Article

Structure of ERK2 bound to PEA-15 reveals a mechanism for rapid release of activated MAPK

Program in Apoptosis and Cell Death Research, Cancer Center, Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA.
Nature Communications (Impact Factor: 11.47). 04/2013; 4:1681. DOI: 10.1038/ncomms2687
Source: PubMed

ABSTRACT

ERK1/2 kinases are the principal effectors of a central signalling cascade that converts extracellular stimuli into cell proliferation and migration responses and, when deregulated, can promote cell oncogenic transformation. The scaffolding protein PEA-15 is a death effector domain protein that directly interacts with ERK1/2 and affects ERK1/2 subcellular localization and phosphorylation. Here, to understand this ERK1/2 signalling complex, we have solved the crystal structures of PEA-15 bound to three different ERK2 phospho-conformers. The structures reveal that PEA-15 uses a bipartite binding mode, occupying two key docking sites of ERK2. Remarkably, PEA-15 can efficiently bind the ERK2 activation loop in the critical Thr-X-Tyr region in different phosphorylation states. PEA-15 binding triggers an extended allosteric conduit in dually phosphorylated ERK2, disrupting key features of active ERK2. At the same time PEA-15 binding protects ERK2 from dephosphorylation, thus setting the stage for immediate ERK activity upon its release from the PEA-15 inhibitory complex.

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    • "It acts as a flexible molecular adaptor by binding to and altering the function of other proteins involved in cell proliferation, apoptosis, and glucose metabolism [27] [28]. Two serine phosphorylation sites present on PEA-15 are very important to its function as they dictate its pathway interactions [26] [29]. In particular, phosphorylation at Ser104 blocks PEA-15 binding and sequestration of ERK1/2, thereby allowing increased ERK1/2 activity [30] [31] [32]. "
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    ABSTRACT: Biomechanical insult contributes to many chronic pathological processes, yet the resulting influences on signal transduction mechanisms are poorly understood. The retina presents an excellent mechanotransduction model, as mechanical strain on sensitive astrocytes of the optic nerve head (ONH) is intimately linked to chronic tissue remodeling and excavation by matrix metalloproteinases (MMPs), and apoptotic cell death. However, the mechanism by which these effects are induced by biomechanical strain is unclear. We previously identified the small adaptor protein, PEA-15 (phosphoprotein enriched in astrocytes), through proteomic analyses of human ONH astrocytes subjected to pathologically relevant biomechanical insult. Under resting conditions PEA-15 is regulated through phosphorylation of two key serine residues to inhibit extrinsic apoptosis and ERK1/2 signaling. However, we surprisingly observed that biomechanical insult dramatically switches PEA-15 phosphorylation and function to uncouple its anti-apoptotic activity, and promote ERK1/2-dependent MMP-2 and MMP-9 secretion. These results reveal a novel cell autonomous mechanism by which biomechanical strain rapidly modifies this signaling pathway to generate altered tissue injury responses.
    Full-text · Article · Nov 2015 · Experimental Cell Research
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    • "Solving the crystal structures of PEA-15 bound to ERK2 has revealed further interesting details. Analyses of these structures revealed that PEA-15 actually protects ERK1/2 from dephosphorylation and in fact acts as a “primer” to hold activated ERK1/2 in a state which is readied for downstream signalling once ERK1/2 is released from the PEA-15 complex (Mace et al., 2013). It appears, therefore, that PEA-15 is not merely a scaffold protein for ERK1/2 localisation but in fact an integral mechanism which can directly regulate ERK1/2 signalling independent of the recognised canonical activation pathway. "
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    ABSTRACT: Phosphoprotein enriched in astrocytes-15 (PEA-15) is a cytoplasmic protein that sits at an important junction in intracellular signalling and can regulate diverse cellular processes, such as proliferation and apoptosis, dependent upon stimulation. Regulation of these processes occurs by virtue of the unique interaction of PEA-15 with other signalling proteins. PEA-15 acts as a cytoplasmic tether for the mitogen-activated protein kinases, extracellular signal-regulated kinase 1/2 (ERK1/2) preventing nuclear localisation. In order to release ERK1/2, PEA-15 requires to be phosphorylated via several potential pathways. PEA-15 (and its phosphorylation state) therefore regulates many ERK1/2-dependent processes, including proliferation, via regulating ERK1/2 nuclear translocation. In addition, PEA-15 contains a death effector domain (DED) which allows interaction with other DED-containing proteins. PEA-15 can bind the DED-containing apoptotic adaptor molecule, Fas-associated death domain protein (FADD) which is also dependent on the phosphorylation status of PEA-15. PEA-15 binding of FADD can inhibit apoptosis as bound FADD cannot participate in the assembly of apoptotic signalling complexes. Through these protein-protein interactions, PEA-15-regulated cellular effects have now been investigated in a number of disease-related studies. Changes in PEA-15 expression and regulation have been observed in diabetes mellitus, cancer, neurological disorders and the cardiovascular system. These changes have been suggested to contribute to the pathology related to each of these disease states. As such, new therapeutic targets based around PEA-15 and its associated interactions are now being uncovered and could provide novel avenues for treatment strategies in multiple diseases.
    Full-text · Article · Mar 2014 · Pharmacology [?] Therapeutics
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    • "Recently, various complex structures between PEA-15 and ERK2 have been reported [8], including a full-length PEA-15 in complex with the T185E ERK2 mutant (PDB ID 4IZ5), PEA-15 DED (residues 1–96) in complexes with unphosphorylated ERK2 (PDB ID 4IZ7) and dual-phosphorylated (pT185 and pY187) ERK2 (PDB ID 4IZA). We also tried to fit the experimental RDC data in the complex to the recently reported crystal structure, 4IZ7, which is closest to our experimental conditions and has the highest resolution among the three structures. "
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    ABSTRACT: Protein conformational changes are commonly associated with the formation of protein complexes. The non-catalytic death effector domains (DEDs) mediate protein-protein interactions in a variety of cellular processes, including apoptosis, proliferation and migration, and glucose metabolism. Here, using NMR residual dipolar coupling (RDC) data, we report a conformational change in the DED of the phosphoprotein enriched in astrocytes, 15 kDa (PEA-15) protein in the complex with a mitogen-activated protein (MAP) kinase, extracellular regulated kinase 2 (ERK2), which is essential in regulating ERK2 cellular distribution and function in cell proliferation and migration. The most significant conformational change in PEA-15 happens at helices α2, α3, and α4, which also possess the highest flexibility among the six-helix bundle of the DED. This crucial conformational change is modulated by the D/E-RxDL charge-triad motif, one of the prominent structural features of DEDs, together with a number of other electrostatic and hydrogen bonding interactions on the protein surface. Charge-triad motif promotes the optimal orientation of key residues and expands the binding interface to accommodate protein-protein interactions. However, the charge-triad residues are not directly involved in the binding interface between PEA-15 and ERK2.
    Full-text · Article · Dec 2013 · PLoS ONE
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