Amiodarone induces stress responses and calcium flux mediated by the cell wall inSaccharomyces cerevisiae

Abstract

We used a proteomic approach to study effects of amiodarone on cells of the yeast Saccharomyces cerevisiae. Amiodarone has been shown to have antifungal activity in vitro and causes a massive increase in cytoplasmic calcium levels ([Ca²⁺]_cyt). Proteomic analysis of cells exposed to amiodarone show that this drug elicits stress responses and points to involvement of proteins associated with the cell wall. We tested several of those proteins for involvement in the Ca²⁺flux. In particular, the amiodarone-induced Ca²⁺flux was decreased in bgl2Δ cells, which have altered levels of β-glucan and chitin. The involvement of the cell wall in the Ca²⁺flux induced by amiodarone treatment was tested by addition of yeast cell-wall components. While mannan inhibited the rise in [Ca²⁺]_cyt, β-glucan potentiated the Ca²⁺flux by 4.5-fold, providing evidence that the cell wall is directly involved in controlling this Ca²⁺flux. This conclusion is corroborated by the inhibition of the Ca²⁺flux by calcofluor, which is known to bind to cell-wall chitin and inhibit cell growth. Zymolyase treatment altered the kinetics of amiodarone-induced calcium flux and uncoupled the inhibitory effect of calcofluor. These effects demonstrate that the cell-wall β-glucan regulates calcium flux elicited by amiodarone.