Phosphorylation-dependent Interaction between Plant Plasma Membrane H+-ATPase and 14-3-3 Proteins

Abstract

The H؉ -ATPase is a key enzyme for the establishment and maintenance of plasma membrane potential and energization of secondary active transport in the plant cell. The phytotoxin fusicoccin induces H ؉ -ATPase activation by promoting the association of 14-3-3 proteins. It is still unclear whether 14-3-3 proteins can represent natural regulators of the proton pump, and factors regulating 14-3-3 binding to the H ؉ -ATPase under physiological conditions are unknown as well. In the present study in vivo and in vitro evidence is provided that 14-3-3 proteins can associate with the H ؉ -ATPase from maize roots also in a fusicoccin-independent manner and that the interaction depends on the phosphorylation status of the proton pump. Furthermore, results indicate that phosphorylation of H ؉ -ATPase influences also the fusicoccin-dependent interaction of 14-3-3 proteins. Finally, a protein phosphatase 2A able to impair the interaction between H ؉

Cold stress affects H + -ATPase and phospholipase D activity in Arabidopsis

“…This hypothesis was corroborated by overlay data, where a similar 14-3-3 association with H þ -ATPase purified from control and stressed plants was observed in vitro (Fig. 5), since it is known that the in overlay experiments the in vitro interaction of H þ -ATPase with a recombinant 14-3-3 protein is completely dependent on the phosphorylation status of the enzyme (Fuglsang et al, 1999;Camoni et al, 2000). Accordingly, the levels of 14-3-3s present in the plasma membrane of control and stressed plants were almost identical after 12 h 4 C treatment (Fig.…”

“…2B) that correlates with a reduced amount of 14-3-3 proteins associated with its C-terminal regulatory domain. It is known that H þ -ATPase is fully activated by binding with 14-3-3 proteins occurring at the extreme C-terminal end of the enzyme as the consequence of the phosphorylation of a specific threonine residue (Fuglsang et al, 1999;Camoni et al, 2000) in the mode III 14-3-3 binding motif. Overlay assay demonstrated that upon 6 h 4 C treatment, the H þ -ATPase lost the ability to bind 14-3-3 proteins in vitro (Fig.…”

Early embryonic expression of ion channels and pumps in chick and Xenopus development

“…The 14-3-3 family of genes encode proteins that are involved in cell cycle control and are implicated in prion diseases (Kumagai et al, 1998;Satoh et al, 1999). Additionally, they have been shown to interact with the H ϩ ATPase and regulate the ion pump's activity (Baunsgaard et al, 1998;Chelysheva et al, 1999;Camoni et al, 2000;Morsomme and Boutry, 2000). Because we detected mRNA of several subunits of the proton pump in embryos (Figs.…”

Adenosine 5′-Monophosphate Inhibits the Association of 14-3-3 Proteins with the Plant Plasma Membrane H+-ATPase

“…In fact, it seems that the activation of H ϩ -ATPase, which depends on its interaction with 14-3-3 proteins, may be regulated, besides the phosphorylation/dephosphorylation of the enzyme (14), by 5Ј-AMP binding to 14-3-3 proteins. Moreover, our findings also suggest that 5Ј-AMP can be a general modulator of 14-3-3-regulated processes in plant cells.…”

“…This finding indicates that 14-3-3 proteins are physiological regulators of the H ϩ -ATPase and raises a question about the mechanisms controlling 14-3-3 association under natural conditions. Although evidence for a phosphorylation-mediated regulation has been reported (12)(13)(14), it is very likely that to integrate a number of stimuli and to achieve fine regulation, multiple mechanisms may occur in the plant cell. Circumstantial evidence of the presence in plant extracts of endogenous ligands able to inhibit the FC-stimulated H ϩ -ATPase activity have been reported (15).…”