Identification, in Vitro Activity and Mode of Action of Phosphoinositide-Dependent-1 Kinase Inhibitors as Antifungal Molecules

Abstract

Although protein kinases have recently emerged as important drug targets, the anti-infective potential of protein kinase inhibitors has not been developed extensively. We identified the mammalian PDK1 inhibitor KP-372-1 as a potent antifungal molecule with activity against yeast and fungal biofilms using a screening strategy for protein kinase inhibitors that block the cell wall stress response in yeast. Genetic and biochemical studies indicate that KP-372-1 inhibits fungal PDK1 orthologs (Pkh kinases) as part of its mode of action and support a role for Pkh kinases in eisosome assembly. Two other structurally distinct molecules that inhibit PDK1, OSU-03012 and UCN-01, also have antifungal activity. Taken together, these data indicate that fungal PDK1 orthologs are promising targets for new antifungal drug development.

Cryptococcus neoformans Phosphoinositide-Dependent Kinase 1 (PDK1) Ortholog Is Required for Stress Tolerance and Survival in Murine Phagocytes

“…Furthermore, we show that C. neoformans, like other pathogenic fungi (33)(34)(35), suppresses production of reactive oxygen species (ROS) by mouse macrophage-like J774 cells and that this process is also PKH2-02 dependent. Taken together with our previous work (17), these data indicate that CnPKH2-02-mediated signaling is crucial to C. neoformans stress tolerance and host-pathogen interactions and, consequently, further support the notion that PKHs represent a highly attractive antifungal drug target.…”

“…As mentioned above, one of our laboratories has recently demonstrated that molecules which inhibit hPDK1 also have antifungal activity and appear to target fungal Pkh kinases as part of their mechanism of action (17). Based on the results from Fig.…”

“…neoformans PDK1 ortholog Pkh2-02 is required for cell wall integrity. Recently, we reported that chemical inhibitors of human PDK1 have potent activity toward C. neoformans and appear to target the PDK1 ortholog Pkh2-02 (17). The function of PDK1 orthologs (S. cerevisiae PKH1/2 [ScPKH1/2] products) in the model yeast S. cerevisiae has been extensively investigated, but no focused studies of PDK1 orthologs in human fungal pathogens had been reported prior to the initiation of our studies.…”

“…Recently, we identified fungal orthologs of human PDK1 kinases as an attractive target for antifungal drug development (17). In order to better understand the function of these kinases in pathogenic fungi, we have carried out a genetics-based study to characterize C. neoformans mutants lacking the hPDK1 ortholog Pkh2-02.…”

“…and Cryptococcus spp. and appear to target the fungal orthologs of PDK1 (17). In S. cerevisiae (18), three kinases have homology to hPDK1, and these genes have been named PKH1, -2, and -3.…”