scholarly journals Early endocytosis as a key to understanding mechanisms of plasma membrane tension regulation in filamentous fungi

2020 ◽  
Vol 112 (12) ◽  
pp. 409-426
Author(s):  
Igor Mazheika ◽  
Oksana Voronko ◽  
Olga Kamzolkina
Keyword(s):  
Plasma Membrane ◽  
Filamentous Fungi ◽  
Membrane Tension ◽  
Tension Regulation

scholarly journals TOR complex 2 (TORC2) signaling and the ESCRT machinery cooperate in the protection of plasma membrane integrity in yeast

2020 ◽  
Vol 295 (34) ◽  
pp. 12028-12044
Author(s):  
Oliver Schmidt ◽  
Yannick Weyer ◽  
Simon Sprenger ◽  
Michael A. Widerin ◽  
Sebastian Eising ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Integrity ◽  
Homeostatic Regulation ◽  
Membrane Tension ◽  
Membrane Remodeling ◽  
Plasma Membrane Integrity ◽  
Endosomal Sorting ◽  
Escrt Machinery ◽  
Evolutionarily Conserved ◽  
Calcineurin Activity

The endosomal sorting complexes required for transport (ESCRT) mediate evolutionarily conserved membrane remodeling processes. Here, we used budding yeast (Saccharomyces cerevisiae) to explore how the ESCRT machinery contributes to plasma membrane (PM) homeostasis. We found that in response to reduced membrane tension and inhibition of TOR complex 2 (TORC2), ESCRT-III/Vps4 assemblies form at the PM and help maintain membrane integrity. In turn, the growth of ESCRT mutants strongly depended on TORC2-mediated homeostatic regulation of sphingolipid (SL) metabolism. This was caused by calcineurin-dependent dephosphorylation of Orm2, a repressor of SL biosynthesis. Calcineurin activity impaired Orm2 export from the endoplasmic reticulum (ER) and thereby hampered its subsequent endosome and Golgi-associated degradation (EGAD). The ensuing accumulation of Orm2 at the ER in ESCRT mutants necessitated TORC2 signaling through its downstream kinase Ypk1, which repressed Orm2 and prevented a detrimental imbalance of SL metabolism. Our findings reveal compensatory cross-talk between the ESCRT machinery, calcineurin/TORC2 signaling, and the EGAD pathway important for the regulation of SL biosynthesis and the maintenance of PM homeostasis.

scholarly journals Homeostasis of Plasma Membrane Tension Through Surface Area Regulation in Epithelial Cells

2016 ◽  
Vol 110 (3) ◽  
pp. 623a
Author(s):  
Andreas Janshoff ◽  
Bastian Brueckner ◽  
Stefan Nehls
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Surface Area ◽  
Membrane Tension

scholarly journals Functional Analysis of Sterol Transporter Orthologues in the Filamentous Fungus Aspergillus nidulans

2015 ◽  
Vol 14 (9) ◽  
pp. 908-921 ◽  
Author(s):  
Nicole Bühler ◽  
Daisuke Hagiwara ◽  
Norio Takeshita
Keyword(s):  
Plasma Membrane ◽  
Aspergillus Nidulans ◽  
Filamentous Fungi ◽  
Gene Deletion ◽  
Fluorescent Protein ◽  
Fungal Growth ◽  
Hyphal Growth ◽  
Apical Plasma Membrane ◽  
Important Species ◽  
Content Type

ABSTRACT Polarized growth in filamentous fungi needs a continuous supply of proteins and lipids to the growing hyphal tip. One of the important membrane compounds in fungi is ergosterol. At the apical plasma membrane ergosterol accumulations, which are called sterol-rich plasma membrane domains (SRDs). The exact roles and formation mechanism of the SRDs remained unclear, although the importance has been recognized for hyphal growth. Transport of ergosterol to hyphal tips is thought to be important for the organization of the SRDs. Oxysterol binding proteins, which are conserved from yeast to human, are involved in nonvesicular sterol transport. In Saccharomyces cerevisiae seven oxysterol-binding protein homologues (OSH1 to -7) play a role in ergosterol distribution between closely located membranes independent of vesicle transport. We found five homologous genes ( oshA to oshE ) in the filamentous fungi Aspergillus nidulans . The functions of OshA-E were characterized by gene deletion and subcellular localization. Each gene-deletion strain showed characteristic phenotypes and different sensitivities to ergosterol-associated drugs. Green fluorescent protein-tagged Osh proteins showed specific localization in the late Golgi compartments, puncta associated with the endoplasmic reticulum, or diffusely in the cytoplasm. The genes expression and regulation were investigated in a medically important species Aspergillus fumigatus , as well as A. nidulans . Our results suggest that each Osh protein plays a role in ergosterol distribution at distinct sites and contributes to proper fungal growth.

scholarly journals Multiple roles for the ESCRT machinery in maintaining plasma membrane homeostasis

2020 ◽  
Author(s):  
Oliver Schmidt ◽  
Yannick Weyer ◽  
Simon Sprenger ◽  
Michael A. Widerin ◽  
Sebastian Eising ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Integrity ◽  
Multiple Roles ◽  
Membrane Tension ◽  
Membrane Remodeling ◽  
Membrane Stress ◽  
Endosomal Sorting ◽  
Protein Levels ◽  
Escrt Machinery ◽  
Calcineurin Phosphatase

ABSTRACTThe endosomal sorting complexes required for transport (ESCRT) execute evolutionary conserved membrane remodeling processes. Here we used budding yeast to explore how the ESCRT machinery contributes to plasma membrane (PM) homeostasis. In response to reduced membrane tension and inhibition of the target of rapamycin complex 2 (TORC2), ESCRT-III/Vps4 assemblies form at the PM and help to maintain membrane integrity. Conversely, the growth of ESCRT mutants strongly depends on TORC2-mediated homeostatic regulation of sphingolipid (SL) metabolism. This is caused by calcineurin phosphatase activity which causes Orm2 to accumulate at the endoplasmic reticulum (ER) in ESCRT mutants. Orm2 is a repressor of SL biosynthesis and its accumulation provokes increased membrane stress. This necessitates TORC2 signaling through its downstream kinase Ypk1 to control Orm2 protein levels and prevent a detrimental imbalance of SL metabolism. Our findings reveal new aspects of antagonistic calcineurin/TORC2 signaling for the regulation of SL biosynthesis and the maintenance of PM homeostasis, and suggest that the ESCRT machinery contributes directly and indirectly to these processes.

scholarly journals Plasma membrane tension regulates eisosome structure and function

2020 ◽  
Vol 31 (4) ◽  
pp. 287-303 ◽  
Author(s):  
Daniel Appadurai ◽  
Lincoln Gay ◽  
Akshay Moharir ◽  
Michael J. Lang ◽  
Mara C. Duncan ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Environmental Changes ◽  
Structure And Function ◽  
Regulatory Proteins ◽  
Nutrient Transporters ◽  
Membrane Tension ◽  
Membrane Stress ◽  
Yeast Plasma Membrane ◽  
And Function

Eisosomes are furrows of the yeast plasma membrane that are involved in the regulation of nutrient transporters and membrane stress pathways. Environmental changes affect plasma membrane tension and fluidity, which change both the eisosome structure and the localization of nutrient transporters and regulatory proteins to the eisosome.

Mechanics of Curved Plasma Membrane Vesicles: Resting Shapes, Membrane Curvature, and In-Plane Shear Elasticity

2004 ◽  
Vol 127 (2) ◽  
pp. 229-236 ◽  
Author(s):  
Tadashi Kosawada ◽  
Kohji Inoue ◽  
Geert W. Schmid-Schönbein
Keyword(s):  
Plasma Membrane ◽  
Cell Membrane ◽  
Membrane Curvature ◽  
Membrane Tension ◽  
Coated Pits ◽  
Plane Shear ◽  
Plasmalemmal Vesicles ◽  
Cell Functions ◽  
Outer Domain ◽  
Shear Elasticity

Highly curved cell membrane structures, such as plasmalemmal vesicles (caveolae) and clathrin-coated pits, facilitate many cell functions, including the clustering of membrane receptors and transport of specific extracellular macromolecules by endothelial cells. These structures are subject to large mechanical deformations when the plasma membrane is stretched and subject to a change of its curvature. To enhance our understanding of plasmalemmal vesicles we need to improve the understanding of the mechanics in regions of high membrane curvatures. We examine here, theoretically, the shapes of plasmalemmal vesicles assuming that they consist of three membrane domains: an inner domain with high curvature, an outer domain with moderate curvature, and an outermost flat domain, all in the unstressed state. We assume the membrane properties are the same in these domains with membrane bending elasticity as well as in-plane shear elasticity. Special emphasis is placed on the effects of membrane curvature and in-plane shear elasticity on the mechanics of vesicle during unfolding by application of membrane tension. The vesicle shapes were computed by minimization of bending and in-plane shear strain energy. Mechanically stable vesicles were identified with characteristic membrane necks. Upon stretch of the membrane, the vesicle necks disappeared relatively abruptly leading to membrane shapes that consist of curved indentations. While the resting shape of vesicles is predominantly affected by the membrane spontaneous curvatures, the membrane shear elasticity (for a range of values recorded in the red cell membrane) makes a significant contribution as the vesicle is subject to stretch and unfolding. The membrane tension required to unfold the vesicle is sensitive with respect to its shape, especially as the vesicle becomes fully unfolded and approaches a relative flat shape.

scholarly journals Membrane Expansion Increases Endocytosis Rate during Mitosis

1999 ◽  
Vol 144 (3) ◽  
pp. 497-506 ◽  
Author(s):  
Drazen Raucher ◽  
Michael P. Sheetz
Keyword(s):  
Plasma Membrane ◽  
Strong Correlation ◽  
Mammalian Cells ◽  
Mechanical Deformation ◽  
Laser Tweezers ◽  
Membrane Tension ◽  
Direct Proportion ◽  
Latex Beads ◽  
Important Regulator ◽  
Membrane Tethers

Mitosis in mammalian cells is accompanied by a dramatic inhibition of endocytosis. We have found that the addition of amphyphilic compounds to metaphase cells increases the endocytosis rate even to interphase levels. Detergents and solvents all increased endocytosis rate, and the extent of increase was in direct proportion to the concentration added. Although the compounds could produce a variety of different effects, we have found a strong correlation with a physical alteration in the membrane tension as measured by the laser tweezers. Plasma membrane tethers formed by latex beads pull back on the beads with a force that was related to the in-plane bilayer tension and membrane– cytoskeletal adhesion. We found that as cells enter mitosis, the membrane tension rises as the endocytosis rate decreases; and as cells exited mitosis, the endocytosis rate increased as the membrane tension decreased. The addition of amphyphilic compounds decreased membrane tension and increased the endocytosis rate. With the detergent, deoxycholate, the endocytosis rate was restored to interphase levels when the membrane tension was restored to interphase levels. Although biochemical factors are clearly involved in the alterations in mitosis, we suggest that endocytosis is blocked primarily by the increase in apparent plasma membrane tension. Higher tensions inhibit both the binding of the endocytic complex to the membrane and mechanical deformation of the membrane during invagination. We suggest that membrane tension is an important regulator of the endocytosis rate and alteration of tension is sufficient to modify endocytosis rates during mitosis. Further, we postulate that the rise in membrane tension causes cell rounding and the inhibition of motility, characteristic of mitosis.

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