Thrombin (PAR-1)-induced proliferation in astrocytes via MAPK involves multiple signaling pathways.
Protease-activated receptors (PARs), newly identified members of G protein-coupled receptors, are widely distributed in the brain. Thrombin evokes multiple cellular responses in a large variety of cells by activating PAR-1, -3, and -4. In cultured rat astrocytes we investigated the signaling pathway of thrombin- and PAR-activating peptide (PAR-AP)-induced cell proliferation. Our results show that PAR activation stimulates proliferation of astrocytes through the ERK pathway. Thrombin stimulates ERK1/2 phosphorylation in a time- and concentration-dependent manner. This effect can be fully mimicked by a specific PAR-1-AP but only to a small degree by PAR-3-AP and PAR-4-AP. PAR-2-AP can induce a moderate ERK1/2 activation as well. Thrombin-stimulated ERK1/2 activation is mainly mediated by PAR-1 via two branches: 1) the PTX-sensitive G protein/(betagamma-subunits)-phosphatidylinositol 3-kinase branch, and 2) the G(q)-PLC-(InsP(3) receptor)/Ca2+ -PKC pathway. Thrombin- or PAR-1-AP-induced ERK activation is partially blocked by a selective EGF receptor inhibitor, AG1478. Nevertheless, transphosphorylation of EGF receptor is unlikely for ERK1/2 activation and is certainly not involved in PAR-1-induced proliferation. The metalloproteinase mechanism involving transactivation of the EGF receptor by released heparin-binding EGF was excluded. EGF receptor activation was detected by the receptor autophosphorylation site, tyrosine 1068. Our data suggest that thrombin-induced mitogenic action in astrocytes occurs independently of EGF receptor transphosphorylation.
Wang
Hong
H
Otto-von-Guericke-Universität Magdeburg, Medizinische Fakultät, Institut für Neurobiochemie, 39120 Magdeburg, Germany.
Ubl
Joachim J
JJ
Stricker
Rolf
R
Reiser
Georg
G
D000818:Animals; D001253:Astrocytes / Q000166:cytology* / Q000201:enzymology*; D020013:Calcium Signaling / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D066246:ErbB Receptors / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006490:Hemostatics / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009946:Organothiophosphorus Compounds / Q000378:metabolism; D037342:Pertussis Toxin / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D044463:Receptor, PAR-1; D018179:Receptors, Thrombin / Q000378:metabolism*; D013917:Thrombin / Q000494:pharmacology
D006490:Hemostatics; D009946:Organothiophosphorus Compounds; D010716:Phosphatidylinositols; D044463:Receptor, PAR-1; D018179:Receptors, Thrombin; C005009:phosacetim; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D013917:Thrombin; D019204:GTP-Binding Proteins