Journal Article

The Cryptococcus neoformans STRIPAK complex controls genome stability, sexual development, and virulence

Fu, Ci, Choi, Jin-Tae, Bahn, Yong-Sun, Peterson, Patricia P., Heitman, Joseph, Cowen, Leah E., Sun, Sheng

2024

Overview

The eukaryotic serine/threonine protein phosphatase PP2A is a heterotrimeric enzyme composed of a scaffold A subunit, a regulatory B subunit, and a catalytic C subunit. Of the four known B subunits, the B”’ subunit (known as striatin) interacts with the multi-protein striatin-interacting phosphatase and kinase (STRIPAK) complex. Orthologs of STRIPAK components were identified in Cryptococcus neoformans , namely PP2AA/Tpd3, PP2AC/Pph22, PP2AB/Far8, STRIP/Far11, SLMAP/Far9, and Mob3. Structural modeling, protein domain analysis, and detected protein-protein interactions suggest C . neoformans STRIPAK is assembled similarly to the human and fungal orthologs. Here, STRIPAK components Pph22, Far8, and Mob3 were functionally characterized. Whole-genome sequencing revealed that mutations in STRIPAK complex subunits lead to increased segmental and chromosomal aneuploidy, suggesting STRIPAK functions in maintaining genome stability. We demonstrate that PPH22 is a haploinsufficient gene: heterozygous PPH22/pph22 Δ mutant diploid strains exhibit defects in hyphal growth and sporulation and have a significant fitness disadvantage when grown in competition against a wild-type diploid. Deletion mutants pph22 Δ, far8 Δ, and mob3 Δ exhibit defects in mating and sexual differentiation, including impaired hyphae, basidia, and basidiospore production. Loss of either PPH22 or FAR8 in a haploid background leads to growth defects at 30°C, severely reduced growth at elevated temperature, abnormal cell morphology, and impaired virulence. Additionally, pph22 Δ strains frequently accumulate suppressor mutations that result in overexpression of another putative PP2A catalytic subunit, PPG1 . The pph22 Δ and far8 Δ mutants are also unable to grow in the presence of the calcineurin inhibitors cyclosporine A or FK506, and thus these mutations are synthetically lethal with loss of calcineurin activity. Conversely, mob3 Δ mutants display increased thermotolerance, capsule production, and melanization, and are hypervirulent in a murine infection model. Taken together, these findings reveal that the C . neoformans STRIPAK complex plays an important role in genome stability, vegetative growth, sexual development, and virulence in this prominent human fungal pathogen.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Aneuploidy / Animals / Biology and Life Sciences / Calcineurin inhibitors / Cell cycle / Cell growth / Cell morphology / Cryptococcosis - microbiology / Cryptococcus / Cryptococcus neoformans / Cryptococcus neoformans - genetics / Cryptococcus neoformans - metabolism / Cryptococcus neoformans - pathogenicity / Cyclosporins / Defects / Deletion mutant / Diploids / DNA sequencing / Enzymes / Female / Fungal Proteins - genetics / Fungal Proteins - metabolism / Fungi / Gene sequencing / Genetic aspects / Genetic regulation / Genetic suppression / Genomes / Genomic Instability / Genomics / High temperature / Hyphae / Infectious diseases / Kinases / Melanization / Mice / Microbiological research / Morphogenesis / Mutants / Mutation / Nucleotide sequencing / Pathogens / Phosphatase / Phosphatases / Phosphorylation / Physical Sciences / Physiological aspects / Protein interaction / Protein kinases / Protein Phosphatase 2 - genetics / Protein Phosphatase 2 - metabolism / Protein-protein interactions / Proteins / Research and Analysis Methods / Sex differentiation / Sexual Development - genetics / Signal transduction / Sporulation / Stability / Tacrolimus / Temperature tolerance / Virulence / Virulence (Microbiology) / Whole genome sequencing / Yeast