Surface immunoglobulin-mediated signal transduction involves rapid phosphorylation and activation of the protooncogene product Raf-1 in human B-cells.
The protooncogene product, Raf-1, is a serine/threonine kinase and has been implicated as an intermediate in signal transduction mechanisms. We examined neoplastic and normal B cells for phosphorylation and activation of Raf-1 protein in response to anti-immunoglobulin antibody (anti-Ig). Anti-Ig induced rapid phosphorylation of Raf-1 protein in both neoplastic B-cells of hairy cell leukemia and normal tonsillar B-cells which proliferated well in response to anti-Ig. The increase in phosphorylation was due primarily to an increase in phosphoserine. The immune complex kinase assay using Histone V-S as an exogenous substrate also showed an increase in Raf-1-associated kinase activity. An inhibitor of protein kinase C, H7, inhibited the proliferation as well as the Raf-1 phosphorylation in response to the proliferative signal of anti-Ig. Further, downregulation of protein kinase C by the treatment with 12-phorbol 13-myristic acid significantly abrogated the induction of Raf-1 phosphorylation. These results suggest that, in human B-cells, Raf-1 protein may be involved in the signal transduction pathway mediated by surface immunoglobulin, and that it may be, at least partially, phosphorylated by activated PKC.
Tamaki
T
T
Second Department of Medicine, Osaka University Medical School, Japan.
Kanakura
Y
Y
Kuriu
A
A
Ikeda
H
H
Mitsui
H
H
Yagura
H
H
Matsumura
I
I
Druker
B
B
Griffin
J D
JD
Kanayama
Y
Y
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D001402:B-Lymphocytes / Q000201:enzymology / Q000276:immunology / Q000502:physiology*; D002478:Cells, Cultured; D004789:Enzyme Activation; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D007700:Kinetics; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000276:immunology; D008213:Lymphocyte Activation; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D011519:Proto-Oncogenes; D011947:Receptors, Antigen, B-Cell / Q000502:physiology*; D015398:Signal Transduction
D007546:Isoquinolines; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D011947:Receptors, Antigen, B-Cell; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011494:Protein Kinases; D019908:Proto-Oncogene Proteins c-raf