Fig. 6.

Kidney-specific with no lysine kinase 1 (KS-WNK1) and WNK4 coexpression results in WNK4 phosphorylation. A: representative Western blot showing the effect of long-variant-WNK1 lacking exon 11 (L-WNK1-Δ11) or KS-WNK1-Δ11, as stated, on Na⁺:Cl⁻ cotransporter (NCC) and WNK4 expression and phosphorylation under control conditions. The blot shows L-WNK1/KS-WNK1, WNK4, pWNK4 S335, pNCC, and NCC, as indicated. The experiment was conducted under both control and low-chloride hypotonic stress (LCHS) conditions, as stated. B: densitometric analysis of the phosphoWNK4/total WNK4 ratio from 4 different experiments. *P < 0.05 vs. H₂O-coinjected oocytes. C: effect of wild-type WNK4 (shaded bars) or WNK4 kinase death (KD) (solid bars) on NCC activity in oocytes injected with NCC cRNA, NCC + L-WNK1-Δ11, or NCC + KS-WNK1-Δ11. Thiazide-sensitive ²²Na⁺ uptake in oocytes injected with NCC alone was set to 100%, and the other groups were normalized accordingly. *P < 0.01; n = 3. D: effect of KS-WNK1 on NCC activity in the absence or presence of WNK4 (shaded bars). Thiazide-sensitive ²²Na⁺ uptake in oocytes injected with NCC alone was set to 100%, and the oocytes injected with KS-WNK1 were normalized accordingly (open bars); thiazide-sensitive ²²Na⁺ uptake in oocytes injected with NCC + WNK4 was set to 100%, and the oocytes injected with KS-WNK1 group were normalized accordingly. *P < 0.0001; n = 3.