Über den Gehalt an membrangebundenen und freien Ribosomen in Saccharomyceszellen nach Hemmung der Proteinsynthese mit Cycloheximid / The Content of Membrane-Bound and Free Ribosomes in Saccharomyces after the Inhibition of Protein Synthesis with Cycloheximid

Abstract After the inhibition of protein synthesis in Saccharomyces cells with cycloheximid, the content of membrane-bound ribosomes decreases significantly, whereas the content of free ribosomes remains the same as the untreated control for a longer period of time. This is further evidence that in yeast cells protein synthesis takes place only on membrane-bound ribosomes.

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Regulation of the leptin content of obese human adipose tissue

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2001.280.3.e399 ◽

2001 ◽

Vol 280 (3) ◽

pp. E399-E404 ◽

Cited By ~ 31

Author(s):

C. D. Russell ◽

M. R. Ricci ◽

R. E. Brolin ◽

E. Magill ◽

S. K. Fried

Keyword(s):

Protein Synthesis ◽

Adipose Tissue ◽

Subcutaneous Tissue ◽

Human Adipose Tissue ◽

Serum Leptin ◽

Inhibition Of Protein Synthesis ◽

Membrane Bound ◽

Per Se ◽

Obese Human

The objective of this study was to determine whether obese human adipose tissue contains preformed stores of leptin and their relationship to secreted leptin. Detergent increased detectable leptin by about twofold, suggesting that leptin is stored in a membrane-bound location. Subcutaneous tissue leptin was ∼1.6-fold higher than omental, paralleling known differences in leptin secretion and expression. The amount of leptin secreted during a 3-h incubation was similar to that of extractable tissue leptin. Tissue leptin levels were maintained over the incubation. Inhibition of protein synthesis decreased tissue leptin content but did not decrease leptin secretion until after 3 h of incubation. Culture of adipose tissue for 2 days with the combination of insulin and dexamethasone, but not with either hormone alone, increased tissue leptin content about twofold in both depots. Although insulin did not affect tissue leptin content, it potentiated leptin secretion (as a % of tissue stores). These data suggest that adipose tissue leptin storage and secretion per se are regulated. Regulation of the release of preformed leptin may modulate serum leptin levels in obese humans.

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Intracellular Transport and Cytotoxicity of the Protein Toxin Ricin

Toxins ◽

10.3390/toxins11060350 ◽

2019 ◽

Vol 11 (6) ◽

pp. 350 ◽

Cited By ~ 14

Author(s):

Natalia Sowa-Rogozińska ◽

Hanna Sominka ◽

Jowita Nowakowska-Gołacka ◽

Kirsten Sandvig ◽

Monika Słomińska-Wojewódzka

Keyword(s):

Cell Death ◽

Protein Synthesis ◽

Host Cell ◽

Intracellular Transport ◽

Ricinus Communis ◽

Yeast Cells ◽

Protein Toxin ◽

Inhibition Of Protein Synthesis ◽

A Chain ◽

Golgi Network

Ricin can be isolated from the seeds of the castor bean plant (Ricinus communis). It belongs to the ribosome-inactivating protein (RIP) family of toxins classified as a bio-threat agent due to its high toxicity, stability and availability. Ricin is a typical A-B toxin consisting of a single enzymatic A subunit (RTA) and a binding B subunit (RTB) joined by a single disulfide bond. RTA possesses an RNA N-glycosidase activity; it cleaves ribosomal RNA leading to the inhibition of protein synthesis. However, the mechanism of ricin-mediated cell death is quite complex, as a growing number of studies demonstrate that the inhibition of protein synthesis is not always correlated with long term ricin toxicity. To exert its cytotoxic effect, ricin A-chain has to be transported to the cytosol of the host cell. This translocation is preceded by endocytic uptake of the toxin and retrograde traffic through the trans-Golgi network (TGN) and the endoplasmic reticulum (ER). In this article, we describe intracellular trafficking of ricin with particular emphasis on host cell factors that facilitate this transport and contribute to ricin cytotoxicity in mammalian and yeast cells. The current understanding of the mechanisms of ricin-mediated cell death is discussed as well. We also comment on recent reports presenting medical applications for ricin and progress associated with the development of vaccines against this toxin.

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