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Hypo‐glycosylated hFSH binds and activates FSH receptors more rapidly than fully‐glycosylated hFSH
Author(s) -
Bousfield George Russell,
Butnev Vladimir Y,
May Jeffrey V,
Harvey David J,
Jiang Chao,
Davis John S
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.592.2
Subject(s) - phosphorylation , glycosylation , receptor , creb , chemistry , protein subunit , medicine , intracellular , endocrinology , biochemistry , biology , transcription factor , gene
Follitropin (FSH) heterodimers possess two potential N‐glycosylation sites on both common α and hormone‐specific β subunits. Hypo‐glycosylated hFSH isolated from lutropin preparations possessed a partially glycosylated FSHβ subunit decorated with one glycan, while there were two in the hFSHα subunit. Mass spectrometry revealed the presence of oligomannose glycans, which are normally rare in hFSH preparations. Hypo‐glycosylated hFSH was 5‐ to 26‐fold more active than fully‐glycosylated hFSH in several FSH radioligand assays. In rat testis homogenate, 125 I‐hypo‐hFSH bound receptors immediately, without the 45–60 min lag observed for 125 I‐fully‐glycosylated hFSH. In porcine granulosa cells, short‐term incubations revealed an earlier onset of cAMP accumulation, protein kinase A (PKA) activity and CREB phosphorylation. Hypo‐glycosylated hFSH increased intracellular cAMP accumulation within one min and PKA‐dependent CREB phosphorylation within 5 min; whereas fully‐glycosylated hFSH induced CREB phosphorylation after a 10–15 min lag. Additionally, CREB phosphorylation was sustained for greater than 60 min in response to hypo‐glycosylated hFSH, but returned to basal within 60 min in response to fully‐glycosylated hFSH. Thus, partial glycosylation of hFSH results in faster binding to its cognate receptor and this is attended by a more rapid cellular response. Supported by NIH grant 5P01 AG‐029531.