Truncated equine LH beta and asparagine(56)-deglycosylated equine LH alpha combine to produce a potent FSH antagonist.
Hybrid hormone preparations were prepared by combining intact and Asn(56)-deglycosylated (N(56)dg) equine (e) LH or FSH alpha subunit preparations with truncated, des(121-149)eLH beta (eLH beta t), immunopurified, intact eLH beta or equine chorionic gonadotropin beta (eCG beta) preparations, and eFSH beta. The LH receptor-binding potencies of N(56)dg-eLH alpha:eLH beta t and N(56)dg-eFSH alpha:eLH beta t hybrids were equivalent to that of eLH; however, both N(56)dg-alpha preparations were only 3-4% as active as eLH in the rat testis Leydig cell bioassay. In the granulosa cell FSH bioassay, eLH alpha:eLH beta t stimulated progesterone synthesis and induced aromatase activity, while N(56)dg-eLH alpha:eLH beta t was completely inactive at doses up to 5 microg. N(56)dg-eLH alpha:eLH beta t inhibited progesterone production and aromatase induction elicited by 0.3 ng eFSH or 2 ng human (h) FSH. The inhibitory activities of N(56)dg-eLH alpha:eLH beta and N(56)dg-eCG alpha:eLH beta t were only 10% that of N(56)dg-eLH alpha:eLH beta t. N(56)dg-eLH alpha:eCG beta did not inhibit progesterone synthesis stimulated by eFSH at all and appeared to further stimulate aromatase induction at the highest dose tested. Preincubation of N(56)dg-eLH alpha:eLH beta and N(56)dg-eLH alpha:eLH beta t for 72 h at 37 C resulted in no loss of FSH receptor-binding activity. Preincubation resulted in 50% loss of receptor-binding activity by the eFSH preparation due to subunit dissociation, while 88% of N(56)dg-eLH alpha:eFSH beta activity was lost following 72 h, 37 C preincubation. While alpha Asn(56) oligosaccharide had no effect on eLH beta hybrid stability, it did contribute to the stability of the eFSH heterodimer.
Butnev
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VY
Department of Biological Sciences, Wichita State University, Wichita, Kansas 67260--0026, USA.
Singh
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Nguyen
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Bousfield
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GR
D000818:Animals; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D005260:Female; D005640:Follicle Stimulating Hormone / Q000037:antagonists & inhibitors*; D015292:Glycoprotein Hormones, alpha Subunit / Q000737:chemistry / Q000378:metabolism*; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism; D006736:Horses; D007986:Luteinizing Hormone / Q000737:chemistry / Q000378:metabolism*; D011869:Radioligand Assay / Q000379:methods; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism
D015292:Glycoprotein Hormones, alpha Subunit; D011994:Recombinant Proteins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone