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Full-Text Articles in Medicine and Health Sciences
Ca2+ Sensor Synaptotagmin-1 Mediates Exocytosis In Mammalian Photoreceptors, Justin J. Grassmeyer, Asia L. Cahill, Cassandra L. Hays, Cody Barta, Rolen M. Quadros, Channabasavaiah B. Gurumurthy, Wallace B. Thoreson
Ca2+ Sensor Synaptotagmin-1 Mediates Exocytosis In Mammalian Photoreceptors, Justin J. Grassmeyer, Asia L. Cahill, Cassandra L. Hays, Cody Barta, Rolen M. Quadros, Channabasavaiah B. Gurumurthy, Wallace B. Thoreson
Journal Articles: Pharmacology & Experimental Neuroscience
To encode light-dependent changes in membrane potential, rod and cone photoreceptors utilize synaptic ribbons to sustain continuous exocytosis while making rapid, fine adjustments to release rate. Release kinetics are shaped by vesicle delivery down ribbons and by properties of exocytotic Ca2+ sensors. We tested the role for synaptotagmin-1 (Syt1) in photoreceptor exocytosis by using novel mouse lines in which Syt1 was conditionally removed from rods or cones. Photoreceptors lacking Syt1 exhibited marked reductions in exocytosis as measured by electroretinography and single-cell recordings. Syt1 mediated all evoked release in cones, whereas rods appeared capable of some slow Syt1-independent release. Spontaneous …
Kiss-And-Run Is A Significant Contributor To Synaptic Exocytosis And Endocytosis In Photoreceptors., Xiangyi Wen, Grant W. Saltzgaber, Wallace B. Thoreson
Kiss-And-Run Is A Significant Contributor To Synaptic Exocytosis And Endocytosis In Photoreceptors., Xiangyi Wen, Grant W. Saltzgaber, Wallace B. Thoreson
Journal Articles: Pharmacology & Experimental Neuroscience
Accompanying sustained release in darkness, rod and cone photoreceptors exhibit rapid endocytosis of synaptic vesicles. Membrane capacitance measurements indicated that rapid endocytosis retrieves at least 70% of the exocytotic membrane increase. One mechanism for rapid endocytosis is kiss-and-run fusion where vesicles briefly contact the plasma membrane through a small fusion pore. Release can also occur by full-collapse in which vesicles merge completely with the plasma membrane. We assessed relative contributions of full-collapse and kiss-and-run in salamander photoreceptors using optical techniques to measure endocytosis and exocytosis of large vs. small dye molecules. Incubation with small dyes (SR101, 1 nm; 3-kDa dextran-conjugated …
Intracellular Calcium Stores Drive Slow Non-Ribbon Vesicle Release From Rod Photoreceptors, Minghui Chen, David Križaj, Wallace B. Thoreson
Intracellular Calcium Stores Drive Slow Non-Ribbon Vesicle Release From Rod Photoreceptors, Minghui Chen, David Križaj, Wallace B. Thoreson
Journal Articles: Pharmacology & Experimental Neuroscience
Rods are capable of greater slow release than cones contributing to overall slower release kinetics. Slow release in rods involves Ca(2+)-induced Ca(2+) release (CICR). By impairing release from ribbons, we found that unlike cones where release occurs entirely at ribbon-style active zones, slow release from rods occurs mostly at ectopic, non-ribbon sites. To investigate the role of CICR in ribbon and non-ribbon release from rods, we used total internal reflection fluorescence microscopy as a tool for visualizing terminals of isolated rods loaded with fluorescent Ca(2+) indicator dyes and synaptic vesicles loaded with dextran-conjugated pH-sensitive rhodamine. We found that rather than …