title: Localization of Src homology 2 domain-containing phosphatase 1 (SHP-1) to lipid rafts in T lymphocytes: functional implications and a role for the SHP-1 carboxyl terminus.
abstract: The protein tyrosine phosphatase Src homology 2 domain-containing phosphatase 1 (SHP-1) has previously been shown to be a negative regulator of signaling mediated via the TCR. A growing body of evidence indicates that the regulated localization of proteins within certain membrane subdomains, referred to as lipid rafts, is important for the successful transduction of signaling events downstream of the TCR. However, considerably less is known about the localization of negative regulators during these lipid raft-dependent signaling events. In this study we have investigated the subcellular localization of SHP-1 and its role in regulation of TCR-mediated signaling. Our studies demonstrate that in a murine T cell hybridoma as well as in primary murine thymocytes, a fraction of SHP-1 localizes to the lipid rafts, both basally and after TCR stimulation. Interestingly, although SHP-1 localized in the nonraft fractions is tyrosine phosphorylated, the SHP-1 isolated from the lipid rafts lacks the TCR-induced tyrosine phosphorylation, suggesting physical and/or functional differences between these two subpopulations. We identify a requirement for the C-terminal residues of SHP-1 in optimal localization to the lipid rafts. Although expression of SHP-1 that localizes to lipid rafts potently inhibits TCR-mediated early signaling events and IL-2 production, the expression of lipid raft-excluded SHP-1 mutants fails to elicit any of the inhibitory effects. Taken together these studies reveal a key role for lipid raft localization of SHP-1 in mediating the inhibitory effects on T cell signaling events.
authors.affiliation: Department of Microbiology and The Beirne Carter Center for Immunology Research, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Vicki C J
authors.initials: VC
authors.lastname: Fawcett
authors.forename: Ulrike
authors.initials: U
authors.lastname: Lorenz
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001666:Binding Sites, Antibody; D002460:Cell Line; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D047908:Intracellular Signaling Peptides and Proteins; D021962:Membrane Microdomains / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D017434:Protein Structure, Tertiary; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000037:antagonists & inhibitors / Q000502:physiology; D017384:Sequence Deletion; D015398:Signal Transduction / Q000276:immunology; D013347:Subcellular Fractions / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology* / Q000201:enzymology*; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains / Q000235:genetics
chemical_list: D000911:Antibodies, Monoclonal; D007376:Interleukin-2; D047908:Intracellular Signaling Peptides and Proteins; D010446:Peptide Fragments; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D014443:Tyrosine; D054645:Protein Phosphatase 1; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C509248:Ptpn6 protein, mouse