The acidic motif of WNK4 is crucial for its interaction with the K channel ROMK

详细信息    查看全文

• 作者：Meena Murthy ; Georgina Cope ; Kevin M. O’ ; Shaughnessy
• 关键词：WNK kinases ; Serine-threonine kinases ; WNK4 ; ROMK ; Protein– ; protein interactions ; Kidney ion transporters ; Xenopus expression system ; GFP-tagged proteins
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2008
• 出版时间：31 October 2008
• 年：2008
• 卷：375
• 期：4
• 页码：651-654
• 全文大小：355 K

文摘

WNK kinases have rapidly emerged as important regulators of Na⁺ and K⁺ homoeostasis in the mammalian kidney where they regulate the trafficking of proteins such as the NaCl-cotransporter (NCCT) and K⁺ channel, ROMK. However, an increasing number of WNK effects are kinase-independent, including their interaction with ROMK, and involve instead protein–protein interactions. Outside of their kinase domain all WNKs contain a unique run of predominantly negatively charged amino acids dubbed the acidic motif, where the WNK4 disease mutations causing Gordon’s syndrome also cluster. To look further at the role of this motif we studied the effects of WNK4 fragments, including one with a deleted acidic motif (ΔAM) and a 10-mer acidic motif peptide on ROMK expression in Xenopus oocytes. We found that an N-terminal fragment of WNK4 (1-620 WNK4) containing the acidic motif retains full activity in inhibiting ROMK currents. However, ΔAM WNK4 is completely inactive and the effect of WNK4 or 1-620 WNK4 can be completely blocked by co-injection of the 10-mer acidic motif peptide. The blocking action of the peptide was sequence specific as a peptide with a randomised sequence was inactive. These results on ROMK currents were paralleled by changes in membrane expression of fluorescent EGFP-ROMK. Finally, we show that 1-620 WNK4 can pull down ROMK and this interaction can be blocked with the acidic motif peptide. These results confirm the important role of the acidic motif of WNK4 in its protein–protein interaction with the ROMK channel.