Membrane potential governs lateral segregation of plasma membrane proteins and lipids in yeast

Abstract

The plasma membrane potential is mainly considered as the driving force for ion and nutrient translocation. Using the yeast Saccharomyces cerevisiae as a model organism, we have discovered a novel role of the membrane potential in the organization of the plasma membrane. Within the yeast plasma membrane, two non-overlapping subcompartments can be visualized. The first one, represented by a network-like structure, is occupied by the proton ATPase, Pma1, and the second one, forming 300-nm patches, houses a number of proton symporters (Can1, Fur4, Tat2 and HUP1) and Sur7, a component of the recently described eisosomes. Evidence is presented that sterols, the main lipid constituent of the plasma membrane, also accumulate within the patchy compartment. It is documented that this compartmentation is highly dependent on the energization of the membrane. Plasma membrane depolarization causes reversible dispersion of the H þ -symporters, not however of the Sur7 protein.Mitochondrial mutants, affected in plasma membrane energization, show a significantly lower degree of membrane protein segregation. In accordance with these observations, depolarized membranes also considerably change their physical properties (detergent sensitivity).

The Sphingolipid Long-chain Base-Pkh1/2-Ypk1/2 Signaling Pathway Regulates Eisosome Assembly and Turnover

“…Further work will be required to identify the specific phosphorylation sites necessary for eisosome assembly and correct distribution on the plasma membrane. The distribution of eisosomes is probably due to their localization to patches on the plasma membrane that are enriched for sterols, proton symporters and the Sur7 protein, which is thought to anchor eisosomes (2). Our data suggest that Pil1 phosphorylation plays a role in localizing eisosomes to these patches.…”

“…Recently, two related Saccharomyces cerevisiae proteins, Pil1 and Lsp1, were shown to comprise novel structures on the cytoplasmic face of the plasma membrane termed eisosomes (1). Eisosomes mark sites for endocytosis of proteins and lipids, and they are sequestered on patches in the plasma membrane rich in sterols and specific protein transporters (2). We showed previously that Pil1 and Lsp1 are phosphorylated in vitro by the Pkh1 and Pkh2 protein kinases (3), which are structural and functional homologs of mammalian phosphoinositidedependent protein kinase 1 (4,5).…”

Eisosome Ultrastructure and Evolution in Fungi, Microalgae, and Lichens

“…Ergosterol is an abundant component of yeast plasma membranes (ϳ50% of total lipid [96]), and yeast eisosomes have been shown to be dramatically enriched in ergosterol compared with the rest of the membrane (18). Since embossed patterns have not been observed in (ergo)sterol-poor membranes (e.g., Golgi vesicles) that also associate with BAR proteins, the embossed patterns of yeast eisosomes suggest that ergosterol may play a role.…”

“…These observations were brought together by Strádalová et al (5), who showed that the membrane compartment occupied by Can1p (MCC) localized to the invaginations seen with freeze fracture EM, and by Karotki et al (6), who showed that Pil1p localizes to the cytoplasmic surfaces of these invaginations. Additional proteins also associate with these punctate domains, in some cases in a transient fashion (17), and the MCC component is reportedly enriched in ergosterol (18) and influenced by phosphoinositide (6,19,20) and sphingolipid (14,17,(21)(22)(23)(24) levels. Hence, the current yeast model (25,26) proposes that Pil1p and Lsp1p, which contain membrane curvatureinducing BAR domains (6,27,28), together with Seg1p (29,30), form a submembrane complex (6) reportedly influenced by Pil1p phosphorylation (25); this complex then either creates or associates with the MCC domains, presumably inducing an inward curvature.…”

C-Terminal Truncations of the Saccharomyces cerevisiae PMA1 H + -ATPase Have Major Impacts on Protein Conformation, Trafficking, Quality Control, and Function

“…It has a characteristic topology, with 10 membrane-spanning elements and three welldefined cytoplasmic domains; the N and C termini are also located in the cytoplasm (3). In recent years, it has served as a useful model for studies of structure-function relationships and membrane biogenesis (4)(5)(6)(7)(8).…”