title: Histamine acting on H1 receptor promotes inhibition of proliferation via PLC, RAC, and JNK-dependent pathways.
abstract: It is well established that histamine modulates cell proliferation through the activation of the histamine H1 receptor (H1R), a G protein-coupled receptor (GPCR) that is known to couple to phospholipase C (PLC) activation via Gq. In the present study, we aimed to determine whether H1R activation modulates Rho GTPases, well-known effectors of Gq/G(11)-coupled receptors, and whether such modulation influences cell proliferation. Experiments were carried out in CHO cells stably expressing H1R (CHO-H1R). By using pull-down assays, we found that both histamine and a selective H1R agonist activated Rac and RhoA in a time- and dose-dependent manner without significant changes in the activation of Cdc42. Histamine response was abolished by the H1R antagonist mepyramine, RGS2 and the PLC inhibitor U73122, suggesting that Rac and RhoA activation is mediated by H1R via Gq coupling to PLC stimulation. Histamine caused a marked activation of serum response factor activity via the H1R, as determined with a serum-responsive element (SRE) luciferase reporter, and this response was inhibited by RhoA inactivation with C3 toxin. Histamine also caused a significant activation of JNK which was inhibited by expression of the Rac-GAP beta2-chimaerin. On the other hand, H1R-induced ERK1/2 activation was inhibited by U73122 but not affected by C3 or beta2-chimaerin, suggesting that ERK1/2 activation was dependent on PLC and independent of RhoA or Rac. [(3)H]-Thymidine incorporation assays showed that both histamine and the H1R agonist inhibited cell proliferation in a dose-dependent manner and that the effect was independent of RhoA but partially dependent on JNK and Rac. Our results reveal that functional coupling of the H1R to Gq-PLC leads to the activation of RhoA and Rac small GTPases and suggest distinct roles for Rho GTPases in the control of cell proliferation by histamine.
authors.affiliation: Laboratorio de Patología y Farmacología Molecular, Instituto de Biología y Medicina Experimental, Buenos Aires, Argentina.
authors.forename: Cintia
authors.initials: C
authors.lastname: Notcovich
authors.forename: Federico
authors.initials: F
authors.lastname: Diez
authors.forename: Maria Rosario
authors.initials: MR
authors.lastname: Tubio
authors.forename: Alberto
authors.initials: A
authors.lastname: Baldi
authors.forename: Marcelo G
authors.initials: MG
authors.lastname: Kazanietz
authors.forename: Carlos
authors.initials: C
authors.lastname: Davio
authors.forename: Carina
authors.initials: C
authors.lastname: Shayo
mesh_terms: D000818:Animals; D016466:CHO Cells; D049109:Cell Proliferation / Q000187:drug effects; D002999:Clone Cells; D006224:Cricetinae; D003412:Cricetulus; D004789:Enzyme Activation / Q000187:drug effects; D017930:Genes, Reporter; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D011969:Receptors, Histamine H1 / Q000378:metabolism*; D027602:Serum Response Element / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects*; D010738:Type C Phospholipases / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: D011969:Receptors, Histamine H1; D006632:Histamine; D008156:Luciferases; D048031:JNK Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D020744:rac GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein