¹Division of Hematology-Oncology, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, PA 15213, USA

²Department of Physiology and Biophysics, Wright State University School of Medicine, Dayton, Ohio, OH 45401, USA

³Department of Molecular Genetics, Institute for Liver Research, Kansai Medical University, Moriguchi 570, Japan

⁴Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, PA 15213, USA

Correspondence to: Seth J Corey, Division of Hematology-Oncology, Children's Hospital of Pittsburgh, 3705 Fifth Avenue, Pittsburgh, Pennsylvania, PA 15213, USA

Granulocyte colony-stimulating factor (G-CSF) is the major hematopoietic factor which controls the production and differentiation of granulocytes. The G-CSF receptor (G-CSFR) belongs to the superfamily of the cytokine receptors, which transduce signals via the activation of cytosolic protein tyrosine kinases (PTK). To determine the role of specific PTK in G-CSF signaling we expressed the human G-CSFR in cell lines derived from DT40 B cells, which lack either the Src-related Lyn or Syk. Wild-type (wt) and syk-deficient cells underwent increased DNA synthesis in response to G-CSF; lyn-deficient cells did not. The purpose of these studies is to identify Lyn's downstream effectors in mediating DNA synthesis. While G-CSF stimulated Ras activity in all cell lines, G-CSF failed to induce the tyrosine phosphorylation of Shc in lyn-deficient cells. G-CSF induced a statistically significant activation of Erk1/Erk2 Kinase or p90Rsk only in the wt cells. G-CSF induced the tyrosine phosphorylation of Cbl and increased activity of PI 3-kinase in wild-type and syk-deficient, but non in lyn-deficient, cells. Inhibition of Shc by over-expression of its SH2 or PTB domains or PI 3-kinase by either treatment with wortmannin or expression of the CblY731F mutant decreased G-CSF-induced DNA synthesis. Thus, the Lyn, Cbl-PI 3-kinase, and Shc/non-Ras-dependent pathways correlate with the ability of cells to respond to G-CSF with increased DNA synthesis. Oncogene (2000) 19, 97-105.

G-CSF; Lyn; PI 3-kinase; Cbl; Shc