Thrombin receptor and RhoA mediate cell proliferation through integrins and cysteine-rich protein 61

FASEB J. 2008 Nov;22(11):4011-21. doi: 10.1096/fj.08-113266. Epub 2008 Aug 7.


A subset of G-protein coupled receptors (GPCRs), including the thrombin receptor (PAR1), elicits mitogenic responses. Thrombin also activates Ras homolog gene family member A (RhoA) and activating protein (AP-1) -mediated gene expression in 1321N1 astrocytoma cells, whereas the nonmitogenic agonist carbachol does not. Transcriptomic analysis was used to explore differential gene induction by these agonists and revealed that the matricellular protein cysteine-rich 61 (Cyr61/CCN1) is selectively induced by thrombin. The ability of GPCR agonists to induce Cyr61 parallels their ability to activate RhoA; agonist-stimulated Cyr61 expression is inhibited by C3 toxin. When Cyr61 is down-regulated using short interfering RNA (siRNA) or short-hairpin RNA (shRNA), thrombin-induced DNA synthesis is significantly attenuated. When Cyr61 expression is induced, it appears in the extracellular compartment and on the cell surface. Extracellular Cyr61 interacts with alpha(5), alpha(6), and beta(1) integrins on these cells, and monoclonal antibodies directed against alpha(5) and beta(1) integrins inhibit thrombin-induced DNA synthesis. Functional blockade of Cyr61 with soluble heparin or anti-Cyr61 antibodies also inhibits thrombin-induced DNA synthesis. Thus Cyr61 is a highly inducible, secreted extracellular factor through which GPCR and RhoA signaling pathways engage integrins that contribute to GPCR-mediated proliferation.

MeSH terms

  • Carbachol / pharmacology
  • Cardiotonic Agents / pharmacology
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cysteine-Rich Protein 61
  • Down-Regulation / drug effects
  • Down-Regulation / physiology*
  • Fibrinolytic Agents / pharmacology
  • Heparin / pharmacology
  • Humans
  • Immediate-Early Proteins / antagonists & inhibitors
  • Immediate-Early Proteins / genetics
  • Immediate-Early Proteins / metabolism*
  • Immediate-Early Proteins / pharmacology
  • Integrins / genetics
  • Integrins / metabolism*
  • Intercellular Signaling Peptides and Proteins / genetics
  • Intercellular Signaling Peptides and Proteins / metabolism*
  • Intercellular Signaling Peptides and Proteins / pharmacology
  • RNA, Small Interfering
  • Receptor, PAR-1 / antagonists & inhibitors
  • Receptor, PAR-1 / genetics
  • Receptor, PAR-1 / metabolism*
  • Signal Transduction*
  • Transcription Factor AP-1 / genetics
  • Transcription Factor AP-1 / metabolism
  • rhoA GTP-Binding Protein / genetics
  • rhoA GTP-Binding Protein / metabolism*


  • CCN1 protein, human
  • Cardiotonic Agents
  • Cysteine-Rich Protein 61
  • Fibrinolytic Agents
  • Immediate-Early Proteins
  • Integrins
  • Intercellular Signaling Peptides and Proteins
  • RNA, Small Interfering
  • Receptor, PAR-1
  • Transcription Factor AP-1
  • RHOA protein, human
  • Carbachol
  • Heparin
  • rhoA GTP-Binding Protein