Identification of complex formation between two intracellular tyrosine kinase substrates: human c-Rel and the p105 precursor of p50 NF-kappa B.
Immune complexes of the product of the c-rel protooncogene and of p105, the p50 NF-kappa B precursor, isolated from human T-lymphoblastoid cell lines are comprised of multiple proteins. Only p105 and human c-Rel (hc-Rel) are common to complexes precipitated with antiserum directed against either p105 or hc-Rel. Both proteins are inducible by phytohemagglutinin (PHA) and phorbol 12-myristate 13-acetate (PMA) and their subcellular distribution is affected by this induction. We demonstrate that the Rel immune complex contains a protein with a molecular weight in the 40 kDa range (p40) which apparently is exclusively cytoplasmic. We were not able to detect p40 in the p105 immune complex, though hc-Rel is present. This indicates that hc-Rel exists in different multi-protein complexes and fits a model of functional regulation mediated by differential protein-protein interaction. We also demonstrate considerable isoform diversity of both hc-Rel and p105. We show that this heterogeneity is, in part, the result of phosphorylation. Furthermore, we demonstrate that p105 and hc-Rel are tyrosine kinase substrates. This finding indicates a role for both proteins in intracellular signal transduction pathways which are modulated by modification of their phosphorylation status.
Neumann
M
M
Freeman Laboratory of Cancer Cell Biology, Cold Spring Harbor Laboratory, New York 11724.
Tsapos
K
K
Scheppler
J A
JA
Ross
J
J
Franza
B R
BR
D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D010835:Phytohemagglutinins; D011498:Protein Precursors / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D020569:Proto-Oncogene Proteins c-rel; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D016328:NF-kappa B; D010835:Phytohemagglutinins; D011498:Protein Precursors; D011518:Proto-Oncogene Proteins; D020569:Proto-Oncogene Proteins c-rel; D011505:Protein-Tyrosine Kinases; D013755:Tetradecanoylphorbol Acetate