Downregulation of cGMP phosphodiesterase induced by expression of GTPase-deficient cone transducin in mouse rod photoreceptors.
| Autor: | Raport CJ; Department of Biochemistry and Howard Hughes Medical Institute, Seattle, Washington 98195., Lem J, Makino C, Chen CK, Fitch CL, Hobson A, Baylor D, Simon MI, Hurley JB |
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| Jazyk: | angličtina |
| Zdroj: | Investigative ophthalmology & visual science [Invest Ophthalmol Vis Sci] 1994 Jun; Vol. 35 (7), pp. 2932-47. |
| Abstrakt: | Purpose: Photoexcitation of vertebrate retinal rod photoreceptors stimulates GTP binding to the transducin alpha subunit. Like other GTP-binding proteins, transducin restores itself to an inactive form by hydrolyzing its bound GTP. The role of GTP hydrolysis in phototransduction was investigated. Methods: A mutant form of cone transducin alpha deficient in its ability to hydrolyze bound GTP was expressed in mouse rod photoreceptors. Results: Expression of the mutant cone transducin alpha at levels threefold to sixfold higher than endogenous rod transducin alpha led to a specific depletion of the transducin target, cGMP phosphodiesterase, and a decrease in the cGMP level. Suction electrode recordings revealed abnormally prolonged flash responses, decreased maximal response amplitudes, and a shift in the stimulus-response relation to higher flash strengths. Conclusions: Rods expressing high levels of GTPase-deficient cone transduction alpha have reduced levels of phosphodiesterase catalytic subunits and cGMP. These changes are associated with prolonged flash responses, reduced dark current, and decreased sensitivity to light. |
| Databáze: | MEDLINE |
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