Aislamiento y caracterización de ABG1, un gen esencial del hongo patógeno oportunista Candida Albicans.

Abstract

The immunoscreening of a cDNA library with a polyclonal germ-tube specific antibody of Candida albicans led to the isolation of a novel gene of C. albicans. The repression of this gene led to the formation of bud chains that decreased in size towards the chain end. On the basis of this altered budding growth the gene was designated ABG1. Western immunoblotting of cellular fractions with a polyclonal antibody immunospecific of Abg1p and experiments of fussion with the GFP of Aequorea victoria that Abg1p was located at the vacuolar and endocytic vesicles membranes of C. albicans. In order to establish the role of ABG1 in the biology of C. albicans construction of a conditional strain for ABG1 under MET3 promoter control was achieved. Thus enabled us to demonstrate that this novel gene is essential for C. albicans. Accordingly with the subcelular localization of Abg1p, phenotypic analysis of the conditional mutant strain revealed alterations in the number, morphology and size of vacuoles. ABG1 repression also resulted in defects in cell division, characterized by a failure in the cytokinesis that lead to the formation of bud chains in yeast cells. When hyphal growth was induced an increased frequency of branching was detected. Loss of ABG1 function also resulted in pleiotropic effects on structure and/or composition of the cell wall. Search of proteins that could be interacting in vivo with Abg1p revealed the possible interaction between Abg1p and one aminopeptidase (Ape2p) and one protein of the heat shock protein (Ssa1p). Thus could suggest a function model for Abg1p in the vacuolar membrane of C. albicans, in which the product of the ABG1 gene would act as the receptor of Ape2p, which would be transported by Ssa1p from the cytosol to the vacuolar membrane. The gene product of ABG1 links vacuolar biology with cellular morphogenesis and cell cycle progression. All of these processes are associated with virulence traits in C. albicans. In addition, Abg1p is the first essential vacuolar protein described in C. albicans and has no homology with mammalian genes, suggesting that this gene product could be regarded as a potential target for antifungal chemoterapy.