# Mechanisms and consequences of impaired glutathione homeostasis in the aging Lens.

> **NIH NIH R01** · AUGUSTA UNIVERSITY · 2020 · $384,063

## Abstract

The age-related decline of lens glutathione is strongly correlated with cataract formation in the human
and in experimental mouse models of glutathione depletion, as recently confirmed in our own studies. The age-
related impairment of lens glutathione biosynthesis enzyme activity has been documented, though the
mechanisms underlying this age-related change are poorly understood. In preliminary studies we made the
paradigm shifting observation that the lens glutathione biosynthesis key enzyme, gamma glutamylcysteine
ligase, catalytic subunit (Gclc) is subject to posttranslational truncation, and that this truncated proteoform
accumulates with age, particularly in the lens cortical and core fiber region. Further studies revealed that the
truncation is linked to the presence of a caspase-3 and 6 like cleavage motif triggering a C-terminal 13kD
truncation and accumulation of a N-terminal 60kD stable proteoform (herein named Gclc60). The latter appears
to engage in strong interaction with cell cytoskeleton proteins and profound cytoplasmic distribution
discrepancies compared to the full length Gclc protein. We hypothesize that truncation of Gclc is a key event in
the pathogenesis of age-related cataract, and that understanding the mechanism of formation of Gclc60 and the
molecular biological consequences of its accumulation are important goals for the design of novel anti-cataract
therapy. Accordingly, the three Specific Aims of this application are Aim 1: to determine the mechanism of Gclc
truncation and its impact on lens GSH homeostasis. In particular, we will test the hypothesis that Gclc60 will
suppresses GSH synthesis resulting in lowered GSH content and will identify the proteases that are
responsible for age-related cleavage. In Aim 2, we will determine the in vivo effects on GCLC truncation and
Gclc60 accumulation by testing a cleavage resistant knockin (KI) mouse model. In particular we hypothesize
that KI mouse lens will significantly retain its GSH levels and biological functions during aging. In Aim3, we will
determine the biological effects resulting from Gclc60 interaction with cytoskeletal proteins, hypothesizing that
Gclc accumulation results in cytoskeletal matrix disorganization.
! 1!

## Key facts

- **NIH application ID:** 9910409
- **Project number:** 5R01EY028158-03
- **Recipient organization:** AUGUSTA UNIVERSITY
- **Principal Investigator:** Xingjun Fan
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $384,063
- **Award type:** 5
- **Project period:** 2018-11-10 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9910409

## Citation

> US National Institutes of Health, RePORTER application 9910409, Mechanisms and consequences of impaired glutathione homeostasis in the aging Lens. (5R01EY028158-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9910409. Licensed CC0.

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