It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods
Among cyclic nucleotide phosphodiesterases (PDEs), PDE6 is unique in serving as an effector enzyme in G protein-coupled signal transduction. In retinal rods and cones, PDE6 is membrane-bound and activated to hydrolyse its substrate, cGMP, by binding of two active G protein α-subunits (Gα*). To inves...
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2018-08-01
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doaj-26903d7c4b264677880df6ed6c4f0dd02020-11-25T02:48:10ZengThe Royal SocietyOpen Biology2046-24412018-08-018810.1098/rsob.180075180075It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rodsBilal M. QureshiElmar BehrmannJohannes SchönebergJustus LoerkeJörg BürgerThorsten MielkeJan GiesebrechtFrank NoéTrevor D. LambKlaus Peter HofmannChristian M. T. SpahnMartin HeckAmong cyclic nucleotide phosphodiesterases (PDEs), PDE6 is unique in serving as an effector enzyme in G protein-coupled signal transduction. In retinal rods and cones, PDE6 is membrane-bound and activated to hydrolyse its substrate, cGMP, by binding of two active G protein α-subunits (Gα*). To investigate the activation mechanism of mammalian rod PDE6, we have collected functional and structural data, and analysed them by reaction–diffusion simulations. Gα* titration of membrane-bound PDE6 reveals a strong functional asymmetry of the enzyme with respect to the affinity of Gα* for its two binding sites on membrane-bound PDE6 and the enzymatic activity of the intermediary 1 : 1 Gα* · PDE6 complex. Employing cGMP and its 8-bromo analogue as substrates, we find that Gα* · PDE6 forms with high affinity but has virtually no cGMP hydrolytic activity. To fully activate PDE6, it takes a second copy of Gα* which binds with lower affinity, forming Gα* · PDE6 · Gα*. Reaction–diffusion simulations show that the functional asymmetry of membrane-bound PDE6 constitutes a coincidence switch and explains the lack of G protein-related noise in visual signal transduction. The high local concentration of Gα* generated by a light-activated rhodopsin molecule efficiently activates PDE6, whereas the low density of spontaneously activated Gα* fails to activate the effector enzyme.https://royalsocietypublishing.org/doi/pdf/10.1098/rsob.180075pde6visual signal transductioncoincidence switchdensity switchnoise filtering |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Bilal M. Qureshi Elmar Behrmann Johannes Schöneberg Justus Loerke Jörg Bürger Thorsten Mielke Jan Giesebrecht Frank Noé Trevor D. Lamb Klaus Peter Hofmann Christian M. T. Spahn Martin Heck |
spellingShingle |
Bilal M. Qureshi Elmar Behrmann Johannes Schöneberg Justus Loerke Jörg Bürger Thorsten Mielke Jan Giesebrecht Frank Noé Trevor D. Lamb Klaus Peter Hofmann Christian M. T. Spahn Martin Heck It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods Open Biology pde6 visual signal transduction coincidence switch density switch noise filtering |
author_facet |
Bilal M. Qureshi Elmar Behrmann Johannes Schöneberg Justus Loerke Jörg Bürger Thorsten Mielke Jan Giesebrecht Frank Noé Trevor D. Lamb Klaus Peter Hofmann Christian M. T. Spahn Martin Heck |
author_sort |
Bilal M. Qureshi |
title |
It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods |
title_short |
It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods |
title_full |
It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods |
title_fullStr |
It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods |
title_full_unstemmed |
It takes two transducins to activate the cGMP-phosphodiesterase 6 in retinal rods |
title_sort |
it takes two transducins to activate the cgmp-phosphodiesterase 6 in retinal rods |
publisher |
The Royal Society |
series |
Open Biology |
issn |
2046-2441 |
publishDate |
2018-08-01 |
description |
Among cyclic nucleotide phosphodiesterases (PDEs), PDE6 is unique in serving as an effector enzyme in G protein-coupled signal transduction. In retinal rods and cones, PDE6 is membrane-bound and activated to hydrolyse its substrate, cGMP, by binding of two active G protein α-subunits (Gα*). To investigate the activation mechanism of mammalian rod PDE6, we have collected functional and structural data, and analysed them by reaction–diffusion simulations. Gα* titration of membrane-bound PDE6 reveals a strong functional asymmetry of the enzyme with respect to the affinity of Gα* for its two binding sites on membrane-bound PDE6 and the enzymatic activity of the intermediary 1 : 1 Gα* · PDE6 complex. Employing cGMP and its 8-bromo analogue as substrates, we find that Gα* · PDE6 forms with high affinity but has virtually no cGMP hydrolytic activity. To fully activate PDE6, it takes a second copy of Gα* which binds with lower affinity, forming Gα* · PDE6 · Gα*. Reaction–diffusion simulations show that the functional asymmetry of membrane-bound PDE6 constitutes a coincidence switch and explains the lack of G protein-related noise in visual signal transduction. The high local concentration of Gα* generated by a light-activated rhodopsin molecule efficiently activates PDE6, whereas the low density of spontaneously activated Gα* fails to activate the effector enzyme. |
topic |
pde6 visual signal transduction coincidence switch density switch noise filtering |
url |
https://royalsocietypublishing.org/doi/pdf/10.1098/rsob.180075 |
work_keys_str_mv |
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