Genistein Restores Functional Interactions between ΔF508-CFTR and ENaC in Xenopus Oocytes

Laurence Suaud,Jinqing Li,Qinshi Jiang,Ronald C Rubenstein,Thomas R Kleyman

doi:10.1074/jbc.m111482200

Abstract

The cystic fibrosis transmembrane conductance regulator (CFTR), in addition to its Cl(-) channel properties, has regulatory interactions with other epithelial ion channels including the epithelial Na(+) channel (ENaC). Both the open probability and surface expression of wild type CFTR Cl(-) channels are increased significantly when CFTR is co-expressed in Xenopus oocytes with alphabetagamma-ENaC, and conversely, the activity of ENaC is inhibited following wild type CFTR activation. Using the Xenopus oocyte expression system, a lack of functional regulatory interactions between DeltaF508-CFTR and ENaC was observed following activation of DeltaF508-CFTR by forskolin and isobutylmethylxanthine (IBMX). Whole cell currents in oocytes expressing ENaC alone decreased in response to genistein but increased in response to a combination of forskolin and IBMX followed by genistein. In contrast, ENaC currents in oocytes co-expressing ENaC and DeltaF508-CFTR remained stable following stimulation with forskolin/IBMX/genistein. Furthermore, co-expression of DeltaF508-CFTR with ENaC enhanced the forskolin/IBMX/genistein-mediated activation of DeltaF508-CFTR. Our data suggest that genistein restores regulatory interactions between DeltaF508-CFTR and ENaC and that combinations of protein repair agents, such as 4-phenylbutyrate and genistein, may be necessary to restore DeltaF508-CFTR function in vivo.

Highlights

The cystic fibrosis phenotype is a result of mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR)1 [1]
We observed that genistein restores functional interactions between ⌬F508-CFTR and epithelial Na؉ channel (ENaC), suggesting that combinations of pharmacologic agents may prove beneficial for the repair of mutant CFTR function
Expression of ⌬F508-CFTR and ENaC in Xenopus Oocytes— The Xenopus oocyte expression system was used to examine the functional expression of ⌬F508-CFTR and its functional interaction with ENaC

Summary

Introduction

The cystic fibrosis phenotype is a result of mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR)1 [1]. Using the Xenopus oocyte expression system, a lack of functional regulatory interactions between ⌬F508-CFTR and ENaC was observed following activation of ⌬F508-CFTR by forskolin and isobutylmethylxanthine (IBMX). Co-expression of ⌬F508-CFTR with ENaC enhanced the forskolin/IBMX/genistein-mediated activation of ⌬F508-CFTR.

Results

Conclusion