SUMOYLATION AND THE ONCOGENIC E17K MUTATION AFFECT AKT1 SUBCELLULAR DISTRIBUTION AND IMPACT ON NANOG-BINDING DYNAMICS TO CHROMATIN IN EMBRYONIC STEM CELLS

FRANCIA, MARCOS GABRIEL; CAMILA OSES ; SABRINA LORENA ROBERTI; MORA RENEÉ GARCIA; COZZA, LUCAS HELIO; MARIA CANDELARIA DIAZ; LEVI, VALERIA; ALEJANDRA SONIA GUBERMAN

Congreso; Stem Cell Niche 2023; 2023

AKT/PKB is a serine-threonine kinase that mediates the action of a wide range of stimuli, regulating diverse processes in various cell types. In embryonic stem cells (ESCs), AKT plays a central role in maintaining pluripotency, specially promoting the expression of Nanog, a key transcription factor. AKT activation depends on its recruitment to the cellular membrane and subsequent phosphorylation, as well as other post-translational modifications (PTMs), including conjugation to the small ubiquitin-related modifier (SUMO), which altogether fine-tune its activity and target specificity. Previous reports indicate that SUMOylation can affect the distribution and accumulation of other proteins in different compartments. In this work, we aimed to investigate the effects of SUMOylation on AKT1 in mouse ESCs. Specifically, we hypothesized that SUMOylation could affect the subcellular distribution of AKT, its interaction and affinity for its targets, and ultimately impacting in its function. To explore this hypothesis, we generated mCherry-fused proteins of AKT1 variants with different SUMOylation capability and analyzed them by confocal microscopy. We found that this PTM impacts in the distribution and heterogeneity of AKT1 in the nucleus and cytoplasm, and also affects the chromatin-binding dynamics of NANOG, as revealed by Fluorescence Correlation Spectroscopy. Remarkably, the oncogenic E17K AKT1 mutant in ESCs produced major changes, increasing the binding of NANOG to its targets in a SUMOylation-dependent manner. These findings demonstrate that SUMOylation modulates AKT1 subcellular distribution, adding an extra layer of regulation to its function.