Faculty Opinions recommendation of Plasma membrane compartmentalization in yeast by messenger RNA transport and a septin diffusion barrier.

Enhancement of the passage of water through membranes is one of the main mechanisms via which cells can maintain their homeostasis under stress conditions, and aquaporins are the main participants in this process. However, in the last few years, a number of studies have reported discrepancies between aquaporin messenger RNA (mRNA) expression and the number of aquaporin proteins synthesised in response to abiotic stress. These observations suggest the existence of post-transcriptional mechanisms which regulate plasma membrane intrinsic protein (PIP) trafficking to the plasma membrane. This indicates that the mRNA synthesis of some aquaporins could be modulated by the accumulation of the corresponding encoded protein, in relation to the turnover of the membranes. This aspect is discussed in terms of the results obtained: on the one hand, with isolated vesicles, in which the level of proteins present provides the membranes with important characteristics such as resistance and stability and, on the other, with isolated proteins reconstituted in artificial liposomes as an in vitro method to address the in vivo physiology of the entire plant.

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Developmental formation of a diffusion barrier in the plasma membrane of the axonal initial segment : single lipid molecule approach

Seibutsu Butsuri ◽

10.2142/biophys.40.s212_2 ◽

2000 ◽

Vol 40 (supplement) ◽

pp. S212

Author(s):

C. Nakada ◽

M. Nozaki ◽

H. Yamashita ◽

K. Yamaguchi ◽

Ken Ritchie ◽

...

Keyword(s):

Plasma Membrane ◽

Diffusion Barrier ◽

Initial Segment ◽

Lipid Molecule ◽

Axonal Initial Segment

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Transferrin receptor hyperexpression in primary erythroblasts is lost on transformation by avian erythroblastosis virus

Blood ◽

10.1182/blood.v100.1.289 ◽

2002 ◽

Vol 100 (1) ◽

pp. 289-298 ◽

Cited By ~ 5

Author(s):

Lioba Lobmayr ◽

Thomas Sauer ◽

Iris Killisch ◽

Matthias Schranzhofer ◽

Robert B. Wilson ◽

...

Keyword(s):

Plasma Membrane ◽

Transferrin Receptor ◽

Messenger Rna ◽

Large Fraction ◽

Regulatory Protein ◽

Regulatory System ◽

Cell Types ◽

Binding Activity ◽

Chicken Cell ◽

Avian Erythroblastosis Virus

Abstract In primary chicken erythroblasts (stem cell factor [SCF] erythroblasts), transferrin receptor (TfR) messenger RNA (mRNA) and protein were hyperexpressed as compared to nonerythroid chicken cell types. This erythroid-specific hyperexpression was abolished in transformed erythroblasts (HD3E22 cells) expressing the v-ErbA and v-ErbB oncogenes of avian erythroblastosis virus. TfR expression in HD3E22 cells could be modulated by changes in exogenous iron supply, whereas expression in SCF erythroblasts was not subject to iron regulation. Measurements of TfR mRNA half-life indicated that hyperexpression in SCF erythroblasts was due to a massive stabilization of transcripts even in the presence of high iron levels. Changes in mRNA binding activity of iron regulatory protein 1 (IRP1), the primary regulator of TfR mRNA stability in these cells, correlated well with TfR mRNA expression; IRP1 activity in HD3E22 cells and other nonerythroid cell types tested was iron dependent, whereas IRP1 activity in primary SCF erythroblasts could not be modulated by iron administration. Analysis of avian erythroblasts expressing v-ErbA alone indicated that v-ErbA was responsible for these transformation-specific alterations in the regulation of iron metabolism. In SCF erythroblasts high amounts of TfR were detected on the plasma membrane, but a large fraction was also located in early and late endosomal compartments, potentially concealing temporary iron stores from the IRP regulatory system. In contrast, TfR was almost exclusively located to the plasma membrane in HD3E22 cells. In summary, stabilization of TfR mRNA and redistribution of Fe-Tf/TfR complexes to late endosomal compartments may contribute to TfR hyperexpression in primary erythroblasts, effects that are lost on leukemic transformation.

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Drosophila ßHeavy-Spectrin is required in polarized ensheathing glia that form a diffusion-barrier around the neuropil

Nature Communications ◽

10.1038/s41467-021-26462-x ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Nicole Pogodalla ◽

Holger Kranenburg ◽

Simone Rey ◽

Silke Rodrigues ◽

Albert Cardona ◽

...

Keyword(s):

Nervous System ◽

Plasma Membrane ◽

Diffusion Barrier ◽

Neuronal Cell ◽

Apical Plasma Membrane ◽

Neuronal Cell Bodies ◽

The Central Nervous System ◽

Basolateral Plasma Membrane ◽

Nervous System Function ◽

Spectrin Cytoskeleton

AbstractIn the central nervous system (CNS), functional tasks are often allocated to distinct compartments. This is also evident in the Drosophila CNS where synapses and dendrites are clustered in distinct neuropil regions. The neuropil is separated from neuronal cell bodies by ensheathing glia, which as we show using dye injection experiments, contribute to the formation of an internal diffusion barrier. We find that ensheathing glia are polarized with a basolateral plasma membrane rich in phosphatidylinositol-(3,4,5)-triphosphate (PIP3) and the Na+/K+-ATPase Nervana2 (Nrv2) that abuts an extracellular matrix formed at neuropil-cortex interface. The apical plasma membrane is facing the neuropil and is rich in phosphatidylinositol-(4,5)-bisphosphate (PIP2) that is supported by a sub-membranous ßHeavy-Spectrin cytoskeleton. ßHeavy-spectrin mutant larvae affect ensheathing glial cell polarity with delocalized PIP2 and Nrv2 and exhibit an abnormal locomotion which is similarly shown by ensheathing glia ablated larvae. Thus, polarized glia compartmentalizes the brain and is essential for proper nervous system function.

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The life cycles of cryptogams

Acta Botanica Malacitana ◽

10.24310/abm.v16i.9126 ◽

1991 ◽

Vol 16 ◽

pp. 5-16

Author(s):

Peter R. Bell

Keyword(s):

Plasma Membrane ◽

Messenger Rna ◽

Gene Dosage ◽

Gene Activation ◽

Life Cycles ◽

Nuclear Surface ◽

Control Points ◽

Cytoplasmic Rna ◽

Abundant Cytoplasm ◽

Gametic Selection

Meiosis and karyogamy are recognized as control points in the life cycle of cryptogams. The control of meiosis is evidently complex and in yeast, and by analogy in all cryptogams, involves progressive gene activation. The causes of the delay in meiosis in diplohaplontic and diplontic organisms, and the manner in which the block is removed remain to be discovered. There is accumulating evidence that cytoplasmic RNA plays an important role in meiotic division. Many features of gametogenesis are still obscure. The tendency to oogamy has provided the opportunity for the laying down of long-lived messenger RNA in the abundant cytoplasm of the female gamete. The sporophytic nature of the developing zygote can in this way be partially pre-determined. There is evidence that this is the situation in the ferns. Specific molecules (probably arabino-galacto-proteins) on the surface of the plasma membrane are likely to account both for gametic selection, and the readiness with which appropriate gametes fuse. The dikaryotic condition indicates that nuclear fusion is not inevitable following plasmogamy. The ultimate fusion of the nuclei may result from quite simple changes in the nuclear surface. Exposure of lipid, for example, would lead to fusion as a result of hydrophobic forces. Aberrations of cryptogamic life cycles are numerous. The nuclear relationships of many aberrant cycles are unknown. In general it appears that the maintenance of sporophytic growth depends upon the presence of at least two sets of chromosomes. Conversely the maintenance of gametophytic growth in cultures obtained aposporously appears to be impossible in the presence of four sets of chromosomes, or more. These results raise important problems of the effect of gene dosage on development.

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Erythrocyte membrane protein band 3: its biosynthesis and incorporation into membranes.

The Journal of Cell Biology ◽

10.1083/jcb.91.3.637 ◽

1981 ◽

Vol 91 (3) ◽

pp. 637-646 ◽

Cited By ~ 28

Author(s):

E Sabban ◽

V Marchesi ◽

M Adesnik ◽

D D Sabatini

Keyword(s):

Plasma Membrane ◽

Electrophoretic Mobility ◽

Messenger Rna ◽

Transmembrane Protein ◽

Band 3 ◽

In Vitro Translation ◽

Intact Cells ◽

Amino Terminal ◽

In Cells

Band 3, a transmembrane protein that provides the anion channel of the erythrocyte plasma membrane, crosses the membrane more than once and has a large amino terminal segment exposes on the cytoplasmic side of the membrane. The biosynthesis of band 3 and the process of its incorporation into membranes were studied in vivo in erythroid spleen cells of anemic mice and in vitro in protein synthesizing cell-free systems programmed with polysomes and messenger RNA (mRNA). In intact cells newly synthesized band 3 is rapidly incorporated into intracellular membranes where it is glycosylated and it is subsequently transferred to the plasma membrane where it becomes sensitive to digestion by exogenous chymotrypsin. The appearance of band 3 in the cell surface is not contingent upon its glycosylation because it proceeds efficiently in cells treated with tunicamycin. The site of synthesis of band 3 in bound polysomes was established directly by in vitro translation experiments with purified polysomes or with mRNA extracted from them. The band-3 polypeptide synthesized in an mRNA-dependent system had the same electrophoretic mobility as that synthesized in cells treated with tunicamycin. When microsomal membranes were present during translation, the in vitro synthesized band-3 polypeptide was cotranslationally glycosylated and inserted into the membranes. This was inferred from the facts that when synthesis was carried out in the presence of membranes the product had a lower electrophoretic mobility and showed partial resistance to protease digestion. Our observations indicate that the primary translation product of band-3 mRNA is not proteolytically processed either co- or posttranslationally. It is, therefore, proposed that the incorporation of band 3 into the endoplasmic reticulum (ER) membrane is initiated by a permanent insertion signal. To account for the cytoplasmic exposure of the amino terminus of the polypeptide we suggest that this signal is located within the interior of the polypeptide. a mechanism that explains the final transmembrane disposition of band 3 in the plasma membrane as resulting from the mode of its incorporation into the ER is presented.

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