Phosphorylation and recruitment of Syk by immunoreceptor tyrosine-based activation motif-based phosphorylation of tamalin.
Tamalin is a scaffold protein that forms a multiple protein assembly including metabotropic glutamate receptors (mGluRs) and several postsynaptic and protein-trafficking scaffold proteins in distinct mode of protein-protein association. In the present investigation, we report that tamalin possesses a typical immunoreceptor tyrosine-based activation motif (ITAM), which enables Syk kinase to ... be recruited and phosphorylated by the Src family kinases. Coimmunoprecipitation analysis of rat brain membrane fractions showed that tamalin is present in a multimolecular protein assembly comprising not only mGluR1 but also c-Src, Fyn, and a protein phosphatase, SHP-2. The protein association of both tamalin and c-Src, as determined by truncation analysis of mGluR1 in COS-7 cells, occurred at the carboxyl-terminal tail of mGluR1. Mutation analysis of tyrosine with phenylalanine in COS-7 cells revealed that paired tyrosines at the ITAM sequence of tamalin are phosphorylated preferentially by c-Src and Fyn, and this phosphorylation can recruit Syk kinase and enables it to be phosphorylated by the Src family kinases. The phosphorylated tyrosines at the ITAM sequence of tamalin were highly susceptible to dephosphorylation by protein-tyrosine phosphatases in COS-7 cells. Importantly, tamalin was endogenously phosphorylated and associated with Syk in retinoic acid-treated P19 embryonal carcinoma cells that undergo neuron-like differentiation. The present investigation demonstrates that tamalin is a novel signaling molecule that possesses a PDZ domain and a PDZ binding motif and mediates Syk signaling in an ITAM-based fashion.
Mesh Terms:
Alternative Splicing, Amino Acid Motifs, Animals, Brain, COS Cells, Carrier Proteins, Cell Line, Cell Membrane, DNA, DNA Mutational Analysis, DNA, Complementary, Enzyme Precursors, Immunoblotting, Intracellular Signaling Peptides and Proteins, Membrane Proteins, Models, Genetic, Mutation, Phenylalanine, Phosphorylation, Precipitin Tests, Protein Structure, Tertiary, Protein Tyrosine Phosphatase, Non-Receptor Type 11, Protein Tyrosine Phosphatases, Protein-Tyrosine Kinases, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-fyn, Rats, Signal Transduction, Transfection, Tretinoin, Tyrosine, src-Family Kinases
Alternative Splicing, Amino Acid Motifs, Animals, Brain, COS Cells, Carrier Proteins, Cell Line, Cell Membrane, DNA, DNA Mutational Analysis, DNA, Complementary, Enzyme Precursors, Immunoblotting, Intracellular Signaling Peptides and Proteins, Membrane Proteins, Models, Genetic, Mutation, Phenylalanine, Phosphorylation, Precipitin Tests, Protein Structure, Tertiary, Protein Tyrosine Phosphatase, Non-Receptor Type 11, Protein Tyrosine Phosphatases, Protein-Tyrosine Kinases, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-fyn, Rats, Signal Transduction, Transfection, Tretinoin, Tyrosine, src-Family Kinases
J. Biol. Chem.
Date: Jul. 30, 2004
PubMed ID: 15173175
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