title: The tumor suppressor DAP kinase is a target of RSK-mediated survival signaling.
abstract: The viability of vertebrate cells depends on a complex signaling interplay between survival factors and cell-death effectors. Subtle changes in the equilibrium between these regulators can result in abnormal cell proliferation or cell death, leading to various pathological manifestations. Death-associated protein kinase (DAPK) is a multidomain calcium/calmodulin (CaM)-dependent Ser/Thr protein kinase with an important role in apoptosis regulation and tumor suppression. The molecular signaling mechanisms regulating this kinase, however, remain unclear. Here, we show that DAPK is phosphorylated upon activation of the Ras-extracellular signal-regulated kinase (ERK) pathway. This correlates with the suppression of the apoptotic activity of DAPK. We demonstrate that DAPK is a novel target of p90 ribosomal S6 kinases (RSK) 1 and 2, downstream effectors of ERK1/2. Using mass spectrometry, we identified Ser-289 as a novel phosphorylation site in DAPK, which is regulated by RSK. Mutation of Ser-289 to alanine results in a DAPK mutant with enhanced apoptotic activity, whereas the phosphomimetic mutation (Ser289Glu) attenuates its apoptotic activity. Our results suggest that RSK-mediated phosphorylation of DAPK is a unique mechanism for suppressing the proapoptotic function of this death kinase in healthy cells as well as Ras/Raf-transformed cells.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Rana
authors.initials: R
authors.lastname: Anjum
authors.forename: Philippe P
authors.initials: PP
authors.lastname: Roux
authors.forename: Bryan A
authors.initials: BA
authors.lastname: Ballif
authors.forename: Steven P
authors.initials: SP
authors.lastname: Gygi
authors.forename: John
authors.initials: J
authors.lastname: Blenis
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology; D017931:DNA Primers; D064550:Death-Associated Protein Kinases; D006801:Humans; D047468:Immunoprecipitation; D020935:MAP Kinase Signaling System / Q000502:physiology*; D013058:Mass Spectrometry; D051379:Mice; D008856:Microscopy, Fluorescence; D009154:Mutation / Q000235:genetics; D034622:RNA Interference; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; D017931:DNA Primers; D064550:Death-Associated Protein Kinases; C069329:RPS6KA1 protein, human; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C512964:Rps6ka1 protein, mouse; D017871:Calcium-Calmodulin-Dependent Protein Kinases