Pituicyte Stellation is Prevented by RhoA-or Cdc42-Dependent Actin Polymerization |
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Authors: | Lia Rosso Patricia M Pierson Claire Golfier Brigitta Peteri-Brunbäck Christophe Deroanne Ellen Van Obberghen-Schilling Jean-Marc Mienville |
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Institution: | (1) CNRS UMR 6548, Laboratoire de Physiologie Cellulaire et Moléculaire Faculté des Sciences, Université de Nice-Sophia Antipolis, 28 Avenue Valrose, Nice Cedex 2, 06108, France;(2) Present address: Centre Intégratif de Génomique, Université de Lausanne, Lausanne, 1015, Switzerland;(3) CNRS UMR 6543, Centre Antoine Lacassagne, Université de Nice-Sophia Antipolis, Nice, France;(4) Present address: Laboratoire de Biologie des Tissus Conjonctifs, Tour de Pathologie B23/3, Sart-Tilman, Liège 1, 4000, Belgium |
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Abstract: | Our aim was to shed light on different steps leading from metabotropic receptor activation to changes in cell shape, such
as those that characterize the morphological plasticity of neurohypophysial astrocytes (pituicytes). Using explant cultures
of adult rat pituicytes, we have previously established that adenosine A1 receptor activation induces stellation via inhibition
of RhoA monomeric GTPase and subsequent disruption of actin stress fibers. Here, we rule out RhoA phosphorylation as a mechanism
for that inhibition. Rather, our results are more consistent with involvement of a GTPase-activating protein (GAP). siRNA
and pull-down experiments suggest that a step downstream of RhoA might involve Cdc42, another GTPase of the Rho family. However,
RhoA activation, e.g., in the presence of serum, induces stress fibers, whereas direct Cdc42 activation appears to confine
actin within a submembrane—i.e., cortical—network, which also prevents stellation. Therefore, we propose that RhoA may activate
Cdc42 in parallel with an effector, such as p160Rho-kinase, that induces and maintains actin stress fibers in a dominant fashion.
Rac1 is not involved in the stellation process per se but appears to induce a dendritogenic effect. Ultimately, it may be
stated that pituicyte stellation is inducible upon mere actin depolymerization, and preventable upon actin organization, be
it in the form of stress fibers or in a cortical configuration. |
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Keywords: | Neurohypophysis Small GTPases Stress fibers Cortical actin Adenosine |
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