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1. (Article ID: 8553)
 
Geißel B, Loiko V, Klugherz I, Zhu Z, Wagener N, Kurzai O, van den Hondel CAMJJ, Wagener J
Azole-induced cell wall carbohydrate patches kill Aspergillus fumigatus
Nature Communications 9(1) (2018) E3098 (1-13)
 

Azole antifungals inhibit the fungal ergosterol biosynthesis pathway, resulting in either growth inhibition or killing of the pathogen, depending on the species. Here we report that azoles have an initial growth-inhibitory (fungistatic) activity against the pathogen Aspergillus fumigatus that can be separated from the succeeding fungicidal effects. At a later stage, the cell wall salvage system is induced. This correlates with successive cell integrity loss and death of hyphal compartments. Time-lapse fluorescence microscopy reveals excessive synthesis of cell wall carbohydrates at defined spots along the hyphae, leading to formation of membrane invaginations and eventually rupture of the plasma membrane. Inhibition of β-1,3-glucan synthesis reduces the formation of cell wall carbohydrate patches and delays cell integrity failure and fungal death. We propose that azole antifungals exert their fungicidal activity by triggering synthesis of cell wall carbohydrate patches that penetrate the plasma membrane, thereby killing the fungus. The elucidated mechanism may be potentially exploited as a novel approach for azole susceptibility testing.

cell wall, Microscopy, antifungal activity, azoles

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2. (Article ID: 8830)
 
Zhang Y, Zeng Y, Men Y, Zhang JG, Liu HM, Sun YX
Structural characterization and immunomodulatory activity of exopolysaccharides from submerged culture of Auricularia auricula-judae
International Journal of Biological Macromolecules 115 (2018) 978-984
 

Submerged culture of Auricularia auricula-judae has been documented, but there have been few studies on the structural characterization and medicinal properties of its exopolysaccharides. In present study, two exopolysaccharides, named CEPSN-1 and CEPSN-2, were isolated from submerged culture of A. auricula-judae, and their structural features as well as immunomodulatory activity were analyzed. The two exopolysaccharides both had a backbone chain composed of (1→4)-α-d-glucose residues in glucopyranose type. At the tested concentration range of 50-200 μg/mL, CEPSN-1 and CEPSN-2 not only showed non-toxicity to RAW 264.7 cells, but also could promote the release of NO and cytokines (IL-6, IL-10 and TNF-α) in the cells. The release of NO was significantly enhanced by the two exopolysaccharides at 100 μg/mL (p < 0.05). The IL-10 secretion was significantly increased by 1.80 and 1.61-fold, compared to the control after treatment with 50 μg/mL of CEPSN-1 and CEPSN-2, respectively (p < 0.05). These results demonstrated that, though their structural feature were different from that of polysaccharides from fruit body, exopolysaccharides of A. auricula-judae from submerged culture with the backbone of (1→4)-α-D-glucan could be explored as potential immunomodulatory agents for the application in complementary medicine or functional foods.

exopolysaccharides, immunomodulatory activity, Structural characterization, A. auricula-judae

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3. (Article ID: 8831)
 
Zhao DQ, Ding X, Hou YL, Hou WR, Liu L, Xu T, Yang DN
Structural characterization, immune regulation and antioxidant activity of a new heteropolysaccharide from Cantharellus cibarius Fr
International Journal of Molecular Medicine 41(5) (2018) 2744-2754
 

A new heteropolysaccharide was extracted and purified from the fruiting bodies of Cantharellus cibarius Fr. The Cantharellus cibarius Fr. polysaccharide (CC-1) had a molecular weight of 61,056 kDa and was mainly formed of the glucose and xylose at ratio of 5:1. Structure identification of CC-1 was analysed by a combined application of total hydrolysis, high performance liquid chromatography (HPLC), methylation analysis, gas chromatography-mass spectrometry (GC-MS), infrared (IR) spectra and nuclear magnetic resonance (NMR) spectroscopy. The experimental results showed that CC-1 had a backbone of 1,4-linked--D-glucose which branched at O-6 and the branches were mainly composed of 61)--D-xylopyranose residue. CC-1 exhibited significant in vitro antioxidant effect and proliferation effect of immune cells. The activity study showed CC-1 has ability to clear the ABTS(+) free radical and DPPH- free radical in a certain range of concentration. The proliferation activity of the immune cells showed that the proliferation effect on B cells was very significant (P<0.001) in the concentration of 0.625-80 mg/ml; and the effect of T cell proliferation was also very significant (P<0.001) in the concentration of 5-20 mg/ml. The result of this study introduced Cantharellus cibarius Fr. as a possible valuable source in exhibiting unique immunoregulatory and antioxidant properties.

structure, polysaccharide, antioxidant effect, proliferation effect, immune cells

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4. (Article ID: 8832)
 
Upadhya R, Baker LG, Lam WC, Specht CA, Donlin MJ, Lodge JK
Cryptococcus neoformans Cda1 and its chitin deacetylase activity are required for fungal pathogenesis
mBio 9(6) (2018) e02087-18 (1
 

Chitin is an essential component of the cell wall of Cryptococcus neoformans conferring structural rigidity and integrity under diverse environmental conditions. Chitin deacetylase genes encode the enyzmes (chitin deacetylases [Cdas]) that deacetylate chitin, converting it to chitosan. The functional role of chitosan in the fungal cell wall is not well defined, but it is an important virulence determinant of C. neoformans Mutant strains deficient in chitosan are completely avirulent in a mouse pulmonary infection model. C. neoformans carries genes that encode three Cdas (Cda1, Cda2, and Cda3) that appear to be functionally redundant in cells grown under vegetative conditions. Here we report that C. neoformans Cda1 is the principal Cda responsible for fungal pathogenesis. Point mutations were introduced in the active site of Cda1 to generate strains in which the enzyme activity of Cda1 was abolished without perturbing either its stability or localization. When used to infect CBA/J mice, Cda1 mutant strains produced less chitosan and were attenuated for virulence. We further demonstrate that C. neoformans Cda genes are transcribed differently during a murine infection from what has been measured in vitro IMPORTANCE Cryptococcus neoformans is unique among fungal pathogens that cause disease in a mammalian host, as it secretes a polysaccharide capsule that hinders recognition by the host to facilitate its survival and proliferation. Even though it causes serious infections in immunocompromised hosts, reports of infection in hosts that are immunocompetent are on the rise. The cell wall of a fungal pathogen, its synthesis, composition, and pathways of remodelling are attractive therapeutic targets for the development of fungicides. Chitosan, a polysaccharide in the cell wall of C. neoformans is one such target, as it is critical for pathogenesis and absent in the host. The results we present shed light on the importance of one of the chitin deacetylases that synthesize chitosan during infection and further implicates chitosan as being a critical factor for the pathogenesis of C. neoformans.

chitosan, fungal virulence, catalytic site, cell wall localization, chitin deacetylase, metal binding site

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