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Activation of rhodopsin gene transcription in cultured retinal precursors of chicken embryo: role of Ca 2+ signaling and hyperpolarization‐activated cation channels
Author(s) -
Bernard Marianne,
Dejos Camille,
Bergès Thierry,
Régnacq Matthieu,
Voisin Pierre
Publication year - 2014
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/jnc.12624
Subject(s) - rhodopsin , biology , calmodulin , microbiology and biotechnology , protein kinase a , transcription factor , reporter gene , phosphorylation , chemistry , retinal , gene expression , biochemistry , gene , enzyme
This study reports that the spontaneous 50‐fold activation of rhodopsin gene transcription, observed in cultured retinal precursors from 13‐day chicken embryo, relies on a Ca 2+ ‐dependent mechanism. Activation of a transiently transfected rhodopsin promoter (luciferase reporter) in these cells was inhibited (60%) by cotransfection of a dominant‐negative form of the cAMP ‐responsive element‐binding protein. Both rhodopsin promoter activity and rhodopsin mRNA accumulation were blocked by Ca 2+ /calmodulin‐dependent kinase II inhibitors, but not by protein kinase A inhibitors, suggesting a role of Ca 2+ rather than cAMP . This was confirmed by the inhibitory effect of general and T‐type selective Ca 2+ channel blockers. Oscillations in Ca 2+ fluorescence (Fluo8) could be observed in 1/10 cells that activated the rhodopsin promoter (DsRed reporter). A robust and reversible inhibition of rhodopsin gene transcription by ZD7288 indicated a role of hyperpolarization‐activated channels (HCN). Cellular localization and developmental expression of HCN1 were compatible with a role in the onset of rhodopsin gene transcription. Together, the data suggest that the spontaneous activation of rhodopsin gene transcription in cultured retinal precursors results from a signaling cascade that involves the pacemaker activity of HCN channels, the opening of voltage‐gated Ca 2+ ‐channels, activation of Ca 2+ /calmodulin‐dependent kinase II and phosphorylation of cAMP ‐responsive element‐binding protein.Rhodopsin gene expression in cultured retinal precursors from chicken embryo relies on a Ca2+‐dependent mechanism whereby hyperpolarization‐activated cyclic nucleotide‐gated channels (HCN) activate T‐type voltage‐dependent Ca2+ channels (VDCC) through membrane depolarization, causing calmodulin‐dependent kinase II (CaMKII) to phosphorylate the cAMP‐responsive element‐binding protein (CREB) and leading to activation of rhodopsin gene transcription. Photoreceptor localization and development of HCN1 channels suggest similar role in vivo .