Korean J Physiol Pharmacol.  2012 Apr;16(2):145-151. 10.4196/kjpp.2012.16.2.145.

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

• Niu M
• Sun Y
• Liu B
• Tang L
• Qiu R

• KMID: 2071761
• DOI: http://doi.org/10.4196/kjpp.2012.16.2.145

Abstract

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.

Keyword

Tautomycetin; Protein phosphatase; Immunosuppressive activity; Anticancer activity

MeSH Terms

Cell Line
Cell Proliferation
Fermentation
Furans
Lipids
Maleic Anhydrides
MCF-7 Cells
Structure-Activity Relationship
Furans
Lipids
Maleic Anhydrides

Figure

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  Fig. 1 Structure of TMC and its analogous compounds.

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  Fig. 2 Effects of TMC and its analogous compounds on inhibition of recombinant PP1 activity. 2 U/ml of recombinant PP1was preincubated with or without indicated concentrations of TMC or its derivatives for 20 min at 30℃, and phosphatase activities were measured as described in materials and methods.

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  Fig. 3 Effects of TMC and its related compounds on cytokine IL-2 secretion. Jurkat T cells (1×106 cells/ml) were pretreated with TMC (0.2 µM) or its analogous compounds (20 µM), and then stimulated with anti-CD3 mAb (10 µg/ml) and anti-CD28 mAb (0.5 µg/ml) at 37℃ for 24 h. IL-2 cytokine levels in conditioned medium were determined using a ELISA kit. Data are expressed as percent of control. The sign * indicates difference (p<0.05) compared to control.

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  Fig. 4 Effects of TMC and its analogous compounds on the viability of MCF-7 cells and in vivo PP1 phosphatase activities in MCF-7 cells. (A) To measure in vivo PP1 activity, MCF-7 cells were treated with indicated concentrations of TMC, TMC-F1 or TMC-Chain for 4 h and cell lysates were assayed for phosphatase activities of PP1 as described in materials and methods. (B) MCF-7 cells were treated with the indicated concentrations of TMC, TMC-F1 or TMC-Chain for 48h. Cell viability was determined by an MTT colorimetric growth assay. The sign * indicates difference (p<0.05) compared to control.

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