Deletion of a small, secreted and cysteine-rich protein Cpl1 leads to increased invasive growth of Cryptococcus neoformans into nutrient agar

Abstract

Invasive growth of yeast cells into nutrient agar is induced by different stresses and contributes to the survival of yeast cells under several adverse conditions. The mechanism of invasive growth of Saccharomyces cerevisiae has been extensively investigated. However, there is very little information about the mechanism of invasive growth of another human pathogen yeast Cryptococcus neoformans. Here, we report that deletion of a small and secreted cysteine-rich protein Cpl1 in C. neoformans JEC21 leads to increased adhesive and invasive growth into nutrient agar. The increased adhesive and invasive growth does not depend on the only known adhesion protein Cfl1 and its main controller Znf2. Cpl1Δ accumulates significantly higher level of intracellular labile zinc ion, leading to increased glucose uptake, higher level of mitochondrial membrane potential, ATP and Reactive Oxygen Species(ROS) production. Higher level of ROS activates Snf1, leading to invasive growth of Cpl1Δ. Three cysteine residues at the N-terminals of the cysteine-rich domain controls the increased invasive growth under nutrient sufficient conditions. This is the first report that a small and secreted cysteine-rich protein negatively regulates invasive growth of C. neoformans through regulating the intracellular labile zinc ion level. The function of this cysteine-rich domain was systematically investigated by site-directed mutagenensis in C. neoformans. The work contributes to understanding the function of this protein family and the invasive growth mechanism in C. neoformans.