MAGI1 recruits Dll1 to cadherin-based adherens junctions and stabilizes it on the cell surface

Delta-Notch signaling plays an essential role in cell fate determination in many tissue types, including the central nervous system. Although the signaling mechanism of Notch has been extensively studied, the behaviors of its ligands are not well understood. In the present study, we found that, in the developing neural tube, Dll1(Delta-like 1) was mainly localized on the processes extending from nascent neurons toward both the pia and the ventricle and accumulated at apical termini, where adherens junctions (AJs) were formed. To understand the mechanism of Dll1 localization, we searched for binding proteins for Dll1 and identified a scaffolding molecule, MAGI1. In the developing spinal cord, MAGI1 mRNA was highly expressed in the ventricular zone, where Dll1 mRNA was expressed. MAGI1 protein accumulated at the AJs formed around the termini of apically extending processes and was partially colocalized with Dll1. MAGI1 bound not only to Dll1 but also to N-cadherin-beta-catenin complexes. In cultured AJ-forming fibroblasts, MAGI1 was localized at AJs, and Dll1 was recruited to these AJs through binding to MAGI1. In addition, Dll1 was stabilized on the cell surface by MAGI1. Taken together, these results suggest that Dll1 is presented on the surface of AJs formed at the apical termini of processes through interaction with MAGI1 to activate Notch on neighboring cells in the developing central nervous system.     

LOX-1 pathway affects the extent of myocardial ischemia-reperfusion injury

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) was originally identified as a receptor for oxidized low-density lipoprotein predominantly expressed in endothelial cells. LOX-1 expression can be induced in cardiomyocytes and that activation of LOX-1 is involved in apoptosis. To investigate possible roles of LOX-1 in myocardial ischemia-reperfusion injury, rats were subjected to coronary artery ligation for 1h followed by reperfusion for 2h. Immunohistochemistry revealed that expression of LOX-1 in cardiac myocytes was induced following ischemia-reperfusion but not ischemia alone. Administration of anti-LOX-1 monoclonal antibody resulted in a nearly 50% reduction in myocardial infarction size compared with that of normal IgG or saline (P<0.05). These findings suggest that activation of the LOX-1 pathway is involved in determining the extent of myocardial ischemia-reperfusion injury and that inhibition of the LOX-1 pathway may provide a novel strategy for treatment of acute myocardial infarction in humans.     

Expression of prostaglandin E(2) receptor subtypes in mouse hair follicles.

We investigated the mRNA distribution of the prostaglandin (PG) E(2) receptor subtypes and cyclooxygenases (COXs) in hair follicles of the mouse dorsal skin. In the 3-week hair follicles, which are in the anagen phase, EP3 and EP4 mRNA were expressed in the dermal papilla cells and the outer root sheath cells located in the hair bulb region, respectively. In the 8-week hair follicles, which are in the telogen phase, the signals for both EP3 and EP4 mRNAs had disappeared. To study the hair cycle-dependent expression of mRNAs for the EPs and COXs, an area of dorsal hair was depilated from 8-week-old mice. On days 8 and 12 after depilation, EP3 and EP4 mRNA were reexpressed in the dermal papilla cells and the outer root sheath cells, and the induction of COX-2 mRNA was also observed in the outer root sheath cells, the upper area of EP4 expression site. These results suggest that EP3 and EP4 receptors may involve in the development and regrowth of the hair follicles.     

Successive glycosyltransfer activity and enzymatic characterization of pectic polygalacturonate 4-alpha-galacturonosyltransferase solubilized from pollen tubes of Petunia axillaris using pyridylaminated oligogalacturonates as substrates

Polygalacturonate 4-alpha-galacturonosyltransferase (pectin synthase) was solubilized from pollen tubes of Petunia axillaris and characterized. To accomplish this, an assay method using fluorogenic pyridylaminated-oligogalacturonic acids (PA-OGAs) as acceptor substrates was developed. When the pollen tube enzyme was solubilized with 0.5% (v/v) Triton X-100 and was incubated with PA-OGA and UDP-galacturonic acid (UDP-GalUA), successive transfer activity of more than 10 GalUAs from UDP-GalUA to the nonreducing end of PA-OGA was observed by diethylaminoethyl high-performance liquid chromatography. This activity was time- and enzyme concentration-dependent. The optimum enzyme activity was observed at pH 7.0 and 30 degrees C. Among the PA-OGAs investigated, those with a degree of polymerization of more than 10 were preferred as substrates. The crude pollen tube enzyme had an apparent K(m) value of 13 microM for the PA-OGA with a degree of polymerization 11 and 170 microM for UDP-GalUA. The characteristics of the P. axillaris pollen tube enzyme and the usefulness of fluorogenic PA-OGAs for the assay of this enzyme are discussed.     

Nitric oxide is proangiogenic in the retina and choroid

Nitric oxide (NO) has been shown to have proangiogenic or antiangiogenic effects depending upon the setting. In this study, we used mice with targeted deletion of one of the three isoforms of nitric oxide synthase (NOS) to investigate the effects of NO in ocular neovascularization. In transgenic mice with increased expression of vascular endothelial growth factor (VEGF) in photoreceptors, deficiency of any of the three isoforms caused a significant decrease in subretinal neovascularization, but no alteration of VEGF expression. In mice with laser-induced rupture of Bruch's membrane, deficiency of inducible NOS (iNOS) or neuronal NOS (nNOS), but not endothelial NOS (eNOS), caused a significant decrease in choroidal neovascularization. In mice with oxygen-induced ischemic retinopathy, deficiency of eNOS, but not iNOS or nNOS caused a significant decrease in retinal neovascularization and decreased expression of VEGF. These data suggest that NO contributes to both retinal and choroidal neovascularization and that different isoforms of NOS are involved in different settings and different disease processes. A broad spectrum NOS inhibitor may have therapeutic potential for treatment of both retinal and choroidal neovascularization.     

Alternative splicing products of the gene for a human nuclear actin-related protein,hArpNbeta/Baf53, that encode a protein isoform,hArpNbetaS, in the cytoplasm

A human nuclear actin-related protein, hArpNbeta/ Baf53, is a component of chromatin remodeling and histone acetyltransferase complexes. We identified two alternative splicing products of the gene for hArpNbeta/ Baf53. They encoded a protein isoform, hArpNbetaS; and its fusion product with green fluorescent protein was to be found in the cytoplasm, not the nucleus. The isoforms may contribute to functional regulation of these complexes.