Fig. 4.

WNK4 is a regulator of NKCC1. (a) Effect of WNK4 on ⁸⁶Rb influx mediated by NKCC1. Oocytes were injected with water or cRNA encoding NKCC1 alone or in combination with cRNA encoding WNK4 as indicated; ⁸⁶Rb influx was measured as described in Methods. Results of a representative experiment are shown; bar graphs represent means ± SE of ⁸⁶Rb influx for each experimental group. (b) Effect of WNK4 on total cellular NKCC1 protein. A Western blot of whole oocyte lysates expressing NKCC1 in the presence or absence of WNK4 is shown. Samples were run in duplicate. The total amount of NKCC1 produced in injected oocytes is not altered by the presence of WNK4. (c and d) Effect of WNK4 on the surface expression of NKCC1. Representative examples of immunofluoresence microscopy of Xenopus ooctyes stained with anti-NKCC1 antibody. Oocytes were injected with cRNA encoding NKCC1 alone (b) or in combination with WNK4 (c) as described in Methods. (Magnifications: ×600.)