title: Syk-independent tyrosine phosphorylation and association of the protein tyrosine phosphatases SHP-1 and SHP-2 with the high affinity IgE receptor.
abstract: Aggregation of the high affinity IgE receptor (Fc epsilonRI), a member of the immune receptor family, results in the activation of protein tyrosine kinases and downstream signaling pathways. The two cytoplasmic Src homology 2 domain-containing protein tyrosine phosphatases, SHP-1 (also called SH-PTP1, PTP1C or HCP) and SHP-2 (also known as SH-PTP2, PTP1D, PTP2C, or Syp), are expressed in the RBL-2H3 rat mast cell line. Here we report that aggregation of Fc epsilonRI induced the tyrosine phosphorylation of both SHP-1 and SHP-2. This phosphorylation was independent of the presence of the protein tyrosine kinase Syk. Both SHP-1 and SHP-2 associated with Fc epsilonRI. Whereas SHP-1 was constitutively associated with the receptor, SHP-2 coprecipitated with Fc epsilonRI only after receptor aggregation. Fusion proteins containing either the full-length or the Src homology 2 domains of SHP-2 directly bound to the tyrosine-phosphorylated beta, but not the gamma, subunit of Fc epsilonRI. In the reciprocal experiments, synthetic phosphorylated peptides based on the immunoreceptor tyrosine-based activation motif of the beta, but not the gamma, subunit precipitated SHP-2. In contrast, neither fusion proteins nor synthetic peptides detected interaction between SHP-1 and Fc epsilonRI. In vitro, both SHP-1 and SHP-2 dephosphorylated tyrosine-phosphorylated beta and gamma subunits of Fc epsilonRI. Therefore, SHP-1 and SHP-2 associate with Fc epsilonRI by different mechanisms and can regulate the extent of the tyrosine phosphorylation of the receptor subunits. Thus, unlike other immune cells in which inhibitory molecules are recruited by accessory proteins, Fc epsilonRI bind molecules that both activate and inhibit signal transduction.
authors.affiliation: Laboratory of Immunology, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892, USA. tk51w@nih.gov
authors.forename: T
authors.initials: T
authors.lastname: Kimura
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: K
authors.initials: K
authors.lastname: Sagawa
authors.forename: K
authors.initials: K
authors.lastname: Sakaguchi
authors.forename: E
authors.initials: E
authors.lastname: Appella
authors.forename: R P
authors.initials: RP
authors.lastname: Siraganian
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004792:Enzyme Precursors / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000276:immunology* / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000276:immunology* / Q000378:metabolism; D051381:Rats; D011940:Receptor Aggregation; D017455:Receptors, IgE / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D000072377:Syk Kinase; D014443:Tyrosine / Q000378:metabolism
chemical_list: D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D017455:Receptors, IgE; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; C000606898:Syk protein, rat; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; C516727:Ptpn11 protein, rat; C509248:Ptpn6 protein, mouse; C509250:Ptpn6 protein, rat