All-trans-retinal shuts down rod cyclic nucleotide-gated ion channels: A novel role for photoreceptor retinoids in the response to bright light?
AUTOR(ES)
Dean, Dylan M.
FONTE
The National Academy of Sciences
RESUMO
In retinal rods, light-induced isomerization of 11-cis-retinal to all-trans-retinal within rhodopsin triggers an enzyme cascade that lowers the concentration of cGMP. Consequently, cyclic nucleotide-gated (CNG) ion channels close, generating the first electrical response to light. After isomerization, all-trans-retinal dissociates from rhodopsin. We now show that all-trans-retinal directly and markedly inhibits cloned rod CNG channels in excised patches. 11-cis-retinal and all-trans-retinol also inhibited the channels, but at somewhat higher concentrations. Single-channel analysis suggests that all-trans-retinal reduces average open probability of rod CNG channels by inactivating channels for seconds at a time. At physiological cGMP levels, all-trans-retinal inhibited in the nanomolar range. Our results suggest that all-trans-retinal may be a potent regulator of the channel in rods during the response to bright light, when there is a large surge in the concentration of all-trans-retinal.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=123074Documentos Relacionados
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