Fig. 3.

An intact WNK3-294A molecule is necessary for the regulation of K-Cl cotransport under isotonic conditions. ⁸⁶Rb⁺ uptake was measured in X. laevis oocytes microinjected with water, KCC4 cRNA alone, or KCC4 cRNA together with cRNA transcribed from each of the following cDNAs: WNK3-D294A (containing kinase-inactive WNK3), WNK3-RD (containing the sequence of the WNK3 regulatory domain only), WNK3-KD-D294A (containing the sequence of the WNK3 kinase domain only, with the D294A mutation), and WNK3-RD + KD-D294A (containing the WNK3 regulatory domain and the kinase domain DA together, but as separate transcripts). Uptakes were performed in isotonic medium (220 mOsm/kg) in the presence (open bars) or absence (filled bars) of extracellular Cl⁻ in the uptake medium. Each bar represents the mean ± SEM of 20 oocytes extracted from two different frogs.