The 14-3-3 Gene Function of Cryptococcus neoformans Is Required for its Growth and Virulence

Abstract

Cryptococcus neoformans is a life-threatening pathogenic yeast that causes devastating meningoencephalitis. The mechanism of cryptococcal brain invasion is largely unknown, and recent studies suggest that its extracellular microvesicles may be involved in the invasion process. The 14-3-3 protein is abundant in the extracellular microvesicles of C. neoformans, and the 14-3-3-GFP fusion has been used as the microvesicle's marker. However, the physiological role of 14-3-3 has not been explored. In this report, we have found that C. neoformans contains a single 14-3-3 gene that apparently is an essential gene. To explore the functions of 14-3-3, we substituted the promoter region of the 14-3-3 with the copper-controllable promoter CTR4. The CTR4 regulatory strain showed an enlarged cell size, drastic changes in morphology, and a decrease in the thickness of the capsule under copper-enriched conditions. Furthermore, the mutant cells produced a lower amount of total proteins in their extracellular microvesicles and reduced adhesion to human brain microvascular endothelial cells in vitro. Proteomic analyses of the protein components under 14-3-3-overexpressed and -suppressed conditions revealed that the 14-3-3 function(s) might be associated with the microvesicle biogenesis. Our results support that 14-3-3 has diverse pertinent roles in both physiology and pathogenesis in C. neoformans. Its gene functions are closely relevant to the pathogenesis of this fungus.

Redundant and Distinct Roles of Two 14-3-3 Proteins in Fusarium sacchari, Pathogen of Sugarcane Pokkah Boeng Disease

“…This study elucidates the pivotal roles of the 14-3-3 protein genes FsBmh1 and FsBmh2 in the development, growth, conidiation, and virulence of F. sacchari, the causative agent of sugarcane Pokkah boeng disease. The observed developmental defects, including pigment loss, growth reduction, and attenuated virulence in the deletion mutants, align with previous findings that 14-3-3 proteins are integral to the regulation of cellular processes in various fungi, such as vegetative development, metabolism, stress response, signaling pathways, transcription factor activity, and pathogenicity [34][35][36][37][38].…”

Subcellular Compartmentalization and Trafficking of the Biosynthetic Machinery for Fungal Melanin

“…Both 14-3-3 isoforms co-localized with the two melanin enzymes tested (Figure 3A–D), suggesting that endosome-derived MVBs might be an important cellular compartment for these melanin enzymes. Consistent with this idea, the activity of laccase, the enzyme responsible for Cryptococcus melanization, is drastically reduced in a strain with low level of the 14-3-3 protein (Li et al, 2015). …”

“…14-3-3 is a marker for MVBs and extracellular vesicles in the fungus Cryptococcus neoformans (Li et al, 2015). 14-3-3 proteins are also found in extracellular vesicles in mammals (Pisitkun et al, 2004).…”

Characteristics and potential clinical applications of the extracellular vesicles of human pathogenic Fungi

“…Intracellular vesicular clusters of S. cerevisiae promote the production and selection of proteins associated with EV secretion [ 39 ]. Moreover, reduced expression of cryptococcal microvesicle marker protein 14-3-3 [ 40 ] decreases the GXM and protein content in EVs and decreases acid phosphatase and laccase activities [ 41 ].…”