Hidden Relationships between N-Glycosylation and Disulfide Bonds in Individual Proteins

Abstract

N-Glycosylation (NG) and disulfide bonds (DBs) are two prevalent co/post-translational modifications (PTMs) that are often conserved and coexist in membrane and secreted proteins involved in a large number of diseases. Both in the past and in recent times, the enzymes and chaperones regulating these PTMs have been constantly discovered to directly interact with each other or colocalize in the ER. However, beyond a few model proteins, how such cooperation affects N-glycan modification and disulfide bonding at selective sites in individual proteins is largely unknown. Here, we reviewed the literature to discover the current status in understanding the relationships between NG and DBs in individual proteins. Our results showed that more than 2700 human proteins carry both PTMs, and fewer than 2% of them have been investigated in the associations between NG and DBs. We summarized both these proteins with the reported relationships in the two PTMs and the tools used to discover the relationships. We hope that, by exposing this largely understudied field, more investigations can be encouraged to unveil the hidden relationships of NG and DBs in the majority of membranes and secreted proteins for pathophysiological understanding and biotherapeutic development.

Discovery and Visualization of the Hidden Relationships among N-Glycosylation, Disulfide Bonds, and Membrane Topology

“…Because SSs and N-glycans are common structural features on MPs, we wanted to further explore whether hidden relationships exist between the two PTMs and TMs in individual proteins at the proteome level. In the past, we observed a complementary relationship between TMs and N-glycans from our experimentally obtained N-glycoproteome [41], and we also discovered a complex relationship between SSs and N-glycans [22] in the literature. Here, we wanted to see whether SSs would behave similarly to the N-glycans in the complementary relation to TMs.…”

“…The examination of the length distribution in various features shows some interesting properties. The length distribution of the human proteome segregated by the TMs predicted by Deep TMHMM is shown in Figure 1A oxidoreductive activity themselves [22,23]. We therefore hypothesize that a close relationship may exist among these structural features.…”

“…An important paralog to the catalytic enzyme STT3A in OST is STT3B, which has oxidoreductase activity that can form mixed disulfide bonds with target proteins through its components MAGT1 or TUSC3 [20,21]. In addition, a number of ER-resident glycoenzymes and glycochaperons also form complexes with thiol-disulfide oxidoreductases or carry oxidoreductive activity themselves [22,23]. We therefore hypothesize that a close relationship may exist among these structural features.…”

Secretome Analysis: Reading Cellular Sign Language to Understand Intercellular Communication

“…Since non-classical secretion mechanisms diverge between human and microbes, the prediction guiding principles are also different. Along the lines of such non-classical prediction, secreted proteins also tend to feature more glycosylations and disulfide bridges for added stability ( 176 ). As such, although not fully predictive, the presence of such modifications and modification sites may also indicate higher confidence in bona fide protein secretion.…”

Molecular characterization of protein translocation pores

“…This lowers the energy barrier for disulfide bond formation by the protein-oxidoreductase PDI1 for glycosylated substrates (Bakshi et al 2022). Formation of disulfide bonds further stabilizes the substrate and effectively hinder the process of oligosaccharide addition by blocking the access of glycoenzymes or chaperone to oligosaccharides (Allen, Naim, and Bulleid 1995).…”