title: Modulation of A1 adenosine receptor expression by cell aggregation and long-term activation of A2a receptors in cultures of avian retinal cells: involvement of the cyclic AMP/PKA pathway.
abstract: The expression of A1 and A2a adenosine receptors is developmentally regulated in the chick retina, but little is known about the factors important for this regulation. Here, we show that cell aggregation and cAMP analogs promote a dramatic increase in A1 receptor expression. Importantly, a long-term stimulation of A2a receptors also promotes an increase of A1 receptor expression accompanied by a down-regulation of A2a receptors. Chick embryo retina cultures grown in the form of aggregates or dispersed cells accumulate cAMP when stimulated with dopamine or the adenosine agonist 2-chloroadenosine. However, inhibition of dopamine-dependent cAMP accumulation by 2-chloroadenosine was observed in aggregate cultures but not in dispersed cell cultures. Accordingly, A1 receptor binding sites were detected in aggregate cultures, but were low or absent from dispersed cell cultures. Interestingly, an increase of A1 binding sites was detected when dispersed cell cultures were treated for 5 days with permeable cAMP analogs, the adenylyl cyclase activator forskolin or A2a receptor agonists. Although a significant amount of A1 receptor protein was detected in dispersed cell cultures by western blot or immunocytochemistry, the long-term stimulation of A2a receptors also promoted an increase of the A1 receptor protein and mRNA, indicating that A2a receptors and cAMP were regulating transcription and/or translation of A1 receptors. We also found an increase of A1 receptors in locations in or near the membrane after treatment with A2a agonist. The long-term stimulation of retinal explants with A2a agonist also promoted an increase of A1 receptor protein. The results indicate that A2a receptors and the cAMP-dependent protein kinase pathway are involved in the regulation of A1 receptor expression during retinal development.
authors.affiliation: Department of Neurobiology and Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, Brazil.
authors.forename: Mariana R
authors.initials: MR
authors.lastname: Pereira
authors.forename: Vanusa R
authors.initials: VR
authors.lastname: Hang
authors.forename: Eliza
authors.initials: E
authors.lastname: Vardiero
authors.forename: Fernando G
authors.initials: FG
authors.lastname: de Mello
authors.forename: Roberto
authors.initials: R
authors.lastname: Paes-de-Carvalho
mesh_terms: D015762:2-Chloroadenosine / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002449:Cell Aggregation; D002478:Cells, Cultured; D002642:Chick Embryo; D000242:Cyclic AMP / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004298:Dopamine / Q000494:pharmacology / Q000502:physiology; D015870:Gene Expression / Q000502:physiology; D007150:Immunohistochemistry; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D043682:Receptor, Adenosine A1 / Q000096:biosynthesis*; D043705:Receptor, Adenosine A2A / Q000096:biosynthesis*; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014970:Xanthines / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D043682:Receptor, Adenosine A1; D043705:Receptor, Adenosine A2A; D014970:Xanthines; D015762:2-Chloroadenosine; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D004298:Dopamine