Isolation and characterization of fatty acid derivatives from an actinomycetes and examination of the effects on activities of phospholipase C and protein kinase C

In our screening to search inhibitors of phosphoinositide(PI)-specific phospholipase C (PI-PLC), two inhibitors, MT965-A and -B were isolated from a culture broth of an actinomycetes. MT965-A and -B were identified as fatty acid derivatives, 14-methylpentadecanoic acid and 16-methyllinoleic acid methyl ester, respectively, based on the spectral data including NMR and MS. Both inhibitors directly inhibited not only in vitro PLC gamma 1 activity but also the platelet-derived growth factor (PDGF)-induced inositol phosphates (IPt) formation in NIH 3T3 gamma 1 cells overexpressing PLC gamma 1. However, the inhibitors enhanced in, vitro protein kinase C (PKC) activity. On examination of the effects of various fatty acids (FAs) on activities of PLC, PKC, and PDGF-induced IPt formation, the unsaturated FAs (UFAs) showed the same activities like the inhibitors, but the saturated FAs (SFAs) did not show similar activities. It was inferred that the chain length, degree of unsaturation, methyl esterification, branching with a methyl group, and cis-configuration were important for their activity.X112sciescopu

Inhibition of PDGF-induced phosphoinositide-turnover by glucopiericidin A

In the search for a substance which would specifically block a particular step in the signal transduction cascade, we identified glucopiericidin A produced by Streptomyces sp, as an inhibitor of phosphoinositide (PI)-turnover in phospholipase-C gamma 1 (PLC-gamma 1) overexpressing NM 3T3 fibroblasts (NIH 3T3 gamma 1). Glucopiericidin A inhibited the formation of inositol phosphate (IPt) in platelet-derived growth factor (PDGF)-stimulated NIH 3T3 gamma 1 cells with an IC50 of 5.0 mu M, In vitro enzyme assay showed the compound had no inhibitory effect on PLC-gamma 1 even at 100 mu M concentration. Glucopiericidin A reduced PDGF-induced tyrosine phosphorylations of proteins, including PDGF receptor and PLC-gamma 1, in the cells. In contrast, glucopiericidin A showed only a slight inhibitory effect on epidermal growth factor (EGF)- (EGF)-induced IPt production and protein tyrosine phosphorylations in A431 cells. These results suggest that glucopiericidin A inhibits PDGF-induced activation of PLC-gamma 1 by reducing the tyrosine kinase activity of the PDGF receptor and it more potently inhibits PI-turnover induced by PDGF than by EGFopen4

Inhibition of PDGF-induced phosphoinositide-turnover by glucopiericidin A

In the search for a substance which would specifically block a particular step in the signal transduction cascade, we identified glucopiericidin A produced by Streptomyces sp, as an inhibitor of phosphoinositide (PI)-turnover in phospholipase-C gamma 1 (PLC-gamma 1) overexpressing NM 3T3 fibroblasts (NIH 3T3 gamma 1). Glucopiericidin A inhibited the formation of inositol phosphate (IPt) in platelet-derived growth factor (PDGF)-stimulated NIH 3T3 gamma 1 cells with an IC50 of 5.0 mu M, In vitro enzyme assay showed the compound had no inhibitory effect on PLC-gamma 1 even at 100 mu M concentration. Glucopiericidin A reduced PDGF-induced tyrosine phosphorylations of proteins, including PDGF receptor and PLC-gamma 1, in the cells. In contrast, glucopiericidin A showed only a slight inhibitory effect on epidermal growth factor (EGF)- (EGF)-induced IPt production and protein tyrosine phosphorylations in A431 cells. These results suggest that glucopiericidin A inhibits PDGF-induced activation of PLC-gamma 1 by reducing the tyrosine kinase activity of the PDGF receptor and it more potently inhibits PI-turnover induced by PDGF than by EGF.X115sciescopu