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
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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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    ABSTRACT: NHERF1 (Na+/H+ exchanger regulatory factor) is a scaffolding protein, consists of two tandem PDZ domains linked to a carboxyl-terminal ezrin- binding region. NHERF1 recruits macromolecular complexes at the apical membrane of epithelial cells in many epithelial tissues. It is involved in trafficking and regulation of transmembrane ion transporters and G protein-coupled receptors. Further, NHERF1 also linked other molecules involved in cell growth and cancer progression, such as PDGFR, PTEN, beta-catenin, EGFR and HER2/neu. In this review, we focus on the role of NHERF1 during cancer development. Evidences of its involvement in cancer development are present in hepatocellular carcinoma, schwannoma, glioblastoma, colorectal cancer and particularly in breast cancer. Recent findings obtained from our laboratory show that cytoplasmic NHERF1 expression increases gradually in breast cancer during carcinogenesis, and its overexpression is associated with aggressive clinical parameters, unfavourable prognosis, and increased tumor hypoxia. Interestingly, also nuclear NHERF1 expression seems to play a role both in carcinogenesis and progression of colorectal cancer. These data suggest that NHERF1 could be a new biomarker of advanced malignancies.
    Cancer biomarkers: section A of Disease markers 06/2014; 14(2):177-184. DOI:10.3233/CBM-130329 · 1.72 Impact Factor
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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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    ABSTRACT: Na+/H+ exchanger regulatory factor 1 (NHERF1) is a scaffold protein known to interact with a number of cancer-related proteins. nherf1 mutations (K172N and D301V) were recently identified in breast cancer cells. To investigate the functional properties of NHERF1, wild-type and cancer-derived nherf1 mutations were stably expressed in SKMES-1 cells respectively. NHERF1-wt overexpression suppressed the cellular malignant phenotypes, including proliferation, migration, and invasion. nherf1 mutations (K172N and D301V) caused complete or partial loss of NHERF1 functions by affecting the PTEN/NHERF1/PDGFRβ complex formation, inactivating NHERF1 inhibition of PDGF-induced AKT and ERK activation, and attenuating the tumor-suppressor effects of NHERF1-wt. These results further demonstrated the functional consequences of breast cancer-derived nherf1 mutations (K172N and D301V), and suggested the causal role of NHERF1 in tumor development and progression.
    FEBS letters 09/2013; 587(20). DOI:10.1016/j.febslet.2013.08.026 · 3.17 Impact Factor
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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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