The docking interaction of caspase-9 with ERK2 provides a mechanism for the selective inhibitory phosphorylation of caspase-9 at threonine 125.
Caspase-9 plays a critical role in the initiation of apoptosis by the mitochondrial pathway. Activation of caspase-9 is inhibited by phosphorylation at Thr(125) by ERK1/2 MAPKs in response to growth factors. Here, we show that phosphorylation of this site is specific for these classical MAPKs and is not strongly induced when JNK and p38alpha/beta MAPKs are activated by anisomycin. By deletion and mutagenic analysis, we identify domains in caspase-9 and ERK2 that mediate their interaction. Binding of ERK2 to caspase-9 and subsequent phosphorylation of caspase-9 requires a basic docking domain (D domain) in the N-terminal prodomain of the caspase. Mutational analysis of ERK2 reveals a (157)TTCD(160) motif required for recognition of caspase-9 that acts independently of the putative common docking domain. Molecular modeling supports the conclusion that Arg(10) in the D domain of caspase-9 interacts with Asp(160) in the TTCD motif of ERK2. Differences in the TTCD motif in other MAPK family members could account for the selective recognition of caspase-9 by ERK1/2. This selectivity may be important for the antiapoptotic role of classical MAPKs in contrast to the proapoptotic roles of stress-activated MAPKs.
Martin
Morag C
MC
Biomedical Research Centre, Ninewells Hospital and Medical School, Level 5, University of Dundee, Dundee DD1 9SY, United Kingdom.
Allan
Lindsey A
LA
Mancini
Erika J
EJ
Clarke
Paul R
PR
D000595:Amino Acid Sequence; D017209:Apoptosis; D053453:Caspase 9 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D013912:Threonine / Q000378:metabolism*
D013912:Threonine; D019950:Mitogen-Activated Protein Kinase 1; D053453:Caspase 9