Assembly and Trafficking of a Multiprotein ROMK (Kir 1.1) Channel Complex by PDZ Interactions

Dana Yoo, Thomas P. Flagg, Olav Olsen, Viswanathan Raghuram, J. Kevin Foskett, Paul A. Welling

Research output: Contribution to journalArticle

Abstract

The ROMK subtypes of inward rectifier K+ channels (Kir 1.1, KCNJ1) mediate potassium secretion and regulate NaCl reabsorption in the kidney. In the present study, the role of the PDZ binding motif in ROMK function is explored. Here we identify the Na/H exchange regulatory factors, NHERF-1 and NHERF-2, as PDZ domain interaction partners of the ROMK channel. Characterization of the basis and consequences of NHERF association with ROMK reveals a PDZ interaction-dependent trafficking process and a coupling mechanism for linking ROMK to a channel modifier protein, the cystic fibrosis transmembrane regulator (CFTR). As measured by antibody binding of external epitope-tagged forms of Kir 1.1 in intact cells, NHERF-1 or NHERF-2 coexpression increased cell surface expression of ROMK. Channel interaction with NHERF proteins and effects of NHERF on ROMK localization were dependent on the presence of the PDZ domain binding motif in ROMK. Both NHERF proteins contain two PDZ domains; recombinant protein-protein binding assays and yeast-two-hybrid studies revealed that ROMK preferentially associates with the second PDZ domain of NHERF-1 and with the first PDZ domain of NHERF-2, precisely opposite of what has been reported for CFTR. Consistent with the scaffolding capacity of the NHERF proteins, coexpression of NHERF-2 with ROMK and CFTR dramatically increases the amount of ROMK protein that coimmunopurifies and functionally interacts with CFTR. Thus NHERF facilitates assembly of a ternary complex containing ROMK and CFTR. These observations raise the possibility that PDZ-based interactions may underscore physiological regulation and membrane targeting of ROMK in the kidney.

Original languageEnglish (US)
Pages (from-to)6863-6873
Number of pages11
JournalJournal of Biological Chemistry
Volume279
Issue number8
DOIs
StatePublished - Feb 20 2004
Externally publishedYes

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PDZ Domains
Cystic Fibrosis
Proteins
sodium-hydrogen exchanger regulatory factor
Inwardly Rectifying Potassium Channel
Kidney
Two-Hybrid System Techniques
Recombinant Proteins
Protein Binding
Yeast
Epitopes
Assays
Potassium
Association reactions
Membranes
Antibodies

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Assembly and Trafficking of a Multiprotein ROMK (Kir 1.1) Channel Complex by PDZ Interactions. / Yoo, Dana; Flagg, Thomas P.; Olsen, Olav; Raghuram, Viswanathan; Foskett, J. Kevin; Welling, Paul A.

In: Journal of Biological Chemistry, Vol. 279, No. 8, 20.02.2004, p. 6863-6873.

Research output: Contribution to journalArticle

Yoo, Dana ; Flagg, Thomas P. ; Olsen, Olav ; Raghuram, Viswanathan ; Foskett, J. Kevin ; Welling, Paul A. / Assembly and Trafficking of a Multiprotein ROMK (Kir 1.1) Channel Complex by PDZ Interactions. In: Journal of Biological Chemistry. 2004 ; Vol. 279, No. 8. pp. 6863-6873.
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AB - The ROMK subtypes of inward rectifier K+ channels (Kir 1.1, KCNJ1) mediate potassium secretion and regulate NaCl reabsorption in the kidney. In the present study, the role of the PDZ binding motif in ROMK function is explored. Here we identify the Na/H exchange regulatory factors, NHERF-1 and NHERF-2, as PDZ domain interaction partners of the ROMK channel. Characterization of the basis and consequences of NHERF association with ROMK reveals a PDZ interaction-dependent trafficking process and a coupling mechanism for linking ROMK to a channel modifier protein, the cystic fibrosis transmembrane regulator (CFTR). As measured by antibody binding of external epitope-tagged forms of Kir 1.1 in intact cells, NHERF-1 or NHERF-2 coexpression increased cell surface expression of ROMK. Channel interaction with NHERF proteins and effects of NHERF on ROMK localization were dependent on the presence of the PDZ domain binding motif in ROMK. Both NHERF proteins contain two PDZ domains; recombinant protein-protein binding assays and yeast-two-hybrid studies revealed that ROMK preferentially associates with the second PDZ domain of NHERF-1 and with the first PDZ domain of NHERF-2, precisely opposite of what has been reported for CFTR. Consistent with the scaffolding capacity of the NHERF proteins, coexpression of NHERF-2 with ROMK and CFTR dramatically increases the amount of ROMK protein that coimmunopurifies and functionally interacts with CFTR. Thus NHERF facilitates assembly of a ternary complex containing ROMK and CFTR. These observations raise the possibility that PDZ-based interactions may underscore physiological regulation and membrane targeting of ROMK in the kidney.

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