scholarly journals The Intraischemic and Early Reperfusion Changes of Protein Synthesis in the Rat Brain. eIF-2α Kinase Activity and Role of Initiation Factors eIF-2α and eIF-4E

1998 ◽  
Vol 18 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Jozef Burda ◽  
M. Elena Martín ◽  
Miroslav Gottlieb ◽  
Mikulas Chavko ◽  
Jozef Marsala ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Cerebral Ischemia ◽  
Kinase Activity ◽  
Transient Cerebral Ischemia ◽  
Initiation Factor ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Early Reperfusion ◽  
Free System

Rats were subjected to the standard four-vessel occlusion model of transient cerebral ischemia (vertebral and carotid arteries). The effects of normothermic ischemia (37°C) followed or not by 30-minute reperfusion, as well as 30-minute postdecapitative ischemia, on translational rates were examined. Protein synthesis rate, as measured in a cell-free system, was significantly inhibited in ischemic rats, and the extent of inhibition strongly depended on duration and temperature, and less on the model of ischemia used. The ability of reinitiation in vitro (by using aurintricarboxylic acid) decreased after ischemia, suggesting a failure in the synthetic machinery at the initiation level. Eukaryotic initiation factor 2 (eIF-2) presented almost basal activity and levels after 30-minute normothermic ischemia, and the amount of phosphorylated eIF-2α in these samples, as well as in sham-control samples, was undetectable. The decrease in the levels of phosphorylated initiation factor 4E (eIF-4E) after 30-minute ischemia (from 32% to 16%) could explain, at least partially, the impairment of initiation during transient cerebral ischemia. After reperfusion, eIF-4E phosphorylation was almost completely restored to basal levels (29%), whereas the level of phosphorylated eIF-2α was higher (13%) than in controls and ischemic samples (both less than 2%). eIF-2α kinase activity in vitro as measured by phosphorylation of endogenous eIF-2 in the presence of ATP/Mg2+, was higher in ischemic samples (8%) than in controls (4%). It seems probable that the failure of the kinase in phosphorylating eIF-2 in vivo during ischemia is due to the depletion of ATP stores. The levels of the double-stranded activated eIF-2α kinase were slightly higher in ischemic animals than in controls. Our results suggest that the modulation of eIF-4E phosphorylation could be implicated in the regulation of translation during ischemia. On the contrary, phosphorylation of eIF-2α, by an eIF-2α kinase already activated during ischemia, represents a plausible mechanism for explaining the inhibition of translation during reperfusion

scholarly journals Phosphorylation of the α subunit of initiation factor 2 correlates with the inhibition of translation following transient cerebral ischaemia in the rat

1994 ◽  
Vol 302 (2) ◽  
pp. 335-338 ◽  
Author(s):  
J Burda ◽  
M E Martín ◽  
A García ◽  
A Alcázar ◽  
J L Fando ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Cerebral Ischaemia ◽  
Ternary Complex ◽  
Initiation Factor ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Vessel Occlusion ◽  
Α Subunit ◽  
Free System ◽  
Initiation Factor 2

Rats were subjected to the standard four-vessel occlusion model of cerebral transient ischaemia (vertebral and carotid arteries) for 15 and 30 min. After a 30 min recirculation period, protein synthesis rate, initiation factor 2 (eIF-2) and guanine nucleotide exchange factor (GEF) activities, and the level of phosphorylation of the alpha subunit of eIF-2 (eIF-2 alpha) were determined in the neocortex region of the brain from sham-operated controls and ischaemic animals. Following reversible cerebral ischaemia, the protein synthesis rate, as measured in a cell-free system, was significantly inhibited (70%) in the ischaemic animals. eIF-2 activity, as measured by its ability to form a ternary complex, also decrease parallel to the decrease in protein synthesis. As eIF-2 activity was assayed in the presence of Mg2+ and GTP-regenerating capacity, the decrease in ternary-complex formation indicated the possible impairment of GEF activity. Since phosphorylated eIF-2 [eIF-2(alpha P)] is a powerful inhibitor of GEF, the levels of phosphorylated eIF-2 alpha were determined, and an increase from 7% phosphorylation in sham control rats to 20% phosphorylation in 15 min and 29% phosphorylation in 30 min in ischaemic rats was observed, providing evidence for a tight correlation of phosphorylation of eIF-2 alpha and inhibition of protein synthesis. Moreover, GEF activity measured in the GDP-exchange assay was in fact inhibited in the ischaemic animals, proving that protein synthesis is impaired by the presence of eIF-2(alpha P), which blocks eIF-2 recycling.

Effect of streptozotocin diabetes on polysomal aggregation and protein synthesis rate in the liver of pregnant rats and their offspring

1995 ◽  
Vol 15 (1) ◽  
pp. 15-20 ◽  
Author(s):  
M. E. Martin ◽  
A. M. Garcia ◽  
L. Blanco ◽  
E. Herrera ◽  
M. Salinas
Keyword(s):  
Protein Synthesis ◽  
Streptozotocin Diabetes ◽  
Diabetic Rats ◽  
Female Rats ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Pregnant Rats ◽  
Free System ◽  
Rna Concentration

To study the effect of diabetes on hepatic protein synthesis and polysomal aggregation in pregnant rats, female rats were treated with streptozotocin prior to conception. Some animals were mated, and studied at day 20 of pregnancy, whereas, others were studied in parallel under non pregnant conditions. The protein synthesis rate measured with an “in vitro” cell-free system was higher in pregnant than in virgin control rats. It decreased with diabetes in both groups, although values remained higher in diabetic pregnant rats than in the virgin animals. The fetuses of diabetic rats had a lower protein synthesis rate than those from controls, although they showed a higher protein synthesis rate than either their respective mothers or virgin rats. Liver RNA concentration was higher in control and diabetic, pregnant rats than in virgin rats, and the effect of diabetes decreasing this parameter was only significant for pregnant rats. Liver RNA concentration in fetuses was lower than in their mothers, and did not differ between control and diabetic animals. The decreased protein synthesis found in diabetic animals was accompanied by disaggregation of heavy polysomes into lighter species, indicating an impairment in peptide-chain initiation.

scholarly journals Neuronal Damage after Repeated 5 Minutes of Ischemia in the Gerbil is Preceded by Prolonged Impairment of Protein Metabolism

1992 ◽  
Vol 12 (3) ◽  
pp. 425-433 ◽  
Author(s):  
R. Widmann ◽  
C. Weber ◽  
P. Bonnekoh ◽  
M. Schlenker ◽  
K.-A. Hossmann
Keyword(s):  
Protein Synthesis ◽  
Cerebral Ischemia ◽  
Neuronal Damage ◽  
Neuronal Injury ◽  
Brain Regions ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Single Episode ◽  
Inhibition Of Protein Synthesis ◽  
The Brain

The effect of single or repeated episodes of cerebral ischemia on protein biosynthesis and neuronal injury was studied in halothane-anesthetized gerbils by autoradiography of [14C]leucine incorporation into brain proteins and light microscopy. For quantification of the protein synthesis rate, the steady-state precursor pool distribution space for labeled and unlabeled free leucine was determined by clamping the specific activity of [14C]leucine in plasma, and by measuring free tissue leucine in samples taken from various parts of the brain. Control values of protein synthesis were 14.6 ± 2.2, 5.8 ± 2.3, 14.2 ± 3.1, and 10.0 ± 3.8 nmol g−1 min−1 (means ± SD) in the frontal cortex, striatum, CA1 sector, and thalamus, respectively. Following a single episode of 5 or 15 min of ischemia, protein synthesis recovered to normal in all brain regions except the CA1 sector, where it returned to only 50% of control after 6 h and to less than 20% after 3 days of recirculation. After three episodes of 5 min of ischemia spaced at 1 h intervals, protein synthesis remained severely suppressed in all brain regions after both 6 h and 3 days of recirculation. Inhibition of protein synthesis after 6 h predicted histological injury after 3 days of recirculation. In animals submitted to a single episode of 5 or 15 min of ischemia, histological damage was restricted to the CA1 sector but injury occurred throughout the brain after three episodes of 5 min of ischemia. These observations demonstrate that persisting inhibition of protein synthesis following cerebral ischemia is an early manifestation of neuronal injury. Prevention of neuronal injury requires restoration of a normal protein synthesis rate.

Glucocorticoid-induced skeletal muscle atrophy in vitro is attenuated by mechanical stimulation

1992 ◽  
Vol 262 (6) ◽  
pp. C1471-C1477 ◽  
Author(s):  
J. A. Chromiak ◽  
H. H. Vandenburgh
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Protein Content ◽  
Total Protein ◽  
Weight Lifting ◽  
Mechanical Activity ◽  
Synthesis Rate ◽  
Protein Synthesis Rate

Glucocorticoids induce rapid atrophy of fast skeletal myofibers in vivo, and either weight lifting or endurance exercise reduces this atrophy by unknown mechanisms. We examined the effects of the synthetic glucocorticoid dexamethasone (Dex) on protein turnover in tissue-cultured avian fast skeletal myofibers and determined whether repetitive mechanical stretch altered the myofiber response to Dex. In static cultures after 3-5 days, 10(-8) M Dex decreased total protein content 42-74%, total protein synthesis rates 38-56%, mean myofiber diameter 35%, myosin heavy chain (MHC) content 86%, MHC synthesis rate 44%, and fibronectin synthesis rate 29%. Repetitive 10% stretch-relaxations of the cultured myofibers for 60 s every 5 min for 3-4 days prevented 52% of the Dex-induced decrease in protein content, 42% of the decrease in total protein synthesis rate, 77% of the decrease in MHC content, 42% of the decrease in MHC synthesis rate, and 67% of the decrease in fibronectin synthesis rate. This in vitro model system will complement in vivo studies in understanding the mechanism by which mechanical activity and glucocorticoids interact to regulate skeletal muscle growth.

scholarly journals P11.36 Ribosome hydroxylase Mina53 is required for Glioblastoma and is involved in regulation of translation rateand fidelity by regulating ribosomal biogenesis

2019 ◽  
Vol 21 (Supplement_3) ◽  
pp. iii51-iii51
Author(s):  
D Pandey ◽  
F Mohammad ◽  
S Weissmann ◽  
P Hallenborg ◽  
B Blagoev ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Proteins ◽  
High Throughput Sequencing ◽  
Affinity Purification ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Ribosomal Biogenesis ◽  
Isolation And Identification ◽  
Knock Down

Abstract Glioblastoma multiforme (GBM) is one of the most aggressive types of tumors with a poor response to standard treatment and a median 5-year survival of less than 5%. Therefore, there is an urgent need for new treatments. Recently, a large number of genome-wide studies have shown that the epigenetic modifiers are frequently deregulated in cancer. Using a mouse GBM model, we performed in vitro and in vivo shRNA screens to identify epigenetic regulators required for the tumorigenic process in GBM. Among these regulators is a ribosome hydroxylase Mina53 which hydroxylates His-39 of ribosomal protein, RPL27a. We have found that the knock-down (KD) of Mina53 reduces the in vitro proliferation and colony forming ability of mouse glioma initiating cells (mGIC) and this is dependent on the catalytic activity of Mina. Knock-down of Mina resulted into a small but significant reduction in the global protein synthesis rate. A tandem affinity purification experiment to identify proteins associated with Mina revealed that it is associated mainly with ribosomal proteins, including its substrate RPL27a. Global proteomic analyses revealed that final amounts and de novo protein synthesis of many ribosomal proteins were reduced upon Mina depletion. Isolation and identification of different polysome fraction bound mRNAs using high-throughput sequencing found that mRNAs encoding many ribosomal proteins have lower number of ribosomes loaded on them in the Mina depleted samples compared to the control. Taken together, this study has found that Mina53 is required for glioblastoma and it regulates translation through regulation of ribosomal biogenesis

scholarly journals Comparison of protein-synthesis rate of alveolar macrophages in vivo and in vitro

1984 ◽  
Vol 217 (3) ◽  
pp. 761-765 ◽  
Author(s):  
M H Oliver ◽  
P J Cole ◽  
G J Laurent
Keyword(s):  
Protein Synthesis ◽  
Alveolar Macrophages ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Novel Method

This paper describes and validates a novel method for measuring rates of protein synthesis of rabbit alveolar macrophages in vivo. A rate of 9.3%/day was obtained, compared with 48.9%/day measured in vitro. This study suggests that the procedures involved in the isolation of alveolar macrophages for study in vitro may themselves activate the cell.

scholarly journals Rates of protein turnover in vivo and in vitro in ventricular muscle of hearts from fed and starved rats

1984 ◽  
Vol 222 (2) ◽  
pp. 395-400 ◽  
Author(s):  
V R Preedy ◽  
D M Smith ◽  
N F Kearney ◽  
P H Sugden
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Protein Turnover ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Ventricular Muscle ◽  
Degradation Rates ◽  
Perfused Hearts

Starvation of 300 g rats for 3 days decreased ventricular-muscle total protein content and total RNA content by 15 and 22% respectively. Loss of body weight was about 15%. In glucose-perfused working rat hearts in vitro, 3 days of starvation inhibited rates of protein synthesis in ventricles by about 40-50% compared with fed controls. Although the RNA/protein ratio was decreased by about 10%, the major effect of starvation was to decrease the efficiency of protein synthesis (rate of protein synthesis relative to RNA). Insulin stimulated protein synthesis in ventricles of perfused hearts from fed rats by increasing the efficiency of protein synthesis. In vivo, protein-synthesis rates and efficiencies in ventricles from 3-day-starved rats were decreased by about 40% compared with fed controls. Protein-synthesis rates and efficiencies in ventricles from fed rats in vivo were similar to values in vitro when insulin was present in perfusates. In vivo, starvation increased the rate of protein degradation, but decreased it in the glucose-perfused heart in vitro. This contradiction can be rationalized when the effects of insulin are considered. Rates of protein degradation are similar in hearts of fed animals in vivo and in glucose/insulin-perfused hearts. Degradation rates are similar in hearts of starved animals in vivo and in hearts perfused with glucose alone. We conclude that the rates of protein turnover in the anterogradely perfused rat heart in vitro closely approximate to the rates in vivo in absolute terms, and that the effects of starvation in vivo are mirrored in vitro.

scholarly journals Metabolic Interventions to Prevent Hypertrophy-Induced Alterations in Contractile Properties In Vitro

2021 ◽  
Vol 22 (7) ◽  
pp. 3620
Author(s):  
Ilvy M. E. Geraets ◽  
Will A. Coumans ◽  
Agnieszka Strzelecka ◽  
Patrick Schönleitner ◽  
Gudrun Antoons ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Glucose Uptake ◽  
Contractile Function ◽  
Contractile Properties ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Adrenergic Stimulation ◽  
Rat Cardiomyocytes ◽  
Functional Changes

(1) Background: The exact mechanism(s) underlying pathological changes in a heart in transition to hypertrophy and failure are not yet fully understood. However, alterations in cardiac energy metabolism seem to be an important contributor. We characterized an in vitro model of adrenergic stimulation-induced cardiac hypertrophy for studying metabolic, structural, and functional changes over time. Accordingly, we investigated whether metabolic interventions prevent cardiac structural and functional changes; (2) Methods: Primary rat cardiomyocytes were treated with phenylephrine (PE) for 16 h, 24 h, or 48 h, whereafter hypertrophic marker expression, protein synthesis rate, glucose uptake, and contractile function were assessed; (3) Results: 24 h PE treatment increased expression of hypertrophic markers, phosphorylation of hypertrophy-related signaling kinases, protein synthesis, and glucose uptake. Importantly, the increased glucose uptake preceded structural and functional changes, suggesting a causal role for metabolism in the onset of PE-induced hypertrophy. Indeed, PE treatment in the presence of a PAN-Akt inhibitor or of a GLUT4 inhibitor dipyridamole prevented PE-induced increases in cellular glucose uptake and ameliorated PE-induced contractile alterations; (4) Conclusions: Pharmacological interventions, forcing substrate metabolism away from glucose utilization, improved contractile properties in PE-treated cardiomyocytes, suggesting that targeting glucose uptake, independent from protein synthesis, forms a promising strategy to prevent hypertrophy and hypertrophy-induced cardiac dysfunction.

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