Evidence for direct involvement of beta-catenin in phorbol ester-induced neurite outgrowth in GT1-1 hypothalamic neurones

Citation
W. Sun et al., Evidence for direct involvement of beta-catenin in phorbol ester-induced neurite outgrowth in GT1-1 hypothalamic neurones, J NEUROENDO, 13(3), 2001, pp. 249-260
Citations number
50
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Neurosciences & Behavoir
Journal title
JOURNAL OF NEUROENDOCRINOLOGY
ISSN journal
0953-8194 → ACNP
Volume
13
Issue
3
Year of publication
2001
Pages
249 - 260
Database
ISI
SICI code
0953-8194(200103)13:3<249:EFDIOB>2.0.ZU;2-Z
Abstract
Gonadotropin-releasing hormone (GnRH) is a pivotal neuroendocrine regulator controlling reproductive functions. However, the scattered distribution of GnRH neurones in the mammalian brain has hindered studies on the developme nt and differentiation of GnRH neurones. In the present study, we used the immortalized GnRH-producing GT1-1 cells to examine whether activation of pr otein kinase C (PKC) pathway with 12-O-tetradecanoyl-13-acetate (TPA) induc es morphological and functional differentiation of GnRH neurones. TPA induc ed neurite outgrowth and inhibited proliferation of GT1-1 cells that were s pecifically antagonized by cotreatment of PKC inhibitor, calphostin C. The functional significance of TPA-induced differentiation of GT1-1 cells was m anifested in part by the changes in the effects of aminobutyric acid (GABA) on intracellular Ca2+ levels. in untreated GT1-1 cells, activation of GABA -A receptor with 10 muM muscimol increased intracellular Ca2+ levels, where as such stimulatory effects disappeared in GT1-1 cells bearing neurites. Ac cordingly, muscimol could not stimulate GnRH release in TPA-treated GT1-1 c ells. To elucidate the molecular mechanism underlying TPA-induced neurite o utgrowth, we performed differential display reverse transcription-polymeras e chain reaction. Among several genes that are affected by TPA treatment, w e found a significant induction of beta -catenin mRNA expression. Along wit h the rapid induction of beta -catenin protein levels, we observed that bet a -catenin was reallocated from cell-cell adhesion sites to the growth cone s within 3 h of TPA treatment. Transient transfection studies with green fl uorescent protein as a reporter gene demonstrated that beta -catenin overex pression alone can promote neurite outgrowth in GT1-1 cells. Moreover, TPA was found to increase the transcription-activational roles of beta -catenin . Together, these data provide evidence that beta -catenin is involved in t he TPA-induced functional differentiation of immortalized GnRH neurones.