June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Glutaminase deficiency disrupts metabolic homeostasis of photoreceptors to induce rapid degeneration
Author Affiliations & Notes
  • Moloy Goswami
    Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States
  • Eric Weh
    Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States
  • Shubha Subramanya
    Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States
  • Hima Bindu Durumulta
    Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
  • Nick Miller
    Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States
  • Sraboni Chaudhury
    Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States
  • HEATHER HAGER
    Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States
  • Anthony Andren
    University of Michigan, Ann Arbor, Michigan, United States
  • Costas A Lyssiotis
    University of Michigan Department of Internal Medicine, Ann Arbor, Michigan, United States
  • Cagri Besirli
    Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States
  • Thomas J Wubben
    Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States
  • Footnotes
    Commercial Relationships   Moloy Goswami None; Eric Weh None; Shubha Subramanya None; Hima Durumulta None; Nick Miller None; Sraboni Chaudhury None; HEATHER HAGER None; Anthony Andren None; Costas Lyssiotis None; Cagri Besirli None; Thomas Wubben None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 1780 – F0329. doi:
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      Moloy Goswami, Eric Weh, Shubha Subramanya, Hima Bindu Durumulta, Nick Miller, Sraboni Chaudhury, HEATHER HAGER, Anthony Andren, Costas A Lyssiotis, Cagri Besirli, Thomas J Wubben; Glutaminase deficiency disrupts metabolic homeostasis of photoreceptors to induce rapid degeneration. Invest. Ophthalmol. Vis. Sci. 2022;63(7):1780 – F0329.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Photoreceptors (PRs) have prodigious energy and biosynthetic demands. Most of the glucose delivered to PRs is converted to lactate, instead of pyruvate, via aerobic glycolysis. Due to this limited pyruvate, PRs need to utilize alternative fuels to supply tricarboxylic acid (TCA) cycle metabolites and support energy production and biomass. Glutamine (Gln) contributes to biosynthesis, energetics, and redox balance in other bioenergetically demanding cells. This study assessed the contribution of Gln catabolism to PR metabolism, function, and survival.

Methods : To study the role of Gln catabolism in vivo in PRs, we generated a rod PR-specific glutaminase (Gls) conditional knockout (Glsfl/fl: Rho-Cre; Gls cKO) and a rod PR-specific tamoxifen inducible Gls conditional knockout (Glsfl/fl:Pde6g-CreERT2). Immunohistochemistry (IHC) and western blot analysis addressed the abundance and location of GLS. The function and survival of PRs was examined using OCT, ERG, and histology. Targeted metabolomics assessed the metabolic state in cKO and control retinas. RT-PCR analyzed the expression of genes involved in glutaminolysis, redox balance, and cell death.

Results : Rod PR-specific knockdown of GLS (Gls cKO) was validated with IHC and western blot, and metabolomics confirmed the substrate of GLS, Gln, was increased, and its product, glutamate, reduced. Gls cKO retinal metabolomics at P14 demonstrated decreased pyruvate, lactate, and aspartate. Correspondingly, the expression of genes involved in pyruvate metabolism, Pdha/b and Pcx, were increased while Pdk was decreased. The expression of transaminase Bcat1 and TCA cycle genes were also increased. Oxidative defense genes, Sod1/2, were upregulated as were markers of apoptosis, necroptosis, and ferroptosis. These molecular changes resulted in the Gls cKO mouse demonstrating comparable outer nuclear layer (ONL) thickness to controls at P14 with rapid and complete PR degeneration thereafter. Increased TUNEL staining in the ONL and GFAP staining was noted at P21. In accordance with these anatomic findings, Gls cKO mice showed significant decreases in scotopic amplitudes via ERG. Inducing knockdown of GLS in mature rod PRs with tamoxifen at P45 also resulted in significant degeneration.

Conclusions : This study demonstrates that GLS-mediated Gln catabolism is essential for PR metabolism, function, and survival.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

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