scholarly journals A Ssd1 homolog impacts trehalose and chitin biosynthesis and contributes to virulence inAspergillus fumigatus

2019 ◽  
Author(s):  
Arsa Thammahong ◽  
Sourabh Dhingra ◽  
Katherine M. Bultman ◽  
Joshua Kerkaert ◽  
Robert A. Cramer
Keyword(s):  
Cell Wall ◽  
Aspergillus Fumigatus ◽  
Mutant Strain ◽  
Filamentous Fungus ◽  
Fungal Cell Wall ◽  
Cell Wall Biosynthesis ◽  
Null Mutant ◽  
Fungal Cell ◽  
Fungal Virulence ◽  
Over Expression

AbstractRegulation of fungal cell wall biosynthesis is critical to maintain cell wall integrity in the face of dynamic fungal infection microenvironments. In this study, we observe that a yeastssd1homolog,ssdA,in the filamentous fungusAspergillus fumigatusis involved in trehalose and cell wall homeostasis. AnssdAnull mutant strain exhibited an increase in trehalose levels and a reduction in colony growth rate. Over-expression ofssdAin contrast perturbed trehalose biosynthesis and reduced conidia germination rates. ThessdAnull mutant strain was more resistant to cell wall perturbing agents while over-expression ofssdApromoted increased sensitivity. Over-expression ofssdAsignificantly increased chitin levels and both loss and over-expression ofssdAaltered sub-cellular localization of the class V chitin synthase CsmA. Strikingly, over-expression ofssdAabolished adherence to abiotic surfaces and severely attenuated the virulence ofA. fumigatusin a murine model of invasive pulmonary aspergillosis. In contrast, despite the severein vitrofitness defects observed upon loss ofssdA,neither surface adherence or murine survival was impacted. In conclusion,A. fumigatusSsdA plays a critical role in cell wall homeostasis that alters fungal-host interactions.ImportanceLife threatening infections caused by the filamentous fungusAspergillus fumigatusare increasing along with a rise in fungal strains resistant to contemporary antifungal therapies. The fungal cell wall and the associated carbohydrates required for its synthesis and maintenance are attractive drug targets given that many genes encoding proteins involved in cell wall biosynthesis and integrity are absent in humans. Importantly, genes and associated cell wall biosynthesis and homeostasis regulatory pathways remain to be fully defined inA. fumigatus.In this study, we identify SsdA, a model yeast Ssd1p homolog, as an important component of trehalose and fungal cell wall biosynthesis inA. fumigatusthat consequently impacts fungal virulence in animal models of infection.

scholarly journals An Ssd1 Homolog Impacts Trehalose and Chitin Biosynthesis and Contributes to Virulence inAspergillus fumigatus

mSphere ◽  
2019 ◽  
Vol 4 (3) ◽  
Author(s):  
Arsa Thammahong ◽  
Sourabh Dhingra ◽  
Katherine M. Bultman ◽  
Joshua D. Kerkaert ◽  
Robert A. Cramer
Keyword(s):  
Cell Wall ◽  
Aspergillus Fumigatus ◽  
Mutant Strain ◽  
Filamentous Fungus ◽  
Fungal Cell Wall ◽  
Cell Wall Biosynthesis ◽  
Null Mutant ◽  
Fungal Cell ◽  
Fungal Virulence ◽  
Content Type

ABSTRACTRegulation of fungal cell wall biosynthesis is critical to maintain cell wall integrity in dynamic fungal infection microenvironments. Genes involved in this response that impact fungal fitness and host immune responses remain to be fully defined. In this study, we observed that a yeastssd1homolog,ssdA, in the filamentous fungusAspergillus fumigatusis involved in trehalose and cell wall homeostasis. AnssdAnull mutant strain exhibited an increase in trehalose levels and a reduction in fungal colony growth rate. In contrast, overexpression ofssdAperturbed trehalose biosynthesis and reduced germination of conidia. ThessdAnull mutant strain was more resistant to cell wall-perturbing agents, while overexpression ofssdAincreased sensitivity. Overexpression ofssdAsignificantly increased chitin levels, and both loss and overexpression ofssdAaltered subcellular localization of the class V chitin synthase CsmA. Strikingly, overexpression ofssdAabolished adherence to abiotic surfaces and severely attenuated the virulence ofA. fumigatusin a murine model of invasive pulmonary aspergillosis. Despite the severein vitrofitness defects observed upon loss ofssdA, neither surface adherence nor murine survival was impacted. In conclusion,A. fumigatusSsdA plays a critical role in cell wall homeostasis impactingA. fumigatus-host interactions.IMPORTANCEThe incidence of life-threatening infections caused by the filamentous fungusAspergillus fumigatusis increasing along with an increase in the number of fungal strains resistant to contemporary antifungal therapies. The fungal cell wall and the associated carbohydrates required for its synthesis and maintenance are attractive drug targets given that many genes encoding proteins involved in cell wall biosynthesis and integrity are absent in humans. Importantly, genes and associated cell wall biosynthesis and homeostasis regulatory pathways remain to be fully defined inA. fumigatus. In this report, we identify SsdA as an important component of trehalose and fungal cell wall biosynthesis inA. fumigatusthat consequently impacts the host immune response and fungal virulence in animal models of infection.

scholarly journals Chitosan Biosynthesis and Virulence in the Human Fungal Pathogen Cryptococcus gattii

mSphere ◽  
2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Woei C. Lam ◽  
Rajendra Upadhya ◽  
Charles A. Specht ◽  
Abigail E. Ragsdale ◽  
Camaron R. Hole ◽  
...  
Keyword(s):  
Cell Wall ◽  
Fungal Pathogen ◽  
Cryptococcus Gattii ◽  
Fungal Cell Wall ◽  
Fungal Pathogenesis ◽  
Protective Response ◽  
Fungal Cell ◽  
Fungal Virulence ◽  
Content Type ◽  
Mammalian Infection

ABSTRACT Cryptococcus gattii R265 is a hypervirulent fungal strain responsible for the recent outbreak of cryptococcosis in Vancouver Island of British Columbia in Canada. It differs significantly from Cryptococcus neoformans in its natural environment, its preferred site in the mammalian host, and its pathogenesis. Our previous studies of C. neoformans have shown that the presence of chitosan, the deacetylated form of chitin, in the cell wall attenuates inflammatory responses in the host, while its absence induces robust immune responses, which in turn facilitate clearance of the fungus and induces a protective response. The results of the present investigation reveal that the cell wall of C. gattii R265 contains a two- to threefold larger amount of chitosan than that of C. neoformans. The genes responsible for the biosynthesis of chitosan are highly conserved in the R265 genome; the roles of the three chitin deacetylases (CDAs) have, however, been modified. To deduce their roles, single and double CDA deletion strains and a triple CDA deletion strain were constructed in a R265 background and were subjected to mammalian infection studies. Unlike C. neoformans where Cda1 has a discernible role in fungal pathogenesis, in strain R265, Cda3 is critical for virulence. Deletion of either CDA3 alone or in combination with another CDA (cda1Δ3Δ or cda2Δ3Δ) or both (cda1Δ2Δ3Δ) rendered the fungus avirulent and cleared from the infected host. Moreover, the cda1Δ2Δ3Δ strain of R265 induced a protective response to a subsequent infection with R265. These studies begin to illuminate the regulation of chitosan biosynthesis of C. gattii and its subsequent effect on fungal virulence. IMPORTANCE The fungal cell wall is an essential organelle whose components provide the first line of defense against host-induced antifungal activity. Chitosan is one of the carbohydrate polymers in the cell wall that significantly affects the outcome of host-pathogen interaction. Chitosan-deficient strains are avirulent, implicating chitosan as a critical virulence factor. C. gattii R265 is an important fungal pathogen of concern due to its ability to cause infections in individuals with no apparent immune dysfunction and an increasing geographical distribution. Characterization of the fungal cell wall and understanding the contribution of individual molecules of the cell wall matrix to fungal pathogenesis offer new therapeutic avenues for intervention. In this report, we show that the C. gattii R265 strain has evolved alternate regulation of chitosan biosynthesis under both laboratory growth conditions and during mammalian infection compared to that of C. neoformans.

scholarly journals Length Specificity and Polymerization Mechanism of (1,3)-β-d-Glucan Synthase in Fungal Cell Wall Biosynthesis

Biochemistry ◽  
2020 ◽  
Vol 59 (5) ◽  
pp. 682-693 ◽  
Author(s):  
Abhishek Chhetri ◽  
Anna Loksztejn ◽  
Hai Nguyen ◽  
Kaila M. Pianalto ◽  
Mi Jung Kim ◽  
...  
Keyword(s):  
Cell Wall ◽  
Fungal Cell Wall ◽  
Cell Wall Biosynthesis ◽  
Fungal Cell ◽  
Glucan Synthase ◽  
Polymerization Mechanism

scholarly journals Chitosan biosynthesis and virulence in the human fungal pathogen Cryptococcus gattii

2019 ◽  
Author(s):  
Woei C. Lam ◽  
Rajendra Upadhya ◽  
Charles A. Specht ◽  
Abigail E. Ragsdale ◽  
Camaron R Hole ◽  
...  
Keyword(s):  
Cell Wall ◽  
Fungal Pathogen ◽  
Cryptococcus Gattii ◽  
Fungal Cell Wall ◽  
Yeast Cells ◽  
Fungal Pathogenesis ◽  
Protective Response ◽  
Fungal Cell ◽  
Fungal Virulence ◽  
Mammalian Infection

AbstractCryptococcus gattii R265 is a hyper-virulent fungal strain responsible for the major outbreak of cryptococcosis in Vancouver Island of British Columbia in 1999. It differs significantly from C. neoformans in its natural environment, its preferred site in the mammalian host, and in the nature and mode of pathogenesis. Our previous studies in C. neoformans have shown that the presence of chitosan, the deacetylated form of chitin, in the cell wall attenuates inflammatory responses in the host, while its absence induces robust immune responses, which in turn facilitate clearance of the fungus and induces a protective response. The results of the present investigation reveal that the cell wall of C. gattii R265 contains 2-3-fold higher amount of chitosan compared to that of C. neoformans. The genes responsible for the biosynthesis of chitosan are highly conserved in the R265 genome; the roles of the three chitin deacetylases (CDA) have however, been modified. To deduce their roles, single, double and a triple CDA deletion strains were constructed in a R265 background and were subjected to mammalian infection studies. Unlike C. neoformans where Cda1 has a discernible role in fungal pathogenesis, in R265 Cda3 is critical for virulence. Deletion of either CDA3 alone (cda3Δ) or in combination with either CDA1 (cda1Δ3Δ) or CDA2 (cda2Δ3Δ) or both (cda1Δ2Δ3Δ) rendered the yeast cells avirulent and were cleared from the infected host. Moreover, the cda1Δ2Δ3Δ strain of R265 induced a protective response to a subsequent infection with R265. These studies shed more light into the regulation of chitosan biosynthesis of C. gattii and its subsequent effect on fungal virulence.ImportanceThe fungal cell wall is an essential organelle whose components provide the first line of defense against host-induced antifungal activity. Chitosan is one of the carbohydrate polymers in the cell wall that significantly affects the outcome of host-pathogen interaction. Chitosan-deficient strains are avirulent, implicating chitosan as a critical virulence factor. C. gattii R265 is an important fungal pathogen of concern due to its ability to cause infections in individuals with no apparent immune dysfunction and an increasing geographical distribution. Characterization of the fungal cell wall and understanding the contribution of individual molecules of the cell wall matrix to fungal pathogenesis offers new therapeutic avenues for intervention. In this report, we show that the C. gattii R265 strain has evolved alternate regulation of chitosan biosynthesis under both laboratory growth conditions and during mammalian infection compared to that of C. neoformans.

scholarly journals M-ficolin is present in Aspergillus fumigatus infected lung and modulates epithelial cell immune responses elicited by fungal cell wall polysaccharides

Virulence ◽  
2017 ◽  
Vol 8 (8) ◽  
pp. 1870-1879 ◽  
Author(s):  
Kasper Jensen ◽  
Kit P. Lund ◽  
Kimmie B. Christensen ◽  
Anne T. Holm ◽  
Lalit Kumar Dubey ◽  
...  
Keyword(s):  
Cell Wall ◽  
Epithelial Cell ◽  
Immune Responses ◽  
Aspergillus Fumigatus ◽  
Fungal Cell Wall ◽  
Cell Wall Polysaccharides ◽  
Fungal Cell

scholarly journals Protein Kinase A and High-Osmolarity Glycerol Response Pathways Cooperatively Control Cell Wall Carbohydrate Mobilization inAspergillus fumigatus

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Leandro José de Assis ◽  
Adriana Manfiolli ◽  
Eliciane Mattos ◽  
João H. T. Marilhano Fabri ◽  
Iran Malavazi ◽  
...  
Keyword(s):  
Cell Wall ◽  
Protein Kinase ◽  
Glycogen Synthesis ◽  
Fungal Cell Wall ◽  
Cell Wall Biosynthesis ◽  
Fungal Cell ◽  
Content Type ◽  
High Osmolarity ◽  
High Osmolarity Glycerol ◽  
Kinase A

ABSTRACTAspergillus fumigatusmitogen-activated protein kinases (MAPKs) are involved in maintaining the normal morphology of the cell wall and providing resistance against cell wall-damaging agents. Upon cell wall stress, cell wall-related sugars need to be synthesized from carbohydrate storage compounds. Here we show that this process is dependent on cAMP-dependent protein kinase A (PKA) activity and regulated by the high-osmolarity glycerol response (HOG) MAPKs SakA and MpkC. These protein kinases are necessary for normal accumulation/degradation of trehalose and glycogen, and the lack of these genes reduces glucose uptake and glycogen synthesis. Alterations in glycogen synthesis were observed for thesakAandmpkCdeletion mutants, which also displayed alterations in carbohydrate exposure on the cell wall. Carbohydrate mobilization is controlled by SakA interaction with PkaC1 and PkaR, suggesting a putative mechanism where the PkaR regulatory subunit leaves the complex and releases the SakA-PkaC1 complex for activation of enzymes involved in carbohydrate mobilization. This work reveals the communication between the HOG and PKA pathways for carbohydrate mobilization for cell wall construction.IMPORTANCEAspergillus fumigatusis an opportunistic human pathogen causing allergic reactions or systemic infections such as invasive pulmonary aspergillosis, especially in immunocompromised patients. The fungal cell wall is the main component responsible for recognition by the immune system, due to the specific composition of polysaccharide carbohydrates exposed on the surface of the fungal cell wall called pathogen-associated molecular patterns (PAMPs). Key enzymes in the fungal cell wall biosynthesis are a good target for fungal drug development. This report elucidates the cooperation between the HOG and PKA pathways in the mobilization of carbohydrates for fungal cell wall biosynthesis. We suggest that the reduced mobilization of simple sugars causes defects in the structure of the fungal cell wall. In summary, we propose that SakA is important for PKA activity, therefore regulating the availability and mobilization of monosaccharides for fungal cell wall biosynthesis during cell wall damage and the osmotic stress response.

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