Characterization of a protein co-factor that mediates protein kinase A regulation of the renal brush border membrane Na+/H+ exchange

Department of Medicine, University of California, Los Angeles School of Medicine, USA.
Journal of Clinical Investigation (Impact Factor: 13.22). 06/1995; 95(5):2143-9. DOI: 10.1172/JCI117903
Source: PubMed


Activation of cAMP-dependent protein kinase A inhibits the renal proximal tubule brush border membrane Na(+)-H+ exchanger by a process involving participation of a regulatory cofactor (NHE-RF) that is distinct from the transporter itself. Recent studies from this laboratory reported a partial amino acid sequence of this putative cofactor (Weinman, E. J., D. H. Steplock, and S. Shenolikar. 1993. J. Clin. Invest. 92:1781-1786). The present experiments detail the structure of the NHE-RF protein as determined from molecular cloning studies. A codon-biased oligonucleotide probe to a portion of the amino acid sequence of the putative cofactor was used to isolate a 1.9-kb cDNA from a rabbit renal library. The encoded protein is 358 amino acids in length and is rich in proline residues. Search of existing data bases indicates that NHE-RF is a unique protein. Using a reticulocyte lysate, the cDNA translated a product of approximately 44 kD, which was recognized by an affinity-purified polyclonal antibody to NHE-RF. Potential phosphorylation sites for protein kinase A are present. The mRNA for the protein is expressed in kidney, proximal small intestine, and liver. Reverse transcription/PCR studies in the kidney indicate the presence of mRNA for NHE-RF in several distinct nephron segments including the proximal tubule.

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Available from: Shirish Shenolikar, Jun 24, 2014
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    • "mediated inhibition of the Na + /H + exchanger isoform 16 3 (NHERF3) [64]. It is a crucial component for the "
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    • "Na + /H + exchanger regulatory factor 1 (NHERF1, also named as EBP50), was first identified as an essential cofactor for cyclic AMP inhibition of Na + /H + exchange in the rabbit renal brush border membrane [1]. It is known to be a scaffold protein highly expressed in the apical membrane of polarized epithelial cells. "
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    • "EBP50 was first identified in the rabbit renal brush border, and it was named NHE-RF (Na+-H+ exchanger regulatory factor) because of its cofactor action on NHE (Na+-H+ exchanger) type 3 [19]. Up to now, many studies have focused on EBP50, which is widely distributed and is particularly rich in tissues with polarized epithelia with numerous ezrin-radirin-moesin (ERM) family members, such as the liver, kidney, small intestine and placenta [20]. "
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