Hierarchical phosphorylation of the TNF-alpha receptor, TNF-R1, by p42Mapk/Erk at basic Pro-directed kinase sites.
Phosphorylation of the TNF-alpha receptor TNF-R1 has been shown to differentially regulate receptor signaling and function and promote changes in its subcellular localization. Previous studies have shown that p42(mapk/erk2) phosphorylates Ser and Thr residues (T236, S240, S244, and S270) in the membrane proximal region of TNF-R1 and that mutation of ... these residues to Glu and Asp residues (TNF-R1.4D/E) mimics the effect of phosphorylation on receptor signaling and localization. In the present study, we investigated whether the initial phosphorylation of these residues by p42(mapk/erk2) promotes hierarchical phosphorylation of additional sites within the cytoplasmic domain of TNF-R1. This question was addressed by investigating the ability of the TNF-R1.4D/E mutant receptor to be phosphorylated in in vitro kinase assays using GST-mutant cytoplasmic domain fusion proteins as substrates and in intact cells following mutant receptor expression. In addition, we determined the location of the additional phosphorylation sites. Incubation of Sepharose bead-bound GST-TNF-R1(207)(-)(425).4D/E fusion protein with lysates containing activated p42(mapk/erk2) led to the phosphorylation of Ser and Thr residues in addition to the previously defined sites at T236, S240, S244, and S270. Deletional mutagenesis localized these residues to a stretch of 14 amino acids that encompasses three basic Pro-directed ([S/T]P) kinase consensus sequences located between residues S256 and T267. Point mutagenesis of T257, S262, and T267 to Ala residues indicated that these sites are targets of phosphorylation by p42(mapk/)(erk2). These findings support the conclusion that p42(mapk/erk2) promotes extensive phosphorylation of the membrane proximal region in a hierarchical fashion at both consensus and nonconsensus ERK-phosphorylation sites.
Mesh Terms:
Animals, Asparagine, COS Cells, Cell Membrane, Cells, Cultured, Cercopithecus aethiops, Consensus Sequence, Cytoplasm, Mice, Mice, Inbred C3H, Mitogen-Activated Protein Kinase 1, Mutagenesis, Site-Directed, Phosphorylation, Proline, Protein Structure, Tertiary, Protein-Serine-Threonine Kinases, Receptors, Tumor Necrosis Factor, Type I, Sequence Deletion, Serine, Tumor Necrosis Factor-alpha
Animals, Asparagine, COS Cells, Cell Membrane, Cells, Cultured, Cercopithecus aethiops, Consensus Sequence, Cytoplasm, Mice, Mice, Inbred C3H, Mitogen-Activated Protein Kinase 1, Mutagenesis, Site-Directed, Phosphorylation, Proline, Protein Structure, Tertiary, Protein-Serine-Threonine Kinases, Receptors, Tumor Necrosis Factor, Type I, Sequence Deletion, Serine, Tumor Necrosis Factor-alpha
Biochemistry
Date: May. 10, 2005
PubMed ID: 15865443
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