Insights into the Localization and Structural Composition of Lipid Rafts in Schizophyllum commune

Lipid rafts are dynamic microdomains within the cell membrane. They contain high levels of sterols, sphingolipids, and specific proteins associated with lipid rafts. These domains act as platforms for signal transduction, membrane trafficking, protein sorting, and polarized growth (Alvarez et al., 2007). The filamentous basidiomycete Schizophyllum commune requires polarized growth, which depends on the transport of proteins and lipids to the hyphal tip through vesicle trafficking. Rafts contain specific proteins like stomatin and striatin. They play a crucial role in cell signalling and signal transduction. Further striatin is known for its protein-protein interactions with caveolin, a well-known raft related protein.
The aim of this work is to investigate the composition of raft domains and the localization and function of rafts in S. commune using two raft-associated proteins: stomatin and striatin. To analyse the overall membrane composition, we performed LC-MS measurements. Sterol-enriched raft domains were visualized by Filipin staining. Further, stomatin and striatin were labelled with the fluorescence proteins dTomato and eGFP, respectively, and visualized by laser scanning microscopy. To investigate the role of stomatin and striatin, we performed a knockout followed by RNA sequencing. The deletion of either stomatin and striatin in S. commune impacted the organism regarding morphological and genetic changes. The RNAseq results of S. commune Δsto showed an upregulation of several cell signalling groups like GPI-anchored proteins, MAPKs, and GPCRs. Further results showed a high effect on membrane-related genes and several membrane transporter groups. The deletion of striatin in S. commune seems to play a significant role in S. commune, especially in the dikaryotic life stage.
The study has shown that raft-associated proteins of S. commune play an important role in hyphal growth, cell signalling, membrane stabilization, and membrane-related components. Enhancing our understanding of the structure and functionality of membrane microdomains in microorganisms could potentially provide valuable insights into mating, the interaction of organisms, and the pathogenesis process.
Alvarez, F. J., Douglas, L. M., & Konopka, J. B. (2007). Sterol-Rich Plasma Membrane Domains in Fungi. Eukaryotic Cell, 6(5).