Phosphorylation of PEA-15 switches its binding specificity from ERK/MAPK to FADD.
Cell signalling pathways that regulate proliferation and those that regulate programmed cell death (apoptosis) are co-ordinated. The proteins and mechanisms that mediate the integration of these pathways are not yet fully described. The phosphoprotein PEA-15 (phosphoprotein enriched in astrocytes) can regulate both the ERK (extracellular-signal-regulated kinase)/MAPK (mitogen-activated protein kinase) pathway and the death receptor-initiated apoptosis pathway. This is the result of PEA-15 binding to the ERK/MAPK or the proapoptotic protein FADD (Fas-activated death domain protein) respectively. The mechanism by which binding of PEA-15 to these proteins is controlled has not been elucidated. PEA-15 is a phosphoprotein containing a Ser-104 phosphorylated by protein kinase C and a Ser-116 phosphorylated by CamKII (calcium/calmodulin-dependent protein kinase II) or AKT. Phosphorylation of Ser-104 is implicated in the regulation of glucose metabolism, while phosphorylation at Ser-116 is required for PEA-15 recruitment to the DISC (death-initiation signalling complex). Moreover, PEA-15 must be phosphorylated at Ser-116 to inhibit apoptosis. In the present study, we report that phosphorylation at Ser-104 blocks ERK binding to PEA-15 in vitro and in vivo, whereas phosphorylation at Ser-116 promotes its binding to FADD. We further characterize phospho-epitope-binding antibodies to these sites. We report that phosphorylation does not influence the distribution of PEA-15 between the cytoplasm and nucleus of the cell since all phosphorylated states are found predominantly in the cytoplasm. We propose that phosphorylation of PEA-15 acts as the switch that controls whether PEA-15 influences proliferation or apoptosis.
Renganathan
Hemamalini
H
Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, 604 Allison Road, Piscataway, NJ 08854, USA.
Vaidyanathan
Hema
H
Knapinska
Anna
A
Ramos
Joe W
JW
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D053200:Fas-Associated Death Domain Protein; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D021381:Protein Transport; D013379:Substrate Specificity; D013755:Tetradecanoylphorbol Acetate
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D047908:Intracellular Signaling Peptides and Proteins; C092039:PEA15 protein, human; D010750:Phosphoproteins; D048049:Extracellular Signal-Regulated MAP Kinases; D013755:Tetradecanoylphorbol Acetate