Thrombin activates mitogen-activated protein kinase in primary astrocyte cultures.
Thrombin is known to evoke numerous inflammatory and proliferative responses in a wide variety of its target cells. Recent studies have demonstrated morphoregulatory and mitogenic effects of thrombin on astroglial cells (astrocytes). The present study deals with thrombin-induced activation of mitogen-activated protein (MAP) kinase in primary cultures of rat astrocytes. Treatment of serum-starved astrocytes with thrombin resulted in a rapid activation of tyrosine (Tyr) phosphorylation of a set of proteins including a prominent one with a molecular mass of 42 kDa (p42). The identity of p42 with MAP kinase was confirmed by MAP kinase-immunoreactivity of isolated [i.e., immunoprecipitated with anti-phosphotyrosine (PY) antibodies] p42 and by increased myelin basic protein (MBP) kinase activity present in MAP kinase immunoprecipitates of thrombin-treated cultures. Pertussis toxin (PTX) pretreatment failed to inhibit thrombin stimulation of p42 phosphorylation, indicating the lack of involvement of PTX sensitive G proteins in the mechanism of activation of MAP kinase by thrombin. Chronic exposure of cultures to phorbol 12-myristate 13-acetate to down-regulate PKC resulted in an attenuation of thrombin-induced p42 Tyr phosphorylation, although H-7, a known PKC inhibitor, failed to block thrombin effect. However, staurosporine, a nonspecific protein kinase inhibitor, prevented the activation of p42 phosphorylation. It is concluded that thrombin induces MAP kinase activation in astrocytes by a mechanism involving a staurosporine-sensitive pathway.
Bhat
N R
NR
Department of Neurology, Medical University of South Carolina, Charleston 29425, USA.
Zhang
P
P
Hogan
E L
EL
D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000201:enzymology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1; D037342:Pertussis Toxin; D010766:Phosphorylation; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology*; D014443:Tyrosine / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D010566:Virulence Factors, Bordetella; D014443:Tyrosine; D037342:Pertussis Toxin; D011505:Protein-Tyrosine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D013917:Thrombin; D013755:Tetradecanoylphorbol Acetate