WWOX Regulates UV/Cold Shock-Mediated Calcium Influx and Nuclear Bubbling in Frostbite

Abstract UV/cold shock-mediated frostbite involves non-apoptotic nuclear bubbling cell death (BCD) and participation of functional WWOX in cells (WWOXf). In contrast, cells with WWOX deficiency or dysfunction (WWOXd) undergo pop-out explosion death (POD). Here, by time-lapse microscopy, when WWOXf cells were exposed to UV or UV/cold shock and then incubated at room temperature, these cells rapidly and sequentially underwent: 1) loss of mitochondrial membrane potential, 2) formation of a nitric oxide (NO)-containing nuclear bubble per cell, 3) WWOX-dependent increase in calcium (Ca2+) influx, 4) shutdown of mRNA and protein synthesis machinery, as determined by RT/PCR and gene chip analysis, and 5) eventual cell death without caspase activation, stress fiber formation and chromosomal DNA fragmentation. In contrast, WWOXd cells exhibited a faster kinetics of stress fiber formation, explosion and death without NO production. Ectopic WWOX restored calcium influx and nuclear bubbling in WWOXd cells. In hairless mice, UV/cold shock rapidly downregulated protein expression in the skin and then liver, which may lead to organ damages. UV/cold shock induced complex formation of antiapoptotic TRAF2 and proapoptotic WWOX and their co-translocation to the nucleus, where the complex dissociation occurred. The observations suggest that WWOX and TRAF2 dissociation is needed for nuclear bubbling and death.