Novel and potent calcium-sensing receptor antagonists: discovery of (5R)-N-[1-ethyl-1-(4-ethylphenyl)propyl]-2,7,7-trimethyl-5-phenyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidine-3-carboxamide monotosylate (TAK-075) as an orally active bone anabolic agent

The calcium-sensing receptor antagonist (CaSR) has been recognized as a promising target of anabolic agents for treating osteoporosis. In the course of developing a new drug candidate for osteoporosis, we found tetrahydropyrazolopyrimidine derivative 1 to be an orally active CaSR antagonist that stimulated transient PTH secretion in rats. However, compound 1 showed poor physical and chemical stability. In order to work out this compound's chemical stability and further understand its in vivo efficacy, we focused on modifying the 2-position of the tetrahydropyrazolopyrimidine. As a result of chemical modification, we discovered (5R)-N-[1-ethyl-1-(4-ethylphenyl)propyl]-2,7,7-trimethyl-5-phenyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidine-3-carboxamide monotosylate 10m (TAK-075), which showed improved solubility, chemical stability, and in vivo efficacy. Furthermore, we describe that evaluating the active metabolite is important during repeated treatment with short-acting CaSR antagonists.     

ARHGAP18, a GTPase-activating protein for RhoA, controls cell shape, spreading, and motility

Rho GTPases are molecular switches that transmit biochemical signals in response to extracellular stimuli to elicit changes in the actin cytoskeleton. Rho GTPases cycle between an active, GTP-bound state and an inactive, GDP-bound state. These states are regulated by two distinct families of proteins-guanine nucleotide exchange factors and GTPase-activating proteins (GAPs). We studied the role of a previously uncharacterized GAP, ARHGAP18 (MacGAP). Overexpression of ARHGAP18 suppressed the activity of RhoA and disrupted stress fiber formation. Conversely, silencing of ARHGAP18 by small interfering RNA transfection-enhanced stress fiber formation and induced rounding of cells. We examined the role of ARHGAP18 in cell spreading and migration. Immunofluorescence analysis revealed that ARHGAP18 was localized to the leading edge during cell spreading and migration. ARHGAP18-knockdown cells showed impaired spreading, premature formation of stress fibers, and sustained activation of RhoA upon cell attachment. In addition, knockdown and overexpression of ARHGAP18 resulted in the inhibition and promotion of cell migration, respectively. Furthermore, ARHGAP18 was required for the polarization of cells for migration. Our results define ARHGAP18 as one of the crucial factors for the regulation of RhoA for the control of cell shape, spreading, and migration.     

Comparative proteomic analysis of Methanothermobacter themautotrophicus ΔH in pure culture and in co-culture with a butyrate-oxidizing bacterium

To understand the physiological basis of methanogenic archaea living on interspecies H(2) transfer, the protein expression of a hydrogenotrophic methanogen, Methanothermobacter thermautotrophicus strain ΔH, was investigated in both pure culture and syntrophic coculture with an anaerobic butyrate oxidizer Syntrophothermus lipocalidus strain TGB-C1 as an H(2) supplier. Comparative proteomic analysis showed that global protein expression of methanogen cells in the model coculture was substantially different from that of pure cultured cells. In brief, in syntrophic coculture, although methanogenesis-driven energy generation appeared to be maintained by shifting the pathway to the alternative methyl coenzyme M reductase isozyme I and cofactor F(420)-dependent process, the machinery proteins involved in carbon fixation, amino acid synthesis, and RNA/DNA metabolisms tended to be down-regulated, indicating restrained cell growth rather than vigorous proliferation. In addition, our proteome analysis revealed that α subunits of proteasome were differentially acetylated between the two culture conditions. Since the relevant modification has been suspected to regulate proteolytic activity of the proteasome, the global protein turnover rate could be controlled under syntrophic growth conditions. To our knowledge, the present study is the first report on N-acetylation of proteasome subunits in methanogenic archaea. These results clearly indicated that physiological adaptation of hydrogenotrophic methanogens to syntrophic growth is more complicated than that of hitherto proposed.     

Combination of hTERT and bmi-1, E6, or E7 induces prolongation of the life span of bone marrow stromal cells from an elderly donor without affecting their neurogenic potential

Murine bone marrow stromal cells differentiate not only into mesodermal derivatives, such as osteocytes, chondrocytes, adipocytes, skeletal myocytes, and cardiomyocytes, but also into neuroectodermal cells in vitro. Human bone marrow stromal cells are easy to isolate but difficult to study because of their limited life span. To overcome this problem, we attempted to prolong the life span of bone marrow stromal cells and investigated whether bone marrow stromal cells modified with bmi-1, hTERT, E6, and E7 retained their differentiated capability, or multipotency. In this study, we demonstrated that the life span of bone marrow stromal cells derived from a 91-year-old donor could be extended and that the stromal cells with an extended life span differentiated into neuronal cells in vitro. We examined the neuronally differentiated cells morphologically, physiologically, and biologically and compared the gene profiles of undifferentiated and differentiated cells. The neuronally differentiated cells exhibited characteristics similar to those of midbrain neuronal progenitors. Thus, the results of this study support the possible use of autologous-cell graft systems to treat central nervous system diseases in geriatric patients.     

Structural and functional analysis of pancreatic islets preserved by pioglitazone in db/db mice

To evaluate preventive effects of pioglitazone on pancreatic beta-cell damage in C57BL/KsJ db/db mice, an obese diabetic animal model, the pancreatic islets were compared morphologically between pioglitazone-treated (100 mg/kg daily po) and untreated db/db mice (n = 7 for each) after a 12-wk intervention (6-18 wk of age). The fasting blood glucose level was significantly improved by the treatment with pioglitazone (260 +/- 12 vs. 554 +/- 62 mg/dl, P < 0.05). The islet mass in the pancreas was significantly greater in pioglitazone-treated mice than in untreated mice (10.2 +/- 1.1 vs. 4.6 +/- 0.2 mg, P < 0.01). Subsequently, biochemical and physiological analyses of the beta-cell function were employed using pioglitazone-treated and untreated db/db mice (n = 6 for each) and pioglitazone-treated and untreated db/+ mice (n = 6 for each). After 2 wk of treatment (10-12 wk of age), the plasma levels of triglyceride and free fatty acid were significantly decreased, whereas the plasma adiponectin level increased significantly compared with the untreated group (65.2 +/- 18.0 vs. 18.3 +/- 1.3 microg/ml, P < 0.05). Pioglitazone significantly reduced the triglyceride content in the islets (43.3 +/- 3.6 vs. 65.6 +/- 7.6 ng/islet, P < 0.05) with improved glucose-stimulated insulin secretion. Pioglitazone showed no significant effects on the biochemical and physiological parameters in db/+ mice. The present study first demonstrated that pioglitazone prevents beta-cell damage in an early stage of the disease progression in db/db mice morphologically and physiologically. Our results suggest that pioglitazone improves glucolipotoxicity by increasing insulin sensitivity and reducing fat accumulation in the pancreatic islets.     

Chlorella virus-encoded deoxyuridine triphosphatases exhibit different temperature optima

A putative deoxyuridine triphosphatase (dUTPase) gene from chlorella virus PBCV-1 was cloned, and the recombinant protein was expressed in Escherichia coli. The recombinant protein has dUTPase activity and requires Mg(2+) for optimal activity, while it retains some activity in the presence of other divalent cations. Kinetic studies of the enzyme revealed a K(m) of 11.7 microM, a turnover k(cat) of 6.8 s(-1), and a catalytic efficiency of k(cat)/K(m) = 5.8 x 10(5) M(-1) s(-1). dUTPase genes were cloned and expressed from two other chlorella viruses IL-3A and SH-6A. The two dUTPases have similar properties to PBCV-1 dUTPase except that IL-3A dUTPase has a lower temperature optimum (37 degrees C) than PBCV-1 dUTPase (50 degrees C). The IL-3A dUTPase differs from the PBCV-1 enzyme by nine amino acids, including two amino acid substitutions, Glu81-->Ser81 and Thr84-->Arg84, in the highly conserved motif III of the proteins. To investigate the difference in temperature optima between the two enzymes, homology modeling and docking simulations were conducted. The results of the simulation and comparisons of amino acid sequence suggest that adjacent amino acids are important in the temperature optima. To confirm this suggestion, three site-directed amino acid substitutions were made in the IL-3A enzyme: Thr84-->Arg84, Glu81-->Ser81, and Glu81-->Ser81 plus Thr84-->Arg84. The single substitutions affected the optimal temperature for enzyme activity. The temperature optimum increased from 37 to 55 degrees C for the enzyme containing the two amino acid substitutions. We postulate that the change in temperature optimum is due to reduction in charge and balkiness in the active cavity that allows more movement of the ligand and protein before the enzyme and substrate complex is formed.