Retinoic acid- and phorbol ester-induced neuronal differentiation down-regulates caveolin expression in GnRH neurons.
GN11 and GT1-7 are immortalized gonadotropin-releasing hormone-positive murine cell lines exhibiting the features of immature olfactory neurons and differentiated hypothalamic neurons, respectively. Using electron microscopy and biochemical assays (RT-PCR and immunoblotting) we determined the presence of numerous caveolae invaginations and of caveolin-1 and -2 mRNAs and proteins in GN11 cells, and their absence in GT1-7 cells. The lack of caveolins in GT1-7 cells might be due to the silencing of gene transcription caused by estrogen receptor alpha whose inhibitory activity in GN11 cells could be counter-balanced by co-expression of caveolin-permissive estrogen receptor beta. To test whether the unique expression of caveolins in GN11 cells is related to their immature state, we treated GN11 cells for 24-72 h with retinoic acid or phorbol ester. Both treatments led to neuronal differentiation of GN11 cells, as shown by emission of long neuritic processes, increased expression of growth cone-associated protein-43 and appearance of voltage-gated K+ and C2+ channel currents. Concurrently, caveolins 1 and 2, and estrogen receptor beta were down-regulated in differentiated GN11, whereas estrogen receptor alpha was unaffected by differentiation. We conclude that caveolin expression in GN11 neurons is down-regulated upon differentiation and up-regulated by estrogen receptor beta.
D'Orlando
Cristina
C
Department of Experimental Medicine, University of Milano-Bicocca, Monza, Italy.
Guzzi
Francesca
F
Gravati
Marta
M
Biella
Gerardo
G
Toselli
Mauro
M
Meneveri
Raffaella
R
Barisani
Donatella
D
Parenti
Marco
M
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001932:Brain Neoplasms; D015220:Calcium Channels / Q000502:physiology; D051242:Caveolin 1 / Q000235:genetics*; D051243:Caveolin 2 / Q000235:genetics*; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D047628:Estrogen Receptor alpha / Q000235:genetics; D047629:Estrogen Receptor beta / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010703:Phorbol Esters / Q000494:pharmacology*; D014212:Tretinoin / Q000494:pharmacology*
D000970:Antineoplastic Agents; D015220:Calcium Channels; C495541:Cav1 protein, mouse; C495545:Cav2 protein, mouse; D051242:Caveolin 1; D051243:Caveolin 2; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D010703:Phorbol Esters; D007987:Gonadotropin-Releasing Hormone; D014212:Tretinoin