Regulated Responses to Irregular Signals

摘要

Experiments on the effects of hormones or cytokines often compare responses of cells incubated in the presence or absence of the activating compound. But in vivo, cells experience variations in the amount of stimulus that may be irregular or pulsatile. Ashalt et al. (p. 242) explored the response of the transcription factor NF-kB (a major mediator of transcriptional responses in immune function) to short pulses of exposure to the cytokine tumor necrosis factor-α (TNFa). Oscillations in the movement of the transcription factor into and out of the nucleus could be synchronized by exposure of cells to pulses of TNFa. Furthermore, whether transcription of particular genes was activated or not, depended on the frequency of stimulation and consequent timing of NFkB translocation. Cells in inflammatory tissues may experience similar changes in stimulation by TNFa, and thus respond in distinct ways, depending on the timing of the signals received in the cells.