Optogenetically engineered calcium oscillations promote autophagy-mediated cell death via AMPK activation.

Autophagy is a double-edged sword for cells; it can lead to both cell survival and death. Calcium (Ca) signalling plays a crucial role in regulating various cellular behaviours, including cell migration, proliferation and death. In this study, we investigated the effects of modulating cytosolic Ca levels on autophagy using chemical and optogenetic methods. Our findings revealed that ionomycin and thapsigargin induce Ca influx to promote autophagy, whereas the Ca chelator BAPTA-AM induces Ca depletion and inhibits autophagy. Furthermore, the optogenetic platform allows the manipulation of illumination parameters, including density, frequency, duty cycle and duration, to create different patterns of Ca oscillations. We used the optogenetic tool Ca-translocating channelrhodopsin, which is activated and opened by 470 nm blue light to induce Ca influx. These results demonstrated that high-frequency Ca oscillations induce autophagy. In addition, autophagy induction may involve Ca-activated adenosine monophosphate (AMP)-activated protein kinases. In conclusion, high-frequency optogenetic Ca oscillations led to cell death mediated by AMP-activated protein kinase-induced autophagy.