Lipid rafts in Schizophyllum commune: insights in localization and composition

The study investigates the growth polarization observed in Schizophyllum commune, a filamentous basidiomycete known for its distinctive growth characteristics. The coordination of the actin cytoskeleton and membrane raft domains is pivotal in establishing and maintaining cellular polarity. Additionally, the role of a less explored membrane microdomain is examined for its potential significance in polarized growth and involvement in cellular signaling pathways. Lipid rafts in fungal membranes are characterized by sphingolipid aggregation and high sterol content, resulting in dynamic and heterogeneous sterol-rich domains. Specific membrane proteins, such as GPI-anchored proteins, are attracted to these domains. While the role of stomatin in sterol-rich domain (SRD) formation has been established in Aspergillus nidulans, the functions and mechanisms in basidiomycetes like S. commune remain largely undefined. This study also highlights striatin, which contains a caveolin-binding sequence, noting that caveolin, a crucial lipid raft protein in mammals, is absent in basidiomycetes. The investigation focuses on three key questions: the composition of raft domains, their localization within filamentous fungal hyphae, and their roles in polarized growth and cytoskeletal signaling in S. commune. Lipid raft-specific protein isolation revealed insights into raft domain composition, targeting stomatin and striatin for localization studies. A stomatin knockout assessed its impact on S. commune, while co-immunoprecipitation of a striatin complex aimed to identify potential caveolin replacement proteins. This study seeks a comprehensive understanding of lipid rafts in basidiomycetes, emphasizing their role in polarized growth and other fungus-specific processes.