Tyrosine Phosphorylation Inhibits the Interaction of 14‐3‐3 Proteins with the Plant Plasma Membrane H⁺‐ATPase

Abstract

Interaction of 14-3-3 proteins with their targets depends not only on the phosphorylation status of the target but also on that of 14-3-3 (Fu et al., 2000). In this work we demonstrated that the maize 14-3-3 isoform GF14-6 is a substrate of the tyrosine kinase insulin growth factor receptor 1. By means of site-directed mutants of GF14-6, we identified Tyr-137 as the specific tyrosine residue phosphorylated by the insulin growth factor receptor 1. Phosphorylation of GF14-6 on Tyr-137 lowered its affinity for a peptide mimicking the 14-3-3 binding site of the plant plasma membrane H+-ATPase. Moreover, phosphorylation in planta of 14-3-3 tyrosine residues, resulting from incubation with the tyrosine phosphatase inhibitor, phenylarsine oxide, decreased their association to the H+-ATPase.

Exposed Loop Domains of Complexed 14-3-3 Proteins Contribute to Structural Diversity and Functional Specificity

“…These data also suggest that these epitopes maintain the same structural conformation regardless of the client-binding state. Also of interest is the fact that GBC mAb 5D6 epitope in loop 6 is in the same region that has been recognized as the site of Ser phosphorylation in mammalian 14-3-3s (Woodcock et al, 2003) and potential Tyr phosphorylation in plant 14-3-3s (Giacometti et al, 2004). This strengthens the argument that loop 6 is accessible at the surface of 14-3-3s, since it must be available to kinases and that loop 6 remains accessible in complexes.…”

Phosphoproteomic identification of targets of the Arabidopsis sucrose nonfermenting-like kinase SnRK2.8 reveals a connection to metabolic processes

“…Most studies of the role of 14-3-3 in cellular regulation have focused on changes in target protein phosphorylation as the initial regulatory event; however, 14-3-3 proteins have been shown to be phosphorylated in animal systems (37,38) and in plants (39)(40)(41). Phosphorylation of 14-3-3 is another way in which these proteins are regulated (29), and in animal systems, a few kinases reportedly phosphorylate 14-3-3.…”

“…Lu et al (41) found that the 14-3-3 was phosphorylated at a Ser residue by plant extracts. The maize GF14-6 (14-3-3) was phosphorylated at Tyr-137 by insulin-like growth factor receptor 1 in vitro (40). The specific kinases that phosphorylate plant non-14-3-3 have not been identified.…”

“…The phosphorylation of 14-3-3 can inhibit the interaction between 14-3-3 and their targets (38,40). The phosphorylation of 14-3-3 in vivo by the casein kinase I inhibits binding to c-Raf.…”

“…The phosphorylation of 14-3-3 in vivo by the casein kinase I inhibits binding to c-Raf. In maize, the phosphorylation of the 14-3-3-named GF14-6 on Tyr-137 inhibits the binding to the H ϩ -ATPase in maize and reduces H ϩ -ATPase activity (40). The phosphorylation of 14-3-3 by SnRK2.8 also may inhibit the interaction between unknown target proteins, and this may change the activity of target proteins.…”