| Popis: |
Cellular stresses elicit signaling cascades that are capable of both mitigating the inciting dysfunction and initiating cell death when the stress cannot be overcome. During endoplasmic reticulum (ER) stress, the transcription factor CHOP is widely recognized to promote cell death. Yet CHOP carries out this function largely by augmenting protein synthesis, which is an essential component of recovery from stress. In addition, the mechanisms that drive cell fate during ER stress have largely been explored under super-physiological experimental conditions that do not permit cellular adaptation. Thus, it is not clear whether CHOP also has a beneficial role during that adaptation. Here, we have created a new, versatile, genetically modifiedChopallele, which we combined with single cell analysis and stresses of physiological intensity, to rigorously examine the contribution of CHOP to cell fate. Surprisingly, we found that, within the cell population, CHOP paradoxically promoted death in some cells but proliferation—and hence recovery—in others. Strikingly, this function of CHOP conferred a stress-specific competitive growth advantage to wild-type cells over cells lacking CHOP. The dynamics of CHOP expression and UPR activation at the single cell level suggested that, by promoting protein synthesis, CHOP maximizes UPR activation which in turn favors stress resolution, subsequent UPR deactivation, and proliferation. Taken together, these findings suggest that CHOP’s function can be better described as a “stress test” that drives cells into either of two mutually exclusive fates—adaptation or death—during stress. They point to a previously unappreciated pro-survival function of CHOP during stresses of physiological intensity. |
