The structure of the periplast components and their association with the plasma membrane in a cryptomonad flagellate

1987 ◽  
Vol 65 (5) ◽  
pp. 1019-1026 ◽  
Author(s):  
Richard Wetherbee ◽  
David R. A. Hill ◽  
Steven J. Brett
Keyword(s):  
Surface Layer ◽  
Plasma Membrane ◽  
Thin Sheet ◽  
Subsequent Development ◽  
Membrane Domains ◽  
Cytoplasmic Surface ◽  
Plate Size ◽  
Degree Of Association ◽  
Distinct Membrane ◽  
Crystalline Array

The periplast of Cryptomonas sp. θ covers most of the cell surface and is composed of the plasma membrane sandwiched between inner and surface periplast components. The surface periplast component is tightly appressed to the plasma membrane and consists of irregularly shaped plates composed of subunits organized into a crystalline array. Noncrystalline material distinguishes plate borders, and changes in plate size and (or) shape may result from the addition or subtraction of subunits at the borders. The inner periplast component is difficult to discern, but normally appears as a thin sheet of material appressed to the cytoplasmic surface of the plasma membrane. The inner periplast component is not closely associated with the plasma membrane at the positions corresponding to plate borders in the overlying surface periplast component. Both periplast components end at the entrance to the vestibulum, which together with the gullet is covered by a surface layer of heptagonal "rosette scales." The size and shape of the surface periplast plates, as well as the degree of association of the inner periplast sheet with the plasma membrane, are mirrored in the P and, to a lesser degree, E fracture faces of the plasma membrane. The presence of distinct membrane domains suggests the plasma membrane may be directly involved in the assembly and subsequent development of the periplast layers.

scholarly journals Fate of plasma membrane during endocytosis. I. Uptake and processing of anti-plasma membrane and control immunoglobulins by cultured fibroblasts.

1979 ◽  
Vol 82 (2) ◽  
pp. 449-465 ◽  
Author(s):  
Y J Schneider ◽  
P Tulkens ◽  
C de Duve ◽  
A Trouet
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Cell Fractionation ◽  
Membrane Domains ◽  
Rat Embryo ◽  
Cultured Fibroblasts ◽  
Absolute Limit ◽  
And Control ◽  
Distinct Membrane ◽  
Selective Mechanism

The uptake and processing by cultured rat embryo fibroblasts of control rabbit immunoglobulins (C IgG) or IgG directed against plasma membrane constituents (anti-PM IgG), and labeled with fluorescein (F) or with radioactive acetate (A), have been investigated by cell fractionation and immunological techniques. Both F and A anti-PM IgGs become bound to the cell surface, by a process that is slow, but largely temperature-independent. In the presence of an excess of high-affinity antibodies, binding reaches an absolute limit which corresponds to extensive coating of the plasma membrane. The anti-PM IgGs remain attached to the membrane for at least several days, even at 37 degrees C, with no significant transfer to lysosomes or degradation. In contrast, C IgGs are handled very differently by the fibroblasts, and their fate is strikingly affected by the type of labeling used. AC IgG is taken up slowly, at a rate proportional to its concentration, and is subsequently broken down in what appears to be lysosomes. Part of the AC IgG also binds to the plasma membrane. FC IgG is taken up many times faster than AC IgG, though with the same strict linearity as a function of concentration. Most of the FC IgG taken up is stored in cytoplasmic granules which behave like lysosomes. For reasons that are not understood, only about half of the stored FC IgG can be broken down. Cells exposed simulatnaously to AC IgG and FC IgG, or to A anti-PM IgG and FC IgG, handle each type of IgG in its characteristic fashion. Kinetic analysis of these results indicates that Ac IgG could be taken up by fluid endocytosis, but that FC IgG must be interiorized by a selective mechanism, presumably adsorptive in nature. That anti-PM antibodies remain stably bound to the plasma membrane and do not interfere with the uptake of FC IgG is interpreted to indicate either that two distinct membrane domains are involved in the two phenomena, or that membrane patches coated with anti-PM IgG participate in endocytosis, and are recycled back to the cell surface after delivering their contents intracellularly.

Membrane microdomains: lessons from microscopy

1995 ◽  
Vol 53 ◽  
pp. 776-777
Author(s):  
J.M. Robinson ◽  
J.M Oliver
Keyword(s):  
Spatial Distribution ◽  
Plasma Membrane ◽  
Epithelial Cells ◽  
Plasma Membranes ◽  
Cell Types ◽  
Imaging Modalities ◽  
Membrane Microdomains ◽  
Membrane Domains ◽  
Lateral Heterogeneity ◽  
Functional Importance

Specialized regions of plasma membranes displaying lateral heterogeneity are the focus of this Symposium. Specialized membrane domains are known for certain cell types such as differentiated epithelial cells where lateral heterogeneity in lipids and proteins exists between the apical and basolateral portions of the plasma membrane. Lateral heterogeneity and the presence of microdomains in membranes that are uniform in appearance have been more difficult to establish. Nonetheless a number of studies have provided evidence for membrane microdomains and indicated a functional importance for these structures.This symposium will focus on the use of various imaging modalities and related approaches to define membrane microdomains in a number of cell types. The importance of existing as well as emerging imaging technologies for use in the elucidation of membrane microdomains will be highlighted. The organization of membrane microdomains in terms of dimensions and spatial distribution is of considerable interest and will be addressed in this Symposium.

scholarly journals Rapid Nonvesicular Transport of Sterol between the Plasma Membrane Domains of Polarized Hepatic Cells

2002 ◽  
Vol 277 (33) ◽  
pp. 30325-30336
Author(s):  
Daniel Wüstner ◽  
Andreas Herrmann ◽  
Mingming Hao ◽  
Frederick R. Maxfield
Keyword(s):  
Plasma Membrane ◽  
Membrane Domains ◽  
Hepatic Cells ◽  
Plasma Membrane Domains

scholarly journals Calnexin revealed as an ether-a-go-go chaperone by getting mutant worms up and going

2018 ◽  
Vol 150 (8) ◽  
pp. 1059-1061
Author(s):  
Jonathan T. Pierce
Keyword(s):  
Ion Channels ◽  
Dynamic Control ◽  
Cell Types ◽  
K Channel ◽  
Membrane Domains ◽  
Excitable Cells ◽  
Patch Clamp Recording ◽  
Cell Excitability ◽  
Distinct Membrane

The role of ion channels in cell excitability was first revealed in a series of voltage clamp experiments by Hodgkin and Huxley in the 1950s. However, it was not until the 1970s that patch-clamp recording ushered in a revolution that allowed physiologists to witness how ion channels flicker open and closed at angstrom scale and with microsecond resolution. The unexpectedly tight seal made by the patch pipette in the whole-cell configuration later allowed molecular biologists to suck up the insides of identified cells to unveil their unique molecular contents. By refining these techniques, researchers have scrutinized the surface and contents of excitable cells in detail over the past few decades. However, these powerful approaches do not discern which molecules are responsible for the dynamic control of the genesis, abundance, and subcellular localization of ion channels. In this dark territory, teams of unknown and poorly understood molecules guide specific ion channels through translation, folding, and modification, and then they shuttle them toward and away from distinct membrane domains via different subcellular routes. A central challenge in understanding these processes is the likelihood that these diverse regulatory molecules may be specific to ion channel subtypes, cell types, and circumstance. In work described in this issue, Bai et al. (2018. J. Gen. Physiol. https://doi.org/10.1085/jgp.201812025) begin to shed light on the biogenesis of UNC-103, a K+ channel found in Caenorhabditis elegans.

scholarly journals Stabilizing membrane domains antagonizes n-alcohol anesthesia

2016 ◽  
Author(s):  
B.B. Machta ◽  
E. Grey ◽  
M. Nouri ◽  
N.L.C. McCarthy ◽  
E.M. Gray ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Phase Separation ◽  
Critical Temperature ◽  
Hydrostatic Pressure ◽  
General Anesthesia ◽  
Membrane Domains ◽  
Strongly Correlated ◽  
Membrane Heterogeneity ◽  
Anesthetic Potency ◽  
Better Than

AbstractDiverse molecules induce general anesthesia with potency strongly correlated both with their hydrophobicity and their effects on certain ion channels. We recently observed that several n-alcohol anesthetics inhibit heterogeneity in plasma membrane derived vesicles by lowering the critical temperature (Tc) for phase separation. Here we exploit conditions that stabilize membrane heterogeneity to further test the correlation between the anesthetic potency of n-alcohols and effects on Tc. First we show that hexadecanol acts oppositely to n-alcohol anesthetics on membrane mixing and antagonizes ethanol induced anesthesia in a tadpole behavioral assay. Second, we show that two previously described ‘intoxication reversers’ raise Tc and counter ethanol’s effects in vesicles, mimicking the findings of previous electrophysiological and behavioral measurements. Third, we find that hydrostatic pressure, long known to reverse anesthesia, also raises Tc in vesicles with a magnitude that counters the effect of butanol at relevant concentrations and pressures. Taken together,these results demonstrate that ΔTc predicts anesthetic potency for n-alcohols better than hydrophobicity in a range of contexts, supporting a mechanistic role for membrane heterogeneity in general anesthesia.

scholarly journals Electron donor cytochrome b5 is required for hyphal tip accumulation of sterol-rich plasma membrane domains and membrane fluidity in Aspergillus fumigatus

2020 ◽  
Author(s):  
Chi Zhang ◽  
Yiran Ren ◽  
Lu Gao ◽  
Huiyu Gu ◽  
Ling Lu
Keyword(s):  
Plasma Membrane ◽  
Aspergillus Fumigatus ◽  
Membrane Fluidity ◽  
Electron Donor ◽  
Cytochrome B5 ◽  
Normal Growth ◽  
Ergosterol Biosynthesis ◽  
Membrane Domains ◽  
Growth Defects ◽  
C Terminus

The electron donor cytochrome b5 (CybE/Cyb5) fuels the activity of the ergosterol biosynthesis-related P450 enzymes/P450s by providing electrons to P450s to promote ergosterol biosynthesis. Previous studies reported that lack of Aspergillus fumigatus (A. fumigatus) CybE reduces the proportion of ergosterol in total sterols and induces severe growth defects. However, the molecular characteristics of CybE and the underlying mechanism for CybE maintaining A. fumigatus growth remain poorly understood. Here, we found that CybE locates at the endoplasmic reticulum by its C-terminus with two transmembrane regions. Therefore, lack of the C-terminus of CybE is able to phenocopy a cybE deletion. Notably, cybE deletion reduced the accumulation of the sterol-rich plasma membrane domains (SRDs, the assembly platform of polarity factors/cell end markers and growth machinery) in hyphal tips and decreased membrane fluidity, which correspond to tardiness of hyphal extension and hypersensitivity to low temperature in cybE deletion mutant. Additionally, overexpressing another electron donor-heme-independent P450 reductase (CPR) significantly rescued growth defects and recovered SRD accumulation in deletion of cybE almost to the wild-type level, suggesting CybE maintaining the growth and deposition of SRDs in hyphal tips attributes to its nature as an electron donor. Protein pull-down assays revealed that CybE probably participates in metabolism and transfer of lipids, construction of cytoskeleton and mitochondria-associated energy metabolism to maintain the SRD accumulation in hyphal tips, membrane fluidity and hyphal extension. Findings in this study give a hint that inhibition of CybE may be an effective strategy for resisting the infection of the human pathogen A. fumigatus. Importance Investigating the knowledge of the growth regulation in the human opportunistic pathogen A. fumigatus is conducive to design new antifungal approach. The electron donor cytochrome b5 (CybE) plays a crucial role in maintaining the normal growth of A. fumigatus, however, the potential mechanism remains elusive. Herein, we characterized the molecular features of CybE and found the C-terminus with two transmembrane domains are required for its ER localization and functions. In addition, we demonstrated that CprA, an electron donor-heme-independent P450 reductase, provides a reciprocal function for the missing cytochrome b5 protein-CybE in A. fumigatus. CybE maintains the normal growth probably via supporting two crucial physiological processes, the SRD accumulation in hyphal tips and membrane fluidity. Therefore, our finding reveals the mechanisms underlying the regulatory effect of CybE on A. fumigatus growth and indicates that inhibition of CybE might be an effective approach for alleviating A. fumigatus infection.

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