Bicuculline regulated protein synthesis is dependent on Homer1 and promotes its interaction with eEF2K through mTORC1‐dependent phosphorylation

Abstract

The regulation of protein synthesis is a vital and finely tuned process in cellular physiology. In neurons, this process is very precisely regulated, as which mRNAs undergo translation is highly dependent on context. One of the most prominent regulators of protein synthesis is the enzyme eukaryotic elongation factor kinase 2 (eEF2K) that regulates the elongation stage of protein synthesis. This kinase and its substrate, eukaryotic elongation factor 2 (eEF2) are important in processes such as neuronal development and synaptic plasticity. eEF2K is regulated by multiple mechanisms including Ca 2+ -ions and the mTORC1 signaling pathway, both of which play key roles in neurological processes such as learning and memory. In such settings, the localized control of protein synthesis is of crucial importance. In this work, we sought to investigate how the localization of eEF2K is controlled and the impact of this on protein synthesis in neuronal cells. In this study, we used both SH-SY5Y neuroblastoma cells and mouse cortical neurons, and pharmacologically and/or genetic approaches to modify eEF2K function. We show that eEF2K activity and localization can be regulated by its binding partner Homer1b/c, a scaffolding protein known for its participation in calcium-regulated signaling pathways. Furthermore, our results indicate that this interaction is regulated by the mTORC1 pathway, through a known phosphorylation site in eEF2K (S396), and that it affects rates of localized protein synthesis at synapses depending on the presence or absence of this scaffolding protein.

eEF2K promotes PD-L1 stabilization through inactivating GSK3β in melanoma

“…Then, we performed immunoprecipitation followed by mass spectrometry to identify eEF2K-interacting proteins. In addition to several reported eEF2K-interacting proteins like eEF2 35 and Homer1, 36 GSK3β, a key regulator of tumor immunity by inducing phosphorylation-dependent PD-L1 proteasomal degradation, 11 was shown to be a potential partner of eEF2K ( figure 3A ). To confirm this result, a co-immunoprecipitation was performed in 293 T cells, and western blot analysis showed that eEF2K associated with GSK3β ( figure 3B ).…”

Chemical signaling in the developing avian retina: Focus on cyclic AMP and AKT-dependent pathways

“…This effect would be due to an increase of arginine availability for NO production since this amino acid would be less directed towards protein synthesis. Some data showed that the protein Homer1b/c plays an important role in this protein synthesis regulation, since lack of this protein impairs this signaling pathway (Gladulich et al, 2021).…”

Roles of eukaryotic elongation factor 2 kinase (eEF2K) in neuronal plasticity, cognition, and Alzheimer disease

“…Phosphorylation of eEF2K at either Ser366 or Ser78 site by mTORC1 results in inhibition of eEF2K activity, leading to dephosphorylation of eEF2 and subsequently increase of general protein synthesis (Kenney et al, 2014). A most recent study suggested that a scaffolding protein Homer1b/c regulates eEF2K activity, and the process is associated with the mTORC1 pathway through phosphorylation of eEF2K at the Ser396 site (Gladulich et al, 2021). Previous studies in rodents indicate that the involvement of mTORC1 in the regulation of long‐term hippocampal synaptic plasticity requires inputs from multiple kinases including AKT (protein kinase B) and ERK (Ma et al, 2011; Tsokas et al, 2007).…”