XI International Meeting on Paracoccidioidomycosis

XI International Meeting on Paracoccidioidomycosis

Resume:115-1

Investigação

115-1	Mechanisms of synthesis and degradation of cell wall alpha glucan in Paracoccidioides brasiliensis
Authors:	Gustavo Nino-vega (IVIC - Instituto Venezolano de Investigaciones Científicas) ; Emma Camacho (IVIC - Instituto Venezolano de Investigaciones Científicas) ; Hector Villalobos (IVIC - Instituto Venezolano de Investigaciones Científicas) ; Laura Barreto (IVIC - Instituto Venezolano de Investigaciones Científicas) ; Gioconda San-blas (IVIC - Instituto Venezolano de Investigaciones Científicas)

Abstract

In Paracoccidioides brasiliensis, α-1,3-glucan is the major neutral cell wall polysaccharide of the pathogenic yeastlike (Y), organised as a sort of outer capsule, replacing almost entirely the β-1,3-glucan, while absent in the mycelial (M) phase. It has been proposed as virulence factor in P. brasiliensis, Blastomyces dermatitidis and Histoplasma capsulatum. Loss of α-(1,3)-glucan in H. capsulatum by RNA interference of the AGS1 gene, produced attenuation of the ability to kill macrophages and colonize murine lungs, demonstrating a role for α-(1,3)-glucan in virulence (Mol Microbiol. 2004;53(1):153-165). Chemical analyses of P. brasiliensis α-1,3-glucan, synthesized by Ags1p, indicated that it is essentially a linear polysaccharide, with < 3% of α-1,4-linked glucose branches, occasionally attached as single units to the α-1,3-backbone. Our group have been researching the different genes possible involved in the synthesis, regulation and hydrolysis of cell wall α-1,3-glucan in P. brasiliensis. A gene with high identity with H. capsulatum α-1,4-amylase, expressed preferentially in the pathogenic Y phase, was identified, and complemented an H. capsulatum amy1 mutant, a result that suggest an important role for its product in the synthesis of α-1,3-glucan in P. brasiliensis. In silico amino acid analysis of the deduced protein led to the identification of all four conserved regions of the α-amylase family, the critical moieties for biological activity and amino acids associated with the specificity to glucosidic α-1,4-linkages. Also, a single gene for an α-1,3-glucanase was identified and its product analysed, showing α-1,3-glucanase activity. In the present work, we summarize our molecular and biochemical data on P. brasiliensis α-1,3-glucan, by proposing mechanisms of synthesis, regulation and hydrolysis of the cell wall α-1,3-glucan in this medically important fungus.਀ This work was supported by Research Project 112 from Instituto Venezolano de Investigaciones Científicas.

Keyword: alpha-1,3-glucan, cell wall, alpha glucanase

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