title: CaMKII-γ mediates phosphorylation of BAD at Ser170 to regulate cytokine-dependent survival and proliferation.
abstract: Phosphorylation of the BH3 (Bcl-2 homology domain 3)-only protein BAD (Bcl-2/Bcl-X(L)-antagonist, causing cell death) can either directly disrupt its association with the pro-survival proteins Bcl-X(L) and/or Bcl-2, or cause association of BAD with 14-3-3 proteins. In the present study, we further characterize phosphorylation of BAD at Ser170, a unique site with unclear function. We provide further evidence that mutation of Ser170 to a phospho-mimetic aspartic acid residue (S170D) can have a profound inhibitory effect on the pro-apoptosis function of BAD. Furthermore, mutated BAD with an alanine substitution inhibited cell proliferation, slowing progression specifically through S-phase. We identify the kinase responsible for phosphorylation at this site as CaMKII-γ (γ isoform of Ca2+/calmodulin-dependent kinase II), but not the other three isoforms of CaMKII, revealing an extraordinary specificity among these closely related kinases. Furthermore, cytokine treatment increased BAD-Ser170-directed CaMKII-γ activity and phosphorylation of CaMKII-γ at an activating site, and CaMKII activity directed to the BAD-Ser170 site was elevated during S-phase. Treating cells with a selective inhibitor of CaMKII caused apoptosis in cells expressing BAD, but not in cells expressing the BAD-S170D mutant. The present study provides support for BAD-Ser170 phosphorylation playing a key role not only in regulating BAD's pro-apoptotic activity, but also in cell proliferation.
authors: Department of Medicine, University of British Columbia, 2775 Laurel Street, Vancouver, BC, Canada, V5Z 1M9.
authors: Payman
authors: P
authors: Hojabrpour
authors: Ivan
authors: I
authors: Waissbluth
authors: Mazyar
authors: M
authors: Ghaffari
authors: Michael E
authors: ME
authors: Cox
authors: Vincent
authors: V
authors: Duronio
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D051379:Mice; D010766:Phosphorylation; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D051025:bcl-Associated Death Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D051025:bcl-Associated Death Protein; D012694:Serine; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2