Src homology 2 domain-containing protein tyrosine phosphatase (SHP) substrate-1 (SHPS-1) is a transmembrane protein that is expressed predominantly in macrophages. Its extracellular region interacts with the transmembrane ligand CD47 expressed on the surface of adjacent cells, and its cytoplasmic region binds the protein tyrosine phosphatases SHP-1 and SHP-2. Phagocytosis of IgG- or complement-opsonized RBCs by peritoneal macrophages derived from mice that express a mutant SHPS-1 protein that lacks most of the cytoplasmic region was markedly enhanced compared with that apparent with wild-type macrophages. This effect was not observed either with CD47-deficient RBCs as the phagocytic target or in the presence of blocking Abs to SHPS-1. Depletion of SHPS-1 from wild-type macrophages by RNA interference also promoted FcγR-mediated phagocytosis of wild-type RBCs. Ligation of SHPS-1 on macrophages by CD47 on RBCs promoted tyrosine phosphorylation of SHPS-1 and its association with SHP-1, whereas tyrosine phosphorylation of SHPS-1 was markedly reduced in response to cross-linking of FcγRs. Treatment with inhibitors of PI3K or of Syk, but not with those of MEK or Src family kinases, abolished the enhancement of FcγR-mediated phagocytosis apparent in macrophages from SHPS-1 mutant mice. In contrast, FcγR-mediated tyrosine phosphorylation of Syk, Cbl, or the γ subunit of FcR was similar in macrophages from wild-type and SHPS-1 mutant mice. These results suggest that ligation of SHPS-1 on macrophages by CD47 promotes the tyrosine phosphorylation of SHPS-1 and thereby prevents the FcγR-mediated disruption of the SHPS-1-SHP-1 complex, resulting in inhibition of phagocytosis. The inhibition of phagocytosis by the SHPS-1-SHP-1 complex may be mediated at the level of Syk or PI3K signaling.
A new langerin ؉ DC subset has recently been identified in murine dermis (langerin ؉ dDC), but the lineage and functional relationships between these cells and langerin ؉ epidermal Langerhans cells (LC) are incompletely characterized. Selective expression of the cell adhesion molecule EpCAM by LC allowed viable LC to be easily distinguished from langerin ؉ dDC in skin and lymphoid tissue and ex vivo as well. Differential expression of EpCAM and langerin revealed the presence of at least 3 distinct skin DC subsets. We determined that LC and langerin ؉ dDC exhibit different migratory capabilities in vitro and repopulate distinct anatomic compartments in skin at different rates after conditional depletion in vivo. Langerin ؉ dDC, in contrast to LC, did not require TGF1 for development. Carefully timed gene gun immunization studies designed to take advantage of the distinct repopulation kinetics of langerin ؉ dDC and LC revealed that langerin ؉ dDC were required for optimal production of -galactosidase-specific IgG2a/c and IgG2b in the acute phase. In contrast, immunization via LC-deficient skin resulted in persistent and strikingly reduced IgG1 and enhanced IgG2a Ab production. Our data support the concepts that LC and langerin ؉ dDC represent distinct DC subsets that have specialized functions and that LC are important immunoregulatory cells. The presence of at least 3 functionally distinct skin DC subsets may have particular relevance for vaccines that are administered epicutaneously.EpCAM ͉ gene gun ͉ langerin ͉ TGF-beta T he remarkable phenotypic heterogeneity of DC, both between and within certain tissues, has been long recognized. To date, however, it has been possible to clearly relate DC phenotype to DC function in only a few instances, even in mice. For example, plasmacytoid DC are recognized as the primary source of virus-induced type I IFN (1), CD8␣ ϩ lymph node DC are largely responsible for cross-presentation of cell-associated antigen to CD8 T cells (2-4), and 33D1-reactive (DCIR2 ϩ ) splenic DC (as compared with CD205 ϩ DC) preferentially stimulate CD4 T cells (5). Epidermal Langerhans cells (LC) represent perhaps the most striking example of an extensively studied tissue DC subpopulation whose function is incompletely understood.LC have long been thought to play pivotal roles in initiating immunity by acquiring antigens that are encountered in skin, migrating to draining LN after activation, and stimulating antigen-specific T cells (6). However, recent studies suggested that LC do not function as essential antigen-presenting cells for anti-viral immune responses (2, 7) or for contact hypersensitivity reactions (8-12) in established murine models. Studies of LC have been challenging, in part, because readily detectable cell surface proteins that are constitutively expressed by epidermal LC and LC that have emigrated from epidermis have not been well recognized. The C-type lectin langerin has been regarded as a pathognomonic LC marker, but recent studies suggest that this protein is present in at le...
Currently, there is no satisfactory treatment for Raynaud's phenomenon (RP) in systemic sclerosis (SSc). Recently, it has been reported that botulinum toxin A (BTX-A) injection was effective for the treatment of RP in SSc patients. The objective was to assess the efficacy and safety of BTX-A on RP in Japanese SSc patients. In the prospective, case series study, 10 Japanese SSc patients with RP received 10 U of BTX-A injections into the hand. The change in severity of RP, including the frequency of attacks/pain, color changes, duration time of RP and the severity of pain, was assessed by Raynaud's score and pain visual analog scale (VAS) at each visit during 16 weeks. The recovery of skin temperature 20 min after cold water stimulation was examined by thermography at baseline and 4 weeks after injection. The number of digital ulcers (DU) and adverse effects were assessed at each visit. BTX-A injection decreased Raynaud's score and pain VAS from 2 weeks after injection, and the suppressive effect was continued until 16 weeks after injection. Skin temperature recovery after cold water stimulation at 4 weeks after injection was significantly enhanced compared with that before injection. All DU in five patients were healed within 12 weeks after injection. Neither systemic nor local adverse effects were observed in all cases. We conclude that BTX-A injection significantly improved the activity of RP in SSc patients without any adverse events, suggesting that BTX-A may have possible long-term preventive and therapeutic potentials for RP in Japanese SSc patients.
SHPS-1 is a transmembrane protein whose extracellular region interacts with CD47 and whose cytoplasmic region undergoes tyrosine phosphorylation and thereby binds the protein tyrosine phosphatase SHP-2. Formation of this complex is implicated in regulation of cell migration by an unknown mechanism. A CD47-Fc fusion protein or antibodies to SHPS-1 inhibited migration of human melanoma cells or of CHO cells overexpressing SHPS-1. Overexpression of wild-type SHPS-1 promoted CHO cell migration, whereas expression of the SHPS-1-4F mutant, which lacks the phosphorylation sites required for SHP-2 binding, had no effect. Antibodies to SHPS-1 failed to inhibit migration of CHO cells expressing SHPS-1-4F. SHPS-1 ligands induced the dephosphorylation of SHPS-1 and dissociation of SHP-2. Antibodies to SHPS-1 also enhanced Rho activity and induced both formation of stress ®bers and adoption of a less polarized morphology in melanoma cells. Our results suggest that engagement of SHPS-1 by CD47 prevents the positive regulation of cell migration by this protein. The CD47± SHPS-1 system and SHP-2 might thus contribute to the inhibition of cell migration by cell±cell contact.
The efficacy and safety of botulinum toxin B (BTX-B) for treatment of Raynaud's phenomenon and digital ulcers in patients with systemic sclerosis was assessed. A total of 45 patients with systemic sclerosis who had Raynaud's phenomenon were blinded and divided randomly into 4 groups: a no-treatment control group, and 3 treatment groups, using 250, 1,000 or 2,000 international units (U) of BTX-B injections in the hand with more severe symptoms. Four weeks after injection, pain/numbness visual analogue scale scores and Raynaud's score in the groups treated with 1,000 and 2,000 U BTX-B were significantly lower than in the control group and the group treated with 250 U BTX-B. These beneficial effects were sustained until 16 weeks after the single injection. At 4 weeks after injection skin temperature recovery in the group treated with 2,000 U BTX-B was significantly improved. The numbers of digital ulcers in the groups treated with 1,000 and 2,000 U BTX-B were significantly lower than in the control group. In conclusion, 1,000 and 2,000 U BTX-B injections significantly suppressed the activity of Raynaud's phenomenon and digital ulcers in patients with SSc without serious adverse events.
SIRP (signal-regulatory protein ) is a transmembrane protein that is expressed in hematopoietic cells
Secretion of the powerful angiogenic factor MFG-E8 by pericytes can bypass the therapeutic effects of anti-VEGF therapy, but the mechanisms by which MGF-E8 acts are not fully understood. In this study, we investigated how this factor acts to promote the growth of melanomas which express it. We found that mouse bone marrow-derived mesenchymal stromal cells (MSC) expressed a substantial amount of MFG-E8. To assess its expression from this cell type we implanted melanoma cells and MSC derived from wild-type (WT) or MFG-E8-deficient (KO) into mice and monitored tumor growth. Tumor growth and M2 macrophages were each attenuated in subjects co-implanted with KO-MSC compared to WT-MSC. In both xenograft tumors and clinical specimens of melanoma, we found that MFG-E8 expression was heightened near blood vessels where MSC could be found. Through in vitro assays we confirmed that WT-MSC-conditioned medium was more potent at inducing M2 macrophage polarization, compared to KO-MSC-conditioned medium. VEGF and ET-1 expression in KO-MSC was significantly lower than in WT-MSC, correlating in vivo with reduced tumor growth and numbers of pericytes and M2 macrophages within tumors. Overall, our results suggested that MFG-E8 acts at two levels, by increasing VEGF and ET-1 expression in MSC and by enhancing M2 polarization of macrophages, to increase tumor angiogenesis.
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