Protein tyrosine phosphatase SHP-1 positively regulates TLR-induced IL-12p40 production in macrophages through inhibition of phosphatidylinositol 3-kinase.

SHP-1 is a cytoplasm protein tyrosine phosphatase expressed primarily in hematopoietic cells. In the immune system, SHP-1 plays critical roles in regulation of many receptor-mediated signaling cascades, and SHP-1 deficiency in mice causes spontaneous inflammation and autoimmunity. Here, we report a unique requirement for SHP-1 in interleukin-12/23 p40 (IL-12p40) production in response to Toll-like receptor (TLR) stimulation in macrophages. Bone marrow-derived macrophages (BMDMs) lacking significant SHP-1 activity display a profound defect in IL-12p40 synthesis in response to lipopolysaccharide, peptidoglycan, and synthetic TLR ligands, while producing normal amounts of other proinflammatory cytokines, such as TNFalpha and IL-6. Inhibition of SHP-1 function in wild-type BMDMs decreases IL-12p40, and expression of functional SHP-1 protein in mutant cells restores IL-12p40 production following TLR ligation. SHP-1 regulation of IL-12p40 transcription requires both its catalytic activity and phosphotyrosine binding by its N-terminal SH2 domain and is mediated via repression of, and interaction with, phosphatidylinositol 3-kinase, without affecting c-Rel activation. In contrast to normal NF-kappaB activation, SHP-1-defective me(v)/me(v) macrophages display a defect in nucleosome remodeling at the IL-12p40 promoter, and phosphatidylinositol 3-kinase inhibition significantly restores normal nucleosome remodeling in me(v)/me(v) macrophages. Thus, there is a critical role for the tyrosine phosphatase activity of SHP-1 for induction of IL-12p40 production in macrophages in response to TLR ligands, a novel mechanism for host regulation of a specific proinflammatory cytokine important in both innate and adaptive immunity.