Activation of src family kinases in human pre-B cells by IL-7.
IL-7 was identified originally as a specific pre-B cell growth factor. We have investigated its signal transduction mechanism by using the human pre-B cell line Nalm-6, and have found that it stimulates tyrosine phosphorylation of various proteins: pp27, pp43, pp54, pp64, pp78, pp90, pp105, and pp120. Antiphosphotyrosine immunoprecipitates from IL-7-stimulated Nalm-6 showed two major proteins of M(r) = 60,000 and 55,000, capable of autophosphorylation. Autophosphorylation was maximal 10 min after the cells were challenged with the cytokine. Antiphosphotyrosine immunoprecipitates from IL-7-stimulated cells also increased tyrosine phosphorylation of the exogenously added substrate histone H2B. Furthermore, by using a polyclonal anti-IL-7 receptor (IL-7R) Ab in Western blotting analysis, we observed that antiphosphotyrosine immunoprecipitates were associated with the IL-7R in a transient manner. These data indicate that the IL-7R associates with tyrosine-phosphorylated proteins as its amino acid sequence is devoid of a putative site of tyrosine phosphorylation. These results were confirmed as several 32P-labeled proteins were visualized after immunoprecipitation by using anti-IL-7R Ab. Anti-IL-7R immunoprecipitates from IL-7-stimulated cells revealed a unique band of M(r) = 60,000 associated with the receptor able to autophosphorylate in the presence of ATP and Mn2+. Hence, we identified p59fyn and p53/56lyn to be stimulated by IL-7. In contrast to p53/56lyn, p59fyn was found to be associated constitutively with the cloned IL-7R. These data emphasize the role of the src family in hematopoiesis.
Seckinger
P
P
Immunology Center of Marseille-Luminy, France.
Fougereau
M
M
D000595:Amino Acid Sequence; D001402:B-Lymphocytes / Q000166:cytology / Q000201:enzymology*; D002454:Cell Differentiation; D004789:Enzyme Activation; D006410:Hematopoiesis; D006801:Humans; D015851:Interleukin-7 / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D010750:Phosphoproteins / Q000378:metabolism; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051076:Proto-Oncogene Proteins c-fyn; D018123:Receptors, Interleukin / Q000737:chemistry / Q000378:metabolism*; D020395:Receptors, Interleukin-7; D015398:Signal Transduction; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D019061:src-Family Kinases
D015851:Interleukin-7; D010455:Peptides; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D018123:Receptors, Interleukin; D020395:Receptors, Interleukin-7; D019000:Phosphotyrosine; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C494957:FYN protein, human; D051076:Proto-Oncogene Proteins c-fyn; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases