Difference in subcellular distribution between 45- and 37-kDa mevalonate pyrophosphate decarboxylase in rat liver

Effects of HSYA on serum and brain cholesterol levels in AD rats based on quantitative proteomics

Backgroud: Hydroxysafflor yellow A (HSYA) has a certain improvement effect on Alzheimer's disease (AD) rats, but its specific mechanism is still unclear. The purpose of this study was to observe the regulatory effect of HSYA on learning and memory ability of AD rats induced by Aβ1-42.Materials and methods: Morris water maze test was used to evaluate the effect of HSYA on the learning and memory ability of AD model rats. To explore the effective targets and potential molecular mechanisms of HSYA in AD treatment based on quantitative proteomics.Results: Through the Morris water maze experiment, we found that after HSYA treatment, the learning ability of rats in the model group has been significantly improved. Quantitative proteomics results showed that among the 11 common differential proteins between the "model/sham operation" comparison group and the "HSYA treatment/model" comparison group, the cholesterol synthesis rate-limiting enzyme mevalonate decarboxylase (Mvd) Western Blot results are consistent with the results of quantitative proteomics analysis. We found that HSYA can inhibit the expression of BACE protein in hippocampus of AD rats and decrease the level of Aβ1-42. Besides, HSYA could also reduce cholesterol levels in serum and hippocampus.Conclusion: In summary, HSYA can effectively improve learning and memory disorders in AD rats, and exert neuroprotective effects by effectively controlling serum and brain cholesterol to down-regulate the expression of BACE and thus reduce the content of Aβ1-42.

Expression profiling of hepatic genes associated with lipid metabolism in nephrotic rats

Hyperlipidemia is one of the major features of nephrotic syndrome (NS). Although many factors have been implicated in the pathogenesis of NS-related dyslipidemia, the underlying mechanisms remain largely uncharacterized. The present study was designed to examine the gene profile associated with lipid metabolism in the livers of nephrotic rats. NS was created in male Sprague-Dawley rats (n = 6) receiving sequential intraperitoneal injections of puromycin aminonucleoside. Analysis by Affymetrix assay, quantitative RT-PCR, and Northern and Western blotting revealed 21 genes associated with cholesterol and fatty acid metabolism. Eight genes involved in cholesterol metabolism, Apo A-I, Acly, Acat, Mpd, Fdps, Ss, Lss, and Nsdhl, were significantly upregulated under NS. Four genes involved in fatty acid biosynthesis, Acc, FAS, ELOVL 2, and ELOVL6, and three critical for triglyceride biosynthesis, Gpam, Agpat 3, and Dgat 1, were significantly upregulated, whereas two genes involved in fatty acid oxidation, Dci and MCAD, were downregulated. Expression of several genes in sterol-regulatory element-binding protein (SREBP)-1 activation was also aberrantly altered in nephrotic livers. The expression and transcriptional activity of SREBP-1 but not SREBP-2 were increased in nephrotic rats as assessed by real-time PCR, immunoblotting, and gel shift assays. The upregulation of hepatic genes involved in cholesterol biosynthesis may play an important role in the pathogenesis of hypercholesterolemia, whereas upregulation of genes participating in hepatic fatty acid and triglyceride biosynthesis and downregulation of genes involved in hepatic fatty acid oxidation may contribute to hypertriglyceridemia in nephrotic rats. Activation of SREBP-1 transcription factor may represent an underlying molecular mechanism of hyperlipidemia in NS.

System-wide analysis of hepatotoxicological responses: tissomics is key

BACKGROUND

Combining diverse data streams across different levels of biological observation, such as molecular, cellular, and clinical chemistry responses, support a system-wide diagnostic approach. Recent progress in slide-based cytometry contributes to the development of tissomics, a high-throughput and high-content phenotyping methodology that provides data-rich profiles of cellular heterogeneity in tissues enabling correlative statistical treatments over multiple scales of biological hierarchies.

METHODS

Phenotypical data are covariants that can be used as biomarkers to identify relevant candidate genes by associating initiating molecular events with phenotypical changes and adverse outcomes. We introduce a procedure of combined statistical and analytical tools to identify and visualize such associations for nonpooled entities. The new utility is applied to a time-controlled, low-dose toxicological study including a control and two xenobiotic compounds.

RESULTS

An integrated analysis identified specific molecular and phenotypical biomarkers, which support the classification of animals in the absence of any visual indicators from pathology readings.

DISCUSSION

The introduction of controlled perturbations to tissues provides a prototypical setting to develop a sensitive, systems-based analysis methodology suitable for a broader range of biomedical applications.

Subcellular distribution of mouse mevalonate pyrophosphate decarboxylase

Mevalonate pyrophosphate decarboxylase (MPD) is considered to be a cytosolic protein. Recently, other groups reported that MPD is mostly located in the peroxisomes. In this study, we examined whether the expression of MPD in mice depends on the proliferation of peroxisomes, and whether MPD is predominantly located in the peroxisomes or the cytosol of mice. No increase in the protein level of MPD was observed in the crude extract of the livers of mice administered with peroxisome proliferative drugs. The result suggests that the expression of MPD is independent of the proliferation of peroxisomes, and may be maintained via a specific regulatory mechanism, different from the regulation of the expression of peroxisome proliferator-activated receptor alpha. When the subcellular distribution of MPD in mouse melanoma (B16F10) cells was examined by cell fractionation, MPD was detected in the cytosol of B16F10 cells, but not in the peroxisomes. In permeabilized B16F10 cells treated with digitonin, which lack cytosolic enzymes, 80% and 20% of MPD, 75% and 25% of lactate dehydrogenase, or 2% and 98% of catalase, existed in the medium and in the cell, respectively. From these results, it indicated that MPD was predominantly located in the cytosol and did not exist in the peroxisomes of B16F10 cells.

Mortalin-MPD (mevalonate pyrophosphate decarboxylase) interactions and their role in control of cellular proliferation

Mortalin (mot-2/GRP75/PBP74/mthsp70) is a member of the hsp70 family of proteins and is differentially distributed in normal and immortal cells. It was shown to be involved in pathways to cell senescence and immortalization. To elucidate its functional aspects, a yeast interactive screen for mortalin (mot-2) binding proteins was performed. Mevalonate pyrophosphate decarboxylase (MPD) was identified as one of the mortalin binding partners. The interactions were confirmed in mammalian cells by two-hybrid assay and in vivo coimmunoprecipitation. MPD is known to furnish prenyl groups required for prenylation, protein modification that is essential for the activity of many proteins including p21(Ras) (Ras). We have examined the effect of MPD-mot-2 interactions on the level and activity of p21(Ras) and its downstream effectors, p44 and p42 MAP kinases (ERK1/ERK2), in Ras-Raf pathway. An overexpression of mot-2 resulted in reduced level of Ras and phosphorylated ERK2. These were rescued by co-expression of MPD from an exogenous promoter demonstrating a functional link between mot-2, MPD, and Ras. Ras and its oncogenic forms act as key players in controlling proliferation of normal and cancerous cells. Assigning mot-2 upstream of p21(Ras) offers an important mechanism for influence over cell proliferation.

Peroxisome proliferative drugs do not induce an increase of rat mevalonate pyrophosphate decarboxylase

To determine whether or not the expression of mevalonate pyrophosphate decarboxylase (MPD) depends on the proliferation of peroxisomes, we examined change in the protein level of MPD in the crude extract, the cytosol and the peroxisome-enriched fraction of the livers of rats administered peroxisome proliferative drugs. No increase of MPD was observed in any of these fractions. These data suggest that the expression of MPD is independent of the proliferation of peroxisomes and may be maintained via a specific regulatory mechanism different from that of the expression of peroxisome proliferator-activated receptor alpha.