Na/H exchange regulatory factor 1, a novel AKT-associating protein, regulates extracellular signal-regulated kinase signaling through a B-Raf-mediated pathway.
Na/H exchange regulatory factor 1 (NHERF1) is a scaffolding protein that regulates signaling and trafficking of several G protein-coupled receptors (GPCRs), including the parathyroid hormone receptor (PTH1R). GPCRs activate extracellular signal-regulated kinase (ERK)1/2 through different mechanisms. Here, we characterized NHERF1 regulation of PTH1R-stimulated ERK1/2. Parathyroid hormone (PTH) stimulated ERK1/2 phosphorylation by a protein kinase A (PKA)-dependent, but protein kinase C-, cyclic adenosine 5'-monophosphate-, and Rap1-independent pathway in Chinese hamster ovary cells stably transfected with the PTH1R and engineered to express NHERF1 under the control of tetracycline. NHERF1 blocked PTH-induced ERK1/2 phosphorylation downstream of PKA. This suggested that NHERF1 inhibitory effects on ERK1/2 occur at a postreceptor locus. Forskolin activated ERK1/2, and this effect was blocked by NHERF1. NHERF1 interacted with AKT and inhibited ERK1/2 activation by decreasing the stimulatory effect of 14-3-3 binding to B-Raf, while increasing the inhibitory influence of AKT negative regulation on ERK1/2 activation. This novel regulatory mechanism provides a new model by which cytoplasmic adapter proteins modulate ERK1/2 activation through a receptor-independent mechanism involving B-Raf.
Wang
Bin
B
Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
Yang
Yanmei
Y
Friedman
Peter A
PA
D048948:14-3-3 Proteins / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D010281:Parathyroid Hormone / Q000494:pharmacology; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011817:Rabbits; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D048948:14-3-3 Proteins; D017931:DNA Primers; C473449:PTH1R protein, human; D010281:Parathyroid Hormone; D010750:Phosphoproteins; D044168:Receptor, Parathyroid Hormone, Type 1; D011994:Recombinant Proteins; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D005576:Colforsin; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases