title: p63RhoGEF couples Gα(q/11)-mediated signaling to Ca2+ sensitization of vascular smooth muscle contractility.
abstract: BACKGROUND
  In normal and diseased vascular smooth muscle (SM), the RhoA pathway, which is activated by multiple agonists through G protein-coupled receptors (GPCRs), plays a central role in regulating basal tone and peripheral resistance. This occurs through inhibition of myosin light chain phosphatase, leading to increased phosphorylation of the myosin regulatory light chain. Although it is thought that specific agonists and GPCRs may couple to distinct RhoA guanine nucleotide exchange factors (GEFs), thus raising the possibility of selective targeting of specific GEFs for therapeutic use, this notion is largely unexplored for SM contraction.
  
  
  OBJECTIVE
  We examine whether p63RhoGEF, known to couple specifically to Gα(q/11) in vitro, is functional in blood vessels as a mediator of RhoA activation and if it is selectively activated by Gα(q/11) coupled agonists.
  
  
  RESULTS
  We find that p63RhoGEF is present across SM tissues and demonstrate that silencing of the endogenous p63RhoGEF in mouse portal vein inhibits contractile force induced by endothelin-1 to a greater extent than the predominantly Gα(12/13)-mediated thromboxane analog U46619. This is because endothelin-1 acts on Gα(q/11) as well as Gα(12/13). Introduction of the exogenous isolated pleckstrin-homology (PH) domain of p63RhoGEF (residues 331-580) into permeabilized rabbit portal vein inhibited Ca2+ sensitized force and activation of RhoA, when phenylephrine was used as an agonist. This reinforces the results based on endothelin-1, because phenylephrine is thought to act exclusively through Gα(q/11).
  
  
  CONCLUSIONS
  We demonstrate that p63RhoGEF selectively couples Gα(q/11) but not Gα(12/13), to RhoA activation in blood vessels and cultured cells and thus mediates the physiologically important Ca2+ sensitization of force induced with Gα(q/11)-coupled agonists. Our results suggest that signaling through p63RhoGEF provides a novel mechanism for selective regulation of blood pressure.
authors: University of Virginia, Charlottesville, VA 22908-0736, USA.
authors: Ko
authors: K
authors: Momotani
authors: Mykhaylo V
authors: MV
authors: Artamonov
authors: Darkhan
authors: D
authors: Utepbergenov
authors: Urszula
authors: U
authors: Derewenda
authors: Zygmunt S
authors: ZS
authors: Derewenda
authors: Avril V
authors: AV
authors: Somlyo
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000494:pharmacology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000502:physiology*; D055785:Gene Knockdown Techniques; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000502:physiology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009119:Muscle Contraction / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D011169:Portal Vein / Q000502:physiology; D011817:Rabbits; D051381:Rats; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D020742:rhoA GTP-Binding Protein / Q000502:physiology
chemical_list: C475063:ARHGEF25 protein, human; D019332:Endothelin-1; C577427:GEFT protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D064067:Rho Guanine Nucleotide Exchange Factors; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D006160:Guanosine Triphosphate; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020742:rhoA GTP-Binding Protein; D002118:Calcium