Epiderstatin

Epiderstatin is a unique glutarimide antibiotic which was found by screening for inhibitors of the signal transduction of epidermal growth factor (EGF). The antibiotic (0.01 microM) was found to reverse the morphology of NRK cells that were infected with a temperature-sensitive mutant of Rous sarcoma virus (srcts-NRK) from the transformed phenotype to the normal phenotype at the permissive temperature (32 degrees C). Epiderstatin did not inhibit the protein kinase activity of p60v-src. The cell cycle progression of src(ts)-NRK cells was blocked at G0/G1 phase, which was caused by the inhibition of biosynthesis of p60v-src but not the transcription of v-src mRNA.

Epiderstatin, a distinctive glutarimide antibiotic isolated from Streptomyces pulveraceus subsp. epiderstagenes, has been revealed to be a potent inhibitor of the signal transduction of epidermal growth factor (EGF). Epiderstatin inhibited the DNA synthesis induced by various peptide growth factors in a mouse epidermal cell line, BALB/MK, without inhibiting protein tyrosine kinase activity of EGF-receptor or serine/threonine kinase activity of protein kinase C. The 50% inhibitory concentration (IC50) value of epiderstatin for the EGF-stimulated incorporation of [3H]thymidine into BALB/MK cells was about 10 nM. When epiderstatin was added to the quiescent cells simultaneously with EGF-stimulation, the cells did not reenter into the growing cell cycle. The action of epiderstatin proceeded from the overexpression of c-fos and the suppression of c-myc transcription when EGF was added to quiescent BALB/MK cells.

A new glutarimide antibiotic named actiketal was isolated from the culture fluid of the epiderstatin-producing streptomycete, Streptomyces pulveraceus subsp. epiderstagenes. The IC50 of the antibiotic for inhibition of the incorporation of [3H]thymidine into epidermal growth factor-stimulated Balb/MK cells was 14.5 microM. The structure of this compound was determined by 1H and 13C NMR spectroscopic analyses using 1H-1H COSY, 13C-1H COSY, heteronuclear multiple-bond correlation spectroscopy, selective 13C-[1H] NOE's techniques.