Drug repurposing screen identifies dopamine signaling and COX inhibition as candidate therapeutic pathways for PIGA-CDG
核心洞察
A screen of 1,520 FDA/EMA-approved drugs in a Drosophila PIGA-CDG (搜索) model identified 90 suppressors, including compounds targeting dopamine signaling and cyclooxygenase (搜索) (COX) enzymes.
Genetic and pharmacological inhibition of the dopamine D2 receptor (搜索) (Dop2R) partially rescued eye, locomotor, and seizure phenotypes across three independent PIGA-CDG (搜索) models.
Increasing dopamine availability via L-DOPA supplementation or dopamine transporter (DAT) inhibition also improved disease phenotypes, supporting dopamine modulation as a candidate therapeutic strategy.
A drug repurposing screen in a Drosophila model of PIGA-CDG (搜索) has uncovered dopamine signaling and cyclooxygenase (搜索) (COX) inhibition as candidate therapeutic pathways for this ultra-rare neurodevelopmental disorder. The study, published in PLOS Genetics, screened 1,520 small molecules from the Prestwick Chemical Library—98% of which are FDA- or EMA-approved—and identified 90 compounds that suppressed the disease phenotype, alongside 52 enhancers and 41 compounds that caused complete lethality.
PIGA-CDG (搜索) is an X-linked recessive disorder caused by partial loss-of-function variants in the Phosphatidylinositol glycan biosynthesis class A (PIGA (搜索)) gene. Fewer than 100 patients have been identified, with approximately 40 partial loss-of-function variants reported. Patients typically present with seizures, intellectual disability, developmental delay, hypotonia, dysmorphic facial features, and reduced life expectancy. There is currently no disease-specific treatment, and only symptom management is available.
A high-throughput screen in a Drosophila eye model
Because ubiquitous PIGA (搜索) knockdown is lethal, the researchers developed a tissue-specific RNA interference (RNAi) model in which PIGA is knocked down only in eye tissue using the eya-GAL4 driver. This produces a smaller eye with a glassy appearance, providing a quantitative phenotype suitable for high-throughput screening. The Drosophila eye is primarily composed of neurons with mechanisms overlapping those in the brain, making it a suitable phenotypic model for PIGA-CDG (搜索).
Using this model, the team raised flies on 5 µM of each drug and quantified eye size, calculating Z-scores relative to DMSO controls. Compounds that suppressed the eye phenotype (Z ≥ 1.5) fell into several recurrent categories, including six drugs targeting dopamine signaling, six targeting COX enzymes, eight acting on adrenergic receptors, and six classified as steroids.
COX inhibition improves the PIGA-CDG eye model
The primary screen identified six COX inhibitors that suppressed the eye phenotype: Naproxen, Fenclofenac, Aceclofenac, Sulindac, Etoricoxib, and Piroxicam. Of these, three drugs increased eye size in validation experiments. Naproxen, available over the counter, significantly increased eye size at all doses tested (9.3%, 15.7%, and 11% increases at 1 µM, 5 µM, and 25 µM, respectively). Fenclofenac increased eye size at 1 µM (15.8% increase) and 5 µM (13.5% increase), while Aceclofenac increased eye size at 25 µM (13.5% increase).
Genetic validation supported these findings. The Drosophila ortholog of human PTGS1 and PTGS2 is Peroxinectin-like (Pxt), which is responsible for prostaglandin synthesis in the fly. Knocking down Pxt in the PIGA (搜索) eye model increased eye size by 7.2%, similar to the effect of NSAID treatment. These data suggest that inhibition of prostaglandin synthesis may be a therapeutic avenue for PIGA-CDG (搜索) patients.
Dopamine D2 receptor inhibition improves multiple PIGA-CDG phenotypes
The researchers prioritized dopamine signaling because PIGA-CDG (搜索) symptoms are primarily neurological and key components of dopamine signaling are conserved between humans and Drosophila. The primary screen identified six dopamine signaling-targeting drugs, all described as dopamine D2 receptor (搜索) (D2R) antagonists: Quetiapine Hemifumarate, Octoclothepin Maleate Salt, Mesoridazine Besylate, Bromopride, Ziprasidone, and Alizapride hydrochloride.
Notably, the tricyclic drugs partially rescued eye size in validation experiments, whereas the non-tricyclics failed to do so. Quetiapine Hemifumarate increased eye size at 25 µM (12.9% increase), Octoclothepin Maleate Salt significantly increased eye size at 50 µM (9.4% increase), and Mesoridazine Besylate increased male eye size by 8.4% at 25 µM.
Genetic inhibition of Dop2R produced an even larger effect. Introducing a hemizygous loss-of-function allele of Dop2R into the PIGA (搜索) eye model significantly increased eye size by 20.2%. Conversely, heterozygous loss of Dop1R1 worsened the phenotype, reducing eye size by 20.4%, consistent with the opposing downstream effects of dopamine 1 and dopamine 2 receptors on cAMP signaling.
Increasing dopamine availability rescues disease phenotypes
The researchers also demonstrated that increasing dopamine availability improves the PIGA-CDG (搜索) model. L-DOPA treatment partially rescued eye size (19.6% increase at 25 µM and 14% increase at 50 µM). Conversely, introducing a heterozygous null allele of ple—which encodes the enzyme responsible for converting tyrosine to L-DOPA, the rate-limiting step in dopamine synthesis—decreased eye size by 6.3%. Loss of the dopamine transporter (DAT), which allows dopamine to remain in the synaptic cleft longer, increased eye size by 16.3%.
The authors note that one PIGA-CDG (搜索) patient has already been treated with Levodopa (L-DOPA), which alleviated his dyskinesia and improved quality of life.
Neurological phenotypes respond to dopaminergic modulation
The same genetic manipulations that improved eye morphology also improved neurological phenotypes. In a pan-neuronal PIGA (搜索) knockdown model with severe locomotor deficits, only about 10% of PIGA knockdown flies could climb in a negative geotaxis assay. Heterozygous loss of Dop2R increased this to approximately 25% of flies leaving the bottom.
In a seizure model using heterozygous null PIGA (搜索) flies, recovery following mechanical stimulation was dramatically improved by dopaminergic modulation. Female heterozygous PIGA null flies showed only 15% recovery within 30 seconds, while 52.9% of PIGA and Dop2R double mutant flies recovered in the same time frame. Males improved from 22.4% to 55%. Loss of DAT produced an even more striking rescue: female PIGA heterozygous nulls improved from 20.3% to 91.7% recovery, and males from 31.7% to 83.1%.
Importantly, pharmacological inhibition of Dop2R using multiple D2R antagonists did not modify seizure phenotypes, and post-eclosion treatment with quetiapine or L-DOPA failed to rescue seizure or locomotor deficits. The authors suggest this may reflect that genetic inhibition of Dop2R is constant throughout development and could rewire neural circuits long term, whereas acute drug use fails to recapitulate this effect.
Implications for CDG therapeutics
The findings parallel prior work from the same laboratory showing that dopamine signaling and synthesis can modify DPAGT1-CDG (搜索), an N-linked glycosylation disorder. The authors note that dopaminergic signaling has now been shown to modify disease phenotypes in three CDG models—PIGA-CDG (搜索), DPAGT1-CDG, and NGLY1-deficiency (搜索)—suggesting that targeting dopaminergic signaling may represent a generalizable therapeutic strategy across congenital disorders of glycosylation.
The researchers caution that drug concentrations used in Drosophila cannot be directly translated to human therapeutic doses due to differences in drug absorption, metabolism, and pharmacokinetics between flies and humans. The compounds identified should therefore be viewed as candidate therapeutics warranting further investigation rather than direct indicators of clinical dosing.
Of the twelve primary drug screen hits tested, six drugs (50%) were validated in dose-response experiments. The authors conclude that more potent or selective D2R or COX inhibitors may provide enhanced efficacy in improving quality of life for individuals with PIGA-CDG (搜索).