Immuno-imaging with confocal and electron microscopy revealed the localization of retinal guanylate cyclase (RetGC) in human and monkey retinas. Using an antibody against a peptide derived from human RetGC, RetGC was found predominantly in the photoreceptor layer in these retinas, although a small amount of RetGC was detected in various other retinal cells. In particular, the cone outer segments were more densely labeled with the antibody than the rod outer segments. The RetGC in outer segments was localized exclusively in the membrane-rich domains, and appeared to be associated with the marginal region of the disk membrane and/or the plasma membrane. The connecting cilium and its cytoplasmic extension never showed immunoreactivity with the antibody. The localization of RetGC in photoreceptor cells is discussed from the viewpoint of mechanisms for the recovery of photoreceptors to the dark level.
"GUCY2D encodes for the retinal-specific guanylate cyclase 2D protein, which has three domains: transmembrane domain, protein kinase domain and guanylate cyclase domain. Subcellular localization showed that GUCY2D is present in disc membranes of outer photoreceptor segments (Liu et al. 1994) and it has the function to restore the level of cGMP in the retina after its depletion which is induced by a photo-mediated phosphodiesterase reaction (Burns and Baylor 2001). "
"These interactive physical parameters between S100B and ROS-GC1 were brought to the functional level in the synaptic layers of the retina where the co-presence of ROS-GC1, GCAP1 and S100B existed (Liu et al., 1994; Cooper et al., 1995; Duda et al., 2002). Below 200 nM, Ca2+ elicited a dose-dependent decrease in guanylate cyclase activity with an IC50 for Ca2+ of 100 nM. "
[Show abstract][Hide abstract] ABSTRACT: A sequel to these authors' earlier comprehensive reviews which covered the field of mammalian membrane guanylate cyclase (MGC) from its origin to the year 2010, this article contains 13 sections. The first is historical and covers MGC from the year 1963-1987, summarizing its colorful developmental stages from its passionate pursuit to its consolidation. The second deals with the establishment of its biochemical identity. MGC becomes the transducer of a hormonal signal and founder of the peptide hormone receptor family, and creates the notion that hormone signal transduction is its sole physiological function. The third defines its expansion. The discovery of ROS-GC subfamily is made and it links ROS-GC with the physiology of phototransduction. Sections ROS-GC, a Ca(2+)-Modulated Two Component Transduction System to Migration Patterns and Translations of the GCAP Signals Into Production of Cyclic GMP are Different cover its biochemistry and physiology. The noteworthy events are that augmented by GCAPs, ROS-GC proves to be a transducer of the free Ca(2+) signals generated within neurons; ROS-GC becomes a two-component transduction system and establishes itself as a source of cyclic GMP, the second messenger of phototransduction. Section ROS-GC1 Gene Linked Retinal Dystrophies demonstrates how this knowledge begins to be translated into the diagnosis and providing the molecular definition of retinal dystrophies. Section Controlled By Low and High Levels of [Ca(2+)]i, ROS-GC1 is a Bimodal Transduction Switch discusses a striking property of ROS-GC where it becomes a "[Ca(2+)]i bimodal switch" and transcends its signaling role in other neural processes. In this course, discovery of the first CD-GCAP (Ca(2+)-dependent guanylate cyclase activator), the S100B protein, is made. It extends the role of the ROS-GC transduction system beyond the phototransduction to the signaling processes in the synapse region between photoreceptor and cone ON-bipolar cells; in section Ca(2+)-Modulated Neurocalcin δ ROS-GC1 Transduction System Exists in the Inner Plexiform Layer (IPL) of the Retinal Neurons, discovery of another CD-GCAP, NCδ, is made and its linkage with signaling of the inner plexiform layer neurons is established. Section ROS-GC Linkage With Other Than Vision-Linked Neurons discusses linkage of the ROS-GC transduction system with other sensory transduction processes: Pineal gland, Olfaction and Gustation. In the next, section Evolution of a General Ca(2+)-Interlocked ROS-GC Signal Transduction Concept in Sensory and Sensory-Linked Neurons, a theoretical concept is proposed where "Ca(2+)-interlocked ROS-GC signal transduction" machinery becomes a common signaling component of the sensory and sensory-linked neurons. Closure to the review is brought by the conclusion and future directions.
"General consensus has been that ROS-GC1 is expressed exclusively in the sensory as well as in the second order neurons of the retina and in the neurons of the pineal gland and the olfactory bulb (Hayashi and Yamazaki, 1991; Goraczniak et al., 1994; Liu et al., 1994; Yang et al., 1995; Venkataraman et al., 2000; Duda et al., 2001a). However, earlier results of these investigators provided the first indication that ROS-GC1 is also expressed outside the neuronal system, in bovine testes and sperm (Jankowska et al., 2007, 2008). "
[Show abstract][Hide abstract] ABSTRACT: ROS-GC1 belongs to the Ca(2+)-modulated sub-family of membrane guanylate cyclases. It primarily exists and is linked with signaling of the sensory neurons - sight, smell, taste, and pinealocytes. Exceptionally, it is also present and is Ca(2+)-modulated in t he non-neuronal cells, the sperm cells in the testes, where S100B protein serves as its Ca(2+) sensor. The present report demonstrates the identification of an additional Ca(2+) sensor of ROS-GC1 in the testes, neurocalcin δ. Through mouse molecular genetic models, it compares and quantifies the relative input of the S100B and neurocalcin δ in regulating the Ca(2+) signaling of ROS-GC1 transduction machinery, and via immunochemistry it demonstrates the co-presence of neurocalcin δ and ROS-GC1 in the spermatogenic cells of the testes. The suggestion is that in more ways than one the Ca(2+)-modulated ROS-GC1 transduction system is linked with the testicular function. This non-neuronal transduction system may represent an illustration of the ROS-GC1 expanding role in the trans-signaling of the neural and non-neural systems.
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