N-linked oligosaccharides direct the differential assembly and secretion of inhibin alpha- and betaA-subunit dimers.
The biosynthetic pathway governing inhibin heterodimer (alpha/beta) and activin homodimer (beta/beta) assembly and secretion from ovarian granulosa cells is not fully understood. Here, we examined the role of inhibin subunit glycosylation in the assembly and secretion of mature inhibin A and activin A. Inhibition of subunit glycosylation by tunicamycin treatment of alpha- and beta(A)-expressing CHO cell lines reduced inhibin but not activin secretion. Dimeric inhibin A is preferentially secreted from parental isogenic wild-type (wt) cell lines (alpha(wt)beta(wt)). Mutation of a single glycosylation site at asparagine 268 (alpha(Delta268)beta(wt)) reduces inhibin secretion by 78% and permits beta/beta assembly and secretion. Conversely, gain of a glycosylation (GOG) site in the analogous region of the beta(A)-subunit (alpha(wt)beta(GOG327)) enhances inhibin A secretion. The present study demonstrates that N-linked glycan sites direct heterodimer vs. homodimer assembly, and prevention of glycosylation abrogates inhibin secretion. These data support a definitive role for site-specific N-glycosylation in governing inhibin/activin dimer assembly and secretion.
Antenos
Monica
M
Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA.
Stemler
Michelle
M
Boime
Irving
I
Woodruff
Teresa K
TK
D028341:Activins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D017931:DNA Primers / Q000235:genetics; D019281:Dimerization; D019143:Evolution, Molecular; D006031:Glycosylation; D028322:Inhibin-beta Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007265:Inhibins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009844:Oligosaccharides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D013347:Subcellular Fractions / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors; D014415:Tunicamycin / Q000494:pharmacology
D017931:DNA Primers; D009844:Oligosaccharides; D016212:Transforming Growth Factor beta; C422405:activin A; C103008:inhibin beta A subunit; C094377:inhibin-alpha subunit; D028341:Activins; D014415:Tunicamycin; D007265:Inhibins; D028322:Inhibin-beta Subunits