Aspergillus fumigatus Trehalose-Regulatory Subunit Homolog Moonlights To Mediate Cell Wall Homeostasis through Modulation of Chitin Synthase Activity

Abstract

Trehalose biosynthesis is found in fungi but not humans. Proteins involved in trehalose biosynthesis are essential for fungal pathogen virulence in humans and plants through multiple mechanisms. Loss of canonical trehalose biosynthesis genes in the human pathogen Aspergillus fumigatus significantly alters cell wall structure and integrity, though the mechanistic link between these virulence-associated pathways remains enigmatic. Here we characterize genes, called tslA and tslB, which encode proteins that contain domains similar to those corresponding to trehalose-6-phosphate phosphatase but lack critical catalytic residues for phosphatase activity. Loss of tslA reduces trehalose content in both conidia and mycelia, impairs cell wall integrity, and significantly alters cell wall structure. To gain mechanistic insights into the role that TslA plays in cell wall homeostasis, immunoprecipitation assays coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to reveal a direct interaction between TslA and CsmA, a type V chitin synthase enzyme. TslA regulates not only chitin synthase activity but also CsmA sub-cellular localization. Loss of TslA impacts the immunopathogenesis of murine invasive pulmonary aspergillosis through altering cytokine production and immune cell recruitment. In conclusion, our data provide a novel model whereby proteins in the trehalose pathway play a direct role in fungal cell wall homeostasis and consequently impact fungus-host interactions.

The Inhibitory Effect of Validamycin A onAspergillus flavus

“…Trehalose pathway is clearly associated with cell wall components, including chitin and beta-glucan, as shown in many previous reports [ 18 , 19 , 42 , 47 ]. Disturbance in substrates of trehalose or enzymes or proteins associated with the trehalose pathway in Aspergillus fumigatus would lead to changes in the cell wall components and structure [ 18 , 19 , 42 , 47 ]. Furthermore, trehalose level and proteins associated with the trehalose pathway may affect exopolysaccharide galactosaminogalactans (GAGs), which are important for fungal adherence and biofilm formation, as shown in A. fumigatus previous reports [ 42 , 47 ].…”

“…Disturbance in substrates of trehalose or enzymes or proteins associated with the trehalose pathway in Aspergillus fumigatus would lead to changes in the cell wall components and structure [ 18 , 19 , 42 , 47 ]. Furthermore, trehalose level and proteins associated with the trehalose pathway may affect exopolysaccharide galactosaminogalactans (GAGs), which are important for fungal adherence and biofilm formation, as shown in A. fumigatus previous reports [ 42 , 47 ]. In this study, we also observed that validamycin A decreased fungal adherence ( Figure 4(c) ).…”

“…Conidia of A. flavus ATCC 204304 from SDA treated with or without 1 μ g/mL validamycin A were collected at day 5 after incubation at 37°C. Trehalose levels of A. flavus conidia were measured, as previously described [ 42 ]. In brief, 2 × 10 8 conidia in 500 uL distilled water with Tween 80 were boiled at 100 o C for 20 min and centrifuged at 11,000 ×g for 10 min.…”

Protein Kinase A and High-Osmolarity Glycerol Response Pathways Cooperatively Control Cell Wall Carbohydrate Mobilization in Aspergillus fumigatus

“…The importance of glycogen for filamentous fungal pathogenesis has been reported previously in plant pathogens (30). Similarly, trehalose is important for germination and for establishing an infection (28, 29, 69, 70). In conclusion, this study reports on the mechanistic signaling and regulation events underlying A.…”

FocSge1 in Fusarium oxysporum f. sp. cubense race 1 is essential for full virulence

“…The radial growth in the calcofluor white medium was relatively more in the deletion and truncated mutants as compared to the wild-type strain indicating that they are capable of resisting it. Inappropriate accumulation of trehalose, glycerol and other osmolytes have been known to regulate stress responses [19][20][21][22]. Intercellular trehalose plays a critical role in free radical scavenging, whereas glycerol affirmatively responds to osmotic stress [23].…”