# Fas Ligand Cleavage regulates ocular homeostasis and glaucoma

> **NIH NIH R01** · SCHEPENS EYE RESEARCH INSTITUTE · 2022 · $619,633

## Abstract

The type II transmembrane protein Fas ligand (Fasl) was first identified as a death receptor ligand that induced
Fas+ target cells to undergo apoptosis. As such, its constitutive expression in the eye has historically been linked
to the phenomenon of immune privilege and its ability to kill activated eye-infiltrating Fas+ effector cells, or eye-infiltrating
Fas+ vascular endothelial cells. However, this notion is confounded by the fact that many non-hematopoietic
cell types in the eye, including retinal ganglion cells (RGCs), constitutively express Fas. In fact,
Fasl-mediated destruction of RGCs is a key factor in glaucoma pathogenesis, either by direct killing of RGCs
and/or by inducing the production of proinflammatory chemokines by Fas+ glial cells (eg. astrocytes), that recruit
proinflammatory cells to the retina and thereby causing neurotoxic inflammation. This apparent conundrum can
be explained if one accepts our hypothesis that constitutive metalloproteinase-mediated cleavage of
membraned-bound Fasl (mFasL), releases a soluble fragment (sFasL) that opposes the neurotoxic activity of
mFasL. This premise is supported by preliminary data showing: (a) mice with a gene-targeted mutation of Fasl
that eliminates this Fasl cleavage site (mFaslmice) develop accelerated glaucoma in spontaneous and
inducible glaucoma models; {b} in healthy eyes, retinal Fasl is constitutively cleaved, but in glaucomatous eyes,
retinal Fasl is membrane-bound; and (c) intravitreal injection of an AAV2-sFasL vector prior to disease onset
can prevent the development of glaucoma, while injection of AAV2-sFasL after disease onset can reverse
functional defects. Together, these data point to Fasl as an important therapeutic target for patients with
glaucoma. However, a number of key questions remain unanswered and will be addressed by the proposed 3
specific aims: (Aim 1) When and how is Fasl cleavage suppressed during the development and progression of
glaucoma and how do ADAM10 and TIMP1 in regulate Fasl cleavage ?; (Aim 2) To what extent does the direct
engagement of Fas, expressed by astrocytes and/or RGCs, contribute to the development of glaucoma?; and
(Aim 3) Can sFasL directly engage Fas to elicit a protective gene expression program? Our research strategy
will involve both accepted and novel experimental tools, including (a) sortase-tagged-Fasl mice (provide by Dr.
Ploegh}, that will greatly facilitate our ability to monitor mFasL vs sFasL protein levels in the eye, {b} Fas-flexed
mice crossed to RGC- and astrocyte/muller-specific ere-deleter lines, that will allow us to identify the importance
of these cells in the development of glaucoma; (c) allophenic (tetraparental) chimeric mice made by fusing Fas+
and Fasn•9 embryos, that will allow us to distinguish direct and indirect effects of Fasl engagement in the context
of glaucoma, and {d} AAV2-sFasL vectors that will allow us to determine if sFasL functions independently of
mFasL. The mechanistic insights gained f...

## Key facts

- **NIH application ID:** 10374484
- **Project number:** 1R01EY032762-01A1
- **Recipient organization:** SCHEPENS EYE RESEARCH INSTITUTE
- **Principal Investigator:** MEREDITH GREGORY-KSANDER
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $619,633
- **Award type:** 1
- **Project period:** 2022-02-01 → 2026-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10374484

## Citation

> US National Institutes of Health, RePORTER application 10374484, Fas Ligand Cleavage regulates ocular homeostasis and glaucoma (1R01EY032762-01A1). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10374484. Licensed CC0.

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