Daily mitochondrial dynamics in cone photoreceptors

Giarmarco, Michelle M.; Brock, Daniel C; Robbings, Brian M.; Cleghorn, Whitney M.; Tsantilas, Kristine; Kuch, Kellie C.; Ge, William; Rutter, Kaitlyn M.; Parker, Edward D

doi:10.1101/2020.04.10.030262

Cited by 7 publications

(9 citation statements)

References 122 publications

(130 reference statements)

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“…Extraction of RNA, cDNA synthesis, and qRT-PCR amplification were conducted as previously described using TATA-box binding protein (tbf) as a reference gene (37,60). Primers are listed in Table I.…”

Section: Qrt-pcr and Identification Of Transcriptsmentioning

confidence: 99%

A highly conserved zebrafish IMPDH retinal isoform produces the majority of guanine and forms dynamic protein filaments in photoreceptor cells

Cleghorn

Burrell

Giarmarco

et al. 2022

Journal of Biological Chemistry

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Inosine monophosphate dehydrogenase (IMPDH) is a key regulatory enzyme in the de novo synthesis of the purine base guanine. Dominant mutations in human IMPDH1 cause photoreceptor degeneration for reasons that are unknown. Here, we sought to provide some foundational information on Impdh1a in the zebrafish retina. We found that in zebrafish, gene subfunctionalization due to ancestral duplication resulted in a predominant retinal variant expressed exclusively in rod and cone photoreceptors. This variant is structurally and functionally similar to the human IMPDH1 retinal variant and shares a reduced sensitivity to GTP-mediated inhibition. We also demonstrated that Impdh1a forms prominent protein filaments in vitro and in vivo in both rod and cone photoreceptor cell bodies, synapses, and to a lesser degree, in outer segments. These filaments changed length and cellular distribution throughout the day consistent with diurnal changes in both mRNA and protein levels. The loss of Impdh1a resulted in a substantial reduction of guanine levels, although cellular morphology and cGMP levels remained normal. Our findings demonstrate a significant role for IMPDH1 in photoreceptor guanine production and provide fundamental new information on the details of this protein in the zebrafish retina.

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Section: Qrt-pcr and Identification Of Transcriptsmentioning

confidence: 99%

A highly conserved zebrafish IMPDH retinal isoform produces the majority of guanine and forms dynamic protein filaments in photoreceptor cells

Cleghorn

Burrell

Giarmarco

et al. 2022

Journal of Biological Chemistry

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“…The resultant lactate would be used as fuel in the Krebs cycle by RPE and MGCs, generating ATP via OXPHOS. However, this hypothesis is contradicted by the high density of mitochondria in photoreceptor inner segments 34 . Moreover, key enzymes for Krebs cycle (CS, FH, SUCLG1) and OXPHOS (COX, ATP synthase γ) were strongly expressed in photoreceptors, but showed little or no expression in RPE or MGCs, in agreement with previous research 35 .…”

Section: Discussionmentioning

confidence: 99%

Retinal metabolism: Evidence for uncoupling of glycolysis and oxidative phosphorylation via Cori-, Cahill-, and mini-Krebs-cycle

Chen

Zizmare

Calbiague

et al. 2022

Preprint

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The retina consumes massive amounts of energy, yet its metabolism remains poorly understood. Here, we manipulated retinal energy metabolism under entirely controlled conditions and utilised 1H-NMR metabolomics, in situ enzyme detection, and cell viability readouts to uncover the pathways of retinal energy production. Our experiments resulted in varying degrees of photoreceptor degeneration, while the inner retina and retinal pigment epithelium were essentially unaffected. Notably, rod photoreceptors relied strongly on oxidative phosphorylation, but only mildly on glycolysis. Conversely, cone photoreceptors were highly dependent on glycolysis but insensitive to electron transport chain decoupling. Moreover, photoreceptors uncouple glycolytic and Krebs-cycle metabolism via three different pathways: 1) the mini-Krebs cycle, fuelled by glutamine and branched chain amino acids, generating N-acetylaspartate; 2) the alanine-generating Cahill cycle; 3) the lactate-releasing Cori cycle. These findings forward the understanding of retinal physiology and pathology, and shed new light on neuronal energy homeostasis and the pathogenesis of neurodegenerative diseases.

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“…50 In the retina, the high level of ROS production by photoreceptors occurs during the day when the photoreceptors are actively involved in the phototransduction of light signals. 51,52 Previous studies suggested that circadian dysfunction increases intracellular ROS level [26][27][28][29][30] and that the accumulation of ROS and dysfunction of ROS homeostasis in retinal cells leads to many types of retinal diseases. 20 Antioxidants are endogenous products that scavenge excessive ROS.…”

Section: Discussionmentioning

confidence: 99%

The circadian clock mediates the response to oxidative stress in a cone photoreceptor‒like (661W) cell line via regulation of glutathione peroxidase activity

Baba

Suen²,

Goyal³

et al. 2022

F1000Res

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Background: The mammalian retina contains an autonomous circadian clock that controls many physiological functions within this tissue. Our previous studies have indicated that disruption of this circadian clock by removing Bmal1 from the retina affects the visual function, retinal circuitry, and cone photoreceptor viability during aging. In the present study, we employed a mouse-derived cone photoreceptor‒like cell, 661W, to investigate which molecular mechanisms of the circadian clock may modulate cone photoreceptor viability during aging. Methods: Bmal1 knockout (BKO) cells were generated from 661W cells using the CRISPR/Cas9 gene editing tool. Deletion of Bmal1 from 661W was verified by western blot and monitoring Per2-luc bioluminescence circadian rhythms. To investigate the effect of Bmal1 removal on an oxidative stress challenge, cells were treated with hydrogen peroxide (H2O2,1 mM) for two hours and then cell viability was assessed. Cells were also cultured and harvested for gene expression analysis and antioxidant assay. Results: Our data indicated that 661W cells contain a functional circadian clock that mediates the response to an oxidative stress challenge in vitro and that such a response is no longer present in the BKO cell. We also hypothesized that the effect was due to the circadian regulation of the intracellular antioxidant defense mechanism. Our results indicated that in 661W cells, the antioxidant defense mechanism is under circadian control, whereas in BKO cells, there is an overall reduction in this antioxidant defense mechanism, and it is no longer under circadian control. Conclusions: Our work supported the notion that the presence of a functional circadian clock and its ability to modulate the response to an oxidative stress is the underlying mechanism that may protect cones during aging.

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Daily mitochondrial dynamics in cone photoreceptors

Cited by 7 publications

References 122 publications

A highly conserved zebrafish IMPDH retinal isoform produces the majority of guanine and forms dynamic protein filaments in photoreceptor cells

A highly conserved zebrafish IMPDH retinal isoform produces the majority of guanine and forms dynamic protein filaments in photoreceptor cells

Retinal metabolism: Evidence for uncoupling of glycolysis and oxidative phosphorylation via Cori-, Cahill-, and mini-Krebs-cycle

The circadian clock mediates the response to oxidative stress in a cone photoreceptor‒like (661W) cell line via regulation of glutathione peroxidase activity

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