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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 …