Discovery of SMP-304, a novel benzylpiperidine derivative with serotonin transporter inhibitory activity and 5-HT1A weak partial agonistic activity showing the antidepressant-like effect

We report the discovery of a novel benzylpiperidine derivative with serotonin transporter (SERT) inhibitory activity and 5-HT_1A receptor weak partial agonistic activity showing the antidepressant-like effect. The 3-methoxyphenyl group and the phenethyl group of compound 1, which has weak SERT binding activity, but potent 5-HT_1A binding activity, were optimized, leading to compound 35 with potent and balanced dual SERT and 5-HT_1A binding activity, but also potent CYP2D6 inhibitory activity. Replacement of the methoxy group in the left part of compound 35 with a larger alkoxy group, such as ethoxy, isopropoxy or methoxy-ethoxy group ameliorated CYP2D6 inhibition, giving SMP-304 as a candidate. SMP-304 with serotonin uptake inhibitory activity and 5-HT_1A weak partial agonistic activity, which could work as a 5-HT_1A antagonist, displayed faster onset of antidepressant-like effect than a representative SSRI paroxetine in an animal model.     

Effect of Ca channel blockers on glycerol levels in Dunaliella tertiolecta under hypoosmotic stress

The role of Ca²⁺ in glycerol dissimilation under hypoosmotic stress in the halotolerant alga Dunaliella tertiolecta was investigated using a pharmacological approach. A stretch-activated Ca²⁺ channel blocker, GdCl₃, inhibited glycerol dissimilation under hypoosmotic stress. However, addition of voltage-dependent Ca²⁺ channel blockers and inhibitors of mitochondrial and endoplasmic reticulum Ca²⁺ channels did not affect the glycerol dissimilation under hypoosmotic stress. The results of the present study suggest that the influx of Ca²⁺ from the extracellular space via the stretch-activated Ca²⁺ channels localized in the plasma membrane is required for the transduction of osmotic signal of D. tertiolecta.     

Inhibition of phosphatidylcholine synthesis via the phosphatidylethanolamine methylation pathway impairs incorporation of bulk lipids into VLDL in cultured rat hepatocytes

Inhibition of phosphatidylcholine (PC) synthesis via the phosphatidylethanolamine (PE) methylation pathway was shown to decrease the secretion of VLDL from primary rat hepatocytes (Nishimaki-Mogami et al. 1996. BIOCHIM: Biophys. Acta. 1304: 21-31). To understand further the role of PE methylation, we determined the effect of bezafibrate, an inhibitor of PE methylation, on VLDL assembly within the microsomal lumen. Bezafibrate was shown to decrease VLDL (triacylglycerol) secretion only when cellular PE methylation was active in the presence of methionine. Pulse-chase experiments showed that bezafibrate treatment did not impair the movement of [(35)S]apolipoprotein (apo)B-48 from microsomal membranes into the lumen. However, bezafibrate treatment resulted in reduced VLDL-[(35)S]apoB-48 and increased [(35)S]apoB-48-containing particles in the HDL density range (HDL-[(35)S]apoB-48) within the lumen. Inhibition of PE methylation by bezafibrate or 3-deazaadenosine after the completion of HDL-[(35)S]apoB-48 assembly effectively decreased VLDL-[(35)S]apoB-48 secretion with a concomitant increase in HDL-[(35)S]apoB-48 secretion. These findings suggest that inhibition of PC synthesis via the PE methylation pathway impairs the stage of bulk triacylglycerol incorporation during the assembly of VLDL.     

Analysis of gene expression profile in p130(Cas)-deficient fibroblasts

p130(Cas) (Cas) is a docking protein that becomes tyrosine phosphorylated in v-Src- or v-Crk-transformed cells and in integrin-stimulated cells. Cas -/- fibroblasts show defects in stress fiber formation, cell spreading, cell migration, and transformation by activated Src. To further characterize the role of Cas in signaling, we compared the expression profile in Cas -/- fibroblasts with that in Cas-re-expressing fibroblasts using the microarray methods. In Cas -/- fibroblasts, the expression of heme oxygenase 1 and caveolin-1 was reduced, but the expression of procollagen 1 alpha 1, procollagen 3 alpha 1, procollagen 11 alpha 1, elastin, periostin, TSC-36, and MARCKS was enhanced. The domains in Cas necessary for the change varied among these genes. Activated Src reduced the expression of most of these genes both in Cas -/- and in Cas +/+ fibroblasts. These results suggest the existence of signaling pathways that emanate from Cas to gene expression.     

A new technique to co-localise membrane proteins with Homer/vesl

The minimal requirements were defined as necessary for cluster formation of the group 1 metabotropic glutamate receptor (mGluR), which is regulated by the Homer/vesl family of scaffolding proteins [Curr. Opin. Neurobiol. 10 (2000) 370]. Cluster formation of G-protein-coupled receptors (GPCRs) plays a fundamental role in signal transduction, particularly at the neuronal synapse. To understand the interaction of mGluR with PSD-Zip45, a Homer/vesl family member, we designed a series of chimeric receptor proteins, consisting of C-terminal mGluR1alpha sequences that were fused to endothelin B receptors (ET(B)Rs). In vitro and in vivo studies revealed that an extended 20 amino acid long C-terminal mGluR1alpha peptide, including the proline-rich core motif PPXXF, is sufficient to induce clustering of chimeric ET(B)R/mGluR1alpha receptors by PSD-Zip45. This result is especially important because it constitutes the basis for a new approach to form two-dimensional crystals of membrane proteins in situ, which may render unstable membrane proteins amenable to electron crystallographic structure determination.     

Participation of the extracellular domain in (pro)renin receptor dimerization

The (pro)renin receptor [(P)RR] induces the catalytic activation of prorenin, as well as the activation of the mitogen-activated protein kinase (MAPK) signaling pathway; as such, it plays an important regulatory role in the renin–angiotensin system. (P)RR is known to form a homodimer, but the region participating in its dimerization is unknown. Using glutathione S-transferase (GST) as a carrier protein and a GST pull-down assay, we investigated the interaction of several (P)RR constructs with full-length (FL) (P)RR in mammalian cells. GST fusion proteins with FL (P)RR (GST-FL), the C-terminal M8-9 fragment (GST-M8-9), the extracellular domain (ECD) of (P)RR (GST-ECD), and the (P)RR ECD with a deletion of 32 amino acids encoded by exon 4 (GST-ECDd4) were retained intracellularly, whereas GST alone was efficiently secreted into the culture medium when transiently expressed in COS-7 cells. Immunofluorescence microscopy showed prominent localization of GST-ECD to the endoplasmic reticulum. The GST pull-down analysis revealed that GST-FL, GST-ECD, and GST-ECDd4 bound FLAG-tagged FL (P)RR, whereas GST-M8-9 showed little or no binding when transiently co-expressed in HEK293T cells. Furthermore, pull-down analysis using His-tag affinity resin showed co-precipitation of soluble (P)RR with FL (P)RR from a stable CHO cell line expressing FL h(P)RR with a C-terminal decahistidine tag. These results indicate that the (P)RR ECD participates in dimerization.     

Promotion of hematopoietic differentiation from mouse induced pluripotent stem cells by transient HoxB4 transduction

Ectopic expression of HoxB4 in embryonic stem (ES) cells leads to an efficient production of hematopoietic cells, including hematopoietic stem/progenitor cells. Previous studies have utilized a constitutive HoxB4 expression system or tetracycline-regulated HoxB4 expression system to induce hematopoietic cells from ES cells. However, these methods cannot be applied therapeutically due to the risk of transgenes being integrated into the host genome. Here, we report the promotion of hematopoietic differentiation from mouse ES cells and induced pluripotent stem (iPS) cells by transient HoxB4 expression using an adenovirus (Ad) vector. Ad vector could mediate efficient HoxB4 expression in ES cell-derived embryoid bodies (ES-EBs) and iPS-EBs, and its expression was decreased during cultivation, showing that Ad vector transduction was transient. A colony-forming assay revealed that the number of hematopoietic progenitor cells with colony-forming potential in HoxB4-transduced cells was significantly increased in comparison with that in non-transduced cells or LacZ-transduced cells. HoxB4-transduced cells also showed more efficient generation of CD41-, CD45-, or Sca-1-positive cells than control cells. These results indicate that transient, but not constitutive, HoxB4 expression is sufficient to augment the hematopoietic differentiation of ES and iPS cells, and that our method would be useful for clinical applications, such as cell transplantation therapy.     

Identification of a SNARE protein required for vacuolar protein transport in Schizosaccharomyces pombe

Intracellular vesicle trafficking is mediated by a set of SNARE proteins in eukaryotic cells. Several SNARE proteins are required for vacuolar protein transport and vacuolar biogenesis in Saccharomyces cerevisiae. A search of the Schizosaccharomyces pombe genome database revealed a total of 17 SNARE-related genes. Although no homologs of Vam3p, Nyv1p, and Vam7p have been found in S. pombe, we identified one SNARE-like protein that is homologous to S. cerevisiae Pep12p. However, the disruptants transport vacuolar hydrolase CPY (SpCPY) to the vacuole normally, suggesting that the Pep12 homolog is not required for vacuolar protein transport in S. pombe cells. To identify the SNARE protein(s) involved in Golgi-to-vacuole protein transport, we have deleted four SNARE homolog genes in S. pombe. SpCPY was significantly missorted to the cell surface on deletion of one of the SNARE proteins, Fsv1p (SPAC6F12.03c), with no apparent S. cerevisiae ortholog. In addition, sporulation, endocytosis, and in vivo vacuolar fusion appear to be normal in fsv1Delta cells. These results showed that Fsv1p is mainly involved in vesicle-mediated protein transport between the Golgi and vacuole in S. pombe cells.     

Molecular cloning of a novel transmembrane protein MOLT expressed by mature oligodendrocytes

A novel oligodendrocyte (OL)-specific cDNA was isolated from brain capillary endothelial cells and characterized. The cDNA encodes a protein of 1099 amino acids that contains a signal peptide and a transmembrane domain. The protein was expressed in mature OLs in vivo and in vitro cell cultures and was thus designated as mature OL transmembrane protein (MOLT). RT-PCR analysis showed that MOLT mRNA was expressed in brain, lung, pancreas, and testis. A polyclonal antibody raised against a part of the mouse MOLT reacted specifically with multipolar OLs possessing radially oriented processes that penetrated into the gray matter. More cells were detected in the white matter, and these had longitudinally oriented processes. In a rat OL lineage culture system, oligodendrocyte precursor cells did not initially produce MOLT mRNA and protein, but when they begun to differentiate into mature OLs, they started expressing MOLT. Consequently, MOLT may function as OLs become mature and may serve as a cell-surface marker for OL differentiation.