Mitochondrial dysfunction in the spinal cord is a hallmark of amyotrophic lateral sclerosis (ALS), but the neurometabolic alterations during early stages of the disease remain unknown. Here, we ...investigated the bioenergetic and proteomic changes in ALS mouse motor neurons and patients' skin fibroblasts. We first observed that SODG93A mice presymptomatic motor neurons display alterations in the coupling efficiency of oxidative phosphorylation, along with fragmentation of the mitochondrial network. The proteome of presymptomatic ALS mice motor neurons also revealed a peculiar metabolic signature with upregulation of most energy-transducing enzymes, including the fatty acid oxidation (FAO) and the ketogenic components HADHA and ACAT2, respectively. Accordingly, FAO inhibition altered cell viability specifically in ALS mice motor neurons, while uncoupling protein 2 (UCP2) inhibition recovered cellular ATP levels and mitochondrial network morphology. These findings suggest a novel hypothesis of ALS bioenergetics linking FAO and UCP2. Lastly, we provide a unique set of data comparing the molecular alterations found in human ALS patients' skin fibroblasts and SODG93A mouse motor neurons, revealing conserved changes in protein translation, folding and assembly, tRNA aminoacylation and cell adhesion processes.
Imatinib is an effective therapy for chronic myeloid leukemia (CML), a myeloproliferative disorder characterized by the expression of the recombinant oncoprotein Bcr-Abl. In this investigation, we ...studied an imatinib-resistant cell line (K562-r) generated from the K562 cell line in which none of the previously described mechanisms of resistance had been detected. A threefold increase in the expression of the heat-shock protein 70 (Hsp70) was detected in these cells. This increase was not associated to heat-shock transcription factor-1 (HSF-1) overexpression or activation. RNA silencing of Hsp70 decreased dramatically its expression (90%), and was accompanied by a 34% reduction in cell viability. Overexpression of Hsp70 in the imatinib-sensitive K562 line induced resistance to imatinib as detected by a large reduction in cell death in the presence of 1 muM of imatinib. Hsp70 level was also increased in blast cells of CML patients resistant to imatinib, whereas the level remained low in responding patients. Taken together, the results demonstrate that overexpression of Hsp70 can lead to both in vitro and in vivo resistance to imatinib in CML cells. Moreover, the overexpression of Hsp70 detected in imatinib-resistant CML patients supports this mechanism and identifies potentially a marker and a therapeutic target of CML evolution.
The role of some serine/threonine kinases in the regulation of mitochondrial physiology is now well established, but little is known about mitochondrial tyrosine kinases. We showed that tyrosine ...phosphorylation of rat brain mitochondrial proteins was increased by in vitro addition of ATP and H2O2, and also during in situ ATP production at state 3, and maximal reactive oxygen species production. The Src kinase inhibitor PP2 decreased tyrosine phosphorylation and respiratory rates at state 3. We found that the 39-kDa subunit of complex I was tyrosine phosphorylated, and we identified putative tyrosine-phosphorylated subunits for the other complexes. We also have strong evidence that the FoF1-ATP synthase alpha chain is probably tyrosine-phosphorylated, but demonstrated that the beta chain is not. The tyrosine phosphatase PTP 1B was found in brain but not in muscle, heart or liver mitochondria. Our results suggest that tyrosine kinases and phosphatases are involved in the regulation of oxidative phosphorylation.
Latex from Caricaceae has been known since 1925 to contain strong lipase activity. However, attempts to purify and identify the enzyme were not successful, mainly because of the lack of solubility of ...the enzyme. Here, we describe the characterization of lipase activity of the latex of Vasconcellea heilbornii and the identification of a putative homologous lipase from Carica papaya. Triacylglycerol lipase activity was enriched 74‐fold from crude latex of Vasconcellea heilbornii to a specific activity (SA) of 57 μmol·min−1·mg−1 on long‐chain triacylglycerol (olive oil). The extract was also active on trioctanoin (SA = 655 μmol·min−1·mg−1), tributyrin (SA = 1107 μmol·min−1·mg−1) and phosphatidylcholine (SA = 923 μmol·min−1·mg−1). The optimum pH ranged from 8.0 to 9.0. The protein content of the insoluble fraction of latex was analyzed by electrophoresis followed by mass spectrometry, and 28 different proteins were identified. The protein fraction was incubated with the lipase inhibitor 14Ctetrahydrolipstatin, and a 45 kDa protein radiolabeled by the inhibitor was identified as being a putative lipase. A C. papaya cDNA encoding a 55 kDa protein was further cloned, and its deduced sequence had 83.7% similarity with peptides from the 45 kDa protein, with a coverage of 25.6%. The protein encoded by this cDNA had 35% sequence identity and 51% similarity to castor bean acid lipase, suggesting that it is the lipase responsible for the important lipolytic activities detected in papaya latex.
Like seed plants, liverworts synthesize and accumulate a myriad of isoprenoid compounds. Using antibodies raised against several isoprenoid biosynthetic enzymes, we investigated their intracellular ...compartmentation by in situ immunolocalization from Marchantia polymorpha. The enzymes examined were deoxy-xylulose phosphate synthase, geranyl diphosphate synthase, farnesyl diphosphate synthase, geranylgeranyl diphosphate synthase, monoterpene synthase, geranylgeranyl diphosphate reductase, phytoene synthase, and phytoene desaturase. Our results show that liverwort oil bodies, which are organelles bound by a single unit membrane, possess isoprenoid biosynthetic enzymes similar to those found in plastids and the cytosol. We postulate that oil bodies play a dynamic role in cell metabolism in addition to their role as sites of essential oil accumulation and sequestration. The occurrence of such enzymes in different cellular compartments might be due to multiple targeting of gene products to various organelles.
In this report, we have shown that the yeast amphiphysin-like protein Rvs167p was localized mainly in small cortical patches throughout the cell in unbudding cells. During budding, the patches were ...polarized at bud emergence site. During mating, Rvs167p was concentrated at the tip of the shmoo. Rvs167p colocalized with actin patches during yeast vegetative growth and mating. Complete disruption of the actin cytoskeleton using Latrunculin-A did not affect Rvs167p localization in patches throughout the cell. In rvs167 mutant cells, actin patches are mislocalized and in rvs161 or abp1 mutant cells, Rvs167p localization is not affected. These observations suggest that Rvs167p may localize the actin cortical complex properly. Finally, the amphiphysin-conserved N-terminal domain of Rvs167p, called the BAR domain, was required but not sufficient for the correct localization of the protein.
A large body of evidence from the past decade supports the existence of functional microdomains in membranes of animal and yeast cells, which play important roles in protein sorting, signal ...transduction, or infection by pathogens. They are based on the dynamic clustering of sphingolipids and cholesterol or ergosterol and are characterized by their insolubility, at low temperature, in nonionic detergents. Here we show that similar microdomains also exist in plant plasma membrane isolated from both tobacco leaves and BY2 cells. Tobacco lipid rafts were found to be greatly enriched in a sphingolipid, identified as glycosylceramide, as well as in a mixture of stigmasterol, sitosterol, 24-methylcholesterol, and cholesterol. Phospho- and glycoglycerolipids of the plasma membrane were largely excluded from lipid rafts. Membrane proteins were separated by one- and two-dimensional gel electrophoresis and identified by tandem mass spectrometry or use of specific antibody. The data clearly indicate that tobacco microdomains are able to recruit a specific set of the plasma membrane proteins and exclude others. We demonstrate the recruitment of the NADPH oxidase after elicitation by cryptogein and the presence of the small G protein NtRac5, a negative regulator of NADPH oxidase, in lipid rafts.
Dipeptidyl‐peptidase III (DPP III) hydrolyses small peptides with a broad substrate specificity. It is thought to be involved in a major degradation pathway of the insect neuropeptide proctolin. We ...report the purification and characterization of a soluble DPP III from 40 g Drosophila melanogaster. Western blot analysis with anti‐(DPP III) serum revealed the purification of two proteins of molecular mass 89 and 82 kDa. MS/MS analysis of these proteins resulted in the sequencing of 45 and 41 peptide fragments, respectively, confirming ≈ 60% of both annotated D. melanogaster DPP III isoforms (CG7415‐PC and CG7415‐PB) predicted at 89 and 82 kDa. Sequencing also revealed the specific catalytic domain HELLGH in both isoforms, indicating that they are both effective in degrading small peptides. In addition, with a probe specific for D. melanogaster DPP III, northern blot analysis of fruit fly total RNA showed two transcripts at ≈ 2.6 and 2.3 kb, consistent with the translation of 89‐kDa and 82‐kDa DPP III proteins. Moreover, the purified enzyme hydrolyzed the insect neuropeptide proctolin (Km≈ 4 µm) at the second N‐terminal peptide bound, and was inhibited by the specific DPP III inhibitor tynorphin. Finally, anti‐(DPP III) immunoreactivity was observed in the central nervous system of D. melanogaster larva, supporting a functional role for DPP III in proctolin degradation. This study shows that DPP III is in actuality synthesized in D. melanogaster as 89‐kDa and 82‐kDa isoforms, representing two native proteins translated from two alternative mRNA transcripts.
Proteome analysis of grape skins during ripening Deytieux, Christelle; Geny, Laurence; Lapaillerie, Delphine ...
Journal of experimental botany,
01/2007, Letnik:
58, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The characterization of proteins isolated from skin tissue is apparently an essential parameter for understanding grape ripening as this tissue contains the key compounds for wine quality. It has ...been particularly difficult to extract proteins from skins for analysis by two-dimensional electrophoresis gels and, therefore, a protocol for this purpose has been adapted. The focus was on the evolution of the proteome profile of grape skin during maturation. Proteome maps obtained at three stages of ripening were compared to assess the extent to which protein distribution differs in grape skin during ripening. The comparative analysis shows that numerous soluble skin proteins evolve during ripening and reveal specific distributions at different stages. Proteins involved in photosynthesis, carbohydrate metabolisms, and stress response are identified as being over-expressed at the beginning of colour-change. The end of colour-change is characterized by the over-expression of proteins involved in anthocyanin synthesis and, at harvest, the dominant proteins are involved in defence mechanisms. In particular, increases in the abundance of different chitinase and β-1,3-glucanase isoforms were found as the berry ripens. This observation can be correlated with the increase of the activities of both of these enzymes during skin ripening. The differences observed in proteome maps clearly show that significant metabolic changes occur in grape skin during this crucial phase of ripening. This comparative analysis provides more detailed characterization of the fruit ripening process.
Cohesin mediates sister chromatid cohesion which is essential for chromosome segregation and repair. Sister chromatid cohesion requires an acetyl‐transferase (Eso1 in fission yeast) counteracting ...Wpl1, promoting cohesin release from DNA. We report here that Wpl1 anti‐cohesion function includes an additional mechanism. A genetic screen uncovered that Protein Phosphatase 4 (PP4) mutants allowed cell survival in the complete absence of Eso1. PP4 co‐immunoprecipitated Wpl1 and cohesin and Wpl1 triggered Rad21 de‐phosphorylation in a PP4‐dependent manner. Relevant residues were identified and mapped within the central domain of Rad21. Phospho‐mimicking alleles dampened Wpl1 anti‐cohesion activity, while alanine mutants were neutral indicating that Rad21 phosphorylation would shelter cohesin from Wpl1 unless erased by PP4. Experiments in post‐replicative cells lacking Eso1 revealed two cohesin populations. Type 1 was released from DNA by Wpl1 in a PP4‐independent manner. Type 2 cohesin, however, remained DNA‐bound and lost its cohesiveness in a manner depending on Wpl1‐ and PP4‐mediated Rad21 de‐phosphorylation. These results reveal that Wpl1 antagonizes sister chromatid cohesion by a novel pathway regulated by the phosphorylation status of the cohesin kleisin subunit.
Synopsis
A genetic screen in fission yeast reveals two parallel anti‐cohesion pathways that are both counteracted by the acetyltransferase Eso1. While type 1 cohesin is released from DNA by Wpl1, type 2 cohesin is rendered non‐cohesive by the combined action of Wpl1 and Protein Phosphatase 4 (PP4).
PP4 ablation bypasses the requirement for the cohesin acetyltransferase Eso1.
In absence of Eso1, Wpl1 induces dephosphorylation of the kleisin cohesin subunit Rad21 and loss of sister chromatid cohesion in a PP4‐dependent manner.
Dephosphorylated Rad21 remains chromatin‐bound but is no longer cohesive.
Phosphorylation of two serine residues in the central domain of Rad21 dampens Wpl1 anti‐cohesion activity unless erased by PP4.
In addition to protecting cohesin from Wpl1‐dependent removal, the acetyltransferase Eso1 also counteracts a novel phosphatase‐mediated mechanism for rendering cohesin on DNA non‐cohesive.
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