Circadian and cAMP-dependent modulation of retinal cone cGMP-gated channels does not require protein synthesis or calcium influx through L-type channels.
Circadian oscillators of chicken retinal cone photoreceptors modulate the gating properties of cGMP-gated channels (CNGCs) such that they have a higher apparent affinity for cGMP during the subjective night. This effect is driven in part by cAMP, which acts through Erk MAP kinase to initiate a cascade leading to modulation of CGNCs. Here, we show that cAMP effects on the gating properties CNGCs persist when protein synthesis is blocked. The effects is cAMP also persist when calcium influx through L-type channels is blocked by nitrendipine. The mechanisms whereby cAMP modulates CNGCs therefore differ from those previously reported to underline regulation of melatonin synthesis and secretion.
Ko
Gladys Y-P
GY
Department of Biology and Biochemistry and Biological Clocks Program, University of Houston, Houston, TX 77204-5001, USA.
Ko
Michael
M
Dryer
Stuart E
SE
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002642:Chick Embryo; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism; D054815:Cyclic Nucleotide-Gated Cation Channels; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D055537:Light Signal Transduction / Q000502:physiology*; D009568:Nitrendipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D054815:Cyclic Nucleotide-Gated Cation Channels; D007473:Ion Channels; D005576:Colforsin; D009568:Nitrendipine; D000242:Cyclic AMP; D048049:Extracellular Signal-Regulated MAP Kinases; D006152:Cyclic GMP; D002118:Calcium