Loss of peptide: N -glycanase causes proteasome dysfunction mediated by a sugar-recognizing ubiquitin ligase

Significance Cytosolic peptide: N -glycanase (NGLY1) is a widely conserved enzyme involved in de– N -glycosylation of N -glycosylated proteins. Mutations in the human NGLY1 gene cause global developmental delay and multisystemic symptoms, but the molecular mechanism underlying pathogenesis remains poorly understood. FBXO6/FBS2, a subunit of the SCF (SKP1–CUL1–F-box protein) ubiquitin ligase complex, recognizes N -glycans of cytosolic glycoproteins in the endoplasmic reticulum–associated degradation (ERAD) pathway. This paper reports that high levels of ERAD glycoprotein substrates abnormally ubiquitinated by SCF FBS2 in the absence of NGLY1 impair the proteasome, contributing to the pathogenesis of NGLY1 deficiency. Importantly, knockout of Fbxo6/Fbs2 rescued the lethality of NGLY1 deficiency in mice, suggesting a strategy for developing therapeutics for this intractable disease.