Anti-tumor activity of dendritic cells transfected with mRNA for receptor for hyaluronan-mediated motility is mediated by CD4+ T cells

Receptor for hyaluronan-mediated motility (RHAMM) is overexpressed in various tumors with high frequency, and was recently identified as an immunogenic antigen by serologic screening of cDNA expression libraries. In this study, we explored whether RHAMM is a potential target for dendritic cell (DC) immunotherapy. We constructed a plasmid for transduction of in vitro-transcribed mRNAs into DCs to efficiently transport the intracellular protein RHAMM into MHC class II compartments by adding a late endosomal/lysosomal sorting signal to the RHAMM gene. Immunization of mice with modified RHAMM mRNA-transfected DCs (DC/RHAMM) induced killing activity against RHAMM-positive tumor cells in splenocytes. To examine whether CD4⁺ and/or CD8⁺ T cells were required for this antitumor immunity, an anti-CD4 or anti-CD8 antibody was administered to mice after immunization with DC/RHAMM. Depletion of CD4⁺ T cells significantly diminished the induction of tumor cell-killing activity in splenocytes, whereas CD8⁺ T cell depletion had no effect. We then investigated the therapeutic effect of DC/RHAMM in a 3-day tumor model of EL4. DC/RHAMM was administered to mice on days 3, 7 and 10 after EL4 tumor inoculation. The treatment markedly inhibited tumor growth compared to control DCs. Moreover, antibody-mediated depletion of CD4⁺ T cells completely abrogated the therapeutic effect of DC/RHAMM, whereas depletion of CD8⁺ T cells had no effect. The results of this preclinical study indicate that DCs transfected with a modified RHAMM mRNA targeted to MHC class II compartments can induce CD4⁺ T cell-mediated antitumor activity in vivo.     

Lysine-Oriented Charges Trigger the Membrane Binding and Activity of Nukacin ISK-1

The antibacterial activities and membrane binding of nukacin ISK-1 and its fragments and mutants were evaluated to delineate the determinants governing structure-function relationships. The tail region (nukacin_1-7) and ring region (nukacin_7-27) were shown to have no antibacterial activity and also had no synergistic effect on each other or even on nukacin ISK-1. Both a fragment with three lysines in the N terminus deleted (nukacin_4-27) and a mutant with three lysines in the N terminus replaced with alanine (K1-3A nukacin ISK-1) imparted very low activity (32-fold lower than nukacin ISK-1) and also exhibited a similar antagonistic effect on nukacin ISK-1. Addition of two lysine residues at the N terminus (+2K nukacin ISK-1) provided no further increased antibacterial activity. Surface plasmon resonance sensorgrams and kinetic rate constants determined by a BIAcore biosensor revealed that nukacin ISK-1 has remarkably higher binding affinity to anionic model membrane than to zwitterionic model membrane. Similar trends of strong binding responses and kinetics were indicated by the high affinities of nukacin ISK-1 and +2K nukacin ISK-1, but there was no binding of tail region, ring region, nukacin_4-27, and K1-3A nukacin ISK-1 to the anionic model membrane. Our findings therefore suggest that the complete structure of nukacin ISK-1 is necessary for its full activity, in which the N-terminus three lysine residues play a crucial role in electrostatic binding to the target membrane and therefore nukacin ISK-1's ability to exert its potent antibacterial activity.     

Stable knock-down of vomeronasal receptor genes in transgenic Xenopus tadpoles

Xenopus V2R (xV2R), a family of G-protein-coupled receptors with seven transmembrane domains, is expressed in the Xenopus vomeronasal organ (VNO). There are six subgroups of xV2R, one of which, xV2RE, is predominantly expressed in the VNO. To understand the function of xV2R during VNO development, we developed a new method to achieve stable siRNA-suppression of the V2RE genes by introducing siRNA expression transgenes into the genomes of unfertilized eggs. We found that some of the derived transgenic tadpoles lacked VNOs and that their olfactory epithelium was fused. With the exception of one tadpole, expression of xV2RE was not detected in morphologically abnormal mutant tadpoles, although the olfactory marker protein and the olfactory receptors were expressed. These results suggest that we successfully produced transgenic tadpoles in which xV2RE expression was stably suppressed by siRNA, and that xV2RE plays a role in the morphogenesis of olfactory organs.     

Peroxisome proliferator-activated receptor alpha-independent peroxisome proliferation

Hepatic peroxisome proliferation, increases in the numerical and volume density of peroxisomes, is believed to be closely related to peroxisome proliferator-activated receptor alpha (PPARalpha) activation; however, it remains unknown whether peroxisome proliferation depends absolutely on this activation. To verify occurrence of PPARalpha-independent peroxisome proliferation, fenofibrate treatment was used, which was expected to significantly enhance PPARalpha dependence in the assay system. Surprisingly, a novel type of PPARalpha-independent peroxisome proliferation and enlargement was uncovered in PPARalpha-null mice. The increased expression of dynamin-like protein 1, but not peroxisome biogenesis factor 11alpha, might be associated with the PPARalpha-independent peroxisome proliferation at least in part.     

Haploinsufficiency in the PPARalpha and LDL receptor genes leads to gender- and age-specific obesity and hyperinsulinemia

When preparing peroxisome proliferator-activated receptor (PPAR)alpha:low-density lipoprotein receptor (LDLR) (-/-) double knockout mice, we unexpectedly found a unique gender- and age-specific obesity in the F1 generation, PPARalpha (+/-):LDLR (+/-), even in mice fed standard chow. Body weights of the male heterozygous mice increased up to about 60 g at 75 weeks of age, then decreased by about 30 g at 100 weeks of age. More than 95% of the heterozygous mice between 35- and 75-week-olds were overweight. Of interest, the obese heterozygous mice also exhibited hyperinsulinemia correlating with moderate insulin resistance. Hepatic gene expression of LDLR was lower than expected in the heterozygous mice, particularly at 50 and 75 weeks of age. In contrast, the hepatic expression of PPARalpha was higher than expected in obese heterozygous mice, but decreased in non-obese older heterozygous mice. Modulated expression of these genes may be partially associated with the onset of the hyperinsulinemia.     

Src tyrosine kinase inhibitor PP2 suppresses ERK1/2 activation and epidermal growth factor receptor transactivation by X-irradiation

Exposure of MDA-MB-468 cells to ionizing radiation (IR) caused biphasic activation of ERK as indicated by its phosphorylation at Thr202/Tyr204. Specific epidermal growth factor receptor (EGFR) inhibitor AG1478 and specific Src inhibitor PP2 inhibited IR-induced ERK1/2 activation but phosphatidylinositol-3 kinase inhibitor wortmannin did not. IR caused EGFR tyrosine phosphorylation, whereas it did not induce EGFR autophosphorylation at Tyr992, Tyr1045, and Tyr1068 or Src-dependent EGFR phosphorylation at Tyr845. SHP-2, which positively regulates EGFR/Ras/ERK signaling cascade, became activated by IR as indicated by its phosphorylation at Tyr542. This activation was inhibited by PP2 not by AG1478, which suggests Src-dependent activation of SHP-2. Src and PTPalpha, which positively regulates Src, became activated as indicated by phosphorylation at Tyr416 and Tyr789, respectively. These data suggest that IR-induced ERK1/2 activation involves EGFR through a Src-dependent pathway that is distinct from EGFR ligand activation.     

Import of peroxisomal membrane proteins: the interplay of Pex3p- and Pex19p-mediated interactions

In contrast to the molecular mechanisms underlying import of peroxisomal matrix proteins, those involving the transport of membrane proteins remain rather elusive. At present, two targeting routes for peroxisomal membrane proteins (PMPs) have been depicted: class I PMPs are targeted from the cytoplasm directly to the peroxisome membrane, and class II PMPs are sorted indirectly to peroxisomes via the endoplasmic reticulum (ER). In addition, three peroxins--Pex3p, Pex16p, and Pex19p - have been identified as essential factors for PMP assembly in several species including humans: Pex19p is a predominantly cytoplasmic protein that shows a broad PMP-binding specificity; Pex3p serves as the membrane-anchoring site for Pex19p; and Pex16p - a protein absent in most yeasts--is thought to provide the initial scaffold for recruiting the protein import machinery required for peroxisome membrane biogenesis. Remarkably, the function of Pex16p does not appear to be conserved between different species. In addition, significant disagreement exists about whether Pex19p has a chaperone-like role in the cytosol or at the peroxisome membrane and/or functions as a cycling import receptor for newly synthesized PMPs. Here we review the recent progress made in our understanding of the role of two key players in PMP biogenesis, Pex3p and Pex19p.     

Vitamin K deficiency reduces testosterone production in the testis through down-regulation of the Cyp11a a cholesterol side chain cleavage enzyme in rats

Vitamin K (K) is an essential factor for the posttranslational modification of blood coagulation factors as well as proteins in the bone matrix (Gla proteins). It is known that K is not only distributed in the liver and bones but also abundantly distributed in the brain, kidney, and gonadal tissues. However, the role of K in these tissues is not well clarified. In this study, we used DNA microarray and identified the genes whose expression was affected in the testis under the K-deficient (K-def) state. The expression of genes involved in the biosynthesis of cholesterol and steroid hormones was decreased in the K-def group. The mRNA levels of Cyp11a - a rate-limiting enzyme in testosterone synthesis - positively correlated with the menaquinone-4 (MK-4) concentration in the testis. Moreover, as compared to the control (Cont) and K-supplemented (K-sup) groups, the K-def group had decreased testosterone concentrations in the plasma and testis. These results suggested that K is involved in steroid production in the testis through the regulation of Cyp11a.     

Disruption of phospholipase Cdelta4 gene modulates the liver regeneration in cooperation with nuclear protein kinase C

Phospholipase Cdelta4 (PLC delta4) gene has been cloned from the cDNA library of regenerating rat liver. Using PLC delta4 gene-disrupted mice (PLC delta4(-/-)), we studied a role of PLC delta4 during liver regeneration after partial hepatectomy (PH). In PLC delta4(-/-), liver regeneration occurred in an apparently normal way. However, BrdU-indices indicated that PLC delta4 gene disruption delayed the onset of DNA synthesis by 2 h. Noticeably, the BrdU-indices in PLC delta4(+/+) remained rather constant throughout S phase, 25-35%, whereas in PLC delta4(-/-), it fluctuated drastically from 25% at 34 h to 65% at late S, 42 h after PH. This fact showed that PLC delta4 gene disruption caused a higher synchronization of cell proliferation. The mRNA for PLC delta4 in PLC delta4(+/+) appeared at late G1, and the expression continued throughout S phase. PLC activity increased transiently in chromatin at the late G1 and S phases in only PLC delta4(+/+), but not in PLC delta4(-/-). The specific increases in PLC activity well correlated with the transient increases of protein kinase C (PKC) alpha in chromatin of PLC delta4(+/+). PKC epsilon also increased transiently in chromatin from PLC delta4(+/+) at late S. It is concluded that PLC delta4 regulates the liver regeneration in cooperation with nuclear PKC alpha and epsilon.