Biological relevance of 14-3-3 acetylation during osteogenic lineage determination

FRONTINI LOPEZ, Y.R.; BUSTOS, D.M.; UHART, MARINA

Mendoza

Congreso; LVI Annual SAIB on line meeting; 2020

SAIB

The 14-3-3 protein family is known to act as a hub for thousands of serine/threonine phosphorylated proteins within the cell.Thus, they act as essential components in various signaling pathways and cellular processes. Although the different 14-3-3paralogs were thought as redundant for many years, specific biological functions have recently been discovered for each ofthem. Because of the importance of phosphorylation in the signal transduction machinery, the regulation of 14-3-3 proteinswas left aside for years. However, its acetylation in an essential residue within their binding pocket, causing its inactivation,was recently published. The present work is the first to report biological results regarding the acetylation of 14-3-3. We firstanalyzed the relative levels of the different 14-3-3 paralogs during the osteogenic differentiation of human adipose-derivedstromal cells. We found that the expression of three out of seven paralogs varied between non-treated and differentiated cells.Among them, specifically the 14-3-3β paralog, but not γ, increased its acetylation during the process. Our results suggestedthat HBO1 could be at least one of the putative N-ε-acetyltransferases responsible for the 14-3-3 post-translationalmodification, as we detected 14-3-3 acetylation by in vitro reaction, and co-localization of the two proteins by indirectimmunofluorescence. Acetylated 14-3-3 proteins signal was observed specifically as nuclear speckles, probably correspondingto the recently described membraneless compartments known as biomolecular condensates. 14-3-3β and γ silencing in 3T3-L1 preadipocytes followed by trans-differentiation to the osteogenic lineage suggested that 14-3-3β paralog, but not γ, impairsthe osteoblastogenesis of the cells, since its knockdown increased significantly their osteogenic potential.