Decreased KLHL3 expression is involved in the pathogenesis of pseudohypoaldosteronism type II caused by cullin 3 mutation in vivo.

BACKGROUND: Pseudohypoaldosteronism type II (PHAII) is a hereditary hypertensive disease caused by mutations in four genes: WNK1, WNK4, Kelch-like3 (KLHL3), and cullin3 (CUL3). Recently, it was revealed that CUL3-KLHL3 E3 ligase complex ubiquitinates WNK1 and WNK4, leading to their degradation, and that a common pathogenesis of PHAII is defective WNK degradation due to CUL3-KLHL3 E3 ligase complex impairment. PHAII-causing CUL3 mutations mediate exon9 skipping, producing a CUL3 protein with a 57-amino acid deletion (Δ403-459). However, the pathogenic effects of KLHL3, an adaptor protein that links WNKs with CUL3, in PHAII caused by CUL3 mutation remain unclear.
METHODS: To clarify detailed pathophysiological mechanisms underlying PHAII caused by CUL3 mutation in vivo, we generated and analyzed knock-in mice carrying the same CUL3 exon9 deletion (CUL3WT/Δex9) as that reported in PHAII patients.
RESULTS: CUL3WT/Δex9 mice exhibited a PHAII-like phenotype. Interestingly, we confirmed markedly decreased KLHL3 expression in CUL3WT/Δex9 mice by confirming the true KLHL3 band in vivo. However, the expression of other KLHL family proteins, such as KLHL2, was comparable between WT and mutant mice.
CONCLUSION: KLHL3 expression was decreased in CUL3WT/Δex9 mice. However, expression levels of other KLHL family proteins were comparable between the wild-type and mutant mice. These findings indicate that the decreased abundance of KLHL3 is a specific phenomenon caused by mutant CUL3 (Δexon9). Our findings would improve our understanding of the pathogenesis of PHAII caused by CUL3 mutation in vivo.