Molecular basis of p38α mapk signaling

• Autores: Nuria Gutierrez Prat
• Directores de la Tesis: Ángel Rodríguez Nebreda (dir. tes.), Albert Tauler Girona (tut. tes.)
• Lectura: En la Universitat de Barcelona ( España ) en 2018
• Idioma: español
• Tribunal Calificador de la Tesis: Bernat Crosas Navarro (presid.), José Miguel Lizcano de Vega (secret.), Rosa Aligué Alemany (voc.)
• Programa de doctorado: Programa de Doctorado en Biomedicina por la Universidad de Barcelona
• Materias:
  • Química
    • Bioquímica
      • Biología molecular
      • Proteínas
  • Ciencias médicas
    • Patología
      • Etress
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• Resumen

  • Cells are often exposed to damaging internal and external stimuli and need to respond accordingly. One of the signaling pathways that is frequently activated by stress involves activation of the kinase p38, which in turn can phosphorylate many substrates including phosphatases that inactivate the pathway. The binding between p38and interacting molecules involves both docking-site mediated interactions and the transient enzyme-substrate interaction through the active site center. While the majority of the p38 protein partners undergo transient contacts, others are able to bind through more stable interactions, potentially allowing p38 to act as scaffolding molecule. So far, most of the functions attributed to p38 are mediated by its kinase activity, and therefore more studies are required to uncover p38 scaffolding functions. We have perfomed in silico screenings to identify p38 partners, but have not been able to find new proteins that interact with p38 in a stable manner. One of the best characterized effectors of p38 is the protein kinase MAPKAPK2 (MK2), which interacts via its C-terminal regulatory domain with the docking groove of p38. Experiments using purified proteins have shown that non-phosphorylated p38 and MK2 can form a tight and rather stable complex in which structural constraints impede the interaction of both kinases with effectors and regulators. It is therefore critical to understand how the interaction between p38 and MK2 is regulated to ensure that they can separate from each other and phosphorylate the required substrates to mediate particular functions. We have found that in cells under homeostatic conditions, endogenous p38 and MK2 form a stable complex that is disrupted upon phosphorylation of both proteins. Depending on the length and intensity of the stimuli, p38 and MK2 undergo different fates. Transient stimulation leads to complex separation and MK2 degradation followed by an increase in MK2 gene expression, and the eventual re-assembly of the p38:MK2 complex. In contrast, when cells are exposed to strong stimuli that lead to sustained p38activation, as it is often the case with stress, both kinases remain phosphorylated, cannot bind to each other and eventually become destabilized, being unable to recover the stand-by state. Taken together, our study highlights the importance of docking interactions in the regulation of the p38:MK2 complex dynamics, which may have implications for different processes regulated by p38 and MK2 signaling. In addition, we have also generated mice that express a kinase-dead form of p38 and provide some evidence of potential p38 kinase-independent functions in vivo. Overall, our results have shed light on the molecular regulation of this signaling pathway.