ATF4 and Miyoshi myopathy: To confirm that Deptor inhibition is responsible for increased UPR signaling, we carried out experiments depleting Deptor in KMS18 and KMS27 MM cell lines and observed that Deptor inhibition activated PERK and IRE1α signaling, as highlighted by the increase in protein levels of ATF4 and XBP1 mRNA splicing, respectively (Figure 4C and 4D).