Centrifugal analysis of undiluted packed human erythrocyte lysates. Studies of the association of glyceraldehyde-phosphate dehydrogenase with the membrane fraction

Dissect new mechanistic insights for geniposide efficacy on the hepatoprotection using multiomics approach

A multi-omics approach could yield in-depth mechanistic insights. Here, we performed an integrated analysis of miRNAome, proteome and metabolome, aimed to investigate the underlying mechanism of active product geniposide in ethanol-induced apoptosis. We found that integrative meta-analysis identified 28 miRNAs, 20 proteins and 7 metabolites significantly differentially expressed, respectively. Further analysis identified geniposide extensively regulated multiple metabolism pathways and the most important related pathway was citrate cycle (TCA cycle). In addition, geniposide can improve energy metabolism benefits using the Extracellular Flux Analyzer. Of particular significance, miR-144-5p exhibits a high positive correlation with oxoglutaric acid, isocitrate dehydrogenase (IDH) 1 and 2 that involved in the TCA cycle. Furthermore,we discovered that miR-144-5p regulates TCA cycle metabolism through IDH1 and IDH2. Collectively, we describe for the first time the hepatoprotective effect of geniposide decreased miR-144-5p level, capable of regulating TCA cycle by directly targeting IDH1 and IDH2 and promoting functional consequences in cells. Integrating metabolomics, miRNAomics and proteomics approach and thereby analyzing microRNAs and proteins as well as metabolites can give valuable information about the functional regulation pattern and action mechanism of natural products.

Fatty acid transport protein 1 and long-chain acyl coenzyme A synthetase 1 interact in adipocytes

The fatty acid transport proteins (FATP) and long-chain acyl coenzyme A synthetase (ACSL) proteins have been shown to play a role in facilitating long-chain fatty acid (LCFA) transport in mammalian cells under physiologic conditions. The involvement of both FATP and ACSL proteins is consistent with the model of vectorial acylation, in which fatty acid transport is coupled to esterification. This study was undertaken to determine whether the functions of these proteins are coordinated through a protein-protein interaction that might serve as a point of regulation for cellular fatty acid transport. We demonstrate for the first time that FATP1 and ACSL1 coimmunoprecipitate in 3T3-L1 adipocytes, indicating that these proteins form an oligomeric complex. The efficiency of FATP1 and ACSL1 coimmunoprecipitation is unaltered by acute insulin treatment, which stimulates fatty acid uptake, or by treatment with isoproterenol, which decreases fatty acid uptake and stimulates lipolysis. Moreover, inhibition of ACSL1 activity in adipocytes impairs fatty acid uptake, suggesting that esterification is essential for fatty acid transport. Together, our findings suggest that a constitutive interaction between FATP1 and ACSL1 contributes to the efficient cellular uptake of LCFAs in adipocytes through vectorial acylation.

Increased membrane activity of glyceraldehyde 3-phosphate dehydrogenase in erythrocytes of patients with homozygous sickle cell anaemia

Membrane-bound glyceraldehyde 3-phosphate dehydrogenase activity was measured in erythrocytes from 43 patients with sickle cell anaemia, 24 heterozygous and 27 controls. A significant increase of the activity was found among the patients but no such difference was observed between the heterozygous and the control individuals. The patients showed nearly non Gaussian distribution of the enzyme activity and were subgrouped on the basis of these results, subgroup I had normal values and subgroup II showed markedly increased activities. The patients in subgroup II had significantly lower blood haemoglobin concentrations and significantly higher lactate dehydrogenase activities in serum than subgroup I. The subgroups did not differ in blood reticulocyte counts, serum bilirubin, serum iron concentrations or band 3 protein content of erythrocyte membranes.

A 1H-NMR study of the activity expressed by lactate dehydrogenase in the human erythrocyte

The activity expressed by lactate dehydrogenase in the human erythrocyte has been compared with the activity displayed by the isolated enzyme in vitro. Enzyme activity was measured by using 1H spin-echo NMR to measure non-invasively the velocity of hydrogen label exchange between the C-2 positions of two methyl-labelled lactate species. This method has significant advantages over a method which has been described previously. The exchange velocity observed in the cell was much lower than that expected based on a comparison with measurements of the exchange velocity in vitro under conditions thought to simulate the intracellular environment. Measurements of enzyme inhibition in cell extracts suggest that the low intracellular activity is due to inhibition of the enzyme by low-molecular-mass compounds present in the cell.

Lack of binding of glyceraldehyde-3-phosphate dehydrogenase to erythrocyte membranes under in vivo conditions

A filtration method is described for separating membrane-free cytoplasm from concentrated erythrocyte haemolysates. The method has been used to assess glyceraldehyde-3-phosphate dehydrogenase binding to erythrocyte membranes. The relative amounts of glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase in the cytoplasm (either oxygenated or deoxygenated) indicate there is no detectable binding of glyceraldehyde-3-phosphate dehydrogenase to the membranes under physiological conditions.

Quantitative characterization of the interactions of aldolase and glyceraldehyde-3-phosphate dehydrogenase with erythrocyte membranes

Results of studies on the interactions of aldolase and glyceraldehyde-3-phosphate dehydrogenase with erythrocyte ghosts have been reinterpreted by making allowance for possible multivalency of the enzymes in regard to their interactions with matrix sites. It is shown that the curvilinearity of the experimental Scatchard plots may be attributed fully to the formation of enzyme-membrane complexes in which tetravalent enzyme may form crosslinks between several membrane sites. This interpretation of the results is preferable to earlier analyses based on heterogeneity of membrane sites in that (a) it takes into account the tetrameric nature of aldolase and glyceraldehyde-3-phosphate dehydrogenase, and (b) it is consistent with experimental demonstrations that band 3 protein is the sole site for enzyme interaction with the erythrocyte matrix. The dependence on ionic strength of the intrinsic association constant for either interaction is such that the binding of neither aldolase nor glyceraldehyde-3-phosphate dehydrogenase could be detected at ionic strengths in excess of 0.08 I. This finding is discussed in relation to the claims and counterclaims concerning the physiological significance of these interactions between glycolytic enzymes and erythrocyte membranes.