ERO1 alpha deficiency increases N-glycosylation of a proangiogenic VEGFA by MAGT1-dependent OST complex

ABSTRACT: N-glycosylation and disulfide bond formation are two essential steps in protein folding, that both take place in the endoplasmic reticulum (ER). These two modifications can influence each other, but the exact timing, as well as the mediators of this important crosstalk, are still not completely elucidated. In previous work, we demonstrated that cells deficient in ER oxidoreductin 1-alpha (ERO1-alpha), a protein disulfide oxidase, are impaired in their ability to secrete Vascular Endothelial Growth Factor-A (VEGF121), a key regulator of vascular homeostasis in health and of metastasis in cancer. Here, to analyze the crosstalk between N-glycosylation and disulfide bond formation in newly synthesized proteins of the ER, we investigated how ERO1-alpha deficit affects glycosylation of VEGF121. We found that reduced ER redox poise imposed by ERO1 deficiency, while slowing down the intracellular formation of disulfide-bonds in VEGF121, promoted the full utilization of its single N-glycosylation consensus site, which lies close to an intra-polypeptide disulfide bridge. Unexpectedly, this hyperglycosylation impairs the kinetics of VEGF121 secretion. Unbiased mass-spectrometric data of VEGF121 immunoprecipitates followed by pathway analysis indicated a stable interaction between VEGF121 and proteins involved in the N-glycosylation in ERO1-alpha knockout, but not wild-type cells. Notably, MAGT1, a thioredoxin-containing protein and part of the post-translational oligosaccharyltransferase complex (OST), was a major hit exclusive to ERO1-deficient cells. We demonstrate that post-translational N-glycosylation VEGF121 is increased under the altered redox poise caused by ERO1 deficit: on the one hand by a reduced rate of formation of its disulfide bridges, and on the other, by the increased trapping potential of MAGT1's thioredoxin domain. These findings have implications for a variety of pathological processes involving altered redox conditions in the ER.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Michele Bianchi  

LAB HEAD: Angela Bachi

PROVIDER: PXD033941 | Pride | 2022-08-29

REPOSITORIES: Pride