Staurosporine induces tyrosine phosphorylation of a 145 kDa protein but does not activate gp140trk in PC12 cells.
Staurosporine, a protein kinase C inhibitor, induces neurite outgrowth in PC12 cells similarly to nerve growth factor (NGF). Since NGF neurotropic effects are transduced by the 'trk' gene product 140 kDa tyrosine kinase receptor, gp140trk, we investigated the role of gp140trk and tyrosine phosphorylations in staurosporine neurotropic effects. A direct correlation between staurosporine neurotropic effects and a novel stimulation of tyrosine phosphorylation of a 145 kDa protein (p145) with the following characteristics has been discovered: (1) Staurosporine specifically induced, among indolcarbazoles-K252a derivatives, in a dose-dependent manner (5-100 nM), p145 tyrosine phosphorylation and neurite outgrowth. (2) Staurosporine-induced p145 tyrosine phosphorylation was selective compared to other neurotropic compounds such as 8-Br-cAMP, acidic and basic fibroblast growth factors and NGF. (3) Staurosporine stimulation of p145 tyrosine phosphorylation gradually increased during the first 8 h of staurosporine treatment coinciding with the initiation of neurotropic effects. (4) K252a, a selective inhibitor of NGF actions, and several tyrphostins did not block staurosporine-induced p145 tyrosine phosphorylation and neurotropic effects. (5) Staurosporine stimulation of p145 tyrosine phosphorylation and neurotropic effects are independent of PKC. (6) Staurosporine did not activate gp140trk-NGF receptor in PC12 cells. The present study proposes staurosporine as a pharmacological tool to study the role of tyrosine phosphorylation pathway(s), such as p145 phosphorylation, in the action of neurotropic agents.
Rasouly
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Department of Pharmacology and Experimental Therapeutics, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Israel.
Lazarovici
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D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D051379:Mice; D008970:Molecular Weight; D016501:Neurites / Q000187:drug effects; D016716:PC12 Cells; D010766:Phosphorylation; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D020813:Receptor, trkB; D017475:Receptors, Nerve Growth Factor / Q000302:isolation & purification / Q000378:metabolism*; D019311:Staurosporine; D014443:Tyrosine / Q000378:metabolism*
D000470:Alkaloids; D017475:Receptors, Nerve Growth Factor; D014443:Tyrosine; D020794:Receptor Protein-Tyrosine Kinases; D020813:Receptor, trkB; D011493:Protein Kinase C; D019311:Staurosporine