For over a decade, phosducin's interaction with the βγ subunits of the G protein, transducin, has been thought to contribute to light adaptation by dynamically controlling the amount of transducin heterotrimer available for activation by photoexcited rhodopsin. In this study we directly tested this hypothesis by characterizing the dark- and light-adapted response properties of phosducin knockout (Pd−/−) rods. Pd−/− rods were notably less sensitive to light than wild-type (WT) rods. The gain of transduction, as measured by the amplification constant using the Lamb-Pugh model of activation, was 32% lower in Pd−/− rods than in WT rods. This reduced amplification correlated with a 36% reduction in the level of transducin βγ-subunit expression, and thus available heterotrimer in Pd−/− rods. However, commonly studied forms of light adaptation were normal in the absence of phosducin. Thus, phosducin does not appear to contribute to adaptation mechanisms of the outer segment by dynamically controlling heterotrimer availability, but rather is necessary for maintaining normal transducin expression and therefore normal flash sensitivity in rods.
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1 September 2007
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August 27 2007
Phosducin Regulates the Expression of Transducin βγ Subunits in Rod Photoreceptors and Does Not Contribute to Phototransduction Adaptation
Claudia M. Krispel,
Claudia M. Krispel
1Center for Neuroscience and Department of Ophthalmology and Vision Science, University of California, Davis, Davis, CA 95618
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Maxim Sokolov,
Maxim Sokolov
2Department of Ophthalmology and Department of Biochemistry, West Virginia University School of Medicine and West Virginia University Eye Institute, Morgantown, WV 26506
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Yen-Ming Chen,
Yen-Ming Chen
1Center for Neuroscience and Department of Ophthalmology and Vision Science, University of California, Davis, Davis, CA 95618
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Hongman Song,
Hongman Song
2Department of Ophthalmology and Department of Biochemistry, West Virginia University School of Medicine and West Virginia University Eye Institute, Morgantown, WV 26506
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Rolf Herrmann,
Rolf Herrmann
3Department of Ophthalmology and Department of Pharmacology, Duke University, Durham, NC 27710
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Vadim Y. Arshavsky,
Vadim Y. Arshavsky
3Department of Ophthalmology and Department of Pharmacology, Duke University, Durham, NC 27710
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Marie E. Burns
Marie E. Burns
1Center for Neuroscience and Department of Ophthalmology and Vision Science, University of California, Davis, Davis, CA 95618
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Claudia M. Krispel
1Center for Neuroscience and Department of Ophthalmology and Vision Science, University of California, Davis, Davis, CA 95618
Maxim Sokolov
2Department of Ophthalmology and Department of Biochemistry, West Virginia University School of Medicine and West Virginia University Eye Institute, Morgantown, WV 26506
Yen-Ming Chen
1Center for Neuroscience and Department of Ophthalmology and Vision Science, University of California, Davis, Davis, CA 95618
Hongman Song
2Department of Ophthalmology and Department of Biochemistry, West Virginia University School of Medicine and West Virginia University Eye Institute, Morgantown, WV 26506
Rolf Herrmann
3Department of Ophthalmology and Department of Pharmacology, Duke University, Durham, NC 27710
Vadim Y. Arshavsky
3Department of Ophthalmology and Department of Pharmacology, Duke University, Durham, NC 27710
Marie E. Burns
1Center for Neuroscience and Department of Ophthalmology and Vision Science, University of California, Davis, Davis, CA 95618
Correspondence to M.E. Burns: [email protected]
Abbreviation used in this paper: WT, wild-type.
Received:
May 07 2007
Accepted:
August 09 2007
Online ISSN: 1540-7748
Print ISSN: 0022-1295
The Rockefeller University Press
2007
J Gen Physiol (2007) 130 (3): 303–312.
Article history
Received:
May 07 2007
Accepted:
August 09 2007
Citation
Claudia M. Krispel, Maxim Sokolov, Yen-Ming Chen, Hongman Song, Rolf Herrmann, Vadim Y. Arshavsky, Marie E. Burns; Phosducin Regulates the Expression of Transducin βγ Subunits in Rod Photoreceptors and Does Not Contribute to Phototransduction Adaptation . J Gen Physiol 1 September 2007; 130 (3): 303–312. doi: https://doi.org/10.1085/jgp.200709812
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