CHRM3 and melanoma: By using OptoSTIM1, an optogenetic tool to open plasma membrane calcium channels (Fig. 6E) (Kyung et al., 2015), or DREADD hM3, an artificial Gq-coupled GPCR (Fig. 6F) (Rogan and Roth, 2011), activation of PLA2 and the following secretion of PGE2 have been visualized in epithelial cells and melanoma cells (Konishi et al., 2021; Watabe et al., 2024).