PKCδ-dependent phosphorylation of PKD1 at S916 site precedes PKD1 S744/S748 active loop phosphorylation. N27 dopaminergic cells were treated with 100 μM H2O2 for 10-90 min and monitored for PKD1Y469, PKD1 S916 and PKD1 S744/S748 phosphorylation (A). N27 dopaminergic cells were treated with or without 50 nM desmopressin for 1 h and monitored for PKD1 Y469 phosphorylation. The cells show PKD1 Y469 phosphorylation when exposed to desmopressin, while carbachol does not cause PKD1 Y469 phosphorylation (B). N27 cells expressing PKD1S916A mutant blocked PKD1 activation during oxidative stress, as seen by Western blotting for PKD1 S744/S748 phosphorylation and HA expression (C). N27 dopaminergic cells were transfected with 1 μM PKCδ siRNA and non-specific siRNA and monitored for PKCδ protein expression and PKD1 S916 phosphorylation after treatment with or without H2O2 (D).