The dimeric versus monomeric status of 14-3-3zeta is controlled by phosphorylation of Ser58 at the dimer interface.
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 (Ser58) located within the dimer interface. Furthermore, by developing an antibody that specifically recognizes 14-3-3zeta phosphorylated on Ser58 and employing native-PAGE and cross-linking techniques, we found that 14-3-3 phosphorylated on Ser58 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.
Woodcock
Joanna M
JM
Cytokine Receptor Laboratory, Division of Human Immunology, Hanson Institute, Institute of Medical and Veterinary Science, G. P. O. Box 14 Rundle Mall, Adelaide, SA 5000, Australia. joanna.woodcock@imvs.sa.gov.au
Murphy
Jane
J
Stomski
Frank C
FC
Berndt
Michael C
MC
Lopez
Angel F
AF
D048948:14-3-3 Proteins; D020816:Amino Acid Motifs; D000818:Animals; D017209:Apoptosis; D003432:Cross-Linking Reagents / Q000494:pharmacology; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D051379:Mice; D008807:Mice, Inbred BALB C; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000737:chemistry*; D015398:Signal Transduction; D014446:Tyrosine 3-Monooxygenase / Q000737:chemistry*
D048948:14-3-3 Proteins; D003432:Cross-Linking Reagents; D011994:Recombinant Proteins; D012694:Serine; D014446:Tyrosine 3-Monooxygenase