부산대학교 도서관

In this study we characterized the effects of radiation injury on the expression and function of the autotaxin (ATX)–LPA 2 GPCR axis. In IEC-6 crypt cells and jejunum enteroids quantitative RT-PCR showed a time- and dose-dependent upregulation of lpa2 in response to γ-irradiation that was abolished by mutation of the NF-κB site in the lpa2 promoter or by inhibition of ATM/ATR kinases with CGK-733, suggesting that lpa2 is a DNA damage response gene upregulated by ATM via NF-κB. The resolution kinetics of the DNA damage marker γ-H2AX in LPA-treated IEC-6 cells exposed to γ-irradiation was accelerated compared to vehicle, whereas pharmacological inhibition of LPA 2 delayed the resolution of γ-H2AX. In LPA 2 -reconstituted MEF cells lacking LPA 1&3 the levels of γ-H2AX decreased rapidly, whereas in Vector MEF were high and remained sustained. Inhibition of ERK1&2 or PI3K/AKT signaling axis by pertussis toxin or the C 311 A/C 314 A/L 351 A mutation in the C-terminus of LPA 2 abrogated the effect of LPA on DNA repair. LPA 2 transcripts in Lin − Sca-1 + c-Kit + enriched for bone marrow stem cells were 27- and 5-fold higher than in common myeloid or lymphoid progenitors, respectively. Furthermore, after irradiation higher residual γ-H2AX levels were detected in the bone marrow or jejunum of irradiated LPA 2 -KO mice compared to WT mice. We found that γ-irradiation increases plasma ATX activity and LPA level that is in part due to the previously established radiation-induced upregulation of TNFα. These findings identify ATX and LPA 2 as radiation-regulated genes that appear to play a physiological role in DNA repair. [ABSTRACT FROM AUTHOR]