Structural assembly of the signaling competent ERK2–RSK1 heterodimeric protein kinase complex

• Published in: Proceedings of the National Academy of Sciences - PNAS 2015-03, Vol.112 (9), p.2711-2716
• Main Authors: Alexa, Anita, Gógl, Gergő, Glatz, Gábor, Garai, Ágnes, Zeke, András, Varga, János, Dudás, Erika, Jeszenői, Norbert, Bodor, Andrea, Hetényi, Csaba, Reményi, Attila
• Format: Article
• Language: English
• Subjects: Biological Sciences; Catalytic Domain; Cell growth; Crystal structure; Humans; Kinases; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase 1 - chemistry; Mitogen-Activated Protein Kinase 1 - genetics; Mitogen-Activated Protein Kinase 1 - metabolism; Multienzyme Complexes - chemistry; Multienzyme Complexes - genetics; Multienzyme Complexes - metabolism; Phosphorylation; Protein Multimerization; Protein Structure, Quaternary; Protein Structure, Secondary; Ribosomal Protein S6 Kinases, 90-kDa - chemistry; Ribosomal Protein S6 Kinases, 90-kDa - genetics; Ribosomal Protein S6 Kinases, 90-kDa - metabolism; Simulation; Structural analysis
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1417571112

Significance Signaling pathways often use kinase cascades, but structural characterization of catalytic complexes between heterodimeric kinase pairs has been elusive. For MAPK–MAPKAPK binary complexes, a high-affinity “docking” interaction holds kinase domains proximal within a tethered complex. This heterodimer provided a unique opportunity to shed light on kinase domain–domain contacts that play a role in the assembly of the transient catalytic complex. Starting out from a new precatalytic extracellular signal regulated kinase 2–ribosomal S6 kinase 1 (ERK2–RSK1) crystallographic complex, where the activation loop of the downstream kinase (RSK1) faced the enzyme's (ERK2) catalytic site, we used molecular dynamics simulation to show how the catalytic ERK2–RSK1 complex forms. Our findings reveal the dynamic process through which transient, physiologically relevant kinase heterodimers form in a prototypical kinase cascade. Mitogen-activated protein kinases (MAPKs) bind and activate their downstream kinase substrates, MAPK-activated protein kinases (MAPKAPKs). Notably, extracellular signal regulated kinase 2 (ERK2) phosphorylates ribosomal S6 kinase 1 (RSK1), which promotes cellular growth. Here, we determined the crystal structure of an RSK1 construct in complex with its activator kinase. The structure captures the kinase–kinase complex in a precatalytic state where the activation loop of the downstream kinase (RSK1) faces the enzyme's (ERK2) catalytic site. Molecular dynamics simulation was used to show how this heterodimer could shift into a signaling-competent state. This structural analysis combined with biochemical and cellular studies on MAPK→MAPKAPK signaling showed that the interaction between the MAPK binding linear motif (residing in a disordered kinase domain extension) and the ERK2 “docking” groove plays the major role in making an encounter complex. This interaction holds kinase domains proximal as they “readjust,” whereas generic kinase domain surface contacts bring them into a catalytically competent state.