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Biomedical subjects

H Teramoto

Publications and source records attributed to H Teramoto.

At least 19 recordsLinked to original sources
PubMed1998

Effector domain mutants of Rho dissociate cytoskeletal changes from nuclear signaling and cellular transformation.

The small GTP-binding Rho proteins control a variety of biological activities, including organization of the actin cytoskeleton, regulation of gene expression and cellular transformation. In contrast, Ras proteins do not induce actin stress fibers, but potently transform cells which exhibit a morphology clearly distinct from that caused by activated forms of Rho. To investigate whether nuclear signaling and oncogenic potential of Rho are a consequence of its profound effect on cytoskeletal organization, we replaced each amino acid in the Rho effector loop with those of Ras, or replaced conserved residues with others known to result in differential signaling capability when introduced into Ras and Rac1. These Rho mutants did not gain the ability to induce the MAPK, JNK or p38 pathways but, surprisingly, all Rho effector loop mutants still continued to induce actin stress fiber formation. However, three of these Rho mutants, with substitutions of leucine-39, glutamic acid-39, or cysteine-42, lost the ability to stimulate gene transcription via the serum response factor (SRF) and failed to induce neoplastic transformation. Thus, these results indicate that cytoskeletal changes are not sufficient to induce the transformed phenotype, and that Rho-effector molecules regulating the actin cytostructure are distinct from those signaling to the nucleus and subverting normal growth control.

3T3 Cells↗
PubMed1998

[A case of intracranial tuberculoma followed by MRI].

A 62-year-old woman with pulmonary tuberculosis was admitted to our hospital. She was completely neurologically free at admission and her CSF was normal. Brain MRI with Gd-DTPA enhancement demonstrated two mass lesions with ring-enhancement in the left temporal lobe and the right frontal lobe. The left temporal lesion had a bright central core with hypointense periphery on T2 weighted image. Extended hyperintense area was observed around this lesions, which represented brain edema. On T1 weighted image, the central core was demonstrated hypointense and its periphery was isointense. After starting antituberculous therapy, MRI revealed paradoxical expansion of left temporal lesion and neurological symptoms worsened temporarily, but, eventually the intracranial lesions diminished in size and disappeared, and the symptoms improved. So we diagnosed her as having intracranial tuberculoma. By long-term following up with MRI, we observed that the central core of the left temporal tuberculoma had changed gradually to hypointense on T2 weighted image and hyperintense on T1 weighted image respectively. We thought that the change of the central core on MRI represented organization of caseated necrosis.

Antitubercular Agents↗
PubMed1997

A human suppressor of c-Jun N-terminal kinase 1 activation by tumor necrosis factor alpha.

Tumor necrosis factor alpha (TNFalpha) has pleiotropic effects on cellular metabolism. One of the signaling paths from the TNFalpha receptor induces a stress-activated protein kinase cascade. Components within this TNFalpha kinase cascade include mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 1 (MEKK1) and stress-activated protein kinase/extracellular signal-regulated kinase kinase (SEK), which regulate the activity of c-Jun N-terminal kinase 1 (JNK1). Currently, molecules upstream of MEKK1 that link TNFalpha receptor to downstream kinases are not well understood. Besides TNFalpha, many other stimuli including several oncoproteins can activate JNK1. In most cases, the signaling cascade(s) leading from oncoproteins to JNK1 is poorly elucidated. We report here that the human T-cell lymphotrophic virus, type I (HTLV-I) oncoprotein, Tax, can activate JNK1. We isolated a novel human cell factor, G-protein pathway suppressor 2 (GPS2), by its ability to bind the HTLV-I oncoprotein, and we show that this factor can potently suppress Tax activation of JNK1. In trying to understand the mechanism of GPS2 activity, we found that it also suppressed TNFalpha activation of JNK1 but not TNFalpha activation of p38 kinase nor phorbol activation of extracellular signal-regulated kinase 2. Because GPS2 has minimal effect on MEKK1- or SEK-regulated JNK1 activity, it could act at a point between the TNFalpha receptor and MEKK1 in the initial step(s) of this kinase cascade. Alternatively, it is not excluded that GPS2 could work in a parallel pathway that leads from TNFalpha to JNK1. GPS2 represents a new molecule that could contribute important insights toward how cytokine- and oncoprotein-mediated signal transduction might converge.

Amino Acid Sequence↗
PubMed1997

Signaling from G protein-coupled receptors to the c-jun promoter involves the MEF2 transcription factor. Evidence for a novel c-jun amino-terminal kinase-independent pathway.

The c-Jun amino-terminal kinases (JNKs) are a subfamily of mitogen-activated protein kinases that phosphorylate c-Jun and ATF2, and it has been postulated that phosphorylated c-Jun enhances its own expression through AP-1 sites on the c-jun promoter. In this study, we asked whether signals activating JNK regulate the c-jun promoter. Using NIH 3T3 cells expressing G protein-coupled m1 acetylcholine receptors as an experimental model, we have recently shown that the cholinergic agonist carbachol, but not platelet-derived growth factor, potently elevates JNK activity. Consistent with these findings, carbachol, but not platelet-derived growth factor, increased the activity of a c-jun promoter-driven reporter gene (for chloramphenicol acetyltransferase). However, coexpression of JNK kinase kinase (MEKK) effectively increased JNK activity, but resulted in surprisingly limited induction of the c-jun promoter. This raised the possibility that pathway(s) distinct from JNK control the c-jun promoter, and prompted us to explore which of its regulatory elements participate in transcriptional control. We observed that deletion of the 3' AP-1 site diminished chloramphenicol acetyltransferase activity in response to carbachol, but only to a limited extent. In contrast, deletion of a MEF2 site dramatically reduced expression, and deletion of both the MEF2 and 3' AP-1 sites abolished induction. Furthermore, cotransfection with MEF2C and MEF2D cDNAs potently enhanced the activity of the c-jun promoter in response to carbachol, and stimulation of m1 receptors, but not direct JNK activation, induced expression of a MEF2-responsive plasmid. Taken together, these data strongly suggest that MEF2 mediates c-jun promoter expression by G protein-coupled receptors through a yet to be identified pathway, distinct from that of JNK.

3T3 Cells↗
PubMed1997

Tyrosine phosphorylation of the vav proto-oncogene product links FcepsilonRI to the Rac1-JNK pathway.

Stimulation of high affinity IgE Fc receptors (FcepsilonRI) in basophils and mast cells activates the tyrosine kinases Lyn and Syk and causes the tyrosine phosphorylation of phospholipase C-gamma, resulting in the Ca2+- and protein kinase C-dependent secretion of inflammatory mediators. Concomitantly, FcepsilonRI stimulation initiates a number of signaling events resulting in the activation of mitogen-activated protein kinase (MAPK) and c-Jun NH2-terminal kinase (JNK), which, in turn, regulate nuclear responses, including cytokine gene expression. To dissect the signaling pathway(s) linking FcepsilonRI to MAPK and JNK, we reconstructed their respective biochemical routes by expression of a chimeric interleukin-2 receptor alpha subunit (Tac)-FcepsilonRI gamma chain (Tacgamma) in COS-7 cells. Cross-linking of Tacgamma did not affect MAPK in COS-7 cells, but when coexpressed with the tyrosine kinase Syk, Tacgamma stimulation potently induced Syk and Shc tyrosine phosphorylation and MAPK activation. In contrast, Tacgamma did not signal JNK activation, even when coexpressed with Syk. Ectopic expression of a hematopoietic-specific guanine nucleotide exchange factor (GEF), Vav, reconstituted the Tacgamma-induced, Syk- and Rac1-dependent JNK activation; and tyrosine-phosphorylation of Vav by Syk stimulated its GEF activity for Rac1. Thus, these data strongly suggest that Vav plays a critical role linking FcepsilonRI and Syk to the Rac1-JNK pathway. Furthermore, these findings define a novel signal transduction pathway involving a multimeric cell surface receptor acting on a cytosolic tyrosine kinase, which, in turn, phosphorylates a GEF, thereby regulating its activity toward a small GTP-binding protein and promoting the activation of a kinase cascade.

Animals↗
PubMed1997

The pathway connecting m2 receptors to the nucleus involves small GTP-binding proteins acting on divergent MAP kinase cascades.

m1 and m2 receptors are traditionally linked to tissue specific functions performed by fully differentiated cells. However, these receptors have been also implicated in growth stimulation. The mechanisms whereby these receptors regulate proliferative signaling pathways are still poorly understood. Furthermore, pharmacological evidence suggest that many growth promoting agents act on Gi coupled receptors, but there is no formal proof that induction of DNA-synthesis results from decreased intracellular levels of cAMP. In our laboratory, we have used the expression of ml and m2 receptors as a model for studying proliferative signaling through G protein-coupled receptors. Currently available evidence suggest that these receptors signal to distinct members of the MAP kinase superfamily, MAP kinase and JNK, through betagamma subunits of heterotrimeric G proteins acting, respectively, on a Ras and Rac1 dependent pathway.

Animals↗
PubMed1996

Signaling from the small GTP-binding proteins Rac1 and Cdc42 to the c-Jun N-terminal kinase/stress-activated protein kinase pathway. A role for mixed lineage kinase 3/protein-tyrosine kinase 1, a novel member of the mixed lineage kinase family.

Certain small GTP-binding proteins control the enzymatic activity of a family of closely related serine-threonine kinases known as mitogen-activated protein kinases (MAPKs). In turn, these MAPKs, such as p44(mapk) and p42(mapk), referred to herein as MAPKs, and stress-activated protein kinases, also termed c-Jun N-terminal kinases (JNKs), phosphorylate and regulate the activity of key molecules that ultimately control the expression of genes essential for many cellular processes. Whereas Ras controls the activation of MAPK, we and others have recently observed that two members of the Rho family of small GTP-binding proteins, Rac1 and Cdc42, regulate the activity of JNKs. The identity of molecules communicating Rac1 and Cdc42 to JNK is still poorly understood. It has been suggested that Pak1 is the most upstream kinase connecting these GTPases to JNK; however, we have observed that coexpression of Pak1 with activated forms of Cdc42 or Rac1 diminishes rather than enhances JNK activation. This prompted us to explore the possibility that kinases other than Pak might participate in signaling from GTP-binding proteins to JNK. In this regard, a computer-assisted search for proteins containing areas of homology to that in Pak1 that is involved in binding to Rac1 and Cdc42 led to the identification of mixed lineage kinase 3 (MLK3), also known as protein-tyrosine kinase 1, as a potential candidate for this function. In this study, we found that MLK3 overexpression is sufficient to activate JNK potently without affecting the phosphorylating activity of MAPK or p38. Furthermore, we present evidence that MLK3 binds the GTP-binding proteins Cdc42 and Rac1 in vivo and that MLK3 mediates activation of MEKK-SEK-JNK kinase cascade by Rac1 and Cdc42. Taken together, these findings strongly suggest that members of the novel MLK family of highly related kinases link small GTP-binding proteins to the JNK signaling pathway.

Animals↗
PubMed1996

The small GTP-binding protein rho activates c-Jun N-terminal kinases/stress-activated protein kinases in human kidney 293T cells. Evidence for a Pak-independent signaling pathway.

Work from a number of laboratories has established a role for certain small GTP-binding proteins in controlling the enzymatic activity of a family of serine-threonine kinases known as mitogen-activated protein kinases (MAPKs). MAPKs have been classified into three subfamilies: extracellular signal-regulated kinases (ERKs), also known as MAPKs; c-Jun N-terminal kinases (JNKs); and p38 kinase. Whereas Ras controls the activation of MAPKs, we and others have recently observed that in certain cells, the small GTP-binding proteins Rac1 and Cdc42 but not Rho regulate the activity of JNKs. Furthermore, because Rac1 and Cdc42 but not Rho bind and activate a kinase known as Pak1, it has been suggested that Pak1 is the most upstream component of the pathway linking these GTPases to JNK. However, in both yeast and mammalian cells, Rho1p, a Rho homologue, and RhoA, respectively, directly interact with a number of proteins, including kinases related to protein kinase C. In addition, in yeast, Rho1p controls the activity of a MAPK cascade involved in bud formation. Considering this diversity of target molecules for small GTP-binding proteins, their likely tissue specific distribution, and the potential role for Rho in signaling to a kinase cascade, we decided to extend our initial analysis, exploring the ability of Ras and Rho-related GTP-binding proteins to activate MAPK or JNK in a variety of cell lines. We found that in the human kidney epithelial cell line, 293T, Cdc42 and all Rho proteins, RhoA, RhoB, and RhoC, but not Rac or Ras can induce activation of JNK. Furthermore, we provide evidence that signaling from Rho proteins to JNK in 293T cells does not involve Pak1. Taken together these findings demonstrate that Rho signals to JNK in a cell type-specific manner and suggest the existence of a novel, Pak1-independent signaling route communicating the Rho family of small GTP-binding proteins to the JNK pathway.

Animals↗
PubMed1996

Signaling from G protein-coupled receptors to c-Jun kinase involves beta gamma subunits of heterotrimeric G proteins acting on a Ras and Rac1-dependent pathway.

Stimulation of a variety of cell surface receptors enhances the enzymatic activity of mitogen-activated protein kinases (MAPKs). MAPKs have been classified in three subfamilies: extracellular signal-regulated kinases (ERKs), stress-activated protein kinases or c-Jun NH2-terminal kinases (SAPKs/JNKs), and p38 kinase. Whereas the pathway linking cell surface receptors to ERKs has been partially elucidated, the mechanism of activation of JNKs is still poorly understood. Recently, we have shown that stimulation of G protein-coupled receptors can effectively induce JNK in NIH 3T3 cells (Coso, O. A., Chiariello, M., Kalinec, G., Kyriakis, J. M., Woodgett, J., and Gutkind, J. S. (1995) J. Biol. Chem. 270, 5620-5624). In the present study, we have used the transient expression in COS-7 cells of m1 and m2 muscarinic receptors (mAChRs) as a model system to study the signaling pathway linking G protein-coupled receptors to JNK. We show that stimulation of either muscarinic receptor subtype leads to JNK activation; however, this effect was not mimicked by expression of activated forms of alphas, alphai2, alphaq, or alpha13 G protein alpha subunits. In contrast, overexpression of Gbetagamma subunits potently induced JNK activity. Furthermore, we show that signaling from m1 and m2 mAChRs to JNK involves betagamma subunits of heterotrimeric G proteins, acting on a Ras and Rac1-dependent pathway.

3T3 Cells↗
PubMed1996

Noncoding RNA for CR20, a cytokinin-repressed gene of cucumber.

The CR20 gene was identified as a cytokinin-repressed gene in excised cotyledons of cucumber. We determined the sequences of some CR20 cDNAs with different structures and sequenced genomic clones for CR20. This gene consisted of three exons, and there were at least three types of transcript, which seemed to be generated by alternative splicing of the second intron. None of the CR20 transcripts included a long open reading frame (ORF). We isolated a cDNA of Arabidopsis thaliana with cucumber CR20 cDNA as a probe. This cDNA for a gene designated AtCR20-1 also lacked a long ORF. A region of 180 nucleotides was conserved in the CR20 RNA of cucumber and the AtCR20-1 RNA of Arabidopsis, although the homology was relatively low when the entire sequences were compared. Each conserved region consisted of seven elements, and seems to form stable secondary structure. These suggest that CR20 RNA may function as an RNA that is not translated into a protein.

Alternative Splicing↗
PubMed1996

Integrins can collaborate with growth factors for phosphorylation of receptor tyrosine kinases and MAP kinase activation: roles of integrin aggregation and occupancy of receptors.

Integrins mediate cell adhesion, migration, and a variety of signal transduction events. These integrin actions can overlap or even synergize with those of growth factors. We examined for mechanisms of collaboration or synergy between integrins and growth factors involving MAP kinases, which regulate many cellular functions. In cooperation with integrins, the growth factors EGF, PDGF-BB, and basic FGF each produced a marked, transient activation of the ERK (extracellular signal-regulated kinase) class of MAP kinase, but only if the integrins were both aggregated and occupied by ligand. Transmembrane accumulation of total tyrosine-phosphorylated proteins, as well as nonsynergistic MAP kinase activation, could be induced by simple integrin aggregation, whereas enhanced transient accumulation of the EGF-receptor substrate eps8 required integrin aggregation and occupancy, as well as EGF treatment. Each type of growth factor receptor was itself induced to aggregate transiently by integrin ligand-coated beads in a process requiring both aggregation and occupancy of integrin receptors, but not the presence of growth factor ligand. Synergism was also observed between integrins and growth factors for triggering tyrosine phosphorylation of EGF, PDGF, and FGF receptors. This collaborative response also required both integrin aggregation and occupancy. These studies identify mechanisms in the signal transduction response to integrins and growth factors that require various combinations of integrin aggregation and ligands for integrin or growth factor receptors, providing opportunities for collaboration between these major regulatory systems.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1996

The level of mRNA transcribed from psaL, which encodes a subunit of photosystem I, is increased by cytokinin in darkness in etiolated cotyledons of cucumber.

A cDNA clone for an mRNA whose level increased within 2 h of the start of treatment with N6-benzyladenine in etiolated cotyledons of cucumber was isolated by differential hybridization. The cDNA was homologous to psaL, which encodes subunit XI (PSI-L) of photosystem I. The accumulation of psaL mRNA was specifically induced by cytokinins or light.

Amino Acid Sequence↗
PubMed1996

[Initial outcome of coronary intervention in elderly patients].

The effect of age on the early results of coronary intervention was examined retrospectively using the initial success rate of coronary angioplasty in 60 patients older than 70 years. Patients were selected from those who underwent coronary angioplasty at the Saiseikai Utsunomiya Hospital from January 1992 to December 1994. There were 267 patients with 350 lesions, 223 men and 44 women, aged from 31 to 79 years (mean age 61.4 +/- 9.8 years). The elderly group consisted of 60 patients (mean age 73.5 +/- 3.0 years) and the control group was 207 patients less than 70 years (mean age 57.9 +/- 8.2 years). Successful coronary dilatation was defined as > 20% reduction of stenosis with residual stenosis < 50%. Body mass index, presence of hypertension or diabetes mellitus and the ratio of smokers were not significantly different between the two groups. The elderly group included more women and patients with hyperlipidemia. Both groups had similar baseline extent of coronary artery disease, distribution of coronary artery stenosis type and left ventricular ejection fraction. The initial success rate for all patients was 93.4%. There was no significant difference in the initial success rate between the elderly and control groups (98.8% and 91.9%, respectively). There was no significant difference in major complication rate between the two groups (6.3% and 11.5%). Multivariate logistic regression analysis showed that only the type of coronary artery stenosis was significantly associated with initial success rate (p < 0.01). These results suggest that coronary intervention can be successfully performed with a low incidence of major complication in elderly patients.

Adult↗
PubMed1995

The small GTP-binding proteins Rac1 and Cdc42 regulate the activity of the JNK/SAPK signaling pathway.

c-Jun amino-terminal kinases (JNKs) and mitogen-activated protein kinases (MAPKs) are closely related; however, they are independently regulated by a variety of environmental stimuli. Although molecules linking growth factor receptors to MAPKs have been recently identified, little is known about pathways controlling JNK activation. Here, we show that in COS-7 cells, activated Ras effectively stimulates MAPK but poorly induces JNK activity. In contrast, mutationally activated Rac1 and Cdc42 GTPases potently activate JNK without affecting MAPK, and oncogenic guanine nucleotide exchange factors for these Rho-like proteins selectively stimulate JNK activity. Furthermore, expression of inhibitory molecules for Rho-related GTPases and dominant negative mutants of Rac1 and Cdc42 block JNK activation by oncogenic exchange factors or after induction by inflammatory cytokines and growth factors. Taken together, these findings strongly support a critical role for Rac1 and Cdc42 in controlling the JNK signaling pathway.

Animals↗
PubMed1995

Polymerase chain reaction fiber analysis and somatic mosaicism in autopsied tissue from a man with Duchenne muscular dystrophy.

Single muscle fibers, obtained at autopsy from a 22-year-old man with Duchenne muscular dystrophy were examined immunocytochemically and also using polymerase chain reaction (PCR). Dystrophin-positive cells were widespread in skeletal, cardiac, smooth muscle, and in brain cells. PCR and Southern blot analyses of DNA from peripheral blood lymphocytes revealed a deletion of exon 45 in the dystrophin gene. With PCR of single fibers, three bands corresponding to exons 44, 45, and 47 were present in the normal control muscle fibers and dystrophin-positive fibers from the patient, while only two bands, exons 44 and 47, were observed in dystrophin-negative fibers. Therefore, in this patient, the genotype of dystrophin-positive fibers differed from that of the dystrophin-negative fibers, possibly because of a somatic mosaicism for deletion in the dystrophin gene. A mutation of the dystrophin gene may have occurred in one cell at an early stage of ontogenesis.

Adult↗
PubMed1995

PCR and immunocytochemical analyses of dystrophin-positive fibers in Duchenne muscular dystrophy.

Immunocytochemical studies on serial sections of muscles from 19 patients with Duchenne muscular dystrophy (DMD) were done using seven kinds of antidystrophin antibodies that span dystrophin. Fifteen of the patients were screened for intragenic deletions by the multiplex polymerase chain reaction (PCR); 7 were also tested, using Southern blots. Dystrophin-positive fibers were detected in 10 of the 19 patients, occurring with a frequency of 0.06-75.7%, as clusters or as single fibers in certain muscle bundles. In 7 of the 10 patients, the fibers stained with all antibodies from the N- through the C-terminal region. However, in one patient, there were dystrophin-positive fibers that stained with an N-terminal antibody (DYS-3) and an antibody specific to the rod region (DYS-1), but not with C-terminal antibody (DYS-2). In 2 patients, there were two kinds of fibers: one that did not stain with DYS-1 or DYS-2 and another that stained with all the antibodies used. Single-fiber PCR analysis in 2 patients showed that the genotype of dystrophin-positive fibers differed from that of dystrophin-negative fibers. These results suggest that the majority of dystrophin-positive fibers are of the same clonal origin, but that some are derived from plural reverse mutations, each with a different translation-frame-repairing modality and somatic mosaicism.

Adolescent↗
PubMed1995

Integrin function: molecular hierarchies of cytoskeletal and signaling molecules.

Integrin receptors play important roles in organizing the actin-containing cytoskeleton and in signal transduction from the extracellular matrix. The initial steps in integrin function can be analyzed experimentally using beads coated with ligands or anti-integrin antibodies to trigger rapid focal transmembrane responses. A hierarchy of transmembrane actions was identified in this study. Simple integrin aggregation triggered localized transmembrane accumulation of 20 signal transduction molecules, including RhoA, Rac1, Ras, Raf, MEK, ERK, and JNK. In contrast, out of eight cytoskeletal molecules tested, only tensin coaccumulated. Integrin aggregation alone was also sufficient to induce rapid activation of the JNK pathway, with kinetics of activation different from those of ERK. The tyrosine kinase inhibitors herbimycin A or genistein blocked both the accumulation of 19 out of 20 signal transduction molecules and JNK- and ERK-mediated signaling. Cytochalasin D had identical effects, whereas three other tyrosine kinase inhibitors did not. The sole exception among signaling molecules was the kinase pp125FAK which continued to coaggregate with alpha 5 beta 1 integrins even in the presence of these inhibitors. Tyrosine kinase inhibition also failed to block the ability of ligand occupancy plus integrin aggregation to trigger transmembrane accumulation of the three cytoskeletal molecules talin, alpha-actinin, and vinculin; these molecules accumulated even in the presence of cytochalasin D. However, it was necessary to fulfill all four conditions, i.e., integrin aggregation, integrin occupancy, tyrosine kinase activity, and actin cytoskeletal integrity, to achieve integrin-mediated focal accumulation of other cytoskeletal molecules including F-actin and paxillin. Integrins therefore mediate a transmembrane hierarchy of molecular responses.

Cell Adhesion↗