Changes of Lipid Composition with Growth Phase of Cryptococcus neoformans

Qualitative and quantitative profiles of phospholipids, neutral lipids, and fatty acid composition in Cr. neoformans during the growth phase were investigated in relation to pyrophosphatidic acid. A marked increase of the total lipid content, which depended on the accumulation of triglyceride in yeast cells with the growth, was observed. The total phospholipid contents in yeast cells remained almostly constant during the exponential phase and slightly decreased in the stationary phase. The major phospholipids of this yeast were phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and cardiolipin, the next groups being pyrophosphatidic acid, phosphatidic acid, lysophos-phatidylcholine, and unidentified components. The amounts of phosphatidylcholine, phosphatidylinositol, and cardiolipin were fairly constant throughout the growth phase, but the amount of phosphatidylethanolamine increased and that of phosphatidylserine decreased with progressive growth. The pyrophosphatidic acid contents were 0.9~0.7% for total phospholipid during the growth phase. The major fatty acids of pyrophosphatidic acid were C_16:0, C_18:1, and C_18:2 acids. The changing patterns of fatty acid composition in pyrophosphatidic acid through the growth phase closely resembled that of phosphatidic acid, which contained larger amounts of C_18:1 acid (35~45%) than C_16:0 acid (30~25%) and C_18:2 acid (30~25%). Phosphatidylserine and phosphatidylinositol contained considerable amounts of saturated fatty acid (C_16:0 acid, more than 55%). On the other hand, phosphatidylcholine, phosphatidylethanolamine, and cardiolipin contained extremely large amounts of unsaturated fatty acid (C_18:1 and C_18:2 acid, 85ç90%).     

Caffeic acid production by simultaneous saccharification and fermentation of kraft pulp using recombinant Escherichia coli

Caffeic acid (3,4-dihydroxycinnamic acid) serves as a building block for thermoplastics and a precursor for biologically active compounds and was recently produced from glucose by microbial fermentation. To produce caffeic acid from inedible cellulose, separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) reactions were compared using kraft pulp as lignocellulosic feedstock. Here, a tyrosine-overproducing Escherichia coli strain was metabolically engineered to produce caffeic acid from glucose by introducing the genes encoding a 4-hydroxyphenyllactate 3-hydroxylase (hpaBC) from Pseudomonas aeruginosa and tyrosine ammonia lyase (fevV) from Streptomyces sp. WK-5344. Using the resulting recombinant strain, the maximum yield of caffeic acid in SSF (233 mg/L) far exceeded that by SHF (37.9 mg/L). In the SSF with low cellulase loads (≤2.5 filter paper unit/g glucan), caffeic acid production was markedly increased, while almost no glucose accumulation was detected, indicating that the E. coli cells experienced glucose limitation in this culture condition. Caffeic acid yield was also negatively correlated with the glucose concentration in the fermentation medium. In SHF, the formation of by-product acetate and the accumulation of potential fermentation inhibitors increased significantly with kraft pulp hydrolysate than filter paper hydrolysate. The combination of these inhibitors had synergistic effects on caffeic acid fermentation at low concentrations. With lower loads of cellulase in SSF, less potential fermentation inhibitors (furfural, 5-hydroxymethyfurfural, and 4-hydroxylbenzoic acid) accumulated in the medium. These observations suggest that glucose limitation in SSF is crucial for improving caffeic acid yield, owing to reduced by-product formation and fermentation inhibitor accumulation.

     

siRNA-mediated inhibition of endogenous Huntington disease gene expression induces an aberrant configuration of the ER network in vitro

Huntingtin is a ubiquitously expressed cytoplasmic protein encoded by the Huntington disease (HD) gene, in which a CAG expansion induces an autosomal dominant progressive neurodegenerative disorder; however, its biological function has not been completely elucidated. Here, we report for the first time that short interfering RNA (siRNA)-mediated inhibition of endogenous Hdh (a mouse homologue of huntingtin) gene expression induced an aberrant configuration of the endoplasmic reticulum (ER) network in vitro. Studies using immunofluorescence microscopy with several ER markers revealed that the ER network appeared to be congregated in various types of cell lines transfected with siRNA directed against Hdh, but not with other siRNAs so far tested. Other subcellular organelles and structures, including the nucleus, Golgi apparatus, mitochondria, lysosomes, microtubules, actin cytoskeletons, cytoplasm, lipid rafts, and plasma membrane, exhibited normal configurations. Western blot analysis of cellular prion protein (PrP(C)) revealed normal glycosylation, which is a simple marker of post-translational modification in the ER and Golgi compartments, and immunofluorescence microscopy detected no altered subcellular distribution of PrP(C) in the post-ER compartments. Further investigation is required to determine whether the distorted ER network, i.e., loss of the huntingtin function, participates in the development of HD.     

Perfusion of hearts with triglyceride-rich particles reproduces the metabolic abnormalities in lipotoxic cardiomyopathy

Hearts with overexpression of anchored lipoprotein lipase (LpL) by cardiomyocytes (hLpL(GPI) mice) develop a lipotoxic cardiomyopathy. To characterize cardiac fatty acid (FA) and triglyceride (TG) metabolism in these mice and to determine whether changes in lipid metabolism precede cardiac dysfunction, hearts from young mice were perfused in Langendorff mode with [14C]palmitate. In hLpL(GPI) hearts, FA uptake and oxidation were decreased by 59 and 82%, respectively. This suggests reliance on an alternative energy source, such as TG. Indeed, these hearts oxidized 88% more TG. Hearts from young hLpL(GPI) mice also had greater uptake of intravenously injected cholesteryl ester-labeled Intralipid and VLDL. To determine whether perfusion of normal hearts would mimic the metabolic alterations found in hLpL(GPI) mouse hearts, wild-type hearts were perfused with [14C]palmitate and either human VLDL or Intralipid (0.4 mM TG). Both sources of TG reduced [14C]palmitate uptake (48% with VLDL and 45% with Intralipid) and FA oxidation (71% with VLDL and 65% with Intralipid). Addition of either heparin or LpL inhibitor P407 to Intralipid-containing perfusate restored [14C]palmitate uptake and confirmed that Intralipid inhibition requires local LpL. Our data demonstrate that reduced FA uptake and oxidation occur before mechanical dysfunction in hLpL(GPI) lipotoxicity. This physiology is reproduced with perfusion of hearts with TG-containing particles. Together, the results demonstrate that cardiac uptake of TG-derived FA reduces utilization of albumin-FA.     

The molecular biology of barophilic bacteria

Many microorganisms from the deep-sea display high-pressure-adapted — also described as barophilic or piezophilic — growth characteristics. Phylogenetic studies have revealed that a large proportion of the barophilic bacteria currently in culture collections belong to a distinct subgroup of the genus Shewanella, referred to as the “barophile branch.“ Many of the basic properties of barophiles that enable their survival at extremes of pressure remain to be elucidated. However, several genes whose expression is regulated by pressure, or which appear to be critical to baroadaptation, have been uncovered. One such operon, whose presence appears to be restricted to the “barophile branch,” has been identifed in DNA samples obtained from sediments recovered in the deepest ocean trench. In the case of another set of pressure-regulated genes, regulatory elements required for pressure signaling have been uncovered. The nature and regulation of these genes is discussed. Received: February 19, 1997 / Accepted: March 3, 1997     

Molecular characterization of a deletion in the HPRT1 gene in a patient with Lesch-Nyhan syndrome

Lesch-Nyhan syndrome is caused by a deficiency of hypoxanthine phosphoribosyltransferase (HPRT) encoded by HPRT1. About 20% of patients have a deletion of HPRT1 and large deletions of HPRT1 are not always fully characterized at the molecular level. Here, we report on a case of Lesch-Nyhan syndrome with a 33-kb deletion involving exon 1 of HPRT1. This novel mutation is caused by a nonhomologous recombination between different classes of interspersed repetitive DNA.     

Cloning of the blasticidin S deaminase gene (BSD) from Aspergillus terreus and its use as a selectable marker for Schizosaccharomyces pombe and Pyricularia oryzae

Aspergillus terreus produces a unique enzyme, blasticidin S deaminase, which catalyzes the deamination of blasticidin S (BS), and in consequence confers high resistance to the antibiotic. A cDNA clone derived from the structural gene for BS deaminase (BSD) was isolated by transforming Escherichia coli with an Aspergillus cDNA expression library and directly selecting for the ability to grow in the presence of the antibiotic. The complete nucleotide sequene of BSD was determined and proved to contain an open reading frame of 393 bp, encoding a polypeptide of 130 amino acids. Comparison of its nulceotide sequence with that of bsr, the BS deaminase gene isolated from Bacillus cereus, indicated no homology and a large difference in codon usage. The activity of BSD expressed in E. coli was easily quantified by an assay based on spectrophotometric recording. The BSD gene was placed in a shuttle vector for Schizosaccharomyces pombe, downstream of the SV40 early region promoter, and this allowed direct selection with BS at high frequency, following transformation into the yeast. The BSD gene was also employed as a selectable marker for Pyricularia oryzae, which could not be transformed to BS resistance by bsr. These results promise that the BSD gene will be useful as a new dominant selectable marker for eukaryotes.     

Epithelial–mesenchymal transition of A549 cells is enhanced by co-cultured with THP-1 macrophages under hypoxic conditions

Epithelial–mesenchymal transition (EMT) is associated with pulmonary fibrosis, including idiopathic pulmonary fibrosis (IPF). In this study, we investigated EMT of human pulmonary epithelial-derived cells (A549). A549 cells was either cultured by itself or co-cultured with THP-1 macrophages under normoxic (21% O₂) and hypoxic (2% O₂) conditions. We evaluated the presence of EMT by determining the expression of EMT markers, E-cadherin, vimentin, and fibronectin. To determine the role of TGF-β1 and IL-1β in EMT of the A549 cells, we analyzed the effects of blocking their activity with TGF-β1 inhibitor or IL-1β neutralizing antibody respectively. The A549 cells presented EMT when they were co-cultured with THP-1 macrophages. The EMT of the A549 cells co-cultured with THP-1 macrophages was exacerbated under hypoxia. In addition, the EMT were prevented by the addition of TGF-β1 type I receptor kinase inhibitor. The hypoxic condition increased the mRNA levels of TGF-β1 in A549 cells and THP-1 macrophages and that of IL-1β in THP-1 macrophages when each cells were co-cultured. Anti-IL-1β neutralizing antibody attenuated TGF-β1 secretion in co-culture media under hypoxic conditions. Thus, the IL-1β from THP-1 macrophages up-regulated the TGF-β1 from A549 cells and THP-1 macrophages, and then the TGF-β1 from both cells induced and promoted the EMT of A549 cells when they were co-cultured under hypoxia. Together, these results demonstrate that the interaction between type II pneumocytes and macrophages under hypoxia is necessary for the development of pulmonary fibrosis.