacy to radiation by methionine stress is supported by the observed down-regulation of RhoB expression, the farnesylated form of which inhibits radiation-induced mitotic cell death (46). Synergy between methionine stress and alkylating agents has been shown in the past (14) but has not been fully investigated.…”

ROCK I-mediated activation of NF-κB by RhoB

“…Thus, RhoB-GG suppresses Ras transformation in NIH 3T3 cells while RhoB-F potentiates transformation [9]. In contrast, RhoB-F can provide resistance to radiation-induced cell death in NIH 3T3 cells while RhoB-GG does not provide such protection [34]. The precise signaling activities that mediate these differences in signaling potential have not been delineated.…”

“…In a recent study Milia et al showed that RhoB-F (but not RhoB-GG) is required to confer resistance to radiation-induced mitotic cell death in mouse embryonic fibroblasts and that this function is dependent on ROCK I [34]. In addition, ROCK I has been reported to mediate thrombininduced NF-κB activation in endothelial cells, which in part can be attributed to increased phosphorylation of the transactivation domain of RelA/p65 [35].…”

FGFR1 Induces Glioblastoma Radioresistance through the PLCγ/Hif1α Pathway

“…As expected, FGFR1 was silenced in the two selected U87 clones [clones 2 and 7; FGFR1(À)U87 cells], which present a significant FGFR1 inhibition of 67.1% and 38.1%, respectively ( We then deciphered the biological pathways sustaining the radioprotective effect of FGFR1 in glioblastoma cells. Because we largely demonstrated that the radiation-induced cell death of solid tumor cells is mitotic cell death (6,11,21,22), we first determined the number of giant multinucleated cells 5 days after 8 Gy irradiation when FGFR1 has been silenced or not. As shown in Fig.…”

“…The number of centrosomes in U87 and LN18 cells was analyzed using immunofluorescence staining for g-tubulin as already described (11,22).…”