A cGMP-gated cation channel in depolarizing photoreceptors of the lizard parietal eye
| Autor: | E C Solessio, King Wai Yau, J T Finn |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
Patch-Clamp Techniques
genetic structures Light Cations Divalent Cyclic Nucleotide-Gated Cation Channels Biology In Vitro Techniques Ion Channels Membrane Potentials chemistry.chemical_compound Animals Photoreceptor Cells Patch clamp Cyclic GMP Vision Ocular Membrane potential Multidisciplinary Cell Membrane Depolarization Inositol trisphosphate Lizards Anatomy Parietal eye chemistry Darkness Biophysics sense organs Signal transduction Ion Channel Gating Visual phototransduction |
| Zdroj: | Nature. 385(6619) |
| ISSN: | 0028-0836 |
| Popis: | Rods and cones of the two vertebrate lateral eyes hyperpolarize when illuminated, a response generated by a cyclic GMP cascade leading to cGMP hydrolysis and consequently the closure of cGMP-gated, non-selective cation channels that are open in darkness. Lizards and other lower vertebrates also have a parietal (third) eye, which contains ciliary photoreceptors that under dark-adapted conditions depolarize to light instead. Depolarizing light responses are characteristic of most invertebrate rhabdomeric photoreceptors, and are thought to involve a phosphoinositide signalling pathway (see, for example, refs 7-9). Surprisingly, we have found in excised membrane patches a cGMP-gated channel that is selectively present at high density on the outer segment (the presumptive light-sensitive part) of the parietal eye photoreceptor. Like the light-activated channel of the cell, it is non-selective among cations. Inositol trisphosphate (InsP3) had no effect on the same membrane patches. These findings suggest that the photoreceptors of the parietal eye, like rods and cones, use a cGMP cascade and not an InsP3-mediated pathway for phototransduction, but in this case light increases cGMP. A unifying principle of evolutionary significance emerges: that phototransductions in various ciliary photoreceptors, whether hyperpolarizing or depolarizing, uniformly use a cGMP cascade and a cGMP-gated channel to generate the light response, although there are rich variations in the details. |
| Databáze: | OpenAIRE |
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