S1P inhibits gap junctions in astrocytes: involvement of G and Rho GTPase/ROCK.
Sphingosine-1-phosphate (S1P) is a potent and pleiotropic bioactive lysophospholipid mostly released by activated platelets that acts on its target cells through its own G protein-coupled receptors. We have previously reported that mouse striatal astrocytes expressed mRNAs for S1P1 and S1P3 receptors and proliferate in response to S1P. Here, we investigated the effect of S1P on gap junctions. We show that a short-term exposure of astrocytes to S1P causes a robust inhibition of gap junctional communication, as demonstrated by dye coupling experiments and double voltage-clamp recordings of junctional currents. The inhibitory effect of S1P on dye coupling involves the activation of both Gi and Rho GTPases. Rho-associated kinase (ROCK) also plays a critical role. The capacity of S1P to activate a Rho/ROCK axis in astrocytes is demonstrated by the typical remodeling of actin cytoskeleton. Connexin43, the protein forming gap junction channels, is a target of the Gi- and Rho/ROCK-mediated signaling cascades. Indeed, as shown by Western blots and confocal immunofluorescence, its nonphosphorylated form increases following S1P treatment and this change does not occur when both cascades are disrupted. This novel effect of S1P may have an important physiopathological significance when considering the proposed roles for astrocyte gap junctions on neuronal survival.
Rouach
Nathalie
N
INSERM U587, Collège de France, 11, Place Marcelin Berthelot, 75005 Paris, France.
Pébay
Alice
A
Même
William
W
Cordier
Jocelyne
J
Ezan
Pascal
P
Etienne
Eric
E
Giaume
Christian
C
Tencé
Martine
M
D000199:Actins / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal; D001253:Astrocytes / Q000187:drug effects*; D015153:Blotting, Western; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000502:physiology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000502:physiology; D017629:Gap Junctions / Q000187:drug effects*; D016391:Genes, src / Q000502:physiology; D008246:Lysophospholipids / Q000494:pharmacology*; D008297:Male; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009431:Neural Conduction; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D015398:Signal Transduction / Q000187:drug effects; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D020741:rho GTP-Binding Proteins / Q000502:physiology*
D000199:Actins; D000911:Antibodies, Monoclonal; D008246:Lysophospholipids; C060506:sphingosine 1-phosphate; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020741:rho GTP-Binding Proteins; D013110:Sphingosine