Constitutive association of SHP-1 with leukocyte-associated Ig-like receptor-1 in human T cells.
The intracellular Src homology 2 (SH2) domain-containing protein tyrosine phosphatase (SHP-1) is a negative regulator of cell signaling and contributes to the establishment of TCR signaling thresholds in both developing and mature T lymphocytes. Although there is much functional data implicating SHP-1 as a regulator of TCR signaling, the molecular basis for SHP-1 activation in T lymphocytes is poorly defined. A modification of the yeast two-hybrid system was employed to identify in T cells phosphotyrosine-containing proteins capable of binding the SH2 domains of SHP-1. From this yeast tri-hybrid screen, the p85beta subunit of phosphatidylinositol 3-kinase and the immunoreceptor tyrosine-based inhibitory motif-containing receptors, leukocyte-associated Ig-like receptor-1 (LAIR-1) and programmed death-1 (PD-1), were identified. Coimmunoprecipitation studies demonstrated that the exclusive phosphotyrosine-containing protein associated with SHP-1 in Jurkat T cells under physiological conditions is LAIR-1. Significantly, this interaction is constitutive and was detected only in the membrane-enriched fraction of cell lysates. Ligand engagement of the SH2 domains of SHP-1 is a prerequisite to activation of the enzyme, and, consistent with an association with LAIR-1, SHP-1 was found to be constitutively active in unstimulated Jurkat T cells. Importantly, a constitutive interaction between LAIR-1 and SHP-1 was also detected in human primary T cells. These results illustrate the sustained recruitment and activation of SHP-1 at the plasma membrane of resting human T cells by an inhibitory receptor. We propose that this mechanism may exert a constitutive negative regulatory role upon T cell signaling.
Sathish
J G
JG
Department of Medicine, University of Wales College of Medicine, Cardiff, Wales, United Kingdom.
Johnson
K G
KG
Fuller
K J
KJ
LeRoy
F G
FG
Meyaard
L
L
Sims
M J
MJ
Matthews
R J
RJ
D020816:Amino Acid Motifs / Q000235:genetics / Q000276:immunology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D020134:Catalytic Domain / Q000235:genetics / Q000276:immunology; D002458:Cell Fractionation; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D051379:Mice; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D011971:Receptors, Immunologic / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D012503:Saponins / Q000494:pharmacology; D013601:T-Lymphocytes / Q000201:enzymology / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D018909:src Homology Domains / Q000235:genetics / Q000276:immunology*
D000911:Antibodies, Monoclonal; D003432:Cross-Linking Reagents; D010750:Phosphoproteins; D011971:Receptors, Immunologic; D012503:Saponins; C108073:leukocyte-associated immunoglobulin-like receptor 1