Purification and characterization of phospholipase B from Candida utilis

Phospholipase B (PLB) from the asporogenous yeast Candida utilis was purified to homogeneity from a culture broth. The apparent molecular mass was 90-110 kDa by SDS-PAGE. The enzyme had two pH optima, one acidic (pH 3.0) and the other alkaline (pH 7.5). At acidic pH the enzyme hydrolyzed all phospholipids tested without metal ions. On the other hand, the PLB showed substrate specificity and required metal ions for alkaline activity.The cDNA sequence of the PLB was analyzed by a combination of several PCR procedures. The PLB encoded a protein consisting of 643 amino acids. The amino acid sequence contained a lipase consensus sequence (GxSxG) and catalytic arginine and aspartic acid motifs which were identified as the catalytic triad in the PLB from Kluyveromyces lactis, suggesting that the catalytic mechanism of the PLB is similar to that of cytosolic phospholipase A(2) (cPLA(2)), found in mammalian tissues.     

Expression analysis of LacZ gene placed in the locus of Cnot7 exhibits its activity in osteoblasts in vivo and in mineralized nodules in vitro

CCR4-NOT complex 7 (Cnot7) was identified as a regulator of gene expression in yeast and evolutionally conserved in mammals. Cnot7 deficient male mice exhibit abnormality in spermatogenesis. As these mice contained construct to express LacZ, we followed the expression patterning in these animals. LacZ was expressed in osteoblasts located in the primary spongiosa in adult mice. Cellular analysis indicated that LacZ is expressed in osteoblasts but not in osteoclasts. In the mineralized nodules formed in the culture of bone marrow cells obtained from Cnot7 +/- mice, LacZ expression was mainly observed in the cells forming mineralized nodules but not in un-mineralized area scattered around the periphery of the nodules. LacZ blue positive cells were gradually depositing minerals along its time course of the in vitro mineralization assay. Cnot7 expression was enhanced by the treatment with BMP. These data suggest that Cnot7 is expressed in osteoblasts and is associated with mineralization.     

Enhanced accumulation of adipocytes in bone marrow stromal cells in the presence of increased extracellular and intracellular [Ca²⁺

The bone marrow stroma contains osteoblasts and adipocytes that have a common precursor: the pluripotent mesenchymal stem cell found in bone marrow stromal cells (BMSCs). Local bone marrow Ca(2+) levels can reach high concentrations due to bone resorption, which is one of the notable features of the bone marrow stroma. Here, we describe the effects of high [Ca(2+)](o) on the accumulation of adipocytes in the bone marrow stroma. Using primary mouse BMSCs, we evaluated the level of adipocyte accumulation by measuring Oil Red O staining and glycerol-3-phosphate dehydrogenase (GPDH) activity. High [Ca(2+)](o) enhanced the accumulation of adipocytes following treatment with both insulin and dexamethasone together but not in the absence of this treatment. This enhanced accumulation was the result of both the accelerated proliferation of BMSCs and their differentiation into adipocytes. Using the fura-2 method, we also showed that high [Ca(2+)](o) induces an increase in [Ca(2+)](i). An intracellular Ca(2+) chelator suppressed the enhancement in adipocyte accumulation due to increased [Ca(2+)](o) in BMSCs. These data suggest a new role for extracellular Ca(2+) in the bone marrow stroma: increased [Ca(2+)](o) induces an increase in [Ca(2+)](i) levels, which in turn enhances the accumulation of adipocytes under certain conditions.     

Gene pathway analysis of the mechanism by which the Rho-associated kinase inhibitor Y-27632 inhibits apoptosis in isolated thawed human embryonic stem cells

Cryopreservation is an essential technique in basic research and clinical applications of human embryonic stem (hES) cells. Cryopreserved hES cells are fragile and undergo post-thaw apoptosis. We performed gene pathway analysis on cryopreserved and thawed hES cells to examine the effect of Y-27632, a Rho-associated kinase (ROCK) inhibitor, on apoptosis and associated molecular events. Y-27632 was added to the cryopreservation solution and/or the post-thaw medium of two hES cell lines (KhES-1, KhES-3). Post-thaw apoptosis was recorded as a function of time using Giemsa staining and the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Apoptosis plateaued 12h after the untreated hES cells were thawed. Gene pathway analysis showed the activation of IL-1β, TGF-β, and their respective receptors (IL-1R, ACVR1C) in the mitogen-activated protein kinase (MAPK) pathway, which resulted in the upregulation of caspase-8 and -10. Quantitative RT-PCR confirmed the upregulation of IL-1β, TGF-β, their respective receptors, and caspase-10 and -3. As these molecules were suppressed by Y-27632, gene pathways involving these molecules probably depend on ROCK activation. The TGF-β receptor antagonist, SB-431542, and an inhibitor of p38MAPK, SB-203580, did not affect apoptosis. Combining Y-27632 with SB-203580, however, resulted in an increase in the survival rate compared with the control. This suggests that the initiation of apoptosis depends on cytokine interactions and multiple ways exist to reduce post-thaw apoptosis in hES cells. Y-27632 can suppress cytokine interactions and the MAPK pathway, thereby reducing the occurrence of apoptosis, and is an effective cryoprotectant for hES cells.     

Ca2+ ion transport through channels formed by α-hemolysin analyzed using a microwell array on a Si substrate

For the functional analysis of ion channel activity, an artificial lipid bilayer suspended over microwells was formed that ruptured giant unilamellar vesicles on a Si substrate. Ca(2+) ion indicators (fluo-4) were confined in the microwells by sealing the microwells with a lipid bilayer. An overhang formed at the microwells prevented the lipid membrane from falling into them and allowed the stable confinement of the fluorescent probes. The transport of Ca(2+) ions through the channels formed by α-hemolysin inserted in a lipid membrane was analyzed by employing the fluorescence intensity change of fluo-4 in the microwells. The microwell volume was very small (1-100 fl), so a highly sensitive monitor could be realized. The detection limit is several tens of ions/s/μm(2), and this is much smaller than the ion current in a standard electrophysiological measurement. Smaller microwells will make it possible to mimic a local ion concentration change in the cells, although the signal to noise ratio must be further improved for the functional analysis of a single channel. We demonstrated that a microwell array with confined fluorescent probes sealed by a lipid bilayer could constitute a basic component of a highly sensitive biosensor array that works with functional membrane proteins. This array will allow us to realize high throughput and parallel testing devices.     

Design and synthesis of pyrrolo[3,2-d]pyrimidine HER2/EGFR dual inhibitors: Improvement of the physicochemical and pharmacokinetic profiles for potent in vivo anti-tumor efficacy

During the course of our studies on a novel HER2/EGFR dual inhibitor (TAK-285), we found an alternative potent pyrrolo[3,2-d]pyrimidine compound (1a). To enhance the pharmacokinetic (PK) profile of this compound, we conducted chemical modifications into its N-5 side chain and conversion of the chemically modified compounds into their salts. Among them, 2cb, the tosylate salt of compound 2c, showed potent HER2/EGFR kinase inhibitory activity (IC₅₀: 11/11 nM) and cellular growth inhibitory activity (BT-474 cell GI₅₀: 56 nM) with a good drug metabolism and PK (DMPK) profile. Furthermore, 2cb exhibited significant in vivo antitumor efficacy in both mouse and rat xenograft models with transplanted 4-1ST gastric cancer cell lines (mouse, T/C = 0%, 2cb po bid at 100 mg/kg; rat, T/C: -1%, 2cb po bid at 25 mg/kg).     

Identification and characterization of cathepsin D in a highly purified sialidase from starfish A. pectinifera

A sialidase [EC 3.2.1.18] from the ovary of starfish Asterina pectinifera was isolated and highly purified by preparative PAGE. The SDS-PAGE separation of the purified enzyme revealed two natures of protein bands, upper (50 kDa) and a lower (47 kDa). To identify the protein, N-terminal amino acid sequence of the upper band was done. The sequence matched with the N-terminal amino acid sequence of human lysosomal mature cathepsin D and cathepsin D activity was also found in all the preparation steps. Protease inhibitor pepstatin A inhibited the proteolysis activity of cathepsin D against a synthetic substrate. The two enzymes sialidase and cathepsin D were separated from each other by using high-performance gel-filtration chromatography. The Western blot analysis and isoelectric focusing showed the co-purified cathepsin D is a 50 kDa protein with a PI value of 4.2.     

Outer arm fucosylation of N-glycans increases in sera of hepatocellular carcinoma patients

Serum glycans are promising markers for early-stage cancer detection, but the research remains challenging because low concentrations of serum glycoproteins are secreted from early-stage tumors. We have established an N-glycan profiling method using liquid chromatography electrospray ionization-mass spectrometry with high sensitive derivative, trimethyl(4-aminophenyl)ammonium chloride (TMAPA). The mass sensitivity of TMAPA-labeled oligosaccharides was enhanced more than 50 times compared with 2-aminopyridine (PA) labeled oligosaccharides, and the analytical period was significantly shortened compared with traditional HPLC 2D-mapping. Using this method, we found about 28 major N-linked oligosaccharides in human sera, and we investigated their alterations in patients who developed hepatocellular carcinoma (HCC). We found that outer arm fucosylation (attached GlcNAc via an alpha 1-3/4 linkage) in highly branched oligosaccharides increased significantly in sera of HCC patients. Normalizing the level of outer arm fucosylation by taking into account platelet concentration allowed us to distinguish more clearly between HCC and LC patients.