A WNK kinase binds and phosphorylates V-ATPase subunit C

Area of Science:

• Plant molecular biology
• Enzymology
• Cellular signaling

Background:

• WNK (with no lysine (K)) protein kinases are conserved enzymes in eukaryotes, characterized by a unique active site.
• Vacuolar H+-ATPases (V-ATPases) are essential proton pumps involved in various cellular processes.
• The regulation of V-ATPase activity by protein kinases is an area of active research.

Purpose of the Study:

• To investigate the interaction between Arabidopsis WNK8 (AtWNK8) and vacuolar H+-ATPase (V-ATPase) subunit C.
• To determine if AtWNK8 can phosphorylate V-ATPase subunits.
• To explore the potential role of WNK kinases in V-ATPase regulation.

Main Methods:

• Co-immunoprecipitation to assess protein-protein interactions.
• In vitro kinase assays using purified AtWNK8 and V-ATPase subunits.
• Mass spectrometry (MALDI-TOF MS) to identify phosphorylation sites.

Main Results:

• Arabidopsis WNK8 (AtWNK8) directly interacts with subunit C of the vacuolar H+-ATPase (AtVHA-C).
• AtWNK8 exhibits autophosphorylation activity and phosphorylates AtVHA-C at multiple sites.
• Phosphorylation of AtVHA-C and other V-ATPase subunits was observed when using V1-complexes as substrates for AtWNK8.

Conclusions:

• Vacuolar H+-ATPases (V-ATPases) are identified as potential targets of WNK protein kinases.
• This study reveals a novel regulatory link between WNK kinase signaling and V-ATPase function in plants.
• The findings open new avenues for understanding cellular homeostasis and signaling pathways involving V-ATPases.