title: Transducin translocation contributes to rod survival and enhances synaptic transmission from rods to rod bipolar cells.
abstract: In rod photoreceptors, several phototransduction components display light-dependent translocation between cellular compartments. Notably, the G protein transducin translocates from rod outer segments to inner segments/spherules in bright light, but the functional consequences of translocation remain unclear. We generated transgenic mice where light-induced transducin translocation is impaired. These mice exhibited slow photoreceptor degeneration, which was prevented if they were dark-reared. Physiological recordings showed that control and transgenic rods and rod bipolar cells displayed similar sensitivity in darkness. After bright light exposure, control rods were more strongly desensitized than transgenic rods. However, in rod bipolar cells, this effect was reversed; transgenic rod bipolar cells were more strongly desensitized than control. This sensitivity reversal indicates that transducin translocation in rods enhances signaling to rod bipolar cells. The enhancement could not be explained by modulation of inner segment conductances or the voltage sensitivity of the synaptic Ca(2+) current, suggesting interactions of transducin with the synaptic machinery.
authors.affiliation: Department of Molecular Physiology and Biophysics and Ophthalmology and Visual Sciences, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Anurima
authors.initials: A
authors.lastname: Majumder
authors.forename: Johan
authors.initials: J
authors.lastname: Pahlberg
authors.forename: Kimberly K
authors.initials: KK
authors.lastname: Boyd
authors.forename: Vasily
authors.initials: V
authors.lastname: Kerov
authors.forename: Saravanan
authors.initials: S
authors.lastname: Kolandaivelu
authors.forename: Visvanathan
authors.initials: V
authors.lastname: Ramamurthy
authors.forename: Alapakkam P
authors.initials: AP
authors.lastname: Sampath
authors.forename: Nikolai O
authors.initials: NO
authors.lastname: Artemyev
mesh_terms: D000818:Animals; D003624:Darkness; D008027:Light; D051379:Mice; D008822:Mice, Transgenic; D021381:Protein Transport; D012162:Retinal Degeneration / Q000517:prevention & control; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D015293:Transducin / Q000378:metabolism* / Q000502:physiology
chemical_list: D015293:Transducin
keywords: SNARE complex; adaptation; palmitoylation; presynaptic modulation; retina