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R. Sharma, V. Venkataraman, T. Duda, N. Vardi, K. Koch; ROS-GC1/GCAP1 Signal Transduction Machinery in the Photoreceptor-Bipolar Synaptic Region . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1068.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Rod outer segment membrane guanylate cyclase (ROS-GC) transduction system is composed of two parts, Ca2+ sensor guanylate cyclase activating protein (GCAP), and ROS-GC. The system is pivotal for the Ca2+-sensitive phototransduction machinery. This study was designed to examine if this system is also operational in the photoreceptor-bipolar synaptic region. Methods:A combination of biochemical analyses involving enzyme assays, reconstitution, peptide competition, cross-linking and immunocytochemical analyses has been used. Results:The results show that the GCAP1/ROS-GC1 transduction system exists in the photoreceptor synaptic (presynaptic) terminals. Thus, the presence of this system and its linkage is not unique to the phototransduction machinery. A new topographic model of ROS-GC1 transduction is proposed. In this model, the catalytic module of ROS-GC1 at its opposite ends is independently regulated by GCAP1- and S100ß-modules. GCAP1 senses the Ca2+ impulse and inhibits the catalytic module; S100ß senses the impulse and stimulates the catalytic module. Conclusions: ROS-GC1 acts as a bimodal Ca2+ signal transduction switch in the photoreceptor bipolar synapse.
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