2 The role of Ca+ as an internal messenger in visual transduction of vertebrate and invertebrate organisms has been explored intensely in the recent past. Since the 2 early 1970s, calcium ions and cyclic GMP (whose levels are controlled by Ca+ in vertebrates) have been recognized as important second messengers. Particularly in 2 the last decade, however, the role of Ca+ in visual transduction has been re-evalu ated and a proliferation of research has documented a multiplicity of roles. 2 It is now evident that Ca+ modulates phototransduction by acting at several 2 sites through a host of small Ca+ -binding proteins. For example, in phototransduction 2 of vertebrates, Ca+-free forms of guanylate cyclase activating proteins (GCAPs) activate guanylate cyclase, modulating levels of cOMP, a key event in the return of photoreceptors to pre-bleach conditions. Defects in genes encoding guanylate cy clase or guanylate cyclase activating proteins lead to severe diseases of the retina (e. g. , Leber congenital amaurosis, rod/cone dystrophy, or cone dystrophy), thus em phasizing the important role of these proteins in phototransduction. Similarly, mu 2 tant genes encoding cation or Ca+ channels (cyclic nucleotide-gated cation chan 2 nels located in the cell membrane and L-type voltage-gated Ca+ channels located at the synapse of photo receptors) lead to retinitis pigmentosa or congenital stationary night blindness. In phototransduction of invertebrate organisms (e. g. , Drosophila 2 and Limulus), the role of Ca+ is similarly central, but distinct, from that of vertebrates.
Inhaltsverzeichnis
1. Calcium and Phototransduction. - 2. The Calcium Gradient Along the Rod Outer Segment. - 3. The Time Course of Light Adaptation in Vertebrate Retinal Rods. - 4. S-Modulin. - 5. Ca2+-Dependent Control of Rhodopsin Phosphorylation: Recoverin and Rhodopsin Kinase. - 6. Recoverin and Rhodopsin Kinase. - 7. Pathological Roles of Recoverin in Cancer-Associated Retinopathy. - 8. Rgs9-1 Phosphorylation and Ca2+. - 9. Phosphorylation by Cyclin-Dependent Protein Kinase 5 of the Regulatory Subunit (p?) of Retinal Cgmp phosphodiesterase (pde6): its Implications in Phototransduction. - 10. Centrins, Anovel Group of Ca2+-Binding Proteins in Vertebrate Photoreceptor Cells. - 11. Tuning Outer Segment Ca2+Homeostasis to Phototransduction in Rods and Cones. - 12. Regulation of the Rod Photoreceptor Cyclic Nucleotide-Gated Channel. - 13. Ca2+-Channels in the Rpe. - 14. THE RETINAL ROD AND CONE Na+/Ca2+-K+EXCHANGERS. - 15. THE COMPLEX OF cGMP-GATED CHANNELAND Na+/Ca2+-K+EXCHANGER IN ROD PHOTORECEPTORS. - 16. Regulation of Voltage-8Ensitive Ca2+Channels in Bipolar Cells by Divalent Cations and Polyamines. - 17. Site-Directed and Natural Mutations in Studying Functional Domains in Guanylyl Cyclase Activating Proteins (Gcaps). - 18. Calmodulin and Ca2+-Binding Proteins (Cabps): Variations on Atheme. - 19. GCAPs: Ca2+-SENSITIVE REGULATORS OF retGC. - 20. Structure and Membrane-Targeting Mechanism of Retinal Ca2+-Binding Proteins, Recoverin and Gcap-2. - 21. Target Recognition of Guanylate Cyclase by Guanylate Cyclase-Activating Proteins. - 22. Mouse Models to Study Gcap Functions in Intact Photoreceptors. - 23. Calcium-Dependent Activation of Guanylate Cyclase by S100b. - 24. The Role of Cadherins in Ca2+-Mediated Cell Adhesion and Inherited Photoreceptor Degeneration. - 25. Guanylate Cyclase Activating Proteins, Guanylate Cyclase and Disease. - 26. Using Mutant Mice to Study the Role of Voltage-Gated Calcium Channels in the Retina. - 27. Caldendrins in the Inner Retina. - 28. Calcium Channels at the Photoreceptor Synapse. - 29. On Bipolar Cells: Following in the Footsteps of Phototransduction. - 30. Ca2+Regulation of Drosophila Phototransduction. - 31. Simultaneous Roles for Ca2+in Excitation and Adaptation of Limulus Ventral Photoreceptors. - 32. Calcium Homeostasis in Fly Photoreceptor Cells. - 33. Photoreceptor Degeneration and Ca2+Influx Through Light-Activated Channels of Drosophila. - 34. The Trp Calcium Channeland Retinal Degeneration.
