Activation of extracellular-regulated kinase pathways in ovarian granulosa cells by the novel growth factor type 1 follicle-stimulating hormone receptor. Role in hormone signaling and cell proliferation

• Published in: The Journal of biological chemistry 2000-09, Vol.275 (36), p.27615
• Main Authors: Babu, P S, Krishnamurthy, H, Chedrese, P J, Sairam, M R
• Format: Article
• Language: English
• Subjects: Animals; Cell Division - drug effects; Cell Line; Chorionic Gonadotropin - pharmacology; Colforsin - pharmacology; Cyclic AMP - metabolism; Enzyme Activation; Enzyme Inhibitors - pharmacology; Female; Follicle Stimulating Hormone - pharmacology; Granulosa Cells - cytology; Granulosa Cells - drug effects; Granulosa Cells - physiology; Humans; Kinetics; Luteinizing Hormone - pharmacology; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases - metabolism; Receptors, FSH - genetics; Receptors, FSH - physiology; Receptors, Somatotropin - genetics; Receptors, Somatotropin - physiology; Recombinant Proteins - metabolism; Recombinant Proteins - pharmacology; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction - drug effects; Signal Transduction - physiology; Swine; Transfection
• ISSN: 0021-9258
• DOI: 10.1074/jbc.M003206200

Follicle-stimulating hormone (FSH) regulated growth and function of the ovarian follicle was previously thought to be mediated solely through activation of G(s)-coupled receptors. In this study, we show for the first time that this function is predominantly mediated through the alternatively spliced and novel growth factor type 1 receptor (oFSH-R3) that is also present in the ovary. Immortalized granulosa cells lacking endogenous FSH receptors, when transfected with either oFSH-R3 cDNA (JC-R3) or the G(s)-coupled oFSH-R1 (JC-R1), expressed the corresponding glycosylated receptor. In JC-R3 or JC-R1 cells labeled with bromodeoxyuridine or [(3)H]thymidine, FSH stimulated the cells to progress through S-phase and divide. The growth promoting effect of recombinant FSH in JC-R3 cells was preceded by the rapid activation of ERK1 and ERK2. This effect was hormone-specific and transient. In JC-R3 cells inhibitors like calphostin C, PD98059, Ag 18, or calcium chelators EGTA or 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM inhibited both mitogen-activated protein kinase activation and bromodeoxyuridine incorporation. FSH induced phosphorylation of the FSH-R3 receptor was blocked by pretreating cells with calphostin C. There was no cAMP induction by FSH in JC-R3 cells. The cAMP independent growth promoting effect of FSH is mediated by activation of Ca(2+) and mitogen-activated protein kinase-dependent pathways. Thus, alternative splicing of a G-protein coupled receptor creates the expression of a novel receptor motif that can mediate a widely recognized function of the glycoprotein hormone.