A Single-chain Bifunctional Gonadotropin Analog Is Secreted from Chinese Hamster Ovary Cells as Two Distinct Bioactive Species

• Published in: The Journal of biological chemistry Vol. 279; no. 43; pp. 44286 - 44293
• Main Authors: Vicenta Garcia-Campayo, Albina Jablonka-Shariff, Irving Boime
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 22.10.2004
• Subjects: Animals; Antibodies, Monoclonal - chemistry; Blotting, Western; CHO Cells; Chorionic Gonadotropin - metabolism; Cricetinae; Culture Media, Conditioned - pharmacology; Dimerization; Dose-Response Relationship, Drug; Follicle Stimulating Hormone - metabolism; Gonadotropins - chemistry; Gonadotropins - metabolism; Ligands; Molecular Conformation; Protein Binding; Protein Conformation; Protein Structure, Tertiary; Radioimmunoassay; Receptors, FSH - metabolism; Recombinant Proteins - chemistry; Structure-Activity Relationship; Time Factors; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M408386200

One of the major developments in exploring structure activity relationships of the glycoprotein hormone family was the genetic engineering of single chains comprised of the common α subunit and one or more of the hormone-specific β subunits tandemly arranged. These studies indicate that there is a structural permissiveness in the quaternary relationships between the subunits and biological activity. However, the conformational relationships between the ligand and the receptor are unclear. Bifunctional triple-domain analogs represent an ideal model to address this issue. Does a single molecule possess the ability to simultaneously interact with both specific receptors or are there two functionally distinct species in the chimeric population? Here we show, using a preadsorption protocol comprised of Chinese hamster ovary cells expressing either the luteinizing hormone (LH)/chorionic gonadotropin (CG) or follicle-stimulating hormone (FSH) receptor, that at least two distinct bioactive populations of the dually active triple-domain chimera FSHβ-CGβ-α are synthesized, each corresponding to a single activity (CG or FSH). Furthermore, we show that these bioactive populations form distinct stable heterodimer-like contacts. That there is not a single biologically active species formed during synthesis of the chimera implies that in vivo the heterodimer exists in multiple conformations and is not a static rigid molecule.