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α 2 ‐Adrenergic receptors activate cyclic AMP‐response element‐binding protein through arachidonic acid metabolism and protein kinase A in a subtype‐specific manner
Author(s) -
Karkoulias Georgios,
Mastrogianni Orthodoxia,
Papathanasopoulos Panagiotis,
Paris Hervé,
Flordellis Christodoulos
Publication year - 2007
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2007.04852.x
Subject(s) - creb , protein kinase a , cyclic amp response element binding protein , biology , mitogen activated protein kinase kinase , protein kinase c , forskolin , kinase , chemistry , endocrinology , medicine , microbiology and biotechnology , biochemistry , transcription factor , stimulation , gene
On incubation with epinephrine, PC12 cells stably expressing α 2 ‐adrenergic receptor (α 2 ‐AR) undergo morphological and biochemical changes characteristic of neuron‐like differentiation. The present study shows that α 2 ‐AR stimulation increases the phosphorylation of the transcription factor cAMP‐response element‐binding protein (CREB), the activity of a CRE‐reporter plasmid and the expression of cyclin D1 with subtype‐dependent efficiency (α 2A ≈ α 2C >> α 2B ). The effects of epinephrine were mimicked by cell exposure to forskolin or to exogenous arachidonic acid (AA) and they were abrogated by prior treatment with the inhibitor of phospholipase C (PLC) (U73122) or the inhibitor of cytochrome P450‐dependent epoxygenase, ketoconazole. On the other hand, treatment of the cells with epinephrine caused activation of protein kinase A (PKA), which was fully abolished by ketoconazole. Inhibition of PKA activity with H89 or ketoconazole abolished the effects of epinephrine on CREB, suggesting that activation of the cAMP/PKA pathway by AA epoxy‐derivatives is responsible for CREB activation by α 2 ‐ARs. The effects of epinephrine were unaffected by LY294002. Furthermore, treatment with staurosporine, tyrphostin AG1478, PP1 or PD98059 did not change the extent of CREB phosphorylation but enhanced its transcriptional activity. Altogether, our results demonstrate that, in PC12 cells, the α 2 ‐AR subtypes cause phosphorylation and activation of CREB through a pathway involving stimulation of PLC, AA release, generation of epoxygenase derivative and increase of PKA activity. They also suggest attenuation of CREB transcriptional activity by mitogen‐activated protein kinase, protein kinase C and Src kinases.