Preeclampsia transforms membrane N-glycome in human placenta

Posttranslational modifications (PTM) which accompany pathological conditions affect protein structure, characteristics and modulate its activity. Glycosylation is one of the most frequent PTM influencing protein folding, localisation and function. Hypertension is a common gestational complication, which can lead to foetal growth restriction (IUGR) and even to foetal or maternal death. In this work we focused on the impact of preeclampsia complicated with IUGR on placental membrane N-glycome. Results have shown that preeclampsia reduced fucosylation of placental glycans, increased the appearance of paucimannosidic and mannosidic structures with lower number of mannose residues and decreased the amount of glycans with more mannose residues. Since preeclampsia is tightly connected to IUGR, glycosylation changes were investigated also on the functional membrane receptors responsible for growth: insulin receptor and the type 1 insulin-like growth factor receptor (IR and IGF1R). It was found that IR present in the IUGR placenta contained significantly less α2,6-Sia. Therefore, glycans on placental membranes alter due to preeclampsia, but changes seen at the level of the entire N-glycome may be different from the changes detected at the level of a specific glycoprotein. The difference recorded due to pathology in one membrane molecule (IR) was not found in another homologous molecule (IGF1R). Thus, besides studying the glycosylation pattern of the entire placental membrane due to preeclampsia, it is inevitable to study directly glycoprotein of interest, as no general assumptions or extrapolations can be made.