Abstract
Glycans attached to immunoglobulin G (IgG) directly affect this antibody effector functions and regulate inflammation at several levels. The composition of IgG glycome changes significantly with age. In women, the most notable change coincides with the perimenopausal period. Aiming to investigate the effect of estrogen on IgG glycosylation, we analysed IgG and total serum glycomes in 36 healthy premenopausal women enrolled in a randomized controlled trial of the gonadotropin-releasing hormone analogue (GnRHAG) leuprolide acetate to lower gonadal steroids to postmenopausal levels and then randomized to transdermal placebo or estradiol (E2) patch. The suppression of gonadal hormones induced significant changes in the IgG glycome, while E2 supplementation was sufficient to prevent changes. The observed glycan changes suggest that depletion of E2 primarily affects B cell glycosylation, while liver glycosylation stays mostly unchanged. To determine whether previously identified IgG GWAS hits RUNX1, RUNX3, SPINK4, and ELL2 are involved in downstream signaling mechanisms, linking E2 with IgG glycosylation, we used the FreeStyle 293-F transient system expressing IgG antibodies with stably integrated CRISPR/dCas9 expression cassettes for gene up- and downregulation. RUNX3 and SPINK4 upregulation using dCas9-VPR resulted in a decreased IgG galactosylation and, in the case of RUNX3, a concomitant increase in IgG agalactosylation.
Highlights
Most proteins in human serum are glycosylated by the covalent addition of diverse glycan structures that fine-tune their function
immunoglobulin G (IgG) glycosylation traits related to galactosylation and sialylation, which were affected by the suppression of E2, are the main components of the glycan age clock of the biological age
We show that estradiol is an important factor in regulating IgG glycosylation in women and that its effects on N-glycosylation are limited explicitly to B cells, as depletion of E2 did not cause Nglycosylation changes of other serum proteins
Summary
Most proteins in human serum are glycosylated by the covalent addition of diverse glycan structures that fine-tune their function. Glycans attached to the Fc part of the IgG molecule affect interactions with different Fc receptors, which is why changes in glycosylation have direct effects on the immune system at multiple levels [2]. A recent intervention study demonstrated that estrogen regulates IgG glycosylation [14], which may explain why perimenopausal females undergo significant changes in the IgG glycome composition. We used data from our recent large genome-wide association study (GWAS) of the IgG glycome [16] to identify candidate genes possibly involved in mediating effects of E2 on IgG glycosylation. The system was modified by stable integration of CRISPR/dCas expression cassette containing either VPR (for gene upregulation) or KRAB (for gene downregulation) Using this system, we were able to demonstrate the effects of selected genes on specific IgG glycans which were previously associated with biological ageing
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
