Differential Effects of Tautomycetin and Its Derivatives on Protein Phosphatase Inhibition, Immunosuppressive Function and Antitumor Activity

In the present work, we studied the structure-activity relationship (SAR) of tautomycetin (TMC) and its derivatives. Further, we demonstrated the correlation between the immunosuppressive fuction, anticancer activity and protein phosphatase type 1 (PP1) inhibition of TMC and its derivatives. We have prepared some TMC derivatives via combinatorial biosynthesis, isolation from fermentation broth or chemical degradation of TMC. We found that the immunosuppressive activity was correlated with anticancer activity for TMC and its analog compounds, indicating that TMC may home at the same targets for its immunosuppressive and anticancer activities. Interestingly, TMC-F1, TMC-D1 and TMC-D2 all retained significant, albeit reduced PP1 inhibitory activity compared to TMC. However, only TMC-D2 showed immunosuppressive and anticancer activities in studies carried out in cell lines. Moreover, TMC-Chain did not show any significant inhibitory activity towards PP1 but showed strong growth inhibitory effect. This observation implicates that the maleic anhydride moiety of TMC is critical for its phosphatase inhibitory activity whereas the C1-C18 moiety of TMC is essential for the inhibition of tumor cell proliferation. Furthermore, we measured in vivo phosphatase activities of PP1 in MCF-7 cell extracts treated with TMC and its related compounds, and the results indicate that the cytotoxicity of TMC doesn't correlate with its in vivo PP1 inhibition activity. Taken together, our study suggests that the immunosuppressive and anticancer activities of TMC are not due to the inhibition of PP1. Our results provide a novel insight for the elucidation of the underlying molecular mechanisms of TMC's important biological functions.

Effects of Tautomycetin on the Proliferation and Fibronectin Secretion in Vascular Smooth Muscle Cells and Glomerular Mesangial Cells / 대한이식학회지

PURPOSE: Proliferation and extracellular matrix (ECM) accumulation in the vascular smooth muscle cell (VSMC) and glomerular mesangial cell (MC) play key roles in the development and the progression of transplant glomerulosclerosis and chronic allograft nephropathy. Tautomycetin (TMC), a newly developed immunosuppressive agent, induces T-lymphocyte apoptosis through the inhibition of tyrosine kinase and protein phosphatase 1. We examined the effects of TMC on platelet-derived growth factor (PDGF)-induced proliferation and ECM synthesis in cultured VSMCs and MCs of Sprague- Dawley rats, and investigated the molecular mechanisms that are involved. METHODS: Different concentrations of TMC were administered 1 hour before the addition of PDGF 10 ng/mL into the growth-arrested and synchronized cells. Cell proliferation was assessed by methylthiazoletetrazolium (MTT) assay. Caspase-3 cleavage, fibronectin secretion, and the activation of Akt, ERK, and p38 MAPK were assessed by Western blot analysis, respectively. RESULTS: PDGF 10 ng/ mL increased cell proliferation, fibronectin secretion, and the activation of Akt, ERK, and p38 MAPK in both VSMCs and MCs. In both cultured cells, TMC at above 1 microgram/mL significantly reduced basal MTT and increased cleavage caspase-3 in a dose-dependent manner. TMC at 100 ng/mL decreased the PDGF-induced VSMC and MC proliferation without cytotoxicity. However, fibronectin secretion and the activation of Akt, ERK, and p38 MAPK were not affected at this low concentration of TMC, respectively. CONCLUSION: The present data demonstrated that low-dose TMC reduced PDGF-induced VSMC and MC proliferation without affecting the fibronectin secretion and cellular kinase activation.

Immunosuppressive Effects of Tautomycetin on T Cells / 대한면역학회지

T cell activation is a critical event for initiation and regulation of immune responses and inhibitors of such signaling pathways are clinically useful for the treatment of patients received allogratt and autoimmune disease. In the course of screening soil microorganisms from the forest of Cheju island in Korea for new immunosuppressive agent, one of Streptomyces species (CK-95441) was found to produce a new immunosuppressant, tautomycetin which also had antifungal activity. Tautomycetin showed the inhibition of T cell proliferation in murine mixed lymphocyte reaction (MLR) and T cell activation induced by concanavalin A. Tautomycetin also blocked the induction of IL-2 gene expression which was examined in Jurkat TAg cell line in which multiple NFAT-binding sites and minimal IL-2 promoter drive the production of B-galactosidase. Also, the level of inhibition in activation-induced IL-2 receptor expression by tautomycetin was greater than those by cyclosporin A measured by flow cytometry. But, Fas ligand-induced apoptosis in Jurkat cells was unaffected by tautomycetin which was measured by DNA fragmentation assay. These results suggested that tautomycetin will be able to be used as a potent immunosuppressive drug following organ transplantation.