Dataset Information

Molecular architecture of photoreceptor phosphodiesterase (PDE6) with activated G protein elucidates the mechanism of visual excitation

ABSTRACT: Photoreceptor phosphodiesterase 6 (PDE6) is the central effector of the visual excitation pathway in both rod and cone photoreceptors, and PDE6 mutations that alter PDE6 structure or regulation can result in several human retinal diseases. The rod PDE6 holoenzyme consists of two catalytic subunits (Pαβ) whose activity is suppressed in the dark by binding of two inhibitory γ-subunits (Pγ). Upon photoactivation of rhodopsin, the heterotrimeric G protein (transducin)is activated, resulting in binding of the activated transducin α-subunit (Gtα) toPDE6, displacement of Pγ from the PDE6 active site, and enzyme activation. Although the biochemistry of this pathway is understood, a lack of detailed structural information about the PDE6 activation mechanism hampers efforts to develop therapeutic interventions for managing PDE6-associated retinal disease. To address this gap, here we used a cross-linking MS-based approach to create a model of the entire interaction surface of Pγ with the regulatory and catalytic domains of Pαβin its nonactivated state. Following reconstitution of PDE6 and activated Gtαwith liposomes and identification of cross-links between Gtα and PDE6 subunits, we determined that the PDE6-Gtα protein complex consists of two Gtα binding sites per holoenzyme. Each Gtα interacts with the catalytic domains of both catalytic subunits and induces major changes in the interaction sites of interaction of the Pγ subunit with the catalytic subunits. These results provide the first structural model for the activated state of the transducin-PDE6-Tα*complex during visual excitation, thereby enhancing our understanding of the molecular etiology of inherited retinal diseases.

INSTRUMENT(S): LTQ Orbitrap

ORGANISM(S): Bos Taurus (bovine)

TISSUE(S): Retinal Rod

SUBMITTER: Rick Cote

LAB HEAD: Rick H. Cote

PROVIDER: PXD015989 | Pride | 2019-11-11

REPOSITORIES: Pride

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The molecular architecture of photoreceptor phosphodiesterase 6 (PDE6) with activated G protein elucidates the mechanism of visual excitation.

Irwin Michael J MJ Gupta Richa R Gao Xiong-Zhuo XZ Cahill Karyn B KB Chu Feixia F Cote Rick H RH

The Journal of biological chemistry 20191105 51

Photoreceptor phosphodiesterase 6 (PDE6) is the central effector of the visual excitation pathway in both rod and cone photoreceptors, and <i>PDE6</i> mutations that alter PDE6 structure or regulation can result in several human retinal diseases. The rod PDE6 holoenzyme consists of two catalytic subunits (Pαβ) whose activity is suppressed in the dark by binding of two inhibitory γ-subunits (Pγ). Upon photoactivation of rhodopsin, the heterotrimeric G protein (transducin) is activated, resulting ...[more]

PMID: 31690623

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Project description:This a model from the article: Network-level analysis of light adaptation in rod cells under normal and altered conditions. Dell'Orco D, Schmidt H, Mariani S, Fanelli F Mol Biosyst2009 Oct; 5(10):1232-46 19756313, Abstract: Photoreceptor cells finely adjust their sensitivity and electrical response according to changes in light stimuli as a direct consequence of the feedback and regulation mechanisms in the phototransduction cascade. In this study, we employed a systems biology approach to develop a dynamic model of vertebrate rod phototransduction that accounts for the details of the underlying biochemistry. Following a bottom-up strategy, we first reproduced the results of a robust model developed by Hamer et al. (Vis. Neurosci., 2005, 22(4), 417), and then added a number of additional cascade reactions including: (a) explicit reactions to simulate the interaction between the activated effector and the regulator of G-protein signalling (RGS); (b) a reaction for the reformation of the G-protein from separate subunits; (c) a reaction for rhodopsin (R) reconstitution from the association of the opsin apoprotein with the 11-cis-retinal chromophore; (d) reactions for the slow activation of the cascade by opsin. The extended network structure successfully reproduced a number of experimental conditions that were inaccessible to prior models. With a single set of parameters the model was able to predict qualitative and quantitative features of rod photoresponses to light stimuli ranging over five orders of magnitude, in normal and altered conditions, including genetic manipulations of the cascade components. In particular, the model reproduced the salient dynamic features of the rod from Rpe65(-/-) animals, a well established model for Leber congenital amaurosis and vitamin A deficiency. The results of this study suggest that a systems-level approach can help to unravel the adaptation mechanisms in normal and in disease-associated conditions on a molecular basis. Note: Figure 7 of the reference is reproduced here. Each plot is obtained by increasing flash strength. More details about generating the plots can be obtained from the comments in the curation figure (go to curation tab). This model originates from BioModels Database: A Database of Annotated Published Models (http://www.ebi.ac.uk/biomodels/). It is copyright (c) 2005-2011 The BioModels.net Team. For more information see the terms of use. To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.

Dataset Information

Molecular architecture of photoreceptor phosphodiesterase (PDE6) with activated G protein elucidates the mechanism of visual excitation

Publications

The molecular architecture of photoreceptor phosphodiesterase 6 (PDE6) with activated G protein elucidates the mechanism of visual excitation.

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