ABSTRACT
Treatment of cells with granulocyte colony-stimulating factor (G-CSF) leads to tyrosine phosphorylation of cellular proteins. G-CSF stimulates both the activation of protein tyrosine kinases Lyn, Jak1, and Jak2 and the association of these enzymes with the G-CSF receptor. Wild-type, lyn-deficient, and syk-deficient chicken B lymphocyte cell lines were transfected with the human G-CSF receptor, and stable transfectants were studied. G-CSF-dependent tyrosyl phosphorylation of Jak1 and Jak2 occurred in all three cell lines. Wild-type and syk-deficient transfectants responded to G-CSF in a dose-responsive fashion with increased thymidine incorporation, but none of the clones of lyn-deficient transfectants did. Ectopic expression of Lyn, but not that of c-Src, in the lyn-deficient cells restored their mitogenic responsiveness to G-CSF. Ectopic expression in wild-type cells of the kinase-inactive form of Lyn, but not of the kinase-inactive form of Jak2, inhibited thymidine incorporation in response to G-CSF. These studies show that the absence of Lyn results in the loss of mitogenic signaling in the G-CSF signaling pathway and that activation of Jak1 or Jak2 is not sufficient to cause mitogenesis.
Subject(s)
DNA Replication , Granulocyte Colony-Stimulating Factor/pharmacology , Proto-Oncogene Proteins , src-Family Kinases/metabolism , Animals , Cell Line , Chickens , Enzyme Activation , Granulocyte Colony-Stimulating Factor/metabolism , Humans , Janus Kinase 1 , Janus Kinase 2 , Precipitin Tests , Protein-Tyrosine Kinases/metabolism , Receptors, Granulocyte Colony-Stimulating Factor/metabolism , Signal Transduction , src Homology DomainsABSTRACT
The chloditan (o.p-DDD, mitotane), which causes the destruction of the human and dog adrenal cortex, on the most essential system of xenobiotic metabolism: glutathione-S-transferase--glutathione has been studied. The effect of o,p-DDD on GSH level and activity of glutathione-S-transferase and glutathione reductase which maintain the level of reduced glutathione was analyzed in the adrenal and liver tissue of rats. This species is resistant to adrenocorticolytic action of o,p-DDD. It was shown that feeding of rats weighting 200-240 g with oil solution of o,p-DDD (75 mg daily) for 3 days causes the decrease in activity of glutathione-S-transferase and content of oxidazed glutathione in the adrenals with simultaneous increase of the content of reduced glutathione. The glutathione-S-transferase and glutathione reductase activity in the liver rises under the effect of o,p-DDD, the decrease of the GSH level being observed. The revealed changes may explain the species sensitivity of animals to o,p-DDD.