Binding of the retinal rod Na+/Ca2+-K+ exchanger to the cGMP-gated channel indicates local Ca(2+)-signaling in vertebrate photoreceptors.
Ca(2+) ions enter the outer segment of rod or cone photoreceptors exclusively through the cGMP-gated channel and are extruded by the Na(+)/Ca(2+)-K(+) exchanger. Recent evidence indicates that in the plasma membrane, the Na(+)/Ca(2+)-K(+) exchanger is associated with the cGMP-gated channel. In this contribution, the possible physiologic significance of this protein complex is considered. Based on recent experimental evidence, the possibility of a direct functional interaction between the cGMP-gated channel and the Na(+)/Ca(2+)-K(+) exchanger is discussed. Furthermore, a quantitative estimation of the cytoplasmic Ca(2+) diffusion at the cGMP-gated channel indicates that Ca(2+) diffusion is largely confined to the complex of the cGMP-gated channel and the associated Na(+)/Ca(2+)-K(+) exchanger molecules.
Bauer
Paul J
PJ
Institute for Biological Information Processing (IBI-1), Research Center Juelich, D-52425 Juelich, Germany. p.j.baer@fz-juelich.de
D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D006152:Cyclic GMP / Q000502:physiology*; D019281:Dimerization; D015640:Ion Channel Gating; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D012374:Rod Cell Outer Segment / Q000502:physiology / Q000648:ultrastructure; D019831:Sodium-Calcium Exchanger / Q000737:chemistry / Q000378:metabolism*
D019831:Sodium-Calcium Exchanger; C074530:potassium-dependent sodium-calcium exchanger; D006152:Cyclic GMP