A subfraction of the yeast endoplasmic reticulum associates with the plasma membrane and has a high capacity to synthesize lipids

Pichler, Harald; Gaigg, Barbara; Hrastnik, Claudia; Achleitner, Georg; Kohlwein, Sepp D.; Zellnig, Günther; Perktold, Andreas; Daum, Günther

doi:10.1046/j.1432-1327.2001.02116.x

Cited by 246 publications

(228 citation statements)

References 46 publications

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“…The extensive network of the ER has multiple positions where it is closely apposed to the PM (Pichler et al 2001;West et al 2011). Previous studies have identified the PM-associated ER as sites of phosphatidylinositol (PI) metabolism, nonvesicular transfer of sterols, and Ca 2þ level regulation (Li and Prinz 2004;Baumann et al 2005;Carrasco and Meyer 2011;Stefan et al 2011).…”

Section: Er and Plasma Membranementioning

confidence: 99%

Endoplasmic Reticulum Structure and Interconnections with Other Organelles

English

Voeltz

2013

Cold Spring Harbor Perspectives in Biology

276

211

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The endoplasmic reticulum (ER) is a large, continuous membrane-bound organelle comprised of functionally and structurally distinct domains including the nuclear envelope, peripheral tubular ER, peripheral cisternae, and numerous membrane contact sites at the plasma membrane, mitochondria, Golgi, endosomes, and peroxisomes. These domains are required for multiple cellular processes, including synthesis of proteins and lipids, calcium level regulation, and exchange of macromolecules with various organelles at ER-membrane contact sites. The ER maintains its unique overall structure regardless of dynamics or transfer at ER-organelle contacts. In this review, we describe the numerous factors that contribute to the structure of the ER.T he endoplasmic reticulum (ER) is a dynamic organelle responsible for many cellular functions, including the synthesis of proteins and lipids, and regulation of intracellular calcium levels. This review focuses on the distinct and complex morphology of the ER. The structure of the ER is complex because of the numerous distinct domains that exist within one continuous membrane bilayer. These domains are shaped by interactions with the cytoskeleton, by proteins that stabilize membrane shape, and by a homotypic fusion machinery that allows the ER membrane to maintain its continuity and identity. The ER also contains domains that contact the plasma membrane (PM) and other organelles including the Golgi, endosomes, mitochondria, lipid droplets, and peroxisomes. ER contact sites with other organelles and the PM are both abundant and dispersed throughout the cytoplasm, suggesting that they too could influence the overall architecture of the ER. As we will discuss here, ER shape and distribution are regulated by many intrinsic and extrinsic forces. ER STRUCTURE AND FORMATION Domains of the ER Are Stabilized by Membrane-Shaping ProteinsThe endoplasmic reticulum (ER) is a large membrane-bound compartment spread throughout the cytoplasm of eukaryotic cells. It is divided into three major morphologies that include the nuclear envelope (NE), peripheral ER cisternae, and an interconnected tubular network

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Section: Er and Plasma Membranementioning

confidence: 99%

Endoplasmic Reticulum Structure and Interconnections with Other Organelles

English

Voeltz

2013

Cold Spring Harbor Perspectives in Biology

276

211

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“…This mechanism also possibly provides an alternative route of transport from the ER to plasma membrane (8). It is proposed that two closely apposed membranes can exchange phospholipids, e.g., via collisional contact.…”

Section: Problems and Solutions In Lipid Transportmentioning

confidence: 99%

“…Charged or aromatic amino acids are typical anchoring residues of naturally occurring membrane-spanning segments (65) which have a characteristic length of around 20-25 residues depending on the type of membrane in which the protein resides (66). Therefore, the lysineflanked peptide KALP23 [GKKL(AL) 8 KKA] and the tryptophan-flanked peptide WALP23 [GWWL(AL) 8 WWA] were used as mimics of naturally occurring R-helices of membrane proteins to study helix-induced translocation. Transbilayer movement was assessed by determining the accessibility of C6NBD-labeled phospholipids to reduction with dithionite.…”

Section: In Vitro Reconstitution Of Flip-flopmentioning

confidence: 99%

Transbilayer Movement of Phospholipids in Biogenic Membranes

et al. 2004

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Biogenic membranes contain the enzymes that synthesize the cell's membrane lipids, of which the phospholipids are the most widespread throughout nature. Being synthesized at and inserted into the cytoplasmic leaflet of biogenic membranes, the phospholipids must migrate to the opposite leaflet to ensure balanced growth of the membrane. In this review, the current knowledge of transbilayer movement of phospholipids in biogenic membranes is summarized and the available data are compared to what is known about lipid translocation in other membranes. On the basis of this, a mechanism is proposed, in which phospholipid translocation in biogenic membranes is mediated via membrane-spanning segments of a subset of proteins, characterized by a small number of transmembrane helices. We speculate that proteins of this subset facilitate lipid translocation via the protein-lipid interface, because they display more dynamic behavior and engage in less stable protein-lipid interactions than larger membrane proteins. Structure, Function, and Assembly of Biomembranes

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“…These steps cannot occur in the plasma membrane itself, but may take place in PAM (plasma membrane associated membrane). PAM is a subfraction of the endoplasmic reticulum in close proximity to the plasma membrane, which was found to be highly enriched in a subset of sterol-synthesizing enzymes (40). Besides other enzymes, the sterol-C24-methyltransferase Erg6p, which converts zymosterol to fecosterol is present in PAM at even higher specific activity than in bulk endoplasmic reticulum.…”

Section: Discussionmentioning

confidence: 99%

“…6A). The membranous structures clearly identified as plasma membrane and peripheral endoplasmic reticulum (40) in wild type appeared to fuse in His-YEH2 resulting in punctuate areas. In contrast to the continuous membrane system seen in wild type the plasma membrane of His-YEH2 looked fuzzy and rigid.…”

Section: Cell Structure Of Strains With Enhanced Steryl Estermentioning

confidence: 98%

YEH2/YLR020c Encodes a Novel Steryl Ester Hydrolase of the Yeast Saccharomyces cerevisiae

Müllner

Deutsch

Leitner

et al. 2005

Journal of Biological Chemistry

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Previous work from our laboratory (Zinser, E., Paltauf, F., and Daum, G. (1993) J. Bacteriol. 175, 2853-2858) demonstrated steryl ester hydrolase activity in the plasma membrane of the yeast Saccharomyces cerevisiae. Here, we show that the gene product of YEH2/ YLR020c, which is homologous to several known mammalian steryl ester hydrolases, is the enzyme catalyzing this reaction. Deletion of yeast YEH2 led to complete loss of plasma membrane steryl ester hydrolase activity whereas overexpression of the gene resulted in a significant elevation of the activity. Purification of enzymatically active Yeh2p close to homogeneity unambiguously identified this protein as a steryl ester hydrolase and thus as the first enzyme of this kind characterized in S. cerevisiae. In addition to evidence obtained in vitro experiments in vivo contributed to the characterization of this novel enzyme. Sterol analysis of yeh2⌬ unveiled a slightly elevated level of zymosterol suggesting that the esterified form of this sterol precursor is a preferred substrate of Yeh2p. However, in strains bearing hybrid proteins with strongly enhanced Yeh2p activity decreased levels of all steryl esters were observed. Thus, it appears that Yeh2p activity is not restricted to distinct steryl esters but rather has broad substrate specificity. The fact that in a yeh2⌬ deletion strain bulk steryl ester mobilization occurred at a similar rate as in wild type suggested that Yeh2p is not the only steryl ester hydrolase but that other enzymes with overlapping function exist in the yeast.Most eukaryotic cells contain and synthesize sterols, which are essential lipid components of membranes. Besides their role in maintaining membrane permeability and fluidity, effects of sterols on aerobic metabolism (1, 2), completion of the cell cycle (3) as well as on sterol uptake (4) and sterol transport (5) have been described. Considering the different functions of sterols it is obvious that sterol homeostasis, including sterol biosynthesis, uptake, transport, storage, utilization, and efflux, has to be a strictly regulated process. Specific sterols present in different eukaryotic cells vary, ergosterol being the major sterol in the yeast Saccharomyces cerevisiae.Besides other regulatory mechanisms esterification of sterols and hydrolysis of steryl esters (STE) 1 play an important role in cellular sterol homeostasis. These processes do not only allow cells to store chemical energy, which can be used in times of deprivation, but also provide an additional means to balance the concentrations of free sterols and fatty acids, which are essential and critical for cell structure and function. In mammalian cells esterification of sterols is catalyzed either by lecithin:cholesteryl acyltransferase (reviewed in Refs. 6 -8) or by the two acyl-CoA:cholesteryl acyltransferases ACAT1 and ACAT2 (reviewed in Ref. 9). Cholesteryl ester hydrolysis occurs by a number of mammalian enzymes many of which have already been identified, among them carboxyl ester lipase (CEL), lysosomal acid lipase...

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A subfraction of the yeast endoplasmic reticulum associates with the plasma membrane and has a high capacity to synthesize lipids

Cited by 246 publications

References 46 publications

Endoplasmic Reticulum Structure and Interconnections with Other Organelles

Endoplasmic Reticulum Structure and Interconnections with Other Organelles

Transbilayer Movement of Phospholipids in Biogenic Membranes

YEH2/YLR020c Encodes a Novel Steryl Ester Hydrolase of the Yeast Saccharomyces cerevisiae

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