A WNK kinase binds and phosphorylates V‐ATPase subunit C

Abstract

WNK (with no lysine (K)) protein kinases are found in many eukaryotes and share a unique active site. Here, we report that a member of the Arabidopsis WNK family (AtWNK8) interacts with subunit C of the vacuolar H⁺‐ATPase (V‐ATPase) via a short C‐terminal domain. AtWNK8 is shown to autophosphorylate intermolecularly and to phosphorylate Arabidopsis subunit C (AtVHA‐C) at multiple sites as determined by MALDI‐TOF MS analysis. Furthermore, we show that AtVHA‐C and other V‐ATPase subunits are phosphorylated when V₁‐complexes are used as substrates for AtWNK8. Taken together, our results provide evidence that V‐ATPases are potential targets of WNK kinases and their associated signaling pathways.