title: Src homology 2 domain-containing inositol-5-phosphatase 1 (SHIP1) negatively regulates TLR4-mediated LPS response primarily through a phosphatase activity- and PI-3K-independent mechanism.
abstract: Src homology 2 (SH2) domain-containing inositol-5-phosphatase 1 (SHIP1) plays important roles in negatively regulating the activation of immune cells primarily via the phosphoinositide 3-kinase (PI-3K) pathway by catalyzing the PI-3K product PtdIns-3,4,5P3 (phosphatidylinositol-3,4,5-triphosphate) into PtdIns-3,4P2. However, the role of SHIP1 in Toll-like receptor 4 (TLR4)-mediated lipopolysaccharide (LPS) response remains unclear. Here we demonstrate that SHIP1 negatively regulates LPS-induced inflammatory response via both phosphatase activity-dependent and -independent mechanisms in macrophages. SHIP1 becomes tyrosine phosphorylated and up-regulated upon LPS stimulation in RAW264.7 macrophages. SHIP1-specific RNA-interfering and SHIP1 overexpression experiments demonstrate that SHIP1 inhibits LPS-induced tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) production by negatively regulating the LPS-induced combination between TLR4 and myeloid differentiation factor 88 (MyD88); activation of Ras (p21(ras) protein), PI-3K, extracellular signal-regulated kinase 1/2 (ERK1/2), p38, and c-Jun NH2-terminal kinase (JNK); and degradation of IkappaB-alpha. SHIP1 also significantly inhibits LPS-induced mitogen-activated protein kinase (MAPK) activation in TLR4-reconstitited COS7 cells. Although SHIP1-mediated inhibition of PI-3K is dependent on its phosphatase activity, phosphatase activity-disrupted mutant SHIP1 remains inhibitory to LPS-induced TNF-alpha production. Neither disrupting phosphatase activity nor using the PI-3K pathway inhibitor LY294002 or wortmannin could significantly block SHIP1-mediated inhibition of LPS-induced ERK1/2, p38, and JNK activation and TNF-alpha production, demonstrating that SHIP1 inhibits LPS-induced activation of MAPKs and cytokine production primarily by a phosphatase activity- and PI-3K-independent mechanism.
authors.affiliation: Institute of Immunology, Second Military Medical University, Shanghai, People's Republic of China.
authors.forename: Huazhang
authors.initials: H
authors.lastname: An
authors.forename: Hongmei
authors.initials: H
authors.lastname: Xu
authors.forename: Minghui
authors.initials: M
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Zhou
authors.forename: Tao
authors.initials: T
authors.lastname: Feng
authors.forename: Cheng
authors.initials: C
authors.lastname: Qian
authors.forename: Runzi
authors.initials: R
authors.lastname: Qi
authors.forename: Xuetao
authors.initials: X
authors.lastname: Cao
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D015153:Blotting, Western; D019556:COS Cells; D002867:Chromones / Q000494:pharmacology; D003720:Densitometry; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D020672:I-kappa B Proteins / Q000378:metabolism; D047468:Immunoprecipitation; D007249:Inflammation; D000072181:Inositol Polyphosphate 5-Phosphatases; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D053594:Myeloid Differentiation Factor 88; D000072000:NF-KappaB Inhibitor alpha; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism / Q000502:physiology*; D010957:Plasmids / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D034622:RNA Interference; D011971:Receptors, Immunologic / Q000378:metabolism*; D013997:Time Factors; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000077191:Wortmannin; D018631:ras Proteins / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000730:Androstadienes; D000943:Antigens, Differentiation; D002867:Chromones; D020672:I-kappa B Proteins; D015850:Interleukin-6; D008070:Lipopolysaccharides; D009025:Morpholines; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C000606205:Nfkbia protein, mouse; D018129:Phosphatidylinositol Phosphates; D011971:Receptors, Immunologic; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C060974:phosphatidylinositol 3,4,5-triphosphate; C060980:phosphatidylinositol 3,4-diphosphate; D000072000:NF-KappaB Inhibitor alpha; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D008156:Luciferases; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; C000606433:Inpp5d protein, mouse; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; D000077191:Wortmannin