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 (Ca²⁺) 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 Ca²⁺ levels on autophagy using chemical and optogenetic methods. Our findings revealed that ionomycin and thapsigargin induce Ca²⁺ influx to promote autophagy, whereas the Ca²⁺ chelator BAPTA-AM induces Ca²⁺ 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 Ca²⁺ oscillations. We used the optogenetic tool Ca²⁺-translocating channelrhodopsin, which is activated and opened by 470 nm blue light to induce Ca²⁺ influx. These results demonstrated that high-frequency Ca²⁺ oscillations induce autophagy. In addition, autophagy induction may involve Ca²⁺-activated adenosine monophosphate (AMP)-activated protein kinases. In conclusion, high-frequency optogenetic Ca²⁺ oscillations led to cell death mediated by AMP-activated protein kinase-induced autophagy.