Anti-IgM-mediated growth inhibition of a human B lymphoma cell line is independent of phosphatidylinositol turnover and protein kinase C activation and involves tyrosine phosphorylation.
The RL cell line is an EBV-negative, surface IgM, IgD-positive B lymphoma line, which is significantly growth arrested in the presence of acrylamide-linked antibodies to the surface IgM receptor. We demonstrate here that activation of protein kinase C (PKC) with PMA abrogates anti-IgM-induced phosphoinositide turnover and Ca2+ mobilization; however, growth inhibition is not affected. In addition, inhibitors of PKC are unable to reverse the anti-IgM-mediated growth inhibition. Two-dimensional gel electrophoresis reveals a different pattern of protein phosphorylation after treatment of RL with PMA or anti-IgM. These data strongly suggest that anti-IgM-induced growth inhibition does not rely on phospholipase C-mediated phosphoinositide turnover, Ca2+ mobilization, or PKC activation. On the other hand, the phosphatase inhibitor orthovanadate results in an augmentation of proteins phosphorylated on tyrosine and the growth inhibition which follows anti-IgM treatment. Furthermore, protein tyrosine kinase inhibitors, genistein and herbimycin A, are able to reverse the anti-IgM-induced inhibition of growth. These data demonstrate that multiple signaling pathways are activated by the interaction of anti-IgM with its ligand, and suggest that tyrosine kinase activation is a critical component of the inhibitory response.
Biological Carcinogenesis and Development Program, Program Resources, Inc./DynCorp, Frederick, MD.
M
M
Beckwith
W J
WJ
Urba
D K
DK
Ferris
C E
CE
Freter
D B
DB
Kuhns
C M
CM
Moratz
D L
DL
Longo
D000888:Antibodies, Anti-Idiotypic / Q000276:immunology*; D004789:Enzyme Activation; D006801:Humans; D006868:Hydrolysis; D007075:Immunoglobulin M / Q000276:immunology*; D016393:Lymphoma, B-Cell / Q000473:pathology*; D010716:Phosphatidylinositols / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism*
D000888:Antibodies, Anti-Idiotypic; D007075:Immunoglobulin M; D010716:Phosphatidylinositols; D014443:Tyrosine; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate