Metal Chelation as a Powerful Strategy to Probe Cellular Circuitry Governing Fungal Drug Resistance and Morphogenesis.
Fungal pathogens have evolved diverse strategies to sense host-relevant cues and coordinate cellular responses, which enable virulence and drug resistance. Defining circuitry controlling these traits opens new opportunities for chemical diversity in therapeutics, as the cognate inhibitors are rarely explored by conventional screening approaches. This has great potential to address the pressing need for new therapeutic strategies for invasive fungal infections, which have a staggering impact on human health. To explore this approach, we focused on a leading human fungal pathogen, Candida albicans, and screened 1,280 pharmacologically active compounds to identify those that potentiate the activity of echinocandins, which are front-line therapeutics that target fungal cell wall synthesis. We identified 19 compounds that enhance activity of the echinocandin caspofungin against an echinocandin-resistant clinical isolate, with the broad-spectrum chelator DTPA demonstrating the greatest synergistic activity. We found that DTPA increases susceptibility to echinocandins via chelation of magnesium. Whole genome sequencing of mutants resistant to the combination of DTPA and caspofungin identified mutations in the histidine kinase gene NIK1 that confer resistance to the combination. Functional analyses demonstrated that DTPA activates the mitogen-activated protein kinase Hog1, and that NIK1 mutations block Hog1 activation in response to both caspofungin and DTPA. The combination has therapeutic relevance as DTPA enhanced the efficacy of caspofungin in a mouse model of echinocandin-resistant candidiasis. We found that DTPA not only reduces drug resistance but also modulates morphogenesis, a key virulence trait that is normally regulated by environmental cues. DTPA induced filamentation via depletion of zinc, in a manner that is contingent upon Ras1-PKA signaling, as well as the transcription factors Brg1 and Rob1. Thus, we establish a new mechanism by which metal chelation modulates morphogenetic circuitry and echinocandin resistance, and illuminate a novel facet to metal homeostasis at the host-pathogen interface, with broad therapeutic potential.
Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
Elizabeth J
http://orcid.org/0000-0002-7827-826X
EJ
Polvi
Department of Molecular Genetics and Microbiology, Medicine, and Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, United States of America.
Anna F
AF
Averette
Department of Molecular Genetics and Microbiology, Medicine, and Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, United States of America.|Department of Biology, University of Texas at San Antonio, San Antonio, Texas, United States of America.
Soo Chan
SC
Lee
Department of Molecular Genetics and Microbiology, Medicine, and Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, United States of America.
Taeyup
T
Kim
Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea.
Yong-Sun
YS
Bahn
Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
Amanda O
http://orcid.org/0000-0003-1764-8439
AO
Veri
Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
Nicole
N
Robbins
Department of Molecular Genetics and Microbiology, Medicine, and Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, United States of America.
Joseph
J
Heitman
Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
Leah E
LE
Cowen
D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D002176:Candida albicans / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity; D002177:Candidiasis / Q000188:drug therapy* / Q000382:microbiology; D000077336:Caspofungin; D002473:Cell Wall / Q000187:drug effects; D002614:Chelating Agents / Q000737:chemistry / Q000494:pharmacology; D025141:Drug Resistance, Fungal / Q000235:genetics; D054714:Echinocandins / Q000494:pharmacology; D016681:Genome, Fungal; D006801:Humans; D055666:Lipopeptides / Q000494:pharmacology; D008670:Metals / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics*; D009024:Morphogenesis / Q000187:drug effects / Q000235:genetics; D009154:Mutation; D004369:Pentetic Acid / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D015398:Signal Transduction
D000935:Antifungal Agents; D002614:Chelating Agents; D054714:Echinocandins; D055666:Lipopeptides; D008670:Metals; D004369:Pentetic Acid; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D000077336:Caspofungin
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