KLHL2 interacts with and ubiquitinates WNK kinases

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Mutations in WNK1 and WNK4 genes cause pseudohypoaldosteronism type II (PHAII), an inherited hypertensive disease.
• KLHL3 and Cullin3 genes were recently identified as additional genetic factors in PHAII.
• Previous work established WNK4 as a substrate for the KLHL3-Cullin3 E3 ligase complex.

Purpose of the Study:

• To investigate if other Kelch-like proteins, specifically KLHL2, interact with and regulate WNK isoforms.
• To explore the role of the KLHL2-Cullin3 complex in WNK protein ubiquitination and degradation.

Main Methods:

• Co-immunoprecipitation assays to assess protein interactions between WNK isoforms and KLHL2/KLHL3.
• Fluorescence correlation spectroscopy to confirm direct KLHL2-WNK interactions.
• HEK293T cell co-expression studies and in vitro ubiquitination assays to evaluate WNK protein abundance and ubiquitination levels.

Main Results:

• KLHL2, similar to KLHL3, co-immunoprecipitated with all four WNK isoforms, indicating broad interaction.
• Direct binding between KLHL2 and WNKs was confirmed using fluorescence correlation spectroscopy.
• Co-expression of KLHL2 and Cullin3 reduced WNK1, WNK3, and WNK4 protein levels and increased WNK4 ubiquitination.

Conclusions:

• The KLHL2-Cullin3 complex interacts with and ubiquitinates WNK isoforms, similar to the KLHL3-Cullin3 complex.
• This suggests KLHL2-Cullin3 acts as an E3 ligase for WNK isoforms, potentially contributing to blood pressure regulation.
• Identifies a novel regulatory pathway involving KLHL2 in WNK protein homeostasis and PHAII pathogenesis.