Proteomic identification of Bcl2-associated athanogene 2 as a novel MAPK-activated protein kinase 2 substrate.
The p38 MAPK cascade is activated by various stresses or cytokines. Downstream of p38 MAPKs, there are diversification and extensive branching of signaling pathways. Fluorescent two-dimensional difference gel electrophoresis of phosphoprotein-enriched samples from HeLa cells in which p38 MAPK activity was either suppressed or activated enabled us to detect approximately 90 candidate spots for factors involved in p38-dependent pathways. Among these candidates, here we identified four proteins including Bcl-2-associated athanogene 2 (BAG2) by peptide mass fingerprintings. BAG family proteins are highly conserved throughout eukaryotes and regulate Hsc/Hsp70-mediated molecular chaperone activities and apoptosis. The results of two-dimensional immunoblots suggested that the phosphorylation of BAG2 was specifically controlled in a p38 MAPK-dependent manner. Furthermore, BAG2 was directly phosphorylated at serine 20 in vitro by MAPK-activated protein kinase 2 (MAPKAP kinase 2), which is known as a primary substrate of p38 MAPK and mediates several p38 MAPK-dependent processes. We confirmed that MAPKAP kinase 2 is also required for phosphorylation of BAG2 in vivo. Thus, p38 MAPK-MAPKAP kinase 2-BAG2 phosphorylation cascade may be a novel signaling pathway for response to extracellular stresses.
Division of Cellular Proteomics, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
Koji
K
Ueda
Hidetaka
H
Kosako
Yasuhisa
Y
Fukui
Seisuke
S
Hattori
D015180:Electrophoresis, Gel, Two-Dimensional; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases; D018832:Molecular Chaperones; D010750:Phosphoproteins / Q000032:analysis / Q000302:isolation & purification; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D040901:Proteomics / Q000379:methods*; D012694:Serine / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2
D018840:HSP70 Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases; D018832:Molecular Chaperones; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D012694:Serine; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2; C492980:BAG2 protein, human