A Novel Mechanism for the Autonomous Termination of Pre-B Cell Receptor Expression via Induction of Lysosome-Associated Protein Transmembrane 5

The expression of the pre-B cell receptor (BCR) is confined to the early stage of B cell development, and its dysregulation is associated with anomalies of B-lineage cells, including leukemogenesis. Previous studies suggested that the pre-BCR signal might trigger the autonomous termination of pre-BCR expression even before the silencing of pre-BCR gene expression to prevent sustained pre-BCR expression. However, the underlying mechanism remains ill defined. Here we demonstrate that the pre-BCR signal induces the expression of lysosome-associated protein transmembrane 5 (LAPTM5), which leads to the prompt downmodulation of the pre-BCR. While LAPTM5 induction had no significant impact on the internalization of cell surface pre-BCR, it elicited the translocation of a large pool of intracellular pre-BCR from the endoplasmic reticulum to the lysosomal compartment concomitantly with a drastic reduction of the level of intracellular pre-BCR proteins. This reduction was inhibited by lysosomal inhibitors, indicating the lysosomal degradation of the pre-BCR. Notably, the LAPTM5 deficiency in pre-B cells led to the augmented expression level of surface pre-BCR. Collectively, the pre-BCR induces the prompt downmodulation of its own expression through the induction of LAPTM5, which promotes the lysosomal transport and degradation of the intracellular pre-BCR pool and, hence, limits the supply of pre-BCR to the cell surface.     

Complement C5a exhibits anxiolytic-like activity via the prostaglandin D2-DP1 receptor system coupled to adenosine A2A and GABAA receptors

We have recently found that central PGD(2) exhibits anxiolytic-like activity. Here we show that complement C5a exhibits anxiolytic-like activity via the PGD(2) system. Centrally administered C5a had anxiolytic-like activity at a dose of 0.3 pmol/mouse in the elevated plus-maze test in mice. C5a-induced anxiolytic-like activity was inhibited by indomethacin, a cyclooxygenase inhibitor, or BWA868C, an antagonist of DP(1) receptor for PGD(2), respectively. The anxiolytic effect of C5a was also blocked by SCH58261 or bicuculline, antagonists of adenosine A(2A) and GABA(A) receptors, respectively, which were activated downstream of PGD(2)-DP(1) receptor. These results suggest that C5a exhibits anxiolytic-like activity via the PGD(2)-DP(1) receptor system coupled to the activation of adenosine A(2A) and GABA(A) receptors.     

Suppression of food intake by a complement C3a agonist [Trp5]-oryzatensin(5-9)

[Trp5]-oryzatensin(5-9) (WPLPR), an agonist peptide for complement C3a receptor, has been designed based on the C-terminal region of ileum-contracting peptide oryzatensin derived from rice protein. We previously reported that WPLPR has anti-analgesic and anti-amnesic activities after central or oral administration. In this study, we found a novel function of WPLPR on food intake. WPLPR suppressed food intake after intracerebroventricular or intraperitoneal (i.p.) administration at a dose of 3-30 nmol/mouse or 30-300 mg/kg, respectively, in fasted mice. Orally administered WPLPR at a dose of 300 mg/kg also decreased food intake. WPLPR decreased gastric emptying after i.p. injection at a dose of 300 mg/kg. The anorexigenic activity of WPLPR was blocked by cyclooxygenase inhibitor or antagonist for prostaglandin (PG) E receptor EP4 subtype. These results suggest that WPLPR decreases food intake through PGE2 production followed by EP4 receptor activation.     

Glycoconjugates in normal human kidney. A histochemical study using 13 biotinylated lectins

The avidin-biotin-peroxidase complex technique was used with 13 lectins to study the glycoconjugates of normal human renal tissue. The evaluated lectins included Triticum vulgaris (WGA), Concanavalin ensiformis (ConA), Phaseolus vulgaris leukoagglutinin and erythroagglutinin (PHA-L and PHA-E), Lens culinaris (LCA), Pisum sativum (PSA), Dolichos biflorus (DBA), Glycine max (SBA), Arachis hypogaea (PNA), Sophora japonica (SJA), Bandeiraea simplicifolia I (BSL-I), Ulex europaeus I (UEA-I) and Ricinus communis I (RCA-I). Characteristic and reproducible staining patterns were observed. WGA and ConA stained all tubules; PHA-L, PHA-E, LCA, PSA stained predominantly proximal tubules; DBA, SBA, PNA, SJA and BSL-I stained predominantly distal portions of nephrons. In glomeruli, WGA and PHA-L stained predominantly visceral epithelial cells; ConA stained predominantly basement membranes and UEA-I stained exclusively endothelial cells. UEA-I also stained endothelial cells of other blood vessels and medullary collecting ducts. Sialidase treatment before staining caused marked changes of the binding patterns of several lectins including a focal loss of glomerular and tubular staining by WGA; an acquired staining of endothelium by PNA and SBA; and of glomeruli by PNA, SBA, PHA-E, LCA, PSA and RCA-I. The known saccharide specificities and binding patterns of the lectins employed in this study allowed some conclusions about the nature and the distribution of the sugar residues in the oligosaccharide chains of renal glycoconjugates. The technique used in this report may be applicable to other studies such as evaluation of normal renal maturation, classification of renal cysts and pathogenesis of nephrotic syndrome. The observations herein reported may serve as a reference for these studies.     

Alteration of ribosomal protein S2 in kasugamycin-resistant mutant derived from Escherichia coli AB312

A new type of kasugamycin-resistant mutant has been isolated from $\text{E. coli}$ K12, strain AB312 (Hfr, $\text{lac,thr,leu,thi,strA,fus}$). In a cell-free protein-synthetic system, the resistance is localized in the ribosome but not in the supernatant fraction. On initiation complex formation, the resistance is associated with the washed ribosome but not with initiation factors. In reconstitution of the 30S ribosomal subunit, the resistance is due to the protein(s) but not to 16S RNA. In two-dimensional electrophoresis, protein S2 is deficient in the 30S ribosomal subunit of kasugamycin-resistant mutant. The results indicate that the kasugamycin-resistance is attributed to alteration of ribosomal protein S2.     

Characterization of a cellular retinol-binding protein from lamprey, Lethenteron japonicum

Lampreys are ancestral representatives of vertebrates known as jawless fish. The Japanese lamprey, Lethenteron japonicum, is a parasitic member of the lampreys known to store large amounts of vitamin A within its body. How this storage is achieved, however, is wholly unknown. Within the body, the absorption, transfer and metabolism of vitamin A are regulated by a family of proteins called retinoid-binding proteins. Here we have cloned a cDNA for cellular retinol-binding protein (CRBP) from the Japanese lamprey, and phylogenetic analysis suggests that lamprey CRBP is an ancestor of both CRBP I and II. The lamprey CRBP protein was expressed in bacteria and purified. Binding of the lamprey CRBP to retinol (Kd of 13.2 nM) was identified by fluorimetric titration. However, results obtained with the protein fluorescence quenching technique indicated that lamprey CRBP does not bind to retinal. Northern blot analysis showed that lamprey CRBP mRNA was ubiquitously expressed, although expression was most abundant in the intestine. Together, these results suggest that lamprey CRBP has an important role in absorbing vitamin A from the blood of host animals.