Séminaire LBM | Dr. Ben Schumann "Chemical precision tools to dissect protein glycosylation"

CHEMICAL PRECISION TOOLS TO DISSECT PROTEIN GLYCOSYLATION

Dr. Ben Schumann

Alterations in glycoprotein expression and composition are an undisputed corollary of cancer development. Consequently, some of the most important tumor biomarkers are heavily glycosylated. Understanding cancer-induced glycoproteome changes is paramount but hampered by experimental limitations. For instance, protein O-GalNAc glycosylation is among the most abundant and important cancer-relevant posttranslational modifications. Glycans are primed by the activities of 20 GalNAc transferase (GalNAc-T1…T20) isoenzymes located in the secretory pathway. Since these transferases are interdependent through compensation and competition, traditional methods of molecular cell biology do not address the complexity of glycoprotein biosynthesis. Furthermore, workflows in mass spec-glycoproteome analysis are often restricted to isolated cell lines that do not adequately reflect the interaction between tumor and microenvironment. Thus, we lack strategies to understand 1) the protein substrate specificities of individual GalNAc-Ts and 2) which glycoproteins are made by cancer cells in response to their microenvironment.
Here, I describe our development of chemical “Precision Tools” to dissect cellular O-GalNAc glycosylation. We employ bump-and-hole (BH) engineering to render GalNAc-Ts receptive to a chemically modified nucleotide-sugar substrate that carries a bioorthogonal tag and is not used by wildtype transferases. Engineering individual transferases allows differential profiling of their protein substrate specificities. We found that establishing a cellular BH system required an artificial biosynthetic pathway to deliver the corresponding nucleotide-sugar to the secretory pathway. Since such metabolic engineering could be introduced into only one cell line in a co-culture system, we employed the principle to develop a tactic for Bio-Orthogonal Cell-specific TAgging of Glycoproteins (BOCTAG). Thus, chemical Precision Tools allow us to profile O-GalNAc glycosylation as a key player in cancer biology.

Ben was trained in synthetic carbohydrate chemistry in the lab of Peter H. Seeberger at the Max Planck Institute of Colloids and Interfaces Potsdam and the FU Berlin (PhD in 2015). Developing vaccines against pathogenic bacteria based on synthetic glycans, Ben learnt to apply his compounds in biological settings in vivo and in vitro, receiving the Award for Excellence in Glycosciences and the Otto Hahn Medal by the Max Planck Society. During his postdoctoral work in the lab of Carolyn R. Bertozzi at Stanford University as a Humboldt fellow, Ben developed an interest for “precision tools” to study glycosylation of human cells. He started as a Group Leader at the Francis Crick Institute and Imperial College London in 2018 to develop such tools, using a combination of
organic and chemo-enzymatic synthesis, molecular and cell biology. The lab was part of a team that received the 2021 RSC Horizon Prize in Chemical Biology. Ben is an EMBO Young Investigator and has received the Biochemical Society Young Investigator Award as well as the RSC Dextra Award in 2023 and the RSC Norman Heatley Award in 2024. He received an ERC Starting Grant in 2023, now covered by UKRI.