Human 14-3-3 Paralogs Differences Uncovered by Cross-Talk of Phosphorylation and Lysine Acetylation

Abstract

The 14-3-3 protein family interacts with more than 700 different proteins in mammals, in part as a result of its specific phospho-serine/phospho-threonine binding activity. Upon binding to 14-3-3, the stability, subcellular localization and/or catalytic activity of the ligands are modified. Seven paralogs are strictly conserved in mammalian species. Although initially thought as redundant, the number of studies showing specialization is growing. We created a protein-protein interaction network for 14-3-3, kinases and their substrates signaling in human cells. We included information of phosphorylation, acetylation and other PTM sites, obtaining a complete representation of the 14-3-3 binding partners and their modifications. Using a computational system approach we found that networks of each 14-3-3 isoform are statistically different. It was remarkable to find that Tyr was the most phosphorylatable amino acid in domains of 14-3-3 epsilon partners. This, together with the over-representation of SH3 and Tyr_Kinase domains, suggest that epsilon could be involved in growth factors receptors signaling pathways particularly. We also found that within zeta’s network, the number of acetylated partners (and the number of modify lysines) is significantly higher compared with each of the other isoforms. Our results imply previously unreported hidden differences of the 14-3-3 isoforms interaction networks. The phosphoproteome and lysine acetylome within each network revealed post-transcriptional regulation intertwining phosphorylation and lysine acetylation. A global understanding of these networks will contribute to predict what could occur when regulatory circuits become dysfunctional or are modified in response to external stimuli.

Plakophilins in Desmosomal Adhesion and Signaling

“…Seven isoforms of 14-3-3 in humans and several hundreds of 14-3-3 binding partners have been identifi ed to date. These proteins are involved in diverse processes like regulation of the cytoskeleton, GTPase function, membrane signaling, cell fate determination, response to insulin and TNF α , cell cycle progression, and apoptosis (Uhart & Bustos, 2013). Interestingly, two of the motifs phosphorylated by AKT2 are putative 14-3-3 binding sites raising the possibility that an interaction with 14-3-3 might be involved in regulating PKP1.…”

Protein Modifications Regulate the Role of 14-3-3γ Adaptor Protein in cAMP-induced Steroidogenesis in MA-10 Leydig Cells

“…Are Acetylated-Phosphorylation of Ser 58 on 14-3-3 was shown to have a role in its self-dimerization (31), and acetylation of 14-3-3 on Lys 49 inhibited the phosphorylation-dependent interactions of this protein with its targets (35). In this study, we developed TAT peptides to compete with Ser 58 phosphorylation (TAT-14-3-3␥ Ser 58 ) and Lys 49 acetylation (TAT-14-3-3␥ Lys 49 ) sites to further assess their function in steroidogenesis (Fig.…”

“…Indeed, acetylation of key lysine residues in vivo indicates a novel regulatory mechanism of 14-3-3 function as this residue is located in the 14-3-3 monomer amphipathic groove through which they bind to their targets. Furthermore, Uhart and Bustos (13) reported cross-talk between 14-3-3 protein acetylation and phosphorylation in which acetylation of 14-3-3⑀ on Lys 49 inhibits the phosphorylation-dependent interactions of this protein with specific targets (35). In the present study, we investigated the effect of 14-3-3␥ acetylation and/or phosphorylation on STAR binding and 14-3-3␥ homodimerization during steroidogenesis.…”

HSPB6 (Hsp20) as a Versatile Molecular Regulator

“…Early investigations performed on rat HspB6 indicated that this protein forms interconvertible oligomers with molecular weights of 43-67 and 300-470 kDa (Kato et al 1994 ;van de Klundert et al 1998 ). Analysis of crude muscle extract by sizeexclusion chromatography or sucrose density gradient detected HspB6 in fractions with apparent molecular weight in the range of 68-540 kDa (Kato et al 1994 ;Brophy et al 1999a ).…”

“…ability to prevent aggregation of partially denatured or unfolded proteins, is common for all small heat shock proteins (McHaourab et al 2009 ;Vos et al 2008 ;Basha et al 2012 ). However, originally in vitro experiments performed with rat HspB6 indicated that the chaperone-like activity of this protein was lower than that of α-crystallin (van de Klundert et al 1998 ). Later studies performed on human HspB6 have shown that depending on the nature of model protein substrate the chaperone-like activity of human HspB6 is comparable to that of αB-crystallin (Bukach et al 2004 ;Mymrikov et al 2010 ;Datskevich et al 2012b ).…”