The lateral compartmentation of the yeast plasma membrane

Abstract

The plasma membrane of Saccharomyces cerevisiae contains large microdomains enriched in ergosterol, which house at least nine integral proteins, including proton symporters. The domains adopt a characteristic structure of furrow-like invaginations typically seen in freeze-fracture pictures of fungal cells. Being stable for the time comparable with the cell cycle duration, they might be considered as fixed islands (rafts) in an otherwise fluid yeast plasma membrane. Rapidly moving endocytic marker proteins avoid the microdomains; the domain-accumulated proton symporters consequently show a reduced rate of substrate-induced endocytosis and turnover.

A Genomewide Screen for Tolerance to Cationic Drugs Reveals Genes Important for Potassium Homeostasis in Saccharomyces cerevisiae

“…Therefore, one might speculate that, even if properly delivered to the membrane, the ERG6 mutation could affect the activity of the Trk1 transporter. In fact, Trk1 was shown previously to be associated with plasma membrane "rafts" (50), a kind of structure that, in many cases, depends on proper sterol biosynthesis (27). Accordingly, the pattern of fluorescence of Trk1-green fluorescent protein (GFP) is notably altered in this mutant, thus providing support for this hypothesis (Fig.…”

Atomic force microscopy – looking at mechanosensors on the cell surface

“…Molecular recognition images were recorded on cells expressing His-tagged elongated sensors using Ni 2+ -NTA tips. Many sensor molecules appeared to form clusters of ,200 nm, which is in the range of the large patches observed by fluorescence microscopy for the microdomains containing the marker protein Can1 (MCC) in S. cerevisiae (Malinsky et al, 2010). Both the surface density of Wsc1 sensors and their tendency to cluster increases when cells are stressed by heat or low osmolarity, which suggests that clustering is a stress response that is intimately connected to signaling.…”

Microcompartments within the yeast plasma membrane

“…The mammalian lipid rafts are thought of as small, freely diffusing, highly dynamic membrane patches being 20 -80 nm in diameter (Simons and Gerl , 2010 ), whereas the yeast disposes of two defined and stable plasma membrane compartments (Figure 1 ) (reviewed in Malinsky et al , 2010 ): 1. In early works, a punctuated distribution was observed for GFP fusions to the arginine permease encoded by CAN1 .…”

“…In addition, more dynamic punctuate structures with somewhat smaller diameters than the MCCs have been detected, which localize to the regions that are different from both the MCCs and the MCPs and are defined by the presence of the TORC2 complex (hence the name MCT, for m embrane c ompartment of T ORC2; Berchtold and Walther , 2009 ). It should be noted that besides these characteristic determinants, other membrane proteins may be more uniformly distributed within the plasma membrane, such as the hexose transporter Hxt1 or the general amino acid permease Gap1 (Malinsky et al , 2010 ). However, the latter distribution has been doubted in a recent publication, in which the distribution of 46 different plasma membrane proteins has been studied with fluorescence tags at high resolution (Spira et al , 2012 ).…”

“…Using the ' awesome power of yeast genetics ' (Forsburg , 2001 ), in combination with biochemical and biophysical approaches, the underlying molecular mechanisms in the formation and physiological role of these rafts are being studied. These data have been reviewed recently (Malinsky et al , 2010 ) and will be updated and discussed here briefly. In subsequent parts of this review, we will focus on two examples of specialized yeast plasma membrane microcompartments, namely, the clustering of cell wall integrity sensors and the role of the yeast bud neck during cytokinesis, culminating in actomyosin ring (AMR) constriction and the formation of the chitinous primary septum.…”