In vitro impact of distinct FSH glycosylation variants on FSH receptor-stimulated signal transduction and functional selectivity

Follicle-stimulating hormone (FSH) exists as different major glycoforms that differ in glycosylation of the hormone-specific β-subunit. Tetra-glycosylated FSH (FSH24) and tri-glycosylated FSH (FSH21) are the most abundant forms found in humans. Employing distinct readouts in HEK293 cells stably expressing the human FSH receptor, we here compared intracellular signaling triggered by human pituitary FSH preparations (FSH21and FSH24) as well as by equine FSH (eFSH), and human recombinant FSH (recFSH), each exhibiting distinct glycosylation patterns. The potencies in eliciting cAMP production were eFSH>FSH21>FSH24>recFSH, whereas in the ERK1/2 activation readout potencies were FSH21≥eFSH>recFSH>FSH24. In β-arrestin 1/2 CRISPR/Cas9 HEK293 KO cells, FSH21 exhibited a preference towards β-arrestin-mediated ERK1/2 activation as revealed by a drastic decrease in pERK during the first 15min exposure to this glycoform. Further, exposure of β-arrestin1/2 KO cells to H89 additionally ...