Identifying understudied protein-related glycoproteome disruption in Congenital Disorders of Glycosylation - PROJECT SUMMARY/ABSTRACT The congenital disorders of glycosylation (CDG) are a group of rare neurometabolic genetic diseases that disrupt glycosylation, the addition of sugar structures to proteins. Many CDG genes encode understudied and potentially druggable proteins. As the most abundant post-translational modification (PTM), glycosylation generates immense biological variability and mediates fundamental biological processes. CDG patients exhibit multiorgan dysfunction, which is often severe with early mortality. Pathophysiology of CDG is attributed to disrupted protein glycosylation; however, the specific identities of hypoglycosylated proteins responsible for most disease manifestations are unknown. Critical unmet needs related to understanding pathomechanisms and effective therapies remain for CDG patients. Here, we propose to utilize mass spectrometry-based technologies to evaluate glycoproteomic disruptions in CDG patient samples with pathogenic variants in druggable, understudied proteins (SLC35A2, SLC35A3, and SLC39A8). Understanding how genetic defects in genes encoding these proteins disrupts glycosylation will provide new scientific insights into the pathophysiology of CDG disease manifestations, may suggest novel treatment strategies, and will inform normal function of glycosylation and these understudied proteins. The druggability of these selected proteins is largely due to their roles as substrate transporters, through which the proteins enable uptake and localization of glycan subunits to the endoplasmic reticulum and Golgi apparatus for glycan synthesis and maturation. Most pathogenic CDG variants are hypomorphic mutations, leading to the hypothesis that increased availability of transporter substrate may overcome protein dysfunction, restore glycosylation, and mitigate disease manifestations. In addition to evaluating glycoproteomic disruption in specimens from affected individuals, this proposal will test whether transporter substrate supplementation can normalize the glycoproteomic disruption of the disease state and overcome underlying protein dysfunction. This study will use using state-of-the-art glycoproteomics technologies and clinically relevant patient samples to elucidate functions of understudied CDG transporter proteins. Pioneering advances in instrumentation, experimental methodologies, and computational approaches in glycoproteomics make identification of glycoproteome disruption finally achievable. These studies will identify hypoglycosylated proteins and glycosites in patient tissues and generate data to address the question of whether substrate supplementation in these CDG may address the underlying causes of disease manifestations. The knowledge and data generated from these studies will be pivotal for applying for funding and carrying out future studies aimed at treating CDG disorders caused by defects in SLC35A2, SLC35A3, and SLC39A8.
