RESUMO
Toll-like receptor (TLR) family members recognize specific molecular patterns within pathogens. Signaling through TLRs results in a proximal event that involves direct binding of adaptor proteins to the receptors. We observed that TIRAP/Mal, an adaptor protein for TLR2 and TLR4, binds protein kinase Cdelta (PKCdelta). TIRAP/Mal GST-fusion protein and a TIRAP/Mal antibody were able to precipitate PKCdelta from rat peritoneal macrophage and THP1 cell lysates. Truncation mutants of TIRAP/Mal showed that the TIR domain of TIRAP/Mal is responsible for binding. TLR2- and TLR4-mediated phosphorylation of p38 MAPK, IKK, and IkappaB in RAW264.7 cells were abolished by depletion of PKCdelta. These results suggest that PKCdelta binding to TIRAP/Mal promotes TLR signaling events.
Assuntos
Glicoproteínas de Membrana/metabolismo , Proteína Quinase C-delta/metabolismo , Receptores de Interleucina-1/metabolismo , Transdução de Sinais , Receptores Toll-Like/metabolismo , Animais , Ativação Enzimática/efeitos dos fármacos , Feminino , Glutationa Transferase/metabolismo , Humanos , Quinase I-kappa B/metabolismo , Lipopolissacarídeos/farmacologia , Glicoproteínas de Membrana/química , Camundongos , Fator 88 de Diferenciação Mieloide/metabolismo , NF-kappa B/metabolismo , Ligação Proteica/efeitos dos fármacos , Proteína Quinase C/antagonistas & inibidores , Proteína Quinase C-delta/antagonistas & inibidores , Inibidores de Proteínas Quinases/farmacologia , Estrutura Terciária de Proteína/efeitos dos fármacos , Ratos , Receptores de Interleucina-1/química , Proteínas Recombinantes de Fusão/metabolismo , Transdução de Sinais/efeitos dos fármacos , Receptores Toll-Like/imunologia , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Lagerstroemin, an ellagitannin isolated from the leaves of Lagerstroemia speciosa (L.) Pers. (Lythraceae), was examined for its biological activities. In rat adipocytes, the compound increased the rate of glucose uptake and decreased the isoproterenol-induced glycerol release. In Chinese hamster ovary cells expressing human insulin receptors, it increased the Erk activity. These insulin-like actions were accompanied by the increased tyrosine-phosphorylation of the beta-subunit of the insulin receptors. Tryptic digestion of the extracellular sites of the insulin receptors markedly increased the effective concentrations of insulin without changing those of lagerstroemin. Thus lagerstroemin was considered to cause its insulin-like actions by a mechanism different from that employed by insulin.
Assuntos
Taninos Hidrolisáveis , Lagerstroemia , Receptor de Insulina/metabolismo , Taninos/farmacologia , Adipócitos/efeitos dos fármacos , Adipócitos/metabolismo , Animais , Células CHO , Cricetinae , Relação Dose-Resposta a Droga , Humanos , Insulina/farmacologia , Masculino , Folhas de Planta , Ratos , Ratos Wistar , Receptor de Insulina/agonistasRESUMO
Toll-like receptor (TLR)-mediated recognition of pathogens represents one of the most important mechanisms of innate immunity. A proximal signaling event of TLR is the direct binding of an adaptor protein MyD88 to TLR and recruitment of the IL-1R-associated kinase (IRAK). In the present study, we examined the effect of several TLR ligands on protein tyrosine phosphorylation in rat macrophages. Macrophage-activating lipopeptide-2 kDa (MALP2) and lipoarabinomannan were used as activators of TLR2, while lipopolysaccharides (LPS) and lipoteichoic acid were used as TLR4 ligands. All these ligands induced tyrosine phosphorylation of proline-rich tyrosine kinase 2 (Pyk2) and its substrate paxillin, an integrin-associated focal adhesion adaptor protein, in the macrophages. PP2, an inhibitor of Src family tyrosine kinases, prevented the TLR-induced phosphorylation of paxillin and Pyk2 without affecting TLR-induced IRAK activation. MALP2 failed to induce paxillin phosphorylation in the macrophages from MyD88-knockout mice. In contrast, the effect of LPS weakened, but was still observed even in the MyD88-deficient cells. Thus, TLR regulate the function of paxillin in an Src family-dependent mechanism through both MyD88-dependent and MyD88-independent pathways.
