Self-assembled PROTACs enable glycoproteins degradation in the living cells

We report here a two-component proteolysis targeting chimeras (PROTACs) strategy selectively targeting <i>O</i>-GalNAcylated and <i>O</i>-GlcNAcylated proteins for proteasomal degradation, which leads to severe toxicity in human cancer cell lines through perturbation of critical metabolic and signaling pathways governed by glycoproteins. Our approach termed as GlyTAC leverages from metabolic incorporation of easily accessible and cell-permeable peracetylated <i>N</i>-acetylglucosamine (GlcNAc) or <i>N</i>-acetylgalactosamine (GalNAc) analogues bearing an azido group into glycoproteins. In the living cells, the azido-modified glycoproteins serve as covalent anchors for the introduction of thalidomide moiety by strain-promoted azide-alkyne cycloaddition (SPAAC) to recruit E3 ligase cereblon (CRBN), resulting in stepwise ubiquitination of 'sensitized' proteins and their degradation by proteasome. We show the efficiency of the system in a series of human cancer cell lines and verify the mechanistic pathway by performing control experiments at each stage of the process. Given the characteristic features of cancer cells including fast nutrient turnover, and overall increase of protein glycosylation, as well as the low cytotoxicity of the individual components, our approach may open a feasible strategy in cancer therapy.