Biomedical subjects

Shigenobu Toné

Publications and source records attributed to Shigenobu Toné.

6 recordsLinked to original sources

PubMed2005

Iris movement mediates vascular apoptosis during rat pupillary membrane regression.

In the course of mammalian lens development, a transient capillary meshwork known as the pupillary membrane (PM) forms, which is located at the pupil area; the PM nourishes the anterior surface of the lens and then regresses to make the optical path clear. Although the involvement of apoptotic process has been reported in the PM regression, the initiating factor remains unknown. We initially found that regression of the PM coincided with the development of iris motility, and iris movement caused cessation and resumption of blood flow within the PM. Therefore, we investigated whether the development of the iris's ability to constrict and dilate functions as an essential signal that induces apoptosis in the PM. Continuous inhibition of iris movement with mydriatic agents from postnatal day 7 to day 12 suppressed apoptosis of the PM and migration of macrophage toward the PM, and resulted in the persistence of PM in rats. The distribution of apoptotic cells in the regressing PM was diffuse and showed no apparent localization. These results indicated that iris movement induced regression of the PM by changing the blood flow within it. This study suggests the importance of the physiological interactions between tissues-in this case, the iris and the PM-as a signal to advance vascular regression during organ development, and defines a novel function of the iris during ocular development in addition to the well-known function, that is, optimization of light transmission into the eye.

Animals↗

PubMed2005

Nuclear transfer of perchloric acid-soluble protein by endoplasmic reticulum stressors.

Perchloric acid-soluble protein (PSP) is highly conserved during evolution from bacteria to mammals. Although PSP has been recognized as an inhibitor of translation and proliferation in vitro, its precise biological role has not yet been elucidated. Since we previously found similar distributions for PSP and the endoplasmic reticulum (ER) and Golgi complex, the intracellular distribution of PSP was analyzed in more detail. Immunofluorescence studies indicated that PSP co-localized with the ER and Golgi complex, since the distribution pattern of PSP was well matched to both of these organelles. An immunoelectron microscopic study revealed PSP was located not only in the cytosol but also on the surface of the outer ER membrane. Since PSP was present on the ER, we speculated that it may be associated with ER function. Therefore, we analyzed whether or not the ER stress response, which is one of the ER functions, affected PSP expression. The results showed that various ER stressors (thapsigargin, A23187, tunicamycin, brefeldin A, and cisplatin) provoked a dramatic change in the localization of PSP from outside of the nucleus to inside the nucleus within 3 h. Moreover, the ER stressors induced PSP expression. These results suggest that PSP is involved in the cellular response to ER stressors, and that the change in localization of PSP from the ER to the nucleus may be associated with ER stress responses.

Active Transport, Cell Nucleus↗

PubMed2004

Activation of the CKI-CDK-Rb-E2F pathway in full genome hepatitis C virus-expressing cells.

Hepatitis C virus (HCV) causes persistent infection in hepatocytes, and this infection is, in turn, strongly associated with the development of hepatocellular carcinoma. To clarify the mechanisms underlying these effects, we established a Cre/loxP conditional expression system for the precisely self-trimmed HCV genome in human liver cells. Passage of hepatocytes expressing replicable full-length HCV (HCR6-Rz) RNA caused up-regulation of anchorage-independent growth after 44 days. In contrast, hepatocytes expressing HCV structural, nonstructural, or all viral proteins showed no significant changes after passage for 44 days. Only cells expressing HCR6-Rz passaged for 44 days displayed acceleration of CDK activity, hyperphosphorylation of Rb, and E2F activation. These results demonstrate that full genome HCV expression up-regulates the CDK-Rb-E2F pathway much more effectively than HCV proteins during passage.

Blotting, Western↗

PubMed2003

Induction of apoptosis by depletion of DNA topoisomerase IIalpha in mammalian cells.

Inactivation of topoisomerase (topo) IIalpha arrests murine embryonic development. In topo IIalpha-depleted embryos, nuclei were partitioned to daughter cells without complete separation and formed an interconnecting droplet-like structure. The present study examined the fates of topo IIalpha-depleted cells with the droplet-like nuclear structure. When the embryos with abnormal nuclei were further incubated, apoptosis was induced along with the formation of fragmented and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling positive nuclei. ICRF-193 treatment of embryos activated caspases. Apoptosis induced by ICRF-193 was suppressed by z-VAD-fmk, a caspase inhibitor, and pifithrin-alpha, a p53 inhibitor. Moreover, when mitosis was blocked by nocodazole, ICRF-193-induced nuclear abnormalities and apoptosis were abolished. These data suggest that cycling through the M-phase is essential for ICRF-193-induced apoptosis. Nuclear abnormalities similar to those of topo IIalpha-depleted embryos were induced in HeLa cells in which topo IIalpha was knocked down by transfection with short interfering RNA (siRNA) against topo IIalpha, followed by induction of apoptosis. Our results suggest that topo IIalpha-depleted cells with the droplet-like nuclear structure induce apoptosis, which is dependent on caspase and p53 activity during the G1 phase in mammalian cells.

Animals↗

PubMed2002

Functional analysis of the 5'-flanking region of the human alanine:glyoxylate aminotransferase gene AGXT.

Primer extension of human liver poly(A)(+) RNA revealed that the main transcription start site of the human alanine:glyoxylate aminotransferase gene (AGXT) is situated near 45 bp upstream from the translation start site. Deletion analysis using the 1203 bp 5'-flanking region of the AGXT gene and a luciferase reporter suggested that the promoter sequence is most likely located 2-325 bp upstream from the translation start site, possibly with enhancer elements 440-700 bp upstream. It was also suggested that the region -2 to -64 is important for the expression of the AGXT gene. The region -2 to -325 has two TATA boxes and some initiator elements.

Base Sequence↗

PubMed2002

A possible intermediate step during apoptotic execution.

Many proteases are known to be involved in apoptosis. Among them, interleukin-1beta converting enzyme (ICE) and its family proteases, which are called caspases, play critical roles in the execution stage of apoptosis. We previously reported that a proteasome-inhibitor, benzyloxycarbonyl Leu-Leu-leucinal (ZLLLal), induced apoptosis in MOLT-4 cells. In the present study, in order to analyze the detailed mechanism of ZLLLal-induced apoptosis, we examined the effect of a caspase-inhibitor, acetyl(Ac)-Tyr-Val-Ala-Asp-chloromethyl ketone (AcYVADcmk), on ZLLLal-induced apoptosis in the cells. Agarose gel electrophoresis revealed that low concentrations of AcYVADcmk efficiently suppressed apoptotic DNA fragmentation. However, the cells presented morphology different from normal, apoptotic or necrotic cells, although DNA fragmentation was suppressed. The same examination was performed on the cells with anti-Fas antibody-induced apoptosis, and the same results were obtained. Some cells with a similar morphology were found even without the caspase-inhibitor in the early stage of anti-Fas antibody-induced physiological apoptosis. In addition, apoptotic cascade was reactivated by washing out the caspase inhibitor from the DNA degradation-suppressed cells. Therefore, this newly found morphological feature shows the presence of a step prior to caspase activation in the cells, and this is the first report presenting the pre-caspase-activated step in the apoptotic cascade.

Amino Acid Chloromethyl Ketones↗