Identification of amino-acids in the alpha-subunit first and third loops that are crucial for the heterospecific follicle-stimulating hormone activity of equid luteinizing hormone/choriogonadotropin.

Autor:	Chopineau M; Physiologie de la Reproduction et des Comportements (PRC), UMR INRA-CNRS 6073, 37380 Nouzilly, France. chopinea@tours.inra.fr, Martinat N, Gibrat JF, Galet C, Lecompte F, Foulon-Gauze F, Pourchet C, Guillou F, Combarnous Y
Jazyk:	angličtina
Zdroj:	European journal of endocrinology [Eur J Endocrinol] 2004 Jun; Vol. 150 (6), pp. 877-84.
DOI:	10.1530/eje.0.1500877
Abstrakt:	Objective: To identify amino-acids in the alpha-subunit important for expression of heterospecific FSH activity of horse (e) LH/choriogonadotropin (CG) (eLH) and donkey (dk) LH/CG (dkLH) (FSH/LH ratio ten times higher for eLH than for dkLH); this FSH activity absolutely requires an equid (donkey or horse) alpha-subunit combined with an equid beta-LH subunit. Design: Chimeric alpha-subunits possessing the first 63 amino-acids of the porcine (p) and the last 33 amino-acids of the donkey alpha-subunit (alphap-dk) and the inverse (alphadk-p) were constructed. Porcine-specific amino-acids were introduced by mutagenesis in donkey alpha-subunit at positions 70, 85, 89, 93 and 96 (alphadk5xmut), 18 (alphadkK18E) or 78 (alphadkI78A). Methods: These different alpha-subunits were co-transfected in COS-7 cells with beta-eLH, beta-dkLH and beta-eFSH. The LH and FSH bioactivities of the dimers were then assessed in two heterologous in vitro bioassays. Results: alphap-dk or alphadk-p exhibited FSH activity when co-expressed with beta-eLH but not with beta-dkLH. alphadkK18E or alphadkI78A gave hybrids with no FSH activity and important LH activity when expressed with beta-dkLH. alphadkI78A/betaeLH displayed an FSH/LH ratio as low as that of dkLH. However, mutation at 78 in alpha-dk had no effect on FSH bioactivity when co-expressed with beta-eFSH. Conclusions: Amino-acids present in both the first two-thirds and the last third of the alpha-subunit of equid LHs are involved in their heterologous biospecificity. Ile alpha78 exerts as strong an influence on it as the beta102-103 residues. By contrast, this residue plays no role in the FSH specificity of eFSH.
Databáze:	MEDLINE
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