Discovery of cercosporamide, a known antifungal natural product, as a selective Pkc1 kinase inhibitor through high-throughput screening.
The Pkc1-mediated cell wall integrity-signaling pathway is highly conserved in fungi and is essential for fungal growth. We thus explored the potential of targeting the Pkc1 protein kinase for developing broad-spectrum fungicidal antifungal drugs through a Candida albicans Pkc1-based high-throughput screening. We discovered that cercosporamide, a broad-spectrum natural antifungal compound, but previously with an unknown mode of action, is actually a selective and highly potent fungal Pkc1 kinase inhibitor. This finding provides a molecular explanation for previous observations in which Saccharomyces cerevisiae cell wall mutants were found to be highly sensitive to cercosporamide. Indeed, S. cerevisiae mutant cells with reduced Pkc1 kinase activity become hypersensitive to cercosporamide, and this sensitivity can be suppressed under high-osmotic growth conditions. Together, the results demonstrate that cercosporamide acts selectively on Pkc1 kinase and, thus, they provide a molecular mechanism for its antifungal activity. Furthermore, cercosporamide and a beta-1,3-glucan synthase inhibitor echinocandin analog, by targeting two different key components of the cell wall biosynthesis pathway, are highly synergistic in their antifungal activities. The synergistic antifungal activity between Pkc1 kinase and beta-1,3-glucan synthase inhibitors points to a potential highly effective combination therapy to treat fungal infections.
Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA.
Andrea
A
Sussman
Karen
K
Huss
Li-Chun
LC
Chio
Steve
S
Heidler
Margaret
M
Shaw
Doreen
D
Ma
Guoxin
G
Zhu
Robert M
RM
Campbell
Tae-Sik
TS
Park
Palaniappan
P
Kulanthaivel
John E
JE
Scott
John W
JW
Carpenter
Mark A
MA
Strege
Matthew D
MD
Belvo
James R
JR
Swartling
Anthony
A
Fischl
Wu-Kuang
WK
Yeh
Chuan
C
Shih
Xiang S
XS
Ye
D000666:Amphotericin B / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000935:Antifungal Agents / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D001572:Benzofurans / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D001681:Biological Assay / Q000379:methods*; D002176:Candida albicans / Q000187:drug effects / Q000201:enzymology; D004357:Drug Synergism; D004789:Enzyme Activation; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests / Q000379:methods; D015394:Molecular Structure; D010718:Phosphatidylserines / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D047071:beta-Glucans / Q000378:metabolism
D000935:Antifungal Agents; D001572:Benzofurans; D005656:Fungal Proteins; D007527:Isoenzymes; D010718:Phosphatidylserines; D047428:Protein Kinase Inhibitors; D047071:beta-Glucans; C085452:cercosporamide; D000666:Amphotericin B; C033363:beta-1,3-glucan; D005964:Glucosyltransferases; C040232:glucan synthase; D011493:Protein Kinase C