High expression of inhibitory receptor SHPS-1 and its association with protein-tyrosine phosphatase SHP-1 in macrophages.
SHPS-1 (or SIRP) is a member of the immunoglobulin (Ig) superfamily abundantly expressed in neurons and other cell types. Within its cytoplasmic domain, it possesses at least two immunoreceptor tyrosine-based inhibitory motifs, which are targets for tyrosine phosphorylation and mediate the recruitment of SHP-2, an Src homology 2 (SH2) domain-containing protein-tyrosine phosphatase. Since other immunoreceptor tyrosine-based inhibitory motifs-containing receptors have critical roles in the negative regulation of hemopoietic cell functions, we wanted to examine the expression of SHPS-1 in cells of hematological lineages. By analyzing a panel of hemopoietic cell lines, evidence was provided that SHPS-1 is abundantly expressed in macrophages and, to a lesser extent, in myeloid cells. No expression was detected in T-cell or B-cell lines. Expression of SHPS-1 could also be documented in normal ex vivo peritoneal macrophages. Further studies showed that SHPS-1 was an efficient tyrosine phosphorylation substrate in macrophages. However, unlike in non-hemopoietic cells, tyrosine-phosphorylated SHPS-1 in macrophages associated primarily with SHP-1 and not SHP-2. Finally, our analyses allowed us to identify several isoforms of SHPS-1 in mouse cells. In part, this heterogeneity was due to differential glycosylation of SHPS-1. Additionally, it was caused by the production of at least two distinct shps-1 transcripts, coding for SHPS-1 polypeptides having different numbers of Ig-like domains in the extracellular region. Taken together, these findings indicate that SHPS-1 is likely to play a significant role in macrophages, at least partially as a consequence of its capacity to recruit SHP-1.
McGill Cancer Centre, McGill University, Montréal, Québec, Canada H3G 1Y6. andrev@med.mcgill.ca
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Veillette
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Thibaudeau
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Latour
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D000943:Antigens, Differentiation; D001854:Bone Marrow Cells / Q000201:enzymology / Q000378:metabolism; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary; D006031:Glycosylation; D047908:Intracellular Signaling Peptides and Proteins; D017737:Macrophages, Peritoneal / Q000201:enzymology / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011971:Receptors, Immunologic; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D017386:Sequence Homology, Amino Acid; D014443:Tyrosine / Q000378:metabolism
D000943:Antigens, Differentiation; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules; C501922:Sirpa protein, mouse; D011971:Receptors, Immunologic; D014443:Tyrosine; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; C509248:Ptpn6 protein, mouse; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases