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Principal Investigator: Todd B Reynolds
Organization: UNIVERSITY OF TENNESSEE KNOXVILLE
Fiscal Year: 2022
Award: $497,866
Funding agency: National Institute of Allergy and Infectious Diseases
Candida albicans and related Candida spp. are responsible for ~400,000 invasive infections/year, which have
an ~50% mortality rate. A crucial virulence trait of C. albicans, and other fungi, is the ability to diminish their
detection by their hosts. The cell wall carbohydrate ß(1,3)-glucan is an important epitope that the immune
systems of humans and other mammals use to recognize and respond to fungal infections through receptors
like Dectin-1 and complement receptor 3 (CR3). Fungi like C. albicans diminish their detection from immune
cells through masking ß(1,3)-glucan under an outer layer of mannosylated glycoproteins (mannan). The
virulence of C. albicans is compromised in conditions where ß(1,3)-glucan is more exposed (unmasked). For
example, echinocandin antifungal drugs, like caspofungin, inhibit ß(1,3)-glucan synthase and cause cell lysis in
vitro, but also induce exposure of ß(1,3)-glucan, even at sublethal concentrations. In addition, a number of
mutants that exhibit increased exposure of ß(1,3)-glucan have decreased virulence. However, a major
research challenge is to understand the impact of ß(1,3)-glucan exposure on virulence during caspofungin
treatment. It has been difficult to differentiate between cidal effects of the drug and the impact of ß(1,3)-glucan
exposure. A challenge closely related to this is that the mechanism by which caspofungin causes ß(1,3)-glucan
exposure is unknown. We have found that we can decouple caspofungin's cidal effects from unmasking,
which allows us to address both of these challenges. This can be done by activating caspofungin-responsive
signaling pathways using a genetic approach rather than the drug, and we have discovered that at least one of
these pathways causes unmasking. The Cek1 MAP kinase (MAPK) pathway is activated by caspofungin
treatment, and we have discovered that genetic activation of this cascade causes unmasking when
hyperactivated, even in the absence of caspofungin. However, unlike the drug, activation of this pathway does
not compromise viability. Thus, we can meet the second challenge by using this pathway to dissect the
mechanism through which unmasking occurs. Moreover, we can meet the first challenge by using the Cek1
pathway as tool to probe how the immune system responds to unmasking during mouse systemic infections
because, unlike caspofungin, it is not cidal. We will address these challenges in three specific aims. In Aim 1
we will elucidate the mechanisms by which the Cek1 cascade regulates ß(1,3)-glucan exposure. There are two
main transcription factors downstream of Cek1 and we will determine how the pathway chooses a particular
one (Cph1) using a combination of genetic, epistasis, and cell biology techniques that will identify how Cek1-
Cph1 is activated to cause unmasking. In Aim 2 we will determine how transcriptional targets of Cek1-Cph1
alter the cell wall to cause unmasking. In Aim 3, we will elucidate how exposure of ß(1,3)-glucan causes
decreased virulence in mice. We will use transgenic mice to define how neutrophils, macrophages, Dectin-1
and/or CR3 participate to reduce the virulence of unmasked C. albicans.
Terms: <ACE2><Address><Alleles><Allelomorphs><Antifungal Agents><Antifungal Drug><Antifungal Therapy><Antigenic Determinants><Architecture><Basal Transcription Factor><Basal transcription factor genes><Binding Determinants><Biology><Blood Neutrophil><Blood Polymorphonuclear Neutrophil><C albicans><C. albicans><C.albicans><CR3><CR3 Receptor><Candida><Candida albicans><Carbohydrates><Caspofungin><Cell Body><Cell Communication and Signaling><Cell Signaling><Cell Wall><Cells><Cellular biology><Chitin><Complement 3 Receptor><Cytolysis><Decision Making><Detection><Drugs><Engineering / Architecture><Epistasis><Epistatic Deviation><Epitopes><Exhibits><Feedback><Fungus Diseases><Gene Transcription><General Transcription Factor Gene><General Transcription Factors><Genes><Genetic><Genetic Epistasis><Genetic Transcription><Glucans><Glucose Polymer><Glycoproteins><Goals><Health><Human><Hyperactivity><Immune><Immune response><Immune system><Immunes><Immunologic Receptors><Immunological Receptors><Immunological response><In Vitro><Infection><Integrin alpha-M beta-2><Integrin alphaMbeta2><Interaction Deviation><Intracellular Communication and Signaling><Life><LoxP-flanked allele><Lysis><MAP Kinase Cascades><MAP Kinase Modules><MAP Kinase Signaling Cascades><MAP kinase><Mac 1><Mac-1 Adhesive Receptor><Mac-1 Antigen><Mac-1 Receptor><Macrophage-1 Antigen><Mammalia><Mammals><Mannan><Mannans><Marrow Neutrophil><Masks><Mediating><Medication><Mice><Mice Mammals><Mitogen-Activated Protein Kinases><Mo1 Antigen Receptor><Mo1 Glycoprotein Receptor><Modern Man><Molecular><Monilia><Murine><Mus><Mycoses><Mφ><Neutrophilic Granulocyte><Neutrophilic Leukocyte><Pathway interactions><Patient outcome><Patient-Centered Outcomes><Patient-Focused Outcomes><Pharmaceutic Preparations><Pharmaceutical Preparations><Polyglucoses><Polymers><Polymorphonuclear Cell><Polymorphonuclear Leukocytes><Polymorphonuclear Neutrophils><Proteins><RNA Expression><Receptor Protein><Regulation><Research><Services><Signal Pathway><Signal Transduction><Signal Transduction Systems><Signaling><Stress><Systemic infection><Techniques><Technology><Testing><Therapeutic Fungicides><Transcription><Transcription Factor Proto-Oncogene><Transcription factor genes><Transgenic Mice><Virulence><allergic/immunologic body system><allergic/immunologic organ system><angiotensin converting enzyme 2><angiotensin converting enzyme II><anti-fungal><anti-fungal agents><anti-fungal drug><anti-fungal therapy><antifungals><biological signal transduction><cell biology><cell type><dectin 1><drug/agent><epistatic relationship><experiment><experimental research><experimental study><floxed><floxed allele><fungal infection><fungal infectious disease treatment><fungus><fungus infection><gene x gene interaction><genetic approach><genetic epistases><genetic strategy><glucan synthase><host response><immune receptor><immune system response><immunoresponse><macrophage><mortality><mutant><neutrophil><novel><overexpress><overexpression><pathway><receptor><tool><trait><transcription factor><upstream kinase><αMβ2>