Journal article
Reproducibility of the rod photoreceptor response depends critically on concentration of the phosphodiesterase effector enzyme
The Journal of neuroscience, Vol.42(11), pp.2180-2189
01/28/2022
DOI: 10.1523/JNEUROSCI.2119-21.2021
PMCID: PMC8936574
PMID: 35091503
Abstract
The high sensitivity of night vision requires that rod photoreceptors reliably and reproducibly signal the absorption of single photons, a process that depends upon tight regulation of intracellular cGMP concentration through the phototransduction cascade. Here in the mouse (
), we studied a single-site
mutation of the gene for the alpha subunit of rod photoreceptor phosphodiesterase (
), made with the aim of removing a noncatalytic binding site for cGMP. This mutation unexpectedly eliminated nearly all
expression and reduced expression of the beta subunit gene (
) to about 5 - 10% of wild-type (WT). The remaining phosphodiesterase had nearly normal specific activity; degeneration was slow, with 50-60% of rods remaining after 6 months. Responses were larger and more sensitive than normal but slower in rise and decay, probably from slower dark turnover of cGMP. Remarkably, responses became much less reproducible than WT, with response variance increasing for amplitude by over 10-fold, and for latency and time-to-peak by over 100-fold. We hypothesize that the increase in variance is the result of greater variability in the dark-resting concentration of cGMP, produced by spatial and temporal nonuniformity in spontaneous PDE activity. This variability decreased as stimuli were made brighter, presumably because of greater spatial uniformity of phototransduction and the approach to saturation. We conclude that the constancy of the rod response depends critically on PDE expression to maintain adequate spontaneous phosphodiesterase activity, so that the concentration of second messenger is relatively uniform throughout the outer segment.
Rod photoreceptors in the vertebrate retina reliably signal the absorption of single photons of light by generating responses that are remarkably reproducible in amplitude and waveform. We show that this reproducibility depends critically on the concentration of the effector enzyme phosphodiesterase (PDE), which metabolizes the second messenger cGMP and generates rod light responses. In rods with the
mutation of the alpha subunit of PDE, only 5 - 10% of PDE is expressed. Single-photon responses then become much more variable than in wild-type rods. We think this variability is caused by spatial and temporal inhomogeneity in the concentration of cGMP in darkness, so that photons absorbed in different parts of the cell produce responses of greatly varying amplitude and waveform.
Details
- Title: Subtitle
- Reproducibility of the rod photoreceptor response depends critically on concentration of the phosphodiesterase effector enzyme
- Creators
- Ala Morshedian - Stein Eye Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CAGabriela Sendek - Stein Eye Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CASze Yin Ng - Stein Eye Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CAKimberly Boyd - Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IARoxana A Radu - Stein Eye Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CAMingyao Liu - Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, ChinaNikolai O Artemyev - Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IAAlapakkam P Sampath - Stein Eye Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CAGordon L Fain - Department of Integrative Biology and Physiology, University of California Los Angeles, Los Angeles, CA
- Resource Type
- Journal article
- Publication Details
- The Journal of neuroscience, Vol.42(11), pp.2180-2189
- DOI
- 10.1523/JNEUROSCI.2119-21.2021
- PMID
- 35091503
- PMCID
- PMC8936574
- NLM abbreviation
- J Neurosci
- eISSN
- 1529-2401
- Grant note
- DOI: 10.13039/100000053, name: HHS | NIH | National Eye Institute, award: EY001844, EY029817, EY010843, EY025002, EY000311; DOI: 10.13039/100001818, name: Research to Prevent Blindness
- Language
- English
- Date published
- 01/28/2022
- Academic Unit
- Molecular Physiology and Biophysics; Iowa Neuroscience Institute; Ophthalmology and Visual Sciences
- Record Identifier
- 9984211794802771
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