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.
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.
Authors: P D Calvert; N V Krasnoperova; A L Lyubarsky; T Isayama; M Nicoló; B Kosaras; G Wong; K S Gannon; R F Margolskee; R L Sidman; E N Pugh; C L Makino; J Lem Journal: Proc Natl Acad Sci U S A Date: 2000-12-05 Impact factor: 11.205
Authors: P A Sieving; M L Fowler; R A Bush; S Machida; P D Calvert; D G Green; C L Makino; C L McHenry Journal: J Neurosci Date: 2001-08-01 Impact factor: 6.167
Authors: Stephen H Tsang; Michael L Woodruff; Chyuan-Sheng Lin; Barry D Jacobson; Matthew C Naumann; Chun Wei Hsu; Richard J Davis; Marianne C Cilluffo; Jeannie Chen; Gordon L Fain Journal: Cell Signal Date: 2011-09-08 Impact factor: 4.315
Authors: Elena V Olshevskaya; Peter D Calvert; Michael L Woodruff; Igor V Peshenko; Andrey B Savchenko; Clint L Makino; Ye-Shih Ho; Gordon L Fain; Alexander M Dizhoor Journal: J Neurosci Date: 2004-07-07 Impact factor: 6.167