Constitutive Association of SHP-1 with Leukocyte-Associated Ig-Like Receptor-1 in Human T Cells

Abstract

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 p85β 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.

The Mouse Homologue of the Leukocyte-Associated Ig-Like Receptor-1 Is an Inhibitory Receptor That Recruits Src Homology Region 2-Containing Protein Tyrosine Phosphatase (SHP)-2, but Not SHP-1

“…Crosslinking of LAIR-1 by mAb in vitro delivers a potent inhibitory signal that is capable of inhibiting cellular functions of NK cells, effector T cells, B cells, and dendritic cell precursors (3)(4)(5)(6). In agreement with the observed inhibitory capacity of LAIR-1, the molecule bears two ITIMs in its cytoplasmic tail and selectively recruits the tyrosine phosphatases SHP-1 (3,(7)(8)(9)(10) and SHP-2 (3,8,10) upon activation.…”

Leukocyte‐associated Ig‐like receptor‐1 has SH2 domain‐containing phosphatase‐independent function and recruits C‐terminal Src kinase

“…LAIR-1 has inhibitory function independent of SHP-1 and SHP-2 LAIR-1 recruits both SHP-1 and SHP-2 [4, [13][14][15]. To determine the contribution of each phosphatase in LAIR-1 signaling, we investigated the function of LAIR-1 in the chicken B cell line DT40.…”

“…In addition, LAIR-1 inhibits the differentiation of peripheral blood precursors towards dendritic cells [10] and induces apoptosis in myeloid leukemia cells [11,12]. LAIR-1 is phosphorylated by Src family kinases and recruits SHP-1 and SHP-2 [4, [13][14][15]. Recently, we identified a mouse homologue of LAIR-1, but unlike human LAIR-1, it does not recruit SHP-1, although it has a similar inhibitory capacity [16].…”

The inhibitory collagen receptor LAIR-1 (CD305)

“…Indeed, hLAIR-1 recruits SHP-1 and SHP-2 [5,28] but not SHIP [33]. Originally, SHP-1 was described as the major LAIR-1-interacting protein [17], and LAIR-1 constitutively associates with SHP-1 in Jurkat cells [34]. However, mLAIR-1 does not interact with SHP-1 and still is a functional inhibitory receptor [12].…”