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.