title: RhoA GTPase switch controls Cx43-hemichannel activity through the contractile system.
abstract: ATP-dependent paracrine signaling, mediated via the release of ATP through plasma membrane-embedded hemichannels of the connexin family, coordinates a synchronized response between neighboring cells. Connexin 43 (Cx43) hemichannels that are present in the plasma membrane need to be tightly regulated to ensure cell viability. In monolayers of bovine corneal endothelial cells (BCEC),Cx43-mediated ATP release is strongly inhibited when the cells are treated with inflammatory mediators, in particular thrombin and histamine. In this study we investigated the involvement of RhoA activation in the inhibition of hemichannel-mediated ATP release in BCEC. We found that RhoA activation occurs rapidly and transiently upon thrombin treatment of BCEC. The RhoA activity correlated with the onset of actomyosin contractility that is involved in the inhibition of Cx43 hemichannels. RhoA activation and inhibition of Cx43-hemichannel activity were both prevented by pre-treatment of the cells with C3-toxin as well as knock down of RhoA by siRNA. These findings provide evidence that RhoA activation is a key player in thrombin-induced inhibition of Cx43-hemichannel activity. This study demonstrates that RhoA GTPase activity is involved in the acute inhibition of ATP-dependent paracrine signaling, mediated by Cx43 hemichannels, in response to the inflammatory mediator thrombin. Therefore, RhoA appears to be an important molecular switch that controls Cx43 hemichannel openings and hemichannel-mediated ATP-dependent paracrine intercellular communication under (patho)physiological conditions of stress.
authors.affiliation: Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Campus Gasthuisberg O/N-1, Faculty of Medicine, KU Leuven, Leuven, Belgium.
authors.forename: Raf
authors.initials: R
authors.lastname: Ponsaerts
authors.forename: Catheleyne
authors.initials: C
authors.lastname: D'hondt
authors.forename: Fréderic
authors.initials: F
authors.lastname: Hertens
authors.forename: Jan B
authors.initials: JB
authors.lastname: Parys
authors.forename: Luc
authors.initials: L
authors.lastname: Leybaert
authors.forename: Johan
authors.initials: J
authors.lastname: Vereecke
authors.forename: Bernard
authors.initials: B
authors.lastname: Himpens
authors.forename: Geert
authors.initials: G
authors.lastname: Bultynck
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics / Q000502:physiology*; D004727:Endothelium / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D055785:Gene Knockdown Techniques; D034741:RNA, Small Interfering; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000502:physiology*
chemical_list: D018031:Connexin 43; D034741:RNA, Small Interfering; D000255:Adenosine Triphosphate; D020742:rhoA GTP-Binding Protein