Investigation into the functions of CLC channels in the filamentous fungus Aspergillus nidulans.

Oddon, E. and Diatloff, Eugene and Roberts, Stephen K. (2004) Investigation into the functions of CLC channels in the filamentous fungus Aspergillus nidulans. Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology, 137 (3 Supp). S196-S197. ISSN 1095-6433

Abstract

The voltage-dependent chloride channel (CLC) family defines a large class of anion-permeable membrane proteins present in all Eukaryotes. In the fungal kingdom, our best knowledge of CLC gene function comes from the study of GEF1, the sole member of the CLC family present in S. cerevisiae. Functional analysis of Gef1 null mutants reveal a role for the chloride channel in intracellular iron and copper metabolism and transport. In contrast to the yeast model, we have identified three CLC homologues in the Aspergillus nidulans genome. This study reports the characterisation of one of the homologues, AnCLCA. AnCLCA is a 909 amino acid polypeptide which functions as a chloride channel when expressed in yeast Gef1 null mutant. To define its role in Aspergillus, we created an AnCLCA null mutant. This mutant shows: * Hypersensitivity to extracellular copper that can be overcome by the addition of N-acetyl cysteine and resulting from an intracellular accumulation of copper. * Reduced activity of copper-dependent superoxide dismutase thus exacerbating sensitivity to reactive oxygen species. * Elevated respiration rates resulting from enhanced copper-dependent cytochrome oxidase activity. On the basis of these results we have proposed a model for the role of AnCLCA in copper metabolism in filamentous fungi and have compared this function to that of Gef1 in yeast. The expression patterns of the three A. nidulans CLCs and their phylogenetic relationship are also presented.