Characterization of inhibitory signaling motifs of the natural killer cell receptor Siglec-7: attenuated recruitment of phosphatases by the receptor is attributed to two amino acids in the motifs.
Siglec-7 (p75/AIRM1) is an inhibitory receptor on human natural killer cells (NK cells) and monocytes. The cytoplasmic domain of Siglec-7 contains two signaling motifs: a membrane-proximal immunoreceptor tyrosine-based inhibitory motif (ITIM) (Ile435-Gln-Tyr-Ala-Pro-Leu440) and a membrane-distal motif (Asn458-Glu-Tyr-Ser-Glu-Ile463). We report here that, upon pervanadate (PV) treatment, Siglec-7 recruited the protein tyrosine ... phosphatases Src homology-2 (SH2) domain-containing protein-tyrosine phosphatase-1 (SHP-1) and SHP-2 less efficiently than did other inhibitory receptors such as Siglec-9 and leukocyte-associated Ig-like receptor (LAIR-1). Alignment of the amino acid sequences of the two Siglecs revealed only three amino acids difference in these motifs. To identify the amino acid(s) critical to recruitment efficiency, we prepared a series of Siglec-7-based mutants in which each of the three amino acids were replaced with the corresponding one of Siglec-9 (I435L, P439S, and N458T mutants). P439S and N458T mutants showed pronounced enhancement of SHP recruitment, but I435L mutant had little effect. A double mutant (P439S, N458T) or triple mutant (I435L, P439S, N458T) recruited SHPs as much as did Siglec-9, indicating that Pro439 in the proximal motif and Asn458 in the distal motif of Siglec-7 attenuate its ability to recruit phosphatases. These amino acids appeared to affect not only phosphatase recruitment but also the subsequent attenuation of Syk phosphorylation.
Mesh Terms:
Amino Acid Motifs, Amino Acid Sequence, Antigens, Differentiation, Myelomonocytic, Base Sequence, Cell Line, DNA Primers, Flow Cytometry, Humans, Intracellular Signaling Peptides and Proteins, Lectins, Molecular Sequence Data, Protein Phosphatase 1, Protein Tyrosine Phosphatase, Non-Receptor Type 11, Protein Tyrosine Phosphatase, Non-Receptor Type 6, Protein Tyrosine Phosphatases, SH2 Domain-Containing Protein Tyrosine Phosphatases, Signal Transduction
Amino Acid Motifs, Amino Acid Sequence, Antigens, Differentiation, Myelomonocytic, Base Sequence, Cell Line, DNA Primers, Flow Cytometry, Humans, Intracellular Signaling Peptides and Proteins, Lectins, Molecular Sequence Data, Protein Phosphatase 1, Protein Tyrosine Phosphatase, Non-Receptor Type 11, Protein Tyrosine Phosphatase, Non-Receptor Type 6, Protein Tyrosine Phosphatases, SH2 Domain-Containing Protein Tyrosine Phosphatases, Signal Transduction
Glycobiology
Date: Jul. 01, 2005
PubMed ID: 15703304
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