Abstract
G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptor (GPCR)-mediated increases in the second messenger cyclic adenosine monophosphate (cAMP) activate the mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK), and in neuroendocrine cells, this pathway leads to cAMP-dependent neuritogenesis mediated through Rap1 and B-Raf. We found that the Rap guanine nucleotide exchange factor Rapgef2 was enriched from primary bovine neuroendocrine cells by cAMP-agarose affinity chromatography and that it was specifically eluted by cAMP. With loss-of-function experiments in the rat neuronal cell line Neuroscreen-1 (NS-1) and gain-of-function experiments in human embryonic kidney 293T cells, we demonstrated that Rapgef2 connected GPCR-dependent activation of adenylate cyclase and increased cAMP concentration with the activation of ERK in neurons and endocrine cells. Furthermore, knockdown of Rapgef2 blocked cAMP- and ERK-dependent neuritogenesis. Our data are consistent with a pathway involving the cAMP-mediated activation of Rapgef2, which then stimulates Rap1, leading to increases in B-Raf, MEK, and ERK activity.
Publication types
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Research Support, N.I.H., Intramural
MeSH terms
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Animals
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Blotting, Western
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Bucladesine / pharmacology
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Cattle
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Cell Line
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Cell Line, Tumor
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Cells, Cultured
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Chromaffin Cells / cytology
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Chromaffin Cells / drug effects
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Chromaffin Cells / metabolism
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Colforsin / pharmacology
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Cyclic AMP / metabolism*
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Cyclic AMP / pharmacology
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Endocrine Cells / cytology
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Endocrine Cells / drug effects
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Endocrine Cells / metabolism*
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Enzyme Activation / drug effects
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Extracellular Signal-Regulated MAP Kinases / metabolism*
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Guanine Nucleotide Exchange Factors / classification
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Guanine Nucleotide Exchange Factors / genetics
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Guanine Nucleotide Exchange Factors / metabolism*
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HEK293 Cells
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Humans
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Nerve Tissue Proteins / classification
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / metabolism*
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Neurons / cytology
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Neurons / drug effects
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Neurons / metabolism*
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PC12 Cells
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Phylogeny
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Pituitary Adenylate Cyclase-Activating Polypeptide / pharmacology
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RNA Interference
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Rats
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Rats, Sprague-Dawley
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Receptors, G-Protein-Coupled / metabolism
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Signal Transduction*
Substances
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Guanine Nucleotide Exchange Factors
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Nerve Tissue Proteins
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Pituitary Adenylate Cyclase-Activating Polypeptide
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RAPGEF2 protein, human
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Receptors, G-Protein-Coupled
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Colforsin
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Bucladesine
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Cyclic AMP
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Extracellular Signal-Regulated MAP Kinases