Cone photoreceptors tonically release glutamate in the dark. Light hyperpolarizes cones and causes a graded reduction in glutamate release. Understanding how cones regulate transmitter release is crucial for understanding how visual information is transmitted to bipolar and horizontal cells. Previous studies have indirectly inferred presynaptic release from cones by measuring postsynaptic responses from these cells. However, many fundamental questions remain because, until now, there has been no direct measure of cone transmitter release. Among the key questions are: 1) What is the spatio-temporal pathway taken by synaptic vesicles as they journey between endocytosis and exocytosis in the cone terminal? 2) What is the quantitative relationship between presynaptic voltage, Ca2+ concentration, and exocytosis? 3) What is the rate of release from cones in the light and dark? 4) How is release modulated by feedback synapses and modulatory transmitters in the outer retina? 5) What is the size and extent of the lateral-inhibition contrast signal on arrays of cone terminals in the retina? Our goal is to answer these questions by directly measuring presynaptic release from cones. We will use the activity-dependent uptake and release of fluorescent lipophilic dyes, including FM1-43, as indicators of endocytosis and exocytosis. Preliminary results show that uptake and release of the dyes into cone terminals are Ca2+ and depolarization-dependent. Electron microscopic studies show localization of """"""""photoconverted"""""""" dye to synaptic vesicles. FM1-43 release occurs rapidly in the dark, is suppressed by light, and is affected by synaptic feedback from HCs. We have monitored FM 1-43 release from individually dissociated cones, groups of cones in retinal slices, and 2-dimensional arrays of cone terminals in intact retinal flat mounts. These preparations allow us to answer subcellular-to systems-level questions about the regulation of cone neurotransmitter release. These results will provide fundamental information about the mechanisms of normal vision and will provide insights about synaptic dysfunction that occur in retinal diseases.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY015514-05
Application #
7385931
Study Section
Biology and Diseases of the Posterior Eye Study Section (BDPE)
Program Officer
Mariani, Andrew P
Project Start
2004-04-01
Project End
2009-11-30
Budget Start
2008-04-01
Budget End
2009-11-30
Support Year
5
Fiscal Year
2008
Total Cost
$357,396
Indirect Cost
Name
University of California Berkeley
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
124726725
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Kassianidou, Elena; Brand, Christoph A; Schwarz, Ulrich S et al. (2017) Geometry and network connectivity govern the mechanics of stress fibers. Proc Natl Acad Sci U S A 114:2622-2627
Kassianidou, Elena; Hughes, Jasmine H; Kumar, Sanjay (2017) Activation of ROCK and MLCK tunes regional stress fiber formation and mechanics via preferential myosin light chain phosphorylation. Mol Biol Cell 28:3832-3843
Dursch, T J; Liu, D E; Oh, Y et al. (2015) Fluorescent solute-partitioning characterization of layered soft contact lenses. Acta Biomater 15:48-54
Liu, D E; Dursch, T J; Oh, Y et al. (2015) Equilibrium water and solute uptake in silicone hydrogels. Acta Biomater 18:112-7
Wang, Tzu-Ming; Holzhausen, Lars C; Kramer, Richard H (2014) Imaging an optogenetic pH sensor reveals that protons mediate lateral inhibition in the retina. Nat Neurosci 17:262-8
Polosukhina, Aleksandra; Litt, Jeffrey; Tochitsky, Ivan et al. (2012) Photochemical restoration of visual responses in blind mice. Neuron 75:271-82
Tian, Miao; Xu, C Shan; Montpetit, Rachel et al. (2012) Rab3A mediates vesicle delivery at photoreceptor ribbon synapses. J Neurosci 32:6931-6
Jackman, Skyler L; Babai, Norbert; Chambers, James J et al. (2011) A positive feedback synapse from retinal horizontal cells to cone photoreceptors. PLoS Biol 9:e1001057
Bartoletti, Theodore M; Jackman, Skyler L; Babai, Norbert et al. (2011) Release from the cone ribbon synapse under bright light conditions can be controlled by the opening of only a few Ca(2+) channels. J Neurophysiol 106:2922-35
Kramer, Richard H; Fortin, Doris L; Trauner, Dirk (2009) New photochemical tools for controlling neuronal activity. Curr Opin Neurobiol 19:544-52

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