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Leukemia Inhibitory Factor Induces the Chemomigration of Immortalized Gonadotropin-Releasing Hormone Neurons through the Independent Activation of the Janus Kinase/Signal Transducer and Activator of Transcription 3, Mitogen-Activated Protein Kinase/Extracellularly Regulated Kinase 1/2, and Phosphatidylinositol 3-Kinase/Akt Signaling Pathways

Department of Endocrinology (P.M., E.D., M.R., A.C., R.Z., M.M., R.M.), Centre of Excellence on Neurodegenerative Diseases, University of Milan, 20133 Milan, Italy; and Division of Internal Medicine (H.W.), Center for Clinical Research, International University of Health and Welfare, Otawara, Tochigi 324-8501, Japan

Address all correspondence and requests for reprints to: Paolo Magni, Department of Endocrinology, Center of Excellence on Neurodegenerative Diseases, University of Milan, via G. Balzaretti, 9, 20133 Milano, Italy. E-mail: paolo.magni{at}unimi.it.

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine of the IL-6 superfamily. LIF acts through a cell-surface receptor complex formed by two subunits, the specific LIF receptor ß (LIFRß) and the glycoprotein 130. Little is known about LIF involvement in modulating the neuroendocrine circuitry governing the reproductive function and, specifically, the development of GnRH-secreting neurons. In the present study, we evaluated the effect of LIF on the in vitro migration of GN11 cells, a model of immature and migratory GnRH neurons, and the signaling pathways involved in this process. GN11 cells expressed both LIFRß and glycoprotein 130 subunits. Exposure of GN11 cells to 100 ng/ml LIF resulted in activation of the Janus kinases (Jaks)/signal transducer and activator of transcription 3, MAPK/ERK1/2, and phosphatidylinositol 3-kinase/protein kinase B/Akt pathways. The selective inhibition of Jaks, MAPK kinase, and phosphatidylinositol 3-kinase indicated that these signaling pathways were activated independently by LIF and that Jak2 is not the main kinase involved in LIF signaling. Exposure of GN11 cells to LIF for 3 h induced a concentration-dependent chemotactic response, with a plateau at 100 ng/ml LIF. LIF was also found to induce chemokinesis of GN11 cells. Furthermore, LIF-promoted GN11 migration was the result of the partial and independent contribution of all the three signaling pathways activated by LIF. The present data, together with the observation that LIF and LIFRß are expressed prenatally in the mouse nasal compartment, would suggest that LIF might participate in the migration of GnRH neurons.