The Dimeric Versus Monomeric Status of 14-3-3ζ Is Controlled by Phosphorylation of Ser58 at the Dimer Interface

Abstract

The 14-3-3 proteins play a central role in the regulation of cell growth, cycling, and apoptosis by modulating the functional activities of key signaling proteins. Through binding to a phosphoserine motif, 14-3-3 alters target proteins activities by sequestering them, relocalizing them, conformationally altering their functional activity, or by promoting interaction with other proteins. These functions of 14-3-3 are facilitated by, if not dependent on, its dimeric structure. We now show that the dimeric status of 14-3-3 is regulated by site-specific serine phosphorylation. We found that a sphingosine-dependent kinase phosphorylates 14-3-3 in vitro and in vivo on a serine residue (Ser 58 ) located within the dimer interface. Furthermore, by developing an antibody that specifically recognizes 14-3-3 phosphorylated on Ser 58 and employing native-PAGE and cross-linking techniques, we found that 14-3-3 phosphorylated on Ser 58 is monomeric both in vitro and in vivo. Phosphorylated 14-3-3 was detected solely as a monomer, indicating that phosphorylation of a single monomer within a dimer is sufficient to disrupt the dimeric structure. Significantly, phosphorylation-induced monomerization did not prevent 14-3-3 binding to a phosphopeptide target. We propose that this regulated monomerization of 14-3-3 controls its ability to modulate the activity of target proteins and thus may have significant implications for 14-3-3 function and the regulation of many cellular processes.

14-3-3 Proteins regulate Akt Thr308 phosphorylation in intestinal epithelial cells

“…However, in some conditions p14-3-3ζS58 and 14-3-3ζ retain its capability to bind its clients but display antagonistic effects in the function of its targets. 2 For this reason, we investigated the effect of overexpressing 14-3-3ζWT, 14-3-3ζS58D (monomeric form) and 14-3-3ζS58A (dimeric form) 34 in the accumulation of LC3 in autophagosomes. 35 As shown in Figure 4g, 14-3-3ζS58D but not 14-3-3ζ WT or 14-3-3ζS58A presence resulted in LC3 accumulation in autophagosomes.…”

Structural basis for protein–protein interactions in the 14-3-3 protein family

“…Using an in vivo-based approach, Chaudhri et al (2) found that the isoform preferentially formed heterodimers with no observable homodimer formation. In addition phosphorylation influences the dimerization process (43,44).…”

Dysregulation of 14‐3‐3 proteins in neurodegenerative diseases with Lewy body or Alzheimer pathology

“…S58 is present in all isoforms except 14‐3‐3 σ and θ ; S185 is present in 14‐3‐3 β , ε , σ , and ζ ; and S/T232 is limited to 14‐3‐3 θ and ζ . Phosphorylation at S58 regulates 14‐3‐3 dimerization,26 while phosphorylation at S185 regulates ligand binding 27, 28. Phosphorylation at either site causes release of proapoptotic factors and cell death 27, 28, 29.…”