RhoA inhibition is a key step in pituicyte stellation induced by A(1)-type adenosine receptor activation.
Pituicyte stellation in vitro represents a useful model with which to study morphological changes that occur in vivo in these cells during times of high neurohypophysial hormone output. This model has helped us establish the hypothesis of a purinergic regulation of pituicyte morphological plasticity. We first show that ATP induces stellation in 37% of pituicytes, an effect that is secondary to the metabolism of ATP to adenosine. Adenosine-induced stellation of pituicytes appears to be mediated by A(1)-type receptors. The effect is independent of intracellular calcium and does not involve the mitogen-activated protein kinase pathway. The basal (nonstellate) state of pituicytes depends on tonic activation of a Rho GTPase because both C3 transferase (a Rho inhibitor) and Y-27632 (an inhibitor of p160Rho kinase) can induce stellation. Lysophosphatidic acid, a Rho activator, blocks the morphogenic effect of adenosine dose-dependently. Using a specific RhoA pull-down assay, we also show that downregulation of activated RhoA is the key event coupling A(1) receptor activation to pituicyte stellation, via F-actin depolymerization and microtubule reorganization. Finally, both vasopressin and oxytocin can prevent or reverse adenosine-induced stellation. The effects of vasopressin, and those of high concentrations of oxytocin, are mediated through V(1a) receptors. Placed within the context of the relevant literature, our data suggest the possibility of a purinergic regulation of pituicyte morphological plasticity and subsequent modulation of hormone release, with these hormones providing a negative feedback mechanism.
Rosso
Lia
L
Laboratoire de Physiologie Cellulaire et Moléculaire, Université de Nice-Sophia Antipolis, Nice, France.
Peteri-Brunbäck
Brigitta
B
Vouret-Craviari
Valérie
V
Deroanne
Christophe
C
Troadec
Jean-Denis
JD
Thirion
Sylvie
S
Van Obberghen-Schilling
Ellen
E
Mienville
Jean-Marc
JM
D000241:Adenosine / Q000378:metabolism / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D048429:Cell Size / Q000502:physiology*; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005246:Feedback / Q000187:drug effects / Q000502:physiology*; D008246:Lysophospholipids / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D010121:Oxytocin / Q000378:metabolism / Q000494:pharmacology; D010904:Pituitary Gland, Posterior / Q000166:cytology* / Q000201:enzymology* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018047:Receptors, Purinergic P1 / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014667:Vasopressins / Q000378:metabolism / Q000494:pharmacology; D020742:rhoA GTP-Binding Protein / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*
D004791:Enzyme Inhibitors; D008246:Lysophospholipids; D018047:Receptors, Purinergic P1; D014667:Vasopressins; D010121:Oxytocin; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D020742:rhoA GTP-Binding Protein; D000241:Adenosine