Host Lung Environment Limits Aspergillus fumigatus Germination through an SskA-Dependent Signaling Response
ABSTRACT Aspergillus fumigatus isolates display significant heterogeneity in growth, virulence, pathology, and inflammatory potential in multiple murine models of invasive aspergillosis. Previous studies have linked the initial germination of a fungal isolate in the airways to the inflammatory and p...
| Main Authors: | , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
American Society for Microbiology
2021-12-01
|
| Series: | mSphere |
| Subjects: | |
| Online Access: | https://journals.asm.org/doi/10.1128/msphere.00922-21 |
| _version_ | 1818873595938471936 |
|---|---|
| author | Marina E. Kirkland McKenzie Stannard Caitlin H. Kowalski Dallas Mould Alayna Caffrey-Carr Rachel M. Temple Brandon S. Ross Lotus A. Lofgren Jason E. Stajich Robert A. Cramer Joshua J. Obar |
| author_facet | Marina E. Kirkland McKenzie Stannard Caitlin H. Kowalski Dallas Mould Alayna Caffrey-Carr Rachel M. Temple Brandon S. Ross Lotus A. Lofgren Jason E. Stajich Robert A. Cramer Joshua J. Obar |
| author_sort | Marina E. Kirkland |
| collection | DOAJ |
| description | ABSTRACT Aspergillus fumigatus isolates display significant heterogeneity in growth, virulence, pathology, and inflammatory potential in multiple murine models of invasive aspergillosis. Previous studies have linked the initial germination of a fungal isolate in the airways to the inflammatory and pathological potential, but the mechanism(s) regulating A. fumigatus germination in the airways is unresolved. To explore the genetic basis for divergent germination phenotypes, we utilized a serial passaging strategy in which we cultured a slow germinating strain (AF293) in a murine-lung-based medium for multiple generations. Through this serial passaging approach, a strain emerged with an increased germination rate that induces more inflammation than the parental strain (herein named LH-EVOL for lung homogenate evolved). We identified a potential loss-of-function allele of Afu5g08390 (sskA) in the LH-EVOL strain. The LH-EVOL strain had a decreased ability to induce the SakA-dependent stress pathway, similar to AF293 ΔsskA and CEA10. In support of the whole-genome variant analyses, sskA, sakA, or mpkC loss-of-function strains in the AF293 parental strain increased germination both in vitro and in vivo. Since the airway surface liquid of the lungs contains low glucose levels, the relationship of low glucose concentration on germination of these mutant AF293 strains was examined; interestingly, in low glucose conditions, the sakA pathway mutants exhibited an enhanced germination rate. In conclusion, A. fumigatus germination in the airways is regulated by SskA through the SakA mitogen-activated protein kinase (MAPK) pathway and drives enhanced disease initiation and inflammation in the lungs. IMPORTANCE Aspergillus fumigatus is an important human fungal pathogen particularly in immunocompromised individuals. Initiation of growth by A. fumigatus in the lung is important for its pathogenicity in murine models. However, our understanding of what regulates fungal germination in the lung environment is lacking. Through a serial passage experiment using lung-based medium, we identified a new strain of A. fumigatus that has increased germination potential and inflammation in the lungs. Using this serially passaged strain, we found it had a decreased ability to mediate signaling through the osmotic stress response pathway. This finding was confirmed using genetic null mutants demonstrating that the osmotic stress response pathway is critical for regulating growth in the murine lungs. Our results contribute to the understanding of A. fumigatus adaptation and growth in the host lung environment. |
| first_indexed | 2024-12-19T12:57:13Z |
| format | Article |
| id | doaj.art-a9d97d6657df4007937c146b431aced9 |
| institution | Directory Open Access Journal |
| issn | 2379-5042 |
| language | English |
| last_indexed | 2024-12-19T12:57:13Z |
| publishDate | 2021-12-01 |
| publisher | American Society for Microbiology |
| record_format | Article |
| series | mSphere |
| spelling | doaj.art-a9d97d6657df4007937c146b431aced92022-12-21T20:20:22ZengAmerican Society for MicrobiologymSphere2379-50422021-12-016610.1128/msphere.00922-21Host Lung Environment Limits Aspergillus fumigatus Germination through an SskA-Dependent Signaling ResponseMarina E. Kirkland0McKenzie Stannard1Caitlin H. Kowalski2Dallas Mould3Alayna Caffrey-Carr4Rachel M. Temple5Brandon S. Ross6Lotus A. Lofgren7Jason E. Stajich8Robert A. Cramer9Joshua J. Obar10Geisel School of Medicine at Dartmouth, Department of Microbiology & Immunology, Lebanon, New Hampshire, USAGeisel School of Medicine at Dartmouth, Department of Microbiology & Immunology, Lebanon, New Hampshire, USAGeisel School of Medicine at Dartmouth, Department of Microbiology & Immunology, Lebanon, New Hampshire, USAGeisel School of Medicine at Dartmouth, Department of Microbiology & Immunology, Lebanon, New Hampshire, USAGeisel School of Medicine at Dartmouth, Department of Microbiology & Immunology, Lebanon, New Hampshire, USAGeisel School of Medicine at Dartmouth, Department of Microbiology & Immunology, Lebanon, New Hampshire, USAGeisel School of Medicine at Dartmouth, Department of Microbiology & Immunology, Lebanon, New Hampshire, USADepartment of Microbiology & Plant Pathology, University of California Riverside, Riverside, California, USADepartment of Microbiology & Plant Pathology, University of California Riverside, Riverside, California, USAGeisel School of Medicine at Dartmouth, Department of Microbiology & Immunology, Lebanon, New Hampshire, USAGeisel School of Medicine at Dartmouth, Department of Microbiology & Immunology, Lebanon, New Hampshire, USAABSTRACT Aspergillus fumigatus isolates display significant heterogeneity in growth, virulence, pathology, and inflammatory potential in multiple murine models of invasive aspergillosis. Previous studies have linked the initial germination of a fungal isolate in the airways to the inflammatory and pathological potential, but the mechanism(s) regulating A. fumigatus germination in the airways is unresolved. To explore the genetic basis for divergent germination phenotypes, we utilized a serial passaging strategy in which we cultured a slow germinating strain (AF293) in a murine-lung-based medium for multiple generations. Through this serial passaging approach, a strain emerged with an increased germination rate that induces more inflammation than the parental strain (herein named LH-EVOL for lung homogenate evolved). We identified a potential loss-of-function allele of Afu5g08390 (sskA) in the LH-EVOL strain. The LH-EVOL strain had a decreased ability to induce the SakA-dependent stress pathway, similar to AF293 ΔsskA and CEA10. In support of the whole-genome variant analyses, sskA, sakA, or mpkC loss-of-function strains in the AF293 parental strain increased germination both in vitro and in vivo. Since the airway surface liquid of the lungs contains low glucose levels, the relationship of low glucose concentration on germination of these mutant AF293 strains was examined; interestingly, in low glucose conditions, the sakA pathway mutants exhibited an enhanced germination rate. In conclusion, A. fumigatus germination in the airways is regulated by SskA through the SakA mitogen-activated protein kinase (MAPK) pathway and drives enhanced disease initiation and inflammation in the lungs. IMPORTANCE Aspergillus fumigatus is an important human fungal pathogen particularly in immunocompromised individuals. Initiation of growth by A. fumigatus in the lung is important for its pathogenicity in murine models. However, our understanding of what regulates fungal germination in the lung environment is lacking. Through a serial passage experiment using lung-based medium, we identified a new strain of A. fumigatus that has increased germination potential and inflammation in the lungs. Using this serially passaged strain, we found it had a decreased ability to mediate signaling through the osmotic stress response pathway. This finding was confirmed using genetic null mutants demonstrating that the osmotic stress response pathway is critical for regulating growth in the murine lungs. Our results contribute to the understanding of A. fumigatus adaptation and growth in the host lung environment.https://journals.asm.org/doi/10.1128/msphere.00922-21Aspergillus fumigatusaspergillosisgerminationinflammation |
| spellingShingle | Marina E. Kirkland McKenzie Stannard Caitlin H. Kowalski Dallas Mould Alayna Caffrey-Carr Rachel M. Temple Brandon S. Ross Lotus A. Lofgren Jason E. Stajich Robert A. Cramer Joshua J. Obar Host Lung Environment Limits Aspergillus fumigatus Germination through an SskA-Dependent Signaling Response mSphere Aspergillus fumigatus aspergillosis germination inflammation |
| title | Host Lung Environment Limits Aspergillus fumigatus Germination through an SskA-Dependent Signaling Response |
| title_full | Host Lung Environment Limits Aspergillus fumigatus Germination through an SskA-Dependent Signaling Response |
| title_fullStr | Host Lung Environment Limits Aspergillus fumigatus Germination through an SskA-Dependent Signaling Response |
| title_full_unstemmed | Host Lung Environment Limits Aspergillus fumigatus Germination through an SskA-Dependent Signaling Response |
| title_short | Host Lung Environment Limits Aspergillus fumigatus Germination through an SskA-Dependent Signaling Response |
| title_sort | host lung environment limits aspergillus fumigatus germination through an sska dependent signaling response |
| topic | Aspergillus fumigatus aspergillosis germination inflammation |
| url | https://journals.asm.org/doi/10.1128/msphere.00922-21 |
| work_keys_str_mv | AT marinaekirkland hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse AT mckenziestannard hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse AT caitlinhkowalski hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse AT dallasmould hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse AT alaynacaffreycarr hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse AT rachelmtemple hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse AT brandonsross hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse AT lotusalofgren hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse AT jasonestajich hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse AT robertacramer hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse AT joshuajobar hostlungenvironmentlimitsaspergillusfumigatusgerminationthroughansskadependentsignalingresponse |