Novel small-molecule modifiers rescue pathology associated with NGLY1 Deficiency in a Caenorhabditis elegans model

Abstract

Functional loss in clearing misfolded proteins is associated with several human diseases. A mutation in one such gene, NGLY1 results in a rare genetic disorder in humans. NGLY1 encodes for Peptide:N-Glycanase (PNGase), which plays a critical role in the Endoplasmic Reticulum Associated Degradation (ERAD) pathway. The clinical pathologies associated with NGLY1 Deficiency in humans include global developmental delay, slowed/restricted movement, hypotonia, and the absence of tears. There is currently no cure or treatment available to delay these pathologies. NGLY1 is an evolutionarily conserved gene with an ortholog in Caenorhabditis elegans (C. elegans) known as png-1. A loss-of-function mutation in the png-1 gene results in pathologies similar in nature to those seen in humans e.g. developmental delay and motor function defects. At the molecular level, png-1 loss has been linked with increased sensitivity to proteasomal stress. The purpose of this study is to utilize C. elegans as a discovery platform to characterize disease pathology and identify compounds with potential to rescue NGLY1 disease pathology. Here we show that C. elegans png-1 mutants show significantly reduced motility, reproductive fitness, mitochondrial health, and lifespan compared to the N2 wild-type. These phenotypes may be directly mediated by loss in protein homeostasis as png-1 mutants have an increased amount of glycosylated proteins and SDS-insoluble proteins (aggregated proteins). Furthermore, we conducted a targeted small molecule screen of known gero-protective compounds using the proteasomal inhibition-induced L1 arrest phenotype of png-1 mutants as a proxy for pathology rescue. We identified quercetin, vitamin D and two other compounds as positive hits from the screen. Moreover, we have also identified a key transcription factor required for the protective effect of the hits. In summary, using png-1 mutant C. elegans model, we have identified compounds and molecular pathways with potential to rescue NGLY1 disease pathology.