cGMP-dependent protein kinase I promotes cell apoptosis through hyperactivation of death-associated protein kinase 2

cGMP-dependent protein kinase-I (cGK-I) induces apoptosis in various cancer cell lines. However, the signaling mechanisms involved remain unknown. Using protein microarray technology, we identified a novel cGK substrate, death-associated protein kinase 2 (DAPK2), which is a Ca2+/calmodulin-regulated serine/threonine kinase. cGK-I phosphorylated DAPK2 at Ser299, Ser367 and Ser368. Interestingly, a phospho-mimic mutant, DAPK2 S299D, significantly enhanced its kinase activity in the absence of Ca2+/calmodulin, while a S367D/S368D mutant did not. Overexpression of DAPK2 S299D also resulted in a twofold increase in apoptosis of human breast cancer MCF-7 cells as compared with wild-type DAPK2. These results suggest that DAPK2 is one of the targets of cGK-I in apoptosis induction.

► DAPK2 was identified as a substrate for cGK-I by a protein microarray analysis.
► cGK-Iβ phosphorylates DAPK2 at Ser299, Ser367 and Ser368.
► Phosphorylation of DAPK2 at Ser299 by cGK-I increases its kinase activity.
► A phospho-mimic DAPK2 mutant strongly induces apoptosis in MCF-7 breast cancer cells.