scholarly journals Membrane Contact Sites in Yeast: Control Hubs of Sphingolipid Homeostasis

Membranes ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 971
Author(s):  
Philipp Schlarmann ◽  
Atsuko Ikeda ◽  
Kouichi Funato
Keyword(s):  
Plasma Membrane ◽  
Intracellular Signaling ◽  
Membrane Lipids ◽  
Sphingolipid Metabolism ◽  
Yeast Saccharomyces Cerevisiae ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
And Function

Sphingolipids are the most diverse class of membrane lipids, in terms of their structure and function. Structurally simple sphingolipid precursors, such as ceramides, act as intracellular signaling molecules in various processes, including apoptosis, whereas mature and complex forms of sphingolipids are important structural components of the plasma membrane. Supplying complex sphingolipids to the plasma membrane, according to need, while keeping pro-apoptotic ceramides in check is an intricate task for the cell and requires mechanisms that tightly control sphingolipid synthesis, breakdown, and storage. As each of these processes takes place in different organelles, recent studies, using the budding yeast Saccharomyces cerevisiae, have investigated the role of membrane contact sites as hubs that integrate inter-organellar sphingolipid transport and regulation. In this review, we provide a detailed overview of the findings of these studies and put them into the context of established regulatory mechanisms of sphingolipid homeostasis. We have focused on the role of membrane contact sites in sphingolipid metabolism and ceramide transport, as well as the mechanisms that prevent toxic ceramide accumulation.

scholarly journals Rational design and implementation of a chemically inducible hetero-trimerization system

2020 ◽  
Author(s):  
Helen D. Wu ◽  
Masaki Kikuchi ◽  
Onur Dagliyan ◽  
Adam K. Aragaki ◽  
Hideki Nakamura ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Biology ◽  
Rational Design ◽  
Membrane Lipids ◽  
Live Cells ◽  
Cell Functions ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Molecular Events ◽  
Membrane Contact

AbstractChemically inducible dimerization (CID) uses a small molecule to induce binding of two different proteins. CID tools exemplified by the FKBP/FRB/rapamycin system have been widely employed to probe molecular events inside and outside cells. While various CID tools are available, chemically inducible trimerization (CIT) has not been developed, due to inherent challenges in designing or identifying a chemical that simultaneously binds three proteins with high affinity and target specificity. Nevertheless, by introducing a third recruitable component, CIT could enable versatile applications. Here, we devised the CIT by rationally splitting FRB and FKBP. Based on cellular and structural datasets, select split pairs of FRB or FKBP underwent efficient trimerization with full length FKBP or FRB, respectively, upon addition of rapamycin. We also demonstrated its potential for cellular applications by rapidly inducing tri-organellar plasma membrane-ER-mitochondria junctions, and by perturbing intended membrane lipids exclusively at the plasma membrane-ER membrane contact sites. By conferring one additional condition to what is achievable with CID, CIT expands the types of manipulation in single live cells, to address cell biology questions otherwise intractable, and engineer cell functions for future synthetic biology applications.

scholarly journals Synaptotagmins at the endoplasmic reticulum–plasma membrane contact sites maintain diacylglycerol homeostasis during abiotic stress

2021 ◽  
Author(s):  
Noemi Ruiz-Lopez ◽  
Jessica Pérez-Sancho ◽  
Alicia Esteban del Valle ◽  
Richard P Haslam ◽  
Steffen Vanneste ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Abiotic Stress ◽  
Fluorescent Protein ◽  
Mechanical Damage ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Green Fluorescent

Abstract Endoplasmic reticulum-plasma membrane contact sites (ER-PM CS) play fundamental roles in all eukaryotic cells. Arabidopsis thaliana mutants lacking the ER-PM protein tether synaptotagmin1 (SYT1) exhibit decreased plasma membrane (PM) integrity under multiple abiotic stresses such as freezing, high salt, osmotic stress and mechanical damage. Here, we show that, together with SYT1, the stress-induced SYT3 is an ER-PM tether that also functions in maintaining PM integrity. The ER-PM CS localization of SYT1 and SYT3 is dependent on PM phosphatidylinositol-4-phosphate and is regulated by abiotic stress. Lipidomic analysis revealed that cold stress increased the accumulation of diacylglycerol at the PM in a syt1/3 double mutant relative to wild type while the levels of most glycerolipid species remain unchanged. Additionally, the SYT1-green fluorescent protein (GFP) fusion preferentially binds diacylglycerol in vivo with little affinity for polar glycerolipids. Our work uncovers a SYT-dependent mechanism of stress adaptation counteracting the detrimental accumulation of diacylglycerol at the PM produced during episodes of abiotic stress.

scholarly journals Mdm1/Snx13 is a novel ER–endolysosomal interorganelle tethering protein

2015 ◽  
Vol 210 (4) ◽  
pp. 541-551 ◽  
Author(s):  
W. Mike Henne ◽  
Lu Zhu ◽  
Zsolt Balogi ◽  
Christopher Stefan ◽  
Jeffrey A. Pleiss ◽  
...  
Keyword(s):  
Neurological Disease ◽  
Lipid Binding ◽  
Sphingolipid Metabolism ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Effector Genes ◽  
Px Domain ◽  
In Trans ◽  
Membrane Contact ◽  
Lysosome Membrane

Although endolysosomal trafficking is well defined, how it is regulated and coordinates with cellular metabolism is unclear. To identify genes governing endolysosomal dynamics, we conducted a global fluorescence-based screen to reveal endomembrane effector genes. Screening implicated Phox (PX) domain–containing protein Mdm1 in endomembrane dynamics. Surprisingly, we demonstrate that Mdm1 is a novel interorganelle tethering protein that localizes to endoplasmic reticulum (ER)–vacuole/lysosome membrane contact sites (MCSs). We show that Mdm1 is ER anchored and contacts the vacuole surface in trans via its lipid-binding PX domain. Strikingly, overexpression of Mdm1 induced ER–vacuole hypertethering, underscoring its role as an interorganelle tether. We also show that Mdm1 and its paralogue Ydr179w-a (named Nvj3 in this study) localize to ER–vacuole MCSs independently of established tether Nvj1. Finally, we find that Mdm1 truncations analogous to neurological disease–associated SNX14 alleles fail to tether the ER and vacuole and perturb sphingolipid metabolism. Our work suggests that human Mdm1 homologues may play previously unappreciated roles in interorganelle communication and lipid metabolism.

The role of membrane contact sites at the bacteria-host interface

2021 ◽  
pp. 1-13
Author(s):  
Chen Jiang ◽  
Xue Huang ◽  
Jia Yao ◽  
Lihua Yu ◽  
Fujing Wei ◽  
...  
Keyword(s):  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact

scholarly journals Kv2 potassium channels form endoplasmic reticulum/plasma membrane junctions via interaction with VAPA and VAPB

2018 ◽  
Vol 115 (31) ◽  
pp. E7331-E7340 ◽  
Author(s):  
Ben Johnson ◽  
Ashley N. Leek ◽  
Laura Solé ◽  
Emily E. Maverick ◽  
Tim P. Levine ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Neuronal Cultures ◽  
Physical Relationship ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Hek Cells ◽  
C Terminus ◽  
Membrane Contact

Kv2.1 exhibits two distinct forms of localization patterns on the neuronal plasma membrane: One population is freely diffusive and regulates electrical activity via voltage-dependent K+ conductance while a second one localizes to micrometer-sized clusters that contain densely packed, but nonconducting, channels. We have previously established that these clusters represent endoplasmic reticulum/plasma membrane (ER/PM) junctions that function as membrane trafficking hubs and that Kv2.1 plays a structural role in forming these membrane contact sites in both primary neuronal cultures and transfected HEK cells. Clustering and the formation of ER/PM contacts are regulated by phosphorylation within the channel C terminus, offering cells fast, dynamic control over the physical relationship between the cortical ER and PM. The present study addresses the mechanisms by which Kv2.1 and the related Kv2.2 channel interact with the ER membrane. Using proximity-based biotinylation techniques in transfected HEK cells we identified ER VAMP-associated proteins (VAPs) as potential Kv2.1 interactors. Confirmation that Kv2.1 and -2.2 bind VAPA and VAPB employed colocalization/redistribution, siRNA knockdown, and Förster resonance energy transfer (FRET)-based assays. CD4 chimeras containing sequence from the Kv2.1 C terminus were used to identify a noncanonical VAP-binding motif. VAPs were first identified as proteins required for neurotransmitter release in Aplysia and are now known to be abundant scaffolding proteins involved in membrane contact site formation throughout the ER. The VAP interactome includes AKAPs, kinases, membrane trafficking machinery, and proteins regulating nonvesicular lipid transport from the ER to the PM. Therefore, the Kv2-induced VAP concentration at ER/PM contact sites is predicted to have wide-ranging effects on neuronal cell biology.

scholarly journals Synaptotagmin-Associated Endoplasmic Reticulum-Plasma Membrane Contact Sites Are Localized to Immobile ER Tubules

2018 ◽  
Vol 178 (2) ◽  
pp. 641-653 ◽  
Author(s):  
Kazuya Ishikawa ◽  
Kentaro Tamura ◽  
Haruko Ueda ◽  
Yoko Ito ◽  
Akihiko Nakano ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact
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