Fungal plasma membrane domains

Abstract

The plasma membrane (PM) performs a plethora of physiological processes, the coordination of which requires spatial and temporal organization into specialized domains of different sizes, stability, protein/lipid composition and overall architecture. Compartmentalization of the PM has been particularly well studied in the yeast Saccharomyces cerevisiae, where five non-overlapping domains have been described: The Membrane Compartments containing the arginine permease Can1 (MCC), the H+-ATPase Pma1 (MCP), the TORC2 kinase (MCT), the sterol transporters Ltc3/4 (MCL), and the cell wall stress mechanosensor Wsc1 (MCW). Additional cortical foci at the fungal PM are the sites where clathrin-dependent endocytosis occurs, the sites where the external pH sensing complex PAL/Rim localizes, and sterol-rich domains found in apically grown regions of fungal membranes. In this review, we summarize knowledge from several fungal species regarding the organization of the lateral PM segregation. We discuss the mechanisms of formation of these domains, and the mechanisms of partitioning of proteins there. Finally, we discuss the physiological roles of the best-known membrane compartments, including the regulation of membrane and cell wall homeostasis, apical growth of fungal cells and the newly emerging role of MCCs as starvation-protective membrane domains.

Life and Death of Fungal Transporters under the Challenge of Polarity

“…Some appear in distinct foci, whereas other evenly mark the entire PM. For example, in S. cerevisiae, several transporters specific for amino acids (Can1, Mup1, Tat2) or uracil (Fur4) transporters are preferentially located in PM microdomains of 200-300 nm called MCC (membrane compartments of Can1), which do not overlap with other microdomains, called MCP or MCL, defined by distinct transporters, such as the H + -ATPase Pma1 or sterol transporters Ltc3/4, respectively [58]. Still, other transporters do not define PM microdomains (e.g., the general amino acid permease Gap1, several sugar transporters, etc.).…”

Liquid-Ordered Phase Formation by Mammalian and Yeast Sterols: A Common Feature With Organizational Differences

“…In fact, Erg and Chol have been considered crucial for the formation of a subset of membrane lipid domains described as being in a liquid ordered (l o ) phase, due to their ability to establish tight interactions with sphingolipids (Simons and Vaz, 2004;Klose et al, 2010). Although both Chol and Erg form l o phases, their respective two kingdoms present fundamental differences in their membrane lipid organization, namely the transient nature and nanoscopic scale of the lipid domains in mammalian cells (Sezgin et al, 2017) versus stable large membrane compartments in yeast (Malinsky and Opekarova, 2016;Athanasopoulos et al, 2019;Zahumensky and Malinsky, 2019). Another distinctive feature is the leaflet distribution of either Chol or Erg: whereas for Chol the literature is not consensual in the evidence for its preferential location in the outer/inner leaflet or its even distribution (Steck and Lange, 2018), regarding Erg interleaflet partition recent results point toward a possible preferential location in the inner leaflet (Solanko et al, 2018).…”

Internalization of the host alkaline pH signal in a fungal pathogen

“…Additionally, it is known that Rim pathway outputs are involved in cell wall remodeling [3,5,9,16,62] and that specific membrane domain characteristics are dependent not only on lipid distribution and composition, but also on the proximity to the fungal cell wall [2,63]. Rim101 regulation of the fungal cell wall at high pH could have direct effects on cell wall turgor pressure and therefore would affect the shape and curvature of the plasma membrane allowing for membrane-associated proteins to establish themselves in microdomains.…”

“…The ability for organisms to effectively recognize and transmit signals relating to changes in the external environment is essential for their survival. For microscopic fungal organisms, the ability to specifically sense increases in extracellular pH is known to be important for the production of secondary metabolites [1], the maintenance of the fungal cell wall [2–6], and virulence in the case of fungal pathogens [7–12]. In many fungi, pH recognition processes include the fungal-specific Rim/Pal alkaline response pathway, [7,8,11,13,14].…”