Mutational analysis of the mechanism of negative regulation by SRC homology 2 domain-containing protein tyrosine phosphatase substrate-1 of phagocytosis in macrophages.
2006 (English)In: Journal of Immunology, ISSN 0022-1767, Vol. 177, no 5, 3123-32 p.Article in journal (Refereed) Published
Src homology 2 domain-containing protein tyrosine phosphatase substrate-1 (SHPS-1) is a transmembrane protein predominantly expressed in macrophages. The binding of CD47 on RBCs to SHPS-1 on macrophages is implicated in inhibition of phagocytosis of the former cells by the latter. We have now shown that forced expression in mouse RAW264.7 macrophages of a mutant version (SHPS-1-4F) of mouse SHPS-1, in which four tyrosine phosphorylation sites are replaced by phenylalanine, markedly promoted Fc gammaR-mediated phagocytosis of mouse RBCs or SRBCs. Forced expression of another mutant form (SHPS-1-deltaCyto) of mouse SHPS-1, which lacks most of the cytoplasmic region, did not promote such phagocytosis. Similarly, forced expression of a rat version of SHPS-1-4F, but not that of rat wild-type SHPS-1 or SHPS-1-deltaCyto, in RAW264.7 cells enhanced Fc gammaR-mediated phagocytosis of RBCs. Tyrosine phosphorylation of endogenous SHPS-1 as well as its association with Src homology 2 domain-containing protein tyrosine phosphatase-1 were not markedly inhibited by expression of SHPS-1-4F. Furthermore, the attachment of IgG-opsonized RBCs to RAW264.7 cells was markedly increased by expression of SHPS-1-4F, and this effect did not appear to be mediated by the interaction between CD47 and SHPS-1. These data suggest that inhibition by SHPS-1 of phagocytosis in macrophages is mediated, at least in part, in a manner independent of the transinteraction between CD47 and SHPS-1. In addition, the cytoplasmic region as well as tyrosine phosphorylation sites in this region of SHPS-1 appear indispensable for this inhibitory action of SHPS-1. Moreover, SHPS-1 may regulate the attachment of RBCs to macrophages by an as yet unidentified mechanism.
Place, publisher, year, edition, pages
2006. Vol. 177, no 5, 3123-32 p.
1-Phosphatidylinositol 3-Kinase/antagonists & inhibitors/metabolism, Animals, Antibodies; Monoclonal/immunology, Antigens; CD47/genetics/metabolism, Antigens; CD8/genetics/metabolism, Erythrocytes/metabolism, Gene Expression Regulation, Intracellular Signaling Peptides and Proteins/antagonists & inhibitors/metabolism, Macrophages/immunology/*metabolism, Mice, Mice; Knockout, Mutation/genetics, Phagocytosis, Phosphotyrosine/metabolism, Protein Kinase Inhibitors/pharmacology, Protein-Tyrosine Kinases/antagonists & inhibitors/metabolism, Rats, Receptors; IgG/immunology/metabolism, Receptors; Immunologic/chemistry/genetics/immunology/*metabolism, src Homology Domains
IdentifiersURN: urn:nbn:se:umu:diva-12277PubMedID: 16920950OAI: oai:DiVA.org:umu-12277DiVA: diva2:151948