Erythropoietin induces tyrosine phosphorylation and activation of phospholipase C-gamma 1 in a human erythropoietin-dependent cell line.
Erythropoietin (Epo) is the major regulator of the proliferation and differentiation of erythroid precursors through interaction with its receptor (Epo-R). Although Epo-R lacks a tyrosine kinase consensus sequence within its intracellular domain, the addition of its ligand to Epo-responsive cells, UT-7/Epo, induces the rapid and transient tyrosine phosphorylation of 145-, 130-, 80-, and 40-kDa cellular proteins. Tyrosine phosphorylation of these proteins occurred dose- and time-dependently. We showed that the tyrosine phosphorylated 145- kDa protein is identical to phospholipase C-gamma 1 (PLC-gamma 1). Tyrosine phosphorylation of this protein is detectable within 30 s and almost reaches the maximum at 1 min. This can last up to 10 min and declines thereafter. Additionally, in Epo-stimulated cells, PLC-gamma 1 become physically associated with 80- and 40-kDa proteins which have been tyrosine-phosphorylated in response to Epo. The activity of PLC-gamma 1 was also investigated using inositol 1,4,5-trisphosphate (Ins-P3) as an indicator. We found that stimulation of UT-7/Epo cells with Epo induces a significant accumulation of Ins-P3. This effect is dose-dependent and occurs very rapidly. The production of Ins-P3 can explain the Epo-induced mobilization of calcium from intracellular stores in these cells. These results demonstrate that Epo induces tyrosine phosphorylation and activation of PLC-gamma 1 to produce Ins-P3 and then it mobilizes calcium from intracellular stores. This signal transduction pathway may play a role in regulating the proliferation of erythroid cells.
Division of Hematology, Jichi Medical School, Tochigi-ken, Japan.
H Y
HY
Ren
N
N
Komatsu
R
R
Shimizu
K
K
Okada
Y
Y
Miura
D002118:Calcium / Q000378:metabolism; D002451:Cell Compartmentation; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D015672:Erythroid Precursor Cells / Q000378:metabolism*; D004921:Erythropoietin / Q000378:metabolism*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D017467:Receptors, Erythropoietin / Q000378:metabolism*
D007527:Isoenzymes; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D017467:Receptors, Erythropoietin; D004921:Erythropoietin; D015544:Inositol 1,4,5-Trisphosphate; C087857:protein kinase C gamma; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D002118:Calcium