Document Detail

Phosphorylation of phosducin accelerates rod recovery from transducin translocation.
MedLine Citation:
PMID:  22491418     Owner:  NLM     Status:  MEDLINE    
PURPOSE: In rods saturated by light, the G protein transducin undergoes translocation from the outer segment compartment, which results in the uncoupling of transducin from its innate receptor, rhodopsin. We measured the kinetics of recovery from this adaptive cellular response, while also investigating the role of phosducin, a phosphoprotein binding transducin βγ subunits in its de-phosphorylated state, in regulating this process.
METHODS: Mice were exposed to a moderate rod-saturating light triggering transducin translocation, and then allowed to recover in the dark while free running. The kinetics of the return of the transducin subunits to the outer segments were compared in transgenic mouse models expressing full-length phosducin, and phosducin lacking phosphorylation sites serine 54 and 71, using Western blot analysis of serial tangential sections of the retina.
RESULTS: In mice expressing normal phosducin, transducin α and βγ subunits returned to the outer segments with a half-time (t(1/2)) of ∼24 and 29 minutes, respectively. In the phosducin phosphorylation mutants, the transducin α subunit moved four times slower, with t(1/2) ∼95 minutes, while the movement of transducin βγ was less affected.
CONCLUSIONS: We demonstrate that the recovery of rod photoreceptors from the ambient saturating levels of illumination, in terms of the return of the light-dispersed transducin subunits to the rod outer segments, occurs six times faster than reported previously. Our data also support the notion that the accumulation of transducin α subunit in the outer segment is driven by its re-binding to the transducin βγ dimer, because this process is accelerated significantly by phosducin phosphorylation.
Marycharmain Belcastro; Hongman Song; Satyabrata Sinha; Chunyan Song; Peter H Mathers; Maxim Sokolov
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2012-05-01
Journal Detail:
Title:  Investigative ophthalmology & visual science     Volume:  53     ISSN:  1552-5783     ISO Abbreviation:  Invest. Ophthalmol. Vis. Sci.     Publication Date:  2012 May 
Date Detail:
Created Date:  2012-05-23     Completed Date:  2012-07-26     Revised Date:  2013-06-26    
Medline Journal Info:
Nlm Unique ID:  7703701     Medline TA:  Invest Ophthalmol Vis Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3084-91     Citation Subset:  IM    
Department of Ophthalmology, West Virginia University, Morgantown, West Virginia, USA.
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MeSH Terms
Blotting, Western
Dark Adaptation
Eye Proteins / metabolism*
Fluorescent Antibody Technique, Indirect
GTP-Binding Protein Regulators / metabolism*
GTP-Binding Protein alpha Subunits / metabolism*
Mice, Knockout
Mice, Transgenic
Phosphoproteins / metabolism*
Polymerase Chain Reaction
Protein Subunits / metabolism
Protein Transport / radiation effects
Retinal Rod Photoreceptor Cells / metabolism*,  radiation effects
Rhodopsin / metabolism
Transducin / metabolism*
Grant Support
Reg. No./Substance:
0/Eye Proteins; 0/GTP-Binding Protein Regulators; 0/GTP-Binding Protein alpha Subunits; 0/Gnat1 protein, mouse; 0/Phosphoproteins; 0/Protein Subunits; 0/phosducin; 9009-81-8/Rhodopsin; EC 3.6.1.-/Transducin

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