Identification of LY83583 as a specific inhibitor of Candida albicans MPS1 protein kinase.

Candida albicans is the most common and virulent fungus causing candidiasis in various parts of the body and can be lethal to immunocompromised patients. All currently known antifungal therapies are drugs which cause serious side effects in the host. An inhibitor specific for fungus survival is an ideal therapeutic. C. albicans MPS1 (monopolar spindle 1) has been reported as a kinase essential to its survival. Because CaMps1p shares limited sequence homology with the human ortholog (hMps1p), we screened for a chemical inhibitor in anticipation of finding one with Candida specific cytotoxicity. In vitro screening using a recombinant catalytic domain of CaMps1p identified LY83583 (6-anilino-5,8-quinolinedione), known as a guanylate cyclase inhibitor, to be blocking CaMps1p kinase activity. In addition to its in vitro kinase inhibition, LY83583 reduced the growth rate of C. albicans. Finally, we compared the inhibitory activity on CaMps1p and hMps1p among inhibitors against those kinases. LY83583 showed specific inhibition for CaMps1p with no effect on hMps1p activity. Conversely, the CaMps1p activity was not affected by known hMps1p inhibitors. These findings suggest that CaMps1p may well be an ideal target molecule for antifungal therapy.

Cytotoxic and EGFR tyrosine kinase inhibitory activities of aglycone derivatives obtained by enzymatic hydrolysis of oleoside-type secoiridoid glucosides, oleuropein and ligustroside.

Hydrolysis of oleoside-type secoiridoid glucosides, oleuropein (1) and ligustroside (2), in the presence of ß-glucosidase provided their aglycones, named (5S,8R,9S)-7-3,4-dihydroxyphenethyl elenolate (3) and (5S,8R,9S)-7-4-hydroxyphenethyl elenolate (4), respectively. The structures of 3 and 4 were identified by spectroscopic means and optical rotation measurements. Evaluation of the cytotoxic and epidermal growth factor receptor (EGFR) tyrosine kinase inhibitory activities of compounds 1-4 showed that compounds 3 and 4 exhibited moderate cytotoxicity against a disease-oriented panel of 39 human cancer cell lines in vitro, whereas compound 3 inhibited the enzyme.

Natural product origins of Hsp90 inhibitors.

The currently used Hsp90 inhibitors, geldanamycin, herbimycin A and radicicol, were isolated many years ago from Streptomyces and fungi originally for their antiprotozoal activity, herbicidal activity and antifungal activity, respectively. In the mid 1980s, it was found that the benzoquinone ansamycin antibiotics (herbimycin A, geldanamycin, and macbecin) reversed v-Src transformed cells to normal phenotypes, and Bcr-abl was subsequently suggested to be the molecular target for the treatment of chronic myelogenous leukemia through a study using herbimycin A for its selective antioncogenic activity. In 1994, these ansamycins were found to bind to Hsp90 and to cause the degradation of client proteins including Src kinases; further efforts to develop anticancer drugs were made using geldanamycin analogs, and 17AAG was chosen as the best candidate for clinical trials. The number of novel natural products isolated from microbial origins is continuing to increase and is doubling every 10 years. Thus, screening of bioactive substances from natural origins, using assays including defined targets, and developing leads toward drugs via optimized derivatization is a conventional but still promising strategy for drug discovery and development.