Development of a bioactive fiber with immobilized synthetic peptides designed from the active site of a beetle defensin

The 9-mer peptides RLYLRIGRR and RLLLRIGRR were immobilized to amino-functionalized cotton fibers by a modification of the SPOT synthesis technique. The antibacterial activities of the peptide-immobilized cotton fibers against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) were investigated. Antibacterial assays revealed that these fibers inhibit the growth of MRSA and the antibacterial activities were maintained after washing and sterilization by autoclaving. The anticancer effect of the peptide-immobilized fiber was also investigated with mouse myeloma cells and human leukemia cells. These results indicate that these fibers have strong growth inhibition activity against bacteria and cancer cells.     

TRPA1 underlies a sensing mechanism for O2

Oxygen (O(2)) is a prerequisite for cellular respiration in aerobic organisms but also elicits toxicity. To understand how animals cope with the ambivalent physiological nature of O(2), it is critical to elucidate the molecular mechanisms responsible for O(2) sensing. Here our systematic evaluation of transient receptor potential (TRP) cation channels using reactive disulfides with different redox potentials reveals the capability of TRPA1 to sense O(2). O(2) sensing is based upon disparate processes: whereas prolyl hydroxylases (PHDs) exert O(2)-dependent inhibition on TRPA1 activity in normoxia, direct O(2) action overrides the inhibition via the prominent sensitivity of TRPA1 to cysteine-mediated oxidation in hyperoxia. Unexpectedly, TRPA1 is activated through relief from the same PHD-mediated inhibition in hypoxia. In mice, disruption of the Trpa1 gene abolishes hyperoxia- and hypoxia-induced cationic currents in vagal and sensory neurons and thereby impedes enhancement of in vivo vagal discharges induced by hyperoxia and hypoxia. The results suggest a new O(2)-sensing mechanism mediated by TRPA1.     

HMG domain containing SSRP1 is required for DNA demethylation and genomic imprinting in Arabidopsis

In Arabidopsis, DEMETER (DME) DNA demethylase contributes to reprogramming of the epigenetic state of the genome in the central cell. However, other aspects of the active DNA demethylation processes remain elusive. Here we show that Arabidopsis SSRP1, known as an HMG domain-containing component of FACT histone chaperone, is required for DNA demethylation and for activation and repression of many parentally imprinted genes in the central cell. Although loss of DNA methylation releases silencing of the imprinted FWA-GFP, double ssrp1-3;met1-3 mutants surprisingly showed limited activation of maternal FWA-GFP in the central cell, and only became fully active after several nuclear divisions in the endosperm. This behavior was in contrast to the dme-1;met1 double mutant in which hypomethylation of FWA-GFP by met1 suppressed the DNA demethylation defect of dme-1. We propose that active DNA demethylation by DME requires SSRP1 function through a distinctly different process from direct DNA methylation control.     

Toxicoproteomic evaluation of carbon nanomaterials in vitro

Carbon nanotubes (CNTs) have already been successfully implemented in various fields, and they are anticipated to have innovative applications in medical science. However, CNTs have asbestos-like properties, such as their nanoscale size and high aspect ratio (>100). Moreover, CNTs may persist in the body for a long time. These properties are thought to cause malignant mesothelioma and lung cancer. However, based on conventional toxicity assessment systems, the carcinogenicity of asbestos and CNTs is unclear. The reason for late countermeasures against asbestos is that reliable, long-term safety assessments have not yet been developed by toxicologists. Therefore, a new type of long-term safety assessment, different from the existing methods, is needed for carbon nanomaterials. Recently, we applied a proteomic approach to the safety assessment of carbon nanomaterials. In this review, we discuss the basic concept of our approach, the results, the problems, and the possibility of a long-term safety assessment for carbon nanomaterials using the toxicoproteomic approach.     

Time-lapse imaging reveals symmetric neurogenic cell division of GFAP-expressing progenitors for expansion of postnatal dentate granule neurons

Granule cells in the hippocampus, a region critical for memory and learning, are generated mainly during the early postnatal period but neurogenesis continues in adulthood. Postnatal neuronal production is carried out by primary progenitors that express glial fibrillary acidic protein (GFAP) and they are assumed to function as stem cells. A central question regarding postnatal dentate neurogenesis is how astrocyte-like progenitors produce neurons. To reveal cell division patterns and the process of neuronal differentiation of astrocyte-like neural progenitors, we performed time-lapse imaging in cultured hippocampal slices from early postnatal transgenic mice with mouse GFAP promoter-controlled enhanced green fluorescent protein (mGFAP-eGFP Tg mice) in combination with a retrovirus carrying a red fluorescent protein gene. Our results showed that the majority of GFAP-eGFP+ progenitor cells that express GFAP, Sox2 and nestin divided symmetrically to produce pairs of GFAP+ cells (45%) or pairs of neuron-committed cells (45%), whereas a minority divided asymmetrically to generate GFAP+ cells and neuron-committed cells (10%). The present results suggest that a substantial number of GFAP-expressing progenitors functions as transient amplifying progenitors, at least in an early postnatal dentate gyrus, although a small population appears to be stem cell-like progenitors. From the present data, we discuss possible cell division patterns of adult GFAP+ progenitors.     

Rac mediates mouse spermatogonial stem cell homing to germline niches by regulating transmigration through the blood-testis barrier

The homing ability of spermatogonial stem cells (SSCs) allows them to migrate into niches after being transplantated into infertile testes. Transplanted SSCs attach to Sertoli cells and transmigrate through the blood-testis barrier (BTB), formed by inter-Sertoli tight junctions, toward niches on the basement membrane. The most critical step is the passage through the BTB, which limits the homing efficiency to <10%. Here we demonstrated the involvement of Rac1 in SSC transmigration. Rac1-deficient SSCs did not colonize the adult testes, but they reinitiated spermatogenesis when transplanted into pup testes without a BTB. Moreover, a dominant-negative Rac1 construct not only reduced the expression of several claudin proteins, which comprise the BTB, but also increased SSC proliferation both in vitro and in vivo. Short hairpin RNA (shRNA) -mediated suppression of claudin3, which was downregulated by Rac inhibition, reduced the SSC homing efficiency. Thus, Rac1 is a critical regulator of SSC homing and proliferation.     

A Novel dnaJ Family Gene,sflA, Encodes an Inhibitor of Flagellation in Marine Vibrio Species

The marine bacterium Vibrio alginolyticus has a single polar flagellum. Formation of that flagellum is regulated positively and negatively by FlhF and by FlhG, respectively. The ΔflhF mutant makes no flagellum, whereas the ΔflhFG double-deletion mutant usually lacks a flagellum. However, the ΔflhFG mutant occasionally reverts to become motile by forming peritrichous flagella. We have isolated a suppressor pseudorevertant from the ΔflhFG strain (ΔflhFG-sup). The suppressor strain forms peritrichous flagella in the majority of cells. We identified candidate suppressor mutations by comparing the genome sequence of the parental strain, VIO5, with the genome sequences of the suppressor strains. Two mutations were mapped to a gene, named sflA (suppressor of ΔflhFG), at the VEA003730 locus of the Vibrio sp. strain EX25 genome. This gene is specific for Vibrio species and is predicted to encode a transmembrane protein with a DnaJ domain. When the wild-type gene was introduced into the suppressor strain, motility was impaired. Introducing a mutant version of the sflA gene into the ΔflhFG strain conferred the suppressor phenotype. Thus, we conclude that loss of the sflA gene is responsible for the suppressor phenotype and that the wild-type SflA protein plays a role in preventing polar-type flagella from forming on the lateral cell wall.     

Binding of Drosophila maternal Mamo protein to chromatin and specific DNA sequences

Alterations in chromatin structure dynamically occur during germline development in Drosophila and are essential for the production of functional gametes. We had previously reported that the maternal factor Mamo, which contains both a BTB/POZ domain and C₂H₂ zinc-finger domains and is enriched in primordial germ cells (PGCs), is required for the regulation of meiotic chromatin structure and the production of functional gametes. However, the molecular mechanisms by which Mamo regulates germline development remained unclear. To evaluate the molecular function of Mamo protein, we have investigated the binding of Mamo to chromatin and DNA sequences. Our data show that Mamo binds to chromatin and specific DNA sequences, particularly the polytene chromosomes of salivary gland cells. Overexpression of Mamo affected the organization of polytene chromosomes. Reduction in maternal Mamo levels impaired the formation of germline-specific chromatin structures in PGCs. Furthermore, we found that the zinc-finger domains of Mamo directly bind to specific DNA sequences. Our results suggest that Mamo plays a role in regulating chromatin structure in PGCs.     

A phosphoramidon-sensitive metalloprotease induces apoptosis of human endothelial cells by Group B Streptococcus

We explored Group B Streptococcus (GBS)-induced apoptosis in human umbilical vein endothelial cells (HUVEC) and the role of phosphoramidon, a zinc metalloprotease inhibitor, in this process. GBS 90186 strain (serotype V, a blood isolate) and concentrated supernatant (CS) were used to investigate the viability and morphological alterations in HUVEC by Trypan blue uptake, electrophoresis in 2 % agarose gel and scanning electron microscopy assays. Apoptosis before and after phosphoramidon-treatment were verified by flow cytometry using annexin V-FITC labeling. Differences were considered significant when P < 0.05 using unpaired Student’s t test. GBS and CS induced HUVEC death by apoptosis (76.5 and 32 %, respectively) with an increasing pro-apoptotic Bax expression and decreasing anti-apoptotic Bcl-2 expression. Caspase-3 was activated during GBS-induced endothelial apoptosis. Phosphoramidon reduced 89.3 and 100 % of GBS and CS cell death by apoptosis, respectively. Some GBS strains may induce cell death by apoptosis with involvement of metalloproteases and signaling through the intrinsic pathway of apoptosis, which may contribute to GBS survival during sepsis of adults and neonates.