Dual Functional Roles for the X-linked Lymphoproliferative Syndrome Gene Product SAP/SH2D1A in Signaling through the Signaling Lymphocyte Activation Molecule (SLAM) Family of Immune Receptors

Liu, Chengjun; Iosef, Cristiana; Jia, Christina Y.H.; Han, V. K. M.; Li, Shawn Shun‐Cheng

doi:10.1074/jbc.m206649200

Cited by 80 publications

(75 citation statements)

References 29 publications

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“…For example, the SH2 domain protein SAP binds simultaneously to both the Fyn SH3 domain and a Tyr phosphorylation motif in the T-cell co-receptor SLAM using two distinct sites, and in so doing, it serves a role of an adaptor for Fyn and SLAM (35)(36)(37). The Numb PTBi domain may bind to both the NPAY motif and the PDZ1 domain in an analogous manner.…”

Section: Discussionmentioning

confidence: 99%

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A Novel PTB-PDZ Domain Interaction Mediates Isoform-specific Ubiquitylation of Mammalian Numb

Nie

McGlade

2004

Journal of Biological Chemistry

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LNX was originally cloned as a Numb PTB-binding molecule, and it was subsequently found to act as a RING finger-type E3 ubiquitin ligase for the ubiquitylation and degradation of mNumb. Numb is a PTB domaincontaining protein that functions as an intrinsic determinant of cell fate in asymmetric cell division. In mammals, four protein isoforms arise from alternative mRNA splicing. Here we report that while all four protein isoforms bind to LNX, only p72 and p66 Numb isoforms are ubiquitylated and degraded. The p72 and p66 Numb proteins differ from the other two isoforms by the presence of an 11-amino acid sequence insert in the PTB domain (PTBi). We demonstrate that the isoform-specific ubiquitylation of mNumb is due to a novel interaction between the first PDZ domain (PDZ1) of LNX and the PTBi variant. Deletion of LNX PDZ1 domain resulted in loss of ubiquitylation and subsequent degradation of the PTBi form of Numb. Interestingly efficient PTBi ubiquitylation not only depends on association with the LNX PDZ1 domain but also requires binding to the canonical PTB-binding motif NPAY in LNX. Thus two distinct modes of PTBi-mediated interaction with LNX work in concert to allow the effective and specific degradation of the p72 and p66 isoforms of mNumb.Controlled protein degradation mediated by ubiquitin-dependent proteolysis underlies the regulation of many critical biological events during the life and death of a cell as well as in health and disease (1). Ubiquitylation of a target protein is achieved through a cascade involving at least three enzymes, namely E1, 1 E2, and E3, which activate and transfer ubiquitin to the substrate in a sequential manner. Polyubiquitylated proteins are recognized by the 26 S proteasome and are subsequently degraded into small peptides (2, 3).E3 ubiquitin ligases are responsible for the specific recognition of a multitude of substrates. Two major classes of E3 have been identified to date characterized by the presence of either a HECT (homologous to E6-AP carboxyl terminus) domain or a RING finger domain. HECT-type E3s catalyze ubiquitylation of a substrate by first forming an E3-ubiquitin thioester intermediate followed by the direct transfer of ubiquitin onto the substrate. On the other hand, RING-type E3s function as scaffolds that bring together the E2 and the target substrate to facilitate efficient transfer of the activated ubiquitin moiety from the E2 to the substrate protein (4). In addition to HECT or RING finger domains, E3 ligases also contain protein interaction modules for substrate recognition. Diversity in the repertoire of E3 substrate selection is achieved by linking a variety of protein interaction modules to the HECT or RING domains. For example, many HECT domain-containing E3s share the WW domain, which is involved in protein-protein interactions and has a role in targeting substrates containing a PY motif for ubiquitylation (5, 6). The RING-type E3 family is composed of two distinct groups, single and multisubunit proteins. Single subunit E3s such as c-Cbl contain...

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Section: Discussionmentioning

confidence: 99%

“…Fluorescein labeling and polarization measurements were performed as described previously (37). Equilibrium binding isotherms were obtained by titrating a fixed concentration of fluorescent PDZ1 with an increasing amount of purified PTBi or PTBo protein (as GST fusions).…”

Section: Methodsmentioning

confidence: 99%

A Novel PTB-PDZ Domain Interaction Mediates Isoform-specific Ubiquitylation of Mammalian Numb

Nie

McGlade

2004

Journal of Biological Chemistry

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“…For transient transfection, the cells were allowed to grow to 50 -70% confluence in 10-cm dishes, and ϳ 5 g of DNA was added with LipofectAMINE (Invitrogen) in serum-free medium. GST pull-down and co-immunoprecipitation experiments were carried out essentially as described (38).…”

Section: Expression Library Screening and Cloning Of Nip-the Drosophilamentioning

confidence: 99%

“…The labeled peptide was cleaved off the resin using trifluoroacetic acid and purified with high pressure liquid chromatography using a Luna C18 column (Phenomonnex). Fluorescence polarization measurements were conducted using established procedures as previously reported (38).…”

Section: Expression Library Screening and Cloning Of Nip-the Drosophilamentioning

confidence: 99%

A Novel Transmembrane Protein Recruits Numb to the Plasma Membrane during Asymmetric Cell Division

Qin

Percival‐Smith

Liu

et al. 2004

Journal of Biological Chemistry

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Numb, an evolutionarily conserved cell fate-determining factor, plays a pivotal role in the development of Drosophila and vertebrate nervous systems. Despite lacking a transmembrane segment, Numb is associated with the cell membrane during the asymmetric cell division of Drosophila neural precursor cells and is selectively partitioned to one of the two progeny cells from a binary cell division. Numb contains an N-terminal phosphotyrosine-binding (PTB) domain that is essential for both the asymmetric localization and the fate specification function of Numb. We report here the isolation and characterization of a novel PTB domain-binding protein, NIP (Numb-interacting protein). NIP is a multipass transmembrane protein that contains two PTB domainbinding, NXXF motifs required for the interaction with Numb. In dividing Drosophila neuroblasts, NIP is colocalized to the cell membrane with Numb in a basal cortical crescent. Expression of NIP in Cos-7 cells recruited Numb from the cytosol to the plasma membrane. This recruitment of Numb to membrane by NIP was dependent on the presence of at least one NXXF site. In Drosophila Schneider 2 cells, NIP and Numb were colocalized at the plasma membrane. Inhibition of NIP expression by RNA interference released Numb to the cytosol. These results suggest that a direct protein-protein interaction between NIP and Numb is necessary and sufficient for the recruitment of Numb to the plasma membrane. Recruitment of Numb to a basal cortical crescent in a dividing neuroblast is essential for Numb to function as an intrinsic cell fate determinant.Asymmetric cell division, which can involve extrinsic and/or intrinsic factors, is a fundamental mechanism of generating cell diversity during the development of complex organisms (1, 2). Extrinsic factors such as Delta and its receptor Notch (3, 4) function in cell-cell communication to specify the fate of cells (5-7). Asymmetric determinants are intrinsic factors that are selectively segregated into one of the two daughter cells when a cell divides (2,8). Consequently, the sibling cell that inherits the asymmetric determinants adopts a different fate from the one that does not. Numb is a member of a growing family of proteins that also includes Prospero, Miranda, Inscuteable, and PON (partner of numb) (9 -14), which act as intrinsic determinants in asymmetric cell division. These proteins were identified through their requirement in the development of Drosophila peripheral and central nervous systems. The external sensory organ in Drosophila is composed of two outer (hair and socket) cells and three inner (sheath, glial, and neuron) cells, which are derived from a single sensory organ precursor through three consecutive asymmetric cell divisions. Numb is selectively partitioned to one of the two daughter cells at each binary division (15). Numb is also required for the development of the central nervous system (16 -18). During delaminating from the neuroectoderm and asymmetric division of a neuroblast, Numb, Prospero, and several other proteins...

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“…The cytoplasmic tail of 2B4 contains four immunoreceptor tyrosinebased switch motifs (ITSM). Once phosphorylated, the immunoreceptor tyrosine-based switch motifs of 2B4 can recruit several signaling molecules including SLAMassociated protein (SAP), SHP-1, SHP-2, SHIP, EAT-2 (also called SH2D1B), PI3 K and Csk [3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Modulation of 2B4 (CD244) activity and regulated SAP expression in human NK cells

et al. 2006

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The adapter protein SAP is important for the signal transduction of the family of SLAMrelated receptors (SRR), which have important immune-modulating functions. The importance of SAP and SRR for a functional immune reaction becomes obvious in patients suffering from X-linked lymphoproliferative disease, which is characterized by non-functional SAP. Here we investigate the regulation of SAP expression in human NK cells. We demonstrate that SAP mRNA expression and protein levels are low in freshly isolated resting NK cells. IL-2 stimulation leads to an up-regulation of SAP expression, which can be enhanced by IL-12, the stimulation of TLR3 by polyinosinic-polycytidylic acid (poly(I:C))and to a lesser extent by IFN-a. EAT-2, a SAP-related adapter protein, is already detectable in resting NK cells and does not change its expression after IL-2 stimulation. The regulation of SAP has functional consequences for the stimulation of NK cell cytotoxicity by 2B4. In resting NK cells, 2B4 stimulation can only enhance NK cell lysis when co-triggered with other activating NK cell receptors. In IL-2-activated NK cells with high SAP expression the triggering of 2B4 alone is sufficient to induce NK cell cytotoxicity, demonstrating a correlation between the regulated SAP expression and the function of 2B4. IntroductionNatural killer (NK) cells represent the first line of defense against stressed, virally infected and malignant cells. The major effector functions of NK cells are cytotoxicity and cytokine release. These responses are regulated by different activating and inhibitory surface receptors [1]. One emerging group of activating NK cell receptors encompasses cell surface molecules of the recently identified family of signaling lymphocyte activation molecule (SLAM)-related receptors (SRR) [2]. This group of Ig-like receptors includes 2B4 (CD244), SLAM (CD150), CD84, Ly-9 (CD229), NTB-A (Ly-108) and CD2-like receptor activating cytotoxic cells (CRACC, CS-1, CD319). 2B4 is expressed on human NK cells, cytotoxic CD8 + T cells, cd T cells and on resting monocytes, eosinophils and basophiles. The cytoplasmic tail of 2B4 contains four immunoreceptor tyrosinebased switch motifs (ITSM). Once phosphorylated, the immunoreceptor tyrosine-based switch motifs of 2B4 can recruit several signaling molecules including SLAMassociated protein (SAP), SHP-1, SHP-2, SHIP, EAT-2 (also called SH2D1B), .The ligand of 2B4 is CD48, a member of the CD2 family of Ig-like receptors, which is expressed on many cell types of the hematopoietic system [8,9] [13]. SAP can function as a natural blocker of SH2 domain-mediated interactions and might therefore prevent the interactions between SHP-2 and possibly SHP-1 with 2B4 [3,7,14], explaining why 2B4 can mediate inhibitory signals in the absence of SAP. SAP is also involved in the positive signaling by 2B4 and other SRR by recruiting and activating the Src family kinase Fyn through an unusual SH2-SH3 domain interaction [15,16].Infection with murine CMV or lymphocytic choriomeningitis virus leads to an up-regu...

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Dual Functional Roles for the X-linked Lymphoproliferative Syndrome Gene Product SAP/SH2D1A in Signaling through the Signaling Lymphocyte Activation Molecule (SLAM) Family of Immune Receptors

Cited by 80 publications

References 29 publications

A Novel PTB-PDZ Domain Interaction Mediates Isoform-specific Ubiquitylation of Mammalian Numb

A Novel PTB-PDZ Domain Interaction Mediates Isoform-specific Ubiquitylation of Mammalian Numb

A Novel Transmembrane Protein Recruits Numb to the Plasma Membrane during Asymmetric Cell Division

Modulation of 2B4 (CD244) activity and regulated SAP expression in human NK cells

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