Biomedical subjects

Y Gahara

Publications and source records attributed to Y Gahara.

7 recordsLinked to original sources

PubMed2000

A novel transcriptional factor with Ser/Thr kinase activity involved in the transforming growth factor (TGF)-beta signalling pathway.

Transforming growth factor-beta (TGF-beta) shows a variety of biological activities in various organs or cells. Recently some factors such as Smads (Sma and Mad proteins) and TGF-beta activating kinase 1 ('TAK1') have been characterized as signalling molecules downstream of TGF-beta. Several TGF-beta response elements have been identified such as cAMP response element, Smad binding element, and recognition sites for activating protein-1 and stimulating protein-1 in various gene promoters. We also reported a TGF-beta response element in the human C-type natriuretic peptide (CNP) gene promoter. In this paper, we report on a novel factor which regulates the TGF-beta response promoter. This factor, named TSF1 (TGF-beta stimulated factor 1), possessed DNA-binding ability and activated the TGF-beta responsive CNP promoter or vascular endothelial growth factor gene promoter which possesses a sequence element analogous to the TGF-beta responsive GC-rich element of the CNP promoter. TSF1 did not directly activate a Smads-dependent promoter from plasminogen activator inhibitor 1 gene, but it showed enhancement in co-operation with Smad3 and Smad4. Interestingly, this factor had the structural features of a Ser/Thr kinase and actually exhibited protein kinase activity. TSF1 mRNA as well as its protein level were stimulated by TGF-beta treatment. Thus, TSF1 is an unique factor with two biological functions, transcriptional regulation and protein phosphorylation, that may be involved in TGF-beta signals.

Amino Acid Sequence↗

PubMed1997

Identification and characterization of a novel gene (neurorep 1) expressed in nerve cells and up-regulated after axotomy.

A novel gene, designated neurorep 1, was isolated by differential hybridization screening from a complementary DNA library constructed from the rat facial nucleus whose nerve had been transected seven days before sampling. In situ hybridization revealed that this gene was up-regulated in the repair stage after axotomy. The deduced protein, Neurorep 1, consists of 293 amino acid residues, and its molecular mass is approximately 34,000. Protein sequence motif search indicates that this protein has an ecto-5'-nucleotidase consensus sequence at the carboxyl terminal region. In vitro studies showed that Neurorep 1 significantly increased the activity of ecto-5'-nucleotidase, which is considered to be involved in regeneration and repair of the central nervous system. Neurorep 1 might play a significant role in the repair process of nerve tissues by its regulation of ecto-5'-nucleotidase activity.

5'-Nucleotidase↗

PubMed1996

Up-regulation of cystatin C by microglia in the rat facial nucleus following axotomy.

Cystatin C, a cysteine proteinase inhibitor, is expressed in the central nervous system (CNS) as well as many other organs of mammals. However, little is known concerning whether its expression is regulated under pathological conditions of the CNS and what types of cells are responsible for this regulation. We performed differential hybridization screening of cDNA libraries derived from the rat facial nucleus and found a cDNA of rat cystatin C to be up-regulated following facial nerve axotomy. In situ hybridization using an RNA probe for rat cystatin C revealed that cystatin C mRNA in the facial nucleus was markedly increased in amount by day 7 after axotomy and was then decreased to the normal level by day 50. The intense signal for cystatin C mRNA in the damaged facial nucleus was localized in the glial cells which had the morphological characteristics of microglia. Light and electron microscopic immunohistochemistry using a rabbit antibody specific for cystatin C confirmed that microglia in the damaged facial nucleus were strongly positive for cystatin C. The immunoreactivity was also found in the extracellular space, consistent with the fact that cells producing cystatin C generally secrete this protein. These results demonstrate that cystatin C is markedly up-regulated by microglia in response to axotomy and is probably secreted by these cells into the extracellular space, suggesting that this proteinase inhibitor has (a) significant function(s) in the processes of neuronal degeneration, regeneration, and/or repair subsequent to axotomy.

Animals↗

PubMed1995

A novel RING-H2 motif protein downregulated by axotomy: its characteristic localization at the postsynaptic density of axosomatic synapse.

Axonal injury and its repair are common and basic neuropathological processes in the CNS, and are composed of a complex of events in a molecular term. In order to get a comprehensive understanding of these processes, we isolated several known and unknown genes which were up-or downregulated in the facial nucleus after transection of the facial nerve by a subtractive/differential screening. Among them, we focus on one downregulated gene, named Neurodap1, because this gene encodes a novel protein carrying the RING-H2 sequence motif categorized in the zinc finger family. Immunoelectron microscopic analysis revealed that the protein encoded by Neurodap1, Neurodap1, was distributed mainly on the cytoplasmic side of the membranes constituting endoplasmic reticulum and Golgi apparatus, supporting the notion of a previously postulated function of RING-H2 motif proteins, that is, involvement in the protein sorting machinery. More interestingly, Neurodap1 was also bound to the postsynaptic density (PSD) region of axosomatic synapses. This fact suggests that Neurodap1 is associated with a specific system sorting proteins to PSD. Therefore, Neurodap1, a newly identified protein as an axotomy-suppressed gene product, might play a significant role in synaptic communication and plasticity through the control of the formation of PSD for maintaining vital functions of nerve cells.

Amino Acid Sequence↗

PubMed1994

Distinctive four promoters collectively direct expression of brain-derived neurotrophic factor gene.

In order to get a deeper insight into comprehensive understanding of gene regulation of brain-derived neurotrophic factor (BDNF), we characterized the transcriptional apparatus of this gene on the basis of the genomic structure. The results in this study revealed that there are at least four distinctive promoters in the BDNF gene; two of them are neuron-specific and the rest are active in some non-neuronal tissues as well as neuronal ones. Although the analyses of the promoter usage pattern clarified many characteristic features in controlling these promoter activities, the most notable finding was that administration of kainic acid resulted in great activation of two out of the four promoters in hippocampal neurons in a regionally different manner and thus indicated the presence of two distinct signal transduction pathways for kainate-induced activation of BDNF gene expression in neurons. The analysis of BDNF gene expression in terms of the promoter usage pattern would provide a new and important insight into understanding a molecular control mechanism of this gene expression.

Animals↗

PubMed1993

Neurofilament deficiency in quail caused by nonsense mutation in neurofilament-L gene.

The existence of a neurofilament-deficient mutant of Japanese quail was recently documented (Yamasaki, H., C. Itakura, and M. Mizutani. 1991. Acta Neuropathol. 82:427-434), but the genetic events leading to the neurofilament deficiency have yet to be determined. Our molecular biological analyses revealed that the expression of neurofilament-L (NF-L) gene was specifically repressed in neurons of this mutant. To search for mutation(s) responsible for the shutdown of this gene expression, we cloned and sequenced the NF-L genes in the wild-type and mutant quails. It is eventually found that the NF-L gene in the mutant includes a nonsense mutation at the deduced amino acid residue 114, indicating that the mutant is incapable of producing even a trace amount of polymerization-competent NF-L protein at any situation. The identification of this nonsense mutation provides us with a solid basis on which molecular mechanisms underlying the alteration in the neuronal cytoskeletal architecture in the mutant should be interpreted.

Amino Acid Sequence↗

PubMed1992

A rat brain-derived neurotrophic factor-encoding gene generates multiple transcripts through alternative use of 5' exons and polyadenylation sites.

As a first step toward clarification of the transcriptional controls of the gene encoding brain-derived neurotrophic factor (BDNF), we cloned and sequenced a rat genomic DNA fragment carrying this gene. RNA blotting analysis using a probe derived from the 3'-flanking region of BDNF revealed that alternative use of 3'-polyadenylation sites generates at least two BDNF transcripts that differ in the size of the 3'-noncoding region. Furthermore, sequence analysis of the 5'-end of the BDNF cDNA revealed the presence of at least six different types of transcripts which were probably derived through alternative use of the multiple 5'-exons. Therefore, a single BDNF gene could produce multiple types of transcripts with different noncoding sequences through alternative use of both 5'-exons and 3'-transcription termination sites.

Alternative Splicing↗