Differential Involvement of Phosphoinositide 3-Kinase in Endogenous Gonadotropin-Releasing Hormone Signalling in Gonadotropes and Somatotropes of Goldfish, Carassius auratus.

Abstract

Event Abstract Back to Event Differential Involvement of Phosphoinositide 3-Kinase in Endogenous Gonadotropin-Releasing Hormone Signalling in Gonadotropes and Somatotropes of Goldfish, Carassius auratus. Joshua G. Pemberton1, James L. Stafford1, Yi Yu1 and John P. Chang1* 1 University of Alberta, Biological Sciences, Canada Two endogenous gonadotropin-releasing hormones (salmon (s)GnRH and chicken (c)GnRH-II) stimulates LH and GH secretion via Ca2+-dependent intracellular signalling pathways in goldfish, Carassius auratus. Whether phosphoinositide 3-kinase (PI3K) mediates GnRH-stimulated LH and GH release and associated intracellular Ca2+ increases ([Ca2+]i) were investigated using hormone release studies with primary cultures of dispersed goldfish pituitary and Fura2 fluorescence Ca2+ imaging in morphologically identified goldfish pituitary somatotropes and gonadotropes. Western blot showed the presence of immunoreactive PI3K p85α, the regulatory subunit for conventional Class IA PI3Ks, in goldfish pituitary and brain tissue extracts and both endogenous GnRH isoforms increased phosphorylation of PI3K p85α in excised pituitary fragments. Selective PI3K inhibitors wortmannin (100 nM) and LY294002 (10 µM) significantly reduced sGnRH- and cGnRH-II-elicited LH release responses from primary cultures of mixed pituitary cells and [Ca2+]i increases in identified gonadotropes. Surprisingly, both PI3K inhibitors reduced the GH release response to the two GnRHs but only attenuated the [Ca2+]i response to cGnRH-II. The effects of PI3K inhibition on hormone release responses were specific to GnRHs and not the result of general decreases in the releasable hormone pool or sensitivity to [Ca2+]i changes as both wortmannin and LY294002 had no effect on Ca2+ ionophore-evoked LH and GH secretion. These results indicate that PI3K is involved upstream of [Ca2+]i increases in mediating LH and GH responses in a cell- and GnRH isoform-specific manner and is the first to implicate PI3K in GnRH-induced LH and GH release in any primary pituitary cell system. Acknowledgements This research was supported by Natural Sciences and Engineering Research Council of Canada (NSERC) individual Discovery Grants to J.P. Chang and J.L. Stafford. Financial support for J.G. Pemberton was provided by the Province of Alberta Queen Elizabeth II Graduate Scholarship, NSERC Alexander Graham Bell Canada Graduate Scholarship (CGS M), and the University of Alberta as a recipient of the Dr. Richard E. Peter Memorial Scholarship, Walter H. Johns Graduate Fellowship and Department of Biological Sciences Teaching Assistantship. Y. Yu was a recipient of a F.S. Chia PhD Recruitment Scholarship from the University of Alberta. We thank Alan Mar and Herman Cortes for their assistance with this study. Keywords: fura2 fluorescence calcium imaging, gonadotropes and somatotropes, gonodotropin-releasing hormone, luteinizing and growth hormone secretion, Phosphoinositide 3-kinase, wortmannin and LY294002 Conference: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology, Ann Arbor, United States, 13 Jul - 16 Jul, 2011. Presentation Type: Poster Topic: Intracellular signaling Citation: Pemberton JG, Stafford JL, Yu Y and Chang JP (2011). Differential Involvement of Phosphoinositide 3-Kinase in Endogenous Gonadotropin-Releasing Hormone Signalling in Gonadotropes and Somatotropes of Goldfish, Carassius auratus.. Front. Endocrinol. Conference Abstract: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology. doi: 10.3389/conf.fendo.2011.04.00079 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Jul 2011; Published Online: 09 Aug 2011. * Correspondence: Prof. John P Chang, University of Alberta, Biological Sciences, Edmonton, Alberta, T6G2E9, Canada, john.chang@ualberta.ca Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Joshua G Pemberton James L Stafford Yi Yu John P Chang Google Joshua G Pemberton James L Stafford Yi Yu John P Chang Google Scholar Joshua G Pemberton James L Stafford Yi Yu John P Chang PubMed Joshua G Pemberton James L Stafford Yi Yu John P Chang Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.