Development of an immunoradiometric assay kit for ventricular myosin light chain I with monoclonal antibodies.
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Antibodies, Monoclonal↗
Biomedical subjects
Y Yazaki
Publications and source records attributed to Y Yazaki.
The role of N-glycosylation of GLUT1 for glucose transport activity.
To elucidate a functional role of N-glycosylation in glucose transporters, we introduced oligonucleotide-directed mutagenesis in GLUT1 cDNA to remove the possible site for N-linked glycosylation. The wild-type and the mutated GLUT1 cDNAs which induced a mutation of Asn at residue 45 to Asp, Tyr, or Gln were transfected and stably expressed into Chinese hamster ovary cells. The expressed wild-type and the mutated GLUT1 was demonstrated to be a broad band of a 45-60-kDa form and a sharp band of a 38-kDa form on Western blot analysis, respectively, indicating no glycosylation in the mutated GLUT1. Although the cell surface labeling of the glucose transporters demonstrated the presence of the glycosylation-defective glucose transporters on the cells surface, photoaffinity labeling of glycosylation-defective GLUT1 with [3H] cytochalasin B and a photoreactive mannose derivative, [3H]2-N-4-(1-azi-2,2,2,trifluoroethyl)benzoyl-1,3-bis(D-mannos+ ++-4-yloxy)-2- propylamine in the membranes was observed to be 40-70 and 15-30% of that of the wild-type GLUT1, respectively. The kinetic study of 2-deoxyglucose uptake revealed that the glycosylation-defective GLUT1 had a 2-2.5-fold greater Km value for 2-deoxyglucose uptake compared with the wild-type GLUT1. These observations strongly suggest that 1) N-glycosylation of GLUT1 glucose transporter is only on Asn 45 and 2) N-glycosylation plays an important role in maintaining a structure of glucose transporter with high affinity for glucose, thus, with high transport activity.
Affinity Labels↗
Occurrence of multiple aberrantly spliced mRNAs upon a donor splice site mutation that causes familial lipoprotein lipase deficiency.
A donor splice site mutation was found in the lipoprotein lipase (LPL) gene of a patient with familial LPL deficiency. The mutation, a G----A substitution, occurred at the first nucleotide of intron 2. Northern blot analysis of total RNA from the patient showed strikingly low levels of LPL-specific mRNAs. Using the polymerase chain reaction, the LPL mRNA splicing was analyzed in detail. The results demonstrated that no normal splicing occurred at the authentic splice site; rather a cryptic splice site 18 bases upstream from the mutation site was preferentially utilized. Although the resulting alteration in mRNA was a minute in-frame 18-base deletion, the amount of the abnormal transcript was only 1/12 that of the normal. In addition to this major cryptic splice site, we also identified multiple minor sites which were utilized at extremely lower efficiencies. Unexpectedly, one of these minor sites was also used as an alternative splice site in the normal subject at a comparably low efficiency. The sequences of these minor cryptic sites possessed many of the characteristics common to those of other normal splice sites, indicating that even such minor sites should have also been selected according to the general rules for splice site selection. These results demonstrate that upon mutation, a broad spectrum of cryptic splice sites is activated in vivo at the sites' respective efficiencies.
Adult↗
The effect of apo E secretion on lipoprotein uptake in transfected cells.
To investigate the role of apolipoprotein E (apo E) secreted by peripheral tissues in local lipoprotein metabolism, we developed a cell strain that constitutively produced and secreted apo E. A fusion plasmid containing rat apo E genomic DNA under control of mouse metallothionein promotor was constructed and transfected into Chinese hamster ovary cells. A stable transformant designated CHO-MAEII constitutively secreted rat apo E mainly in the form of sialylated free protein. The secretion was further enhanced by metal induction up to 1 micrograms apo E/ml per 12 h. When incubated with 125I-labeled very low density lipoprotein (125I-VLDL) at 37 degrees C, CHO-MAEII took up and degraded 125I-VLDL with higher affinity than control cells. Furthermore, considerable amount of methylated 125I-VLDL was degraded by CHO-MAEII, while no methylated 125I-VLDL was degraded by control cells. No significant differences were found in the uptake of 125I-LDL. The data indicated that apo E molecules secreted by CHO-MAEII were transferred to 125-VLDL particles, which caused a higher affinity of these particles for LDL receptors on the cells. It is suggested that apo E secreted from peripheral tissues enhances the uptake of lipoproteins by themselves or by surrounding cells in the local environment which demand cholesterol and express LDL receptors. CHO-MAEII was a good model for these 'auto- or paracrine-like functions' of apo E.
Animals↗
Substitution of arginine for histidine at position 209 in the alpha-subunit of the human insulin receptor. A mutation that impairs receptor dimerization and transport of receptors to the cell surface.
Receptors for insulin and epidermal growth factor contain cysteine-rich domains in the extracellular portion of the molecule. His209 (insulin receptor numbering system) is 1 of 2 amino acid residues that are identically conserved in the cysteine-rich domains of insulin receptors, epidermal growth factor receptors, and other homologous receptors. Previously, we have identified a patient with leprechaunism who is homozygous for a mutation substituting Arg for His209 in the insulin receptor gene (Kadowaki, T., Kadowaki, H., Rechler, M. M., Serrano-Rios, M., Roth, J., Gorden, P., and Taylor, S. I. (1990) J. Clin. Invest. 86, 254-264). In this investigation, the Arg209 mutant receptor was expressed by transfection of mutant cDNA into NIH-3T3 cells. The mutation impairs several steps in the post-translational processing of the insulin receptor:dimerization of 190-kDa proreceptors into a disulfide linked species, proteolytic cleavage of the proreceptor into alpha- and beta-subunits, and terminal processing of the high mannose form of N-linked oligosaccharide into complex carbohydrate. In addition, the defects in post-translational processing within the endoplasmic reticulum and Golgi apparatus are associated with a marked inhibition in transport of receptors to the plasma membrane. Nevertheless, a small number (approximately 10%) of the receptors are transported to the cell surface. These receptors on the cell surface bind insulin with normal affinity and have normal tyrosine kinase activity.
3T3 Cells↗
Establishment and erythroid differentiation of a cytokine-dependent human leukemic cell line F-36: a parental line requiring granulocyte-macrophage colony-stimulating factor or interleukin-3, and a subline requiring erythropoietin.
We have established a new nonlymphoid leukemic cell ine from a patient with myelodysplastic syndrome (MDS), which progressed to overt leukemia. The parental cell line and a subline derived from this line have absolute dependency on several cytokines for their long-term survival and growth. The parental line designated F-36P requires granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) for continuous growth, while a subline designated F-36E can be maintained in the presence of erythropoietin (Epo) alone. When these cytokines are depleted, both the parental and the subline cells die within several days, even in medium supplemented with fetal calf serum (FCS). F-36E, maintained in the presence of Epo, constitutively synthesizes hemoglobin at a significant level. F-36P, which is usually maintained in the presence of GM-CSF or IL-3, can be induced to synthesize hemoglobin when GM-CSF or IL-3 is substituted by Epo. The surface marker profile shows that the F-36P cells are positive for the leukocyte common antigen (CD45) and some common multilineage markers such as CD13, CD33, and CD34, and negative for T- and B-cell antigens and mature myelomonocytic antigens. However, some monoclonal antibodies recognizing erythroid and platelet glycoproteins react with these cells. Thus, this cell line has a multilineage phenotype, suggesting that the transformation event occurred in a multipotent stem cell. It is also evident that the F-36 cells can be induced to differentiate into the erythroid lineage in the presence of Epo. This, to our knowledge, is the first description of a human leukemic cell line that can be stimulated to synthesize hemoglobin by Epo.
Antigens, Surface↗
Differential phenotypic expression by three mutant alleles in familial lecithin:cholesterol acyltransferase deficiency.
Familial deficiency of lecithin:cholesterol acyltransferase (LCAT) is an autosomal recessive disorder characterised by abnormalities of all plasma lipoprotein classes and by abnormal deposition of unesterified cholesterol in tissues. To elucidate the molecular basis of the disease, the LCAT genes of three unrelated Japanese patients were amplified by means of the polymerase chain reaction. Direct sequencing of the amplified fragments covering all exons and junctions showed that the patients are homozygotes for separate gene mutations. In one patient a 3 bp insertion, which should cause a substantial change in the enzyme structure, was found in exon 4; he had near absence of LCAT mass and activity. Two separate missense mutations were identified in exon 6 of the other two patients, who produced functionally defective enzymes that differed widely in specific activity. The replacement of asparagine228 with positively charged lysine completely abolished enzyme activity, whereas the other, conservative, aminoacid substitution (methionine293----isoleucine) gave rise to a partially defective enzyme. These results show that distinct mutations cause differences in plasma LCAT activity and LCAT mass, ultimately leading to differential phenotypic expression of familial LCAT deficiency.
Adult↗
Hepatic and renal expression of rat apolipoprotein E under control of the metallothionein promoter in transgenic mice.
We created three lines of transgenic mice with an integrated rat genomic apolipoprotein E gene fused with the mouse metallothionein I promoter. These lines transcribed rat apoE mRNA in the liver and/or in the kidney and expressed significant amounts of rat apoE in plasma. Enhancement of the plasma level by treatment with Zn ion or Bi ion was observed.
Animals↗
Expression of the GLUT1 glucose transporter increases thymidine uptake in Chinese hamster ovary cells at low glucose concentrations.
An increase in expression of the GLUT1 glucose transporter gene has been observed to be associated with an increase in glucose transport activity upon oncogenic transformation of the cells. Increased expression of this glucose transporter isoform has been also observed in fetal tissues. To investigate the consequences of this phenomenon on cellular metabolism and cell growth, an expression vector containing the GLUT1 glucose transporter complementary DNA was transfected into Chinese hamster ovary cells. Overexpression of this glucose transporter isoform resulted in an increase in not only glucose uptake and utilization but also thymidine uptake when cells were exposed to glucose-deficient conditions. This increase in glucose metabolism and DNA synthesis may play an important role on the growth and/or survival of cancer cells and fetal tissues.
3-O-Methylglucose↗
Polymorphism in exon 4a of the human GLUT4/ muscle-fat facilitative glucose transporter gene detected by SSCP.
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Base Sequence↗
The glucose transport activity of GLUT1 is markedly decreased by substitution of a single amino acid with a different charge at residue 415.
GLUT1 glucose transporter cDNA was modified to introduce a single amino acid substitution of aspartic acid for asparagine 415, which is conserved among all facilitative glucose transporter isoforms. Although a significant amount of the mutated transporter was expressed into plasma membranes of Chinese hamster ovary cells by transfection with expression vector, almost no increase in glucose transport activity was observed. Analysis of glucose uptake with Lineweaver-Burk plot depicts that the mutation induced a marked decrease (more than 5-fold) in turnover number and a slight increase (1.5-fold) in Km compared with the wild-type GLUT1. Results obtained with cytochalasin B and ethylidene glucose suggested that the inner but not outer glucose binding site was modulated. These results suggest that asparagine 415 is located close to the inner glucose binding site and the putative inner gate of GLUT1 glucose transporter and that an ionic charge in this domain might play an important role in the rate of conformational change between an inward-facing form and an outward-facing form of glucose transporter.
Animals↗
cDNA cloning of a myosin heavy chain isoform in embryonic smooth muscle and its expression during vascular development and in arteriosclerosis.
Adult rabbit smooth muscles contain two types of myosin heavy chain (MHC) isoforms, SM1 and SM2 which are generated through alternative RNA splicing from a single gene (Nagai, R., Kuro-o, M., Babij, P. & Periasamy, M. (1989) J. Biol. Chem. 264, 9734-9737). We previously reported that the expression of SM1 and SM2 during vascular development is differentially regulated at the level of RNA splicing, whereby SM1 is constitutively expressed from early development but SM2 appear after birth (Kuro-o, M., Nagai, R., Tsuchimochi, H., Katoh, H., Yazaki, Y., Ohkubo, A. & Takaku, F. (1989) J. Biol. Chem. 264, 18272-18275). We also demonstrated that embryonic vascular smooth muscles contain a third type of MHC isoform, referred to as SMemb in this report, which comigrates on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with SM2. In the present study we have isolated and characterized a cDNA clone (FSMHC34) for SMemb. FSMHC34 encodes the light meromyosin region including the carboxyl terminus and showed 70% amino acid sequence identity with SM1 or SM2. SMemb is a nonmuscle-type MHC and identical with brain MHC, but clearly distinct from 196-kDa nonmuscle MHC in cultured smooth muscle cells. The expression of SMemb was predominant in embryonic and perinatal aortas, but down-regulated with vascular development. Interestingly SMemb was reexpressed in proliferating smooth muscle cells of arteriosclerotic neointimas. These results suggest that smooth muscle proliferation is coupled to the expression of SMemb and that dedifferentiation of smooth muscles toward the embryonic phenotype is involved in the mechanisms underlying atherosclerosis.
Aging↗
Mechanical loading stimulates cell hypertrophy and specific gene expression in cultured rat cardiac myocytes. Possible role of protein kinase C activation.
To examine the molecular mechanisms by which mechanical stimuli induce cardiac hypertrophy and specific gene expression, we cultured rat neonatal cardiocytes in deformable dishes and imposed an in vitro mechanical load by stretching the adherent cells. Myocyte stretching increased total cell RNA content and mRNA levels of c-fos and skeletal alpha-actin. Nuclear run-off transcription assay revealed that this increase in c-fos mRNA level by stretching at least partially reflects changes in the transcriptional status. The transfected chloramphenicol acetyltransferase gene linked to upstream sequences of the fos gene indicated that sequences containing a serum response element were required for efficient transcription by stretching and that sequences containing a cAMP/calcium response element might not be involved in the c-fos response to myocyte stretching. The accumulation of c-fos mRNA by stretching was suppressed by protein kinase C inhibitors at the transcriptional level and inhibited markedly by down-regulation of protein kinase C. Moreover, myocyte stretching increased inositol phosphate levels, and activation of protein kinase C by phorbol esters stimulated the expression of c-fos and skeletal alpha-actin genes. These findings suggest that mechanical stimuli (myocyte stretching) might directly induce cardiac hypertrophy and specific gene expression possibly via protein kinase C activation.
Actins↗
Expression of perforin in infiltrating cells in murine hearts with acute myocarditis caused by coxsackievirus B3.
BACKGROUND: Cell-mediated autoimmunity has been strongly implicated in the pathogenesis of viral myocarditis. METHODS AND RESULTS: Using a murine model of acute myocarditis caused by coxsackievirus B3, we analyzed the phenotypes and morphology of the infiltrating cells in the hearts by immunofluorescence and electron microscopy. We also examined the expression of a cytolytic factor, perforin, in the infiltrating cells by immunoperoxidase and in situ hybridization. We found that the dominant population of the infiltrating cells were asialo GM1 positive, were negative for T-cell markers, and had electron-dense cytoplasmic granules, which is consistent with a morphology of large granular lymphocytes. Perforin was found in the cytoplasmic granules of the infiltrating cells expressing perforin messenger RNA. These findings provide for the first time the direct evidence that the first wave of cell infiltration in hearts mainly consists of killer cells and strongly suggests that perforin plays, in part, an important role in myocardial cell damage involved in acute viral myocarditis. T-helper cells and cytotoxic T lymphocytes made up the second wave of cell infiltration. CONCLUSIONS: As we previously reported, the expression of major histocompatibility complex class I antigen on cardiac myocytes induced by the infiltrating cells, such as killer cells, may facilitate the interaction between cardiac myocytes and cytotoxic T lymphocytes, and may lead to further myocardial cell damage in a later phase.
Acute Disease↗
Heterogeneous mutations in the human lipoprotein lipase gene in patients with familial lipoprotein lipase deficiency.
The DNA sequences were determined for the lipoprotein lipase (LPL) gene from five unrelated Japanese patients with familial LPL deficiency. The results demonstrated that all five patients are homozygotes for distinct point mutations dispersed throughout the LPL gene. Patient 1 has a G-to-A transition at the first nucleotide of intron 2, which abolishes normal splicing. Patient 2 has a nonsense mutation in exon 3 (Tyr61----Stop) and patient 3 in exon 8 (Trp382----Stop). The latter mutation emphasizes the importance of the carboxy-terminal portion of the enzyme in the expression of LPL activity. Missense mutations were identified in patient 4 (Asp204----Glu) and patient 5 (Arg243----His) in the strictly conserved amino acids. Expression study of both mutant genes in COS-1 cells produced inactive enzymes, establishing the functional significance of the two mis-sense mutations. In these patients, postheparin plasma LPL mass was either virtually absent (patients 1 and 2) or significantly decreased (patients 3-5). To detect these mutations more easily, we developed a rapid diagnostic test for each mutation. We also determined the DNA haplotypes for patients and confirmed the occurrence of multiple mutations on the chromosomes with an identical haplotype. These results demonstrate that familial LPL deficiency is a heterogeneous genetic disease caused by a wide variety of gene mutations.
Adolescent↗
Mechanisms of cardiac hypertrophy and injury--possible role of protein kinase C activation.
To examine the molecular mechanisms by which mechanical stimuli induced cardiac hypertrophy and injury, we cultured rat neonatal cardiocytes in deformable dishes and imposed an in vitro mechanical load by stretching the adherent cells. Myocyte stretching increased total cell RNA content and mRNA levels of c-fos. Marked accumulation of c-fos mRNA followed increases in intracellular Na+ and protein kinase C activation. The accumulation of c-fos mRNA by cardiocyte stretching was suppressed by protein kinase C inhibitors but not by stretch channel blockers. Moreover, myocyte stretching increased inositol phosphate levels, and activation of protein kinase C by phorbolesters stumulated the expression of c-fos. We also examined TGF beta expression in the heart. TGF beta is known to be stimulated by protein kinase C activation, and the mRNA level of TGF beta was increased in in vivo heart by pressure overload. Furthermore, collagen synthesis was stimulated by TGF beta in cultured fibroblasts from hearts. These findings suggest that hemodynamic overload may stimulate cardiac hypertrophy and induce cardiac injury (fibrosis) through protein kinase C activation.
Animals↗
[Aortic pulse wave velocity in patients with coronary atherosclerosis--a comparison with coronary angiographic findings].
This study was conducted to investigate the relationship between aortic pulse wave velocity (PWV) and coronary atherosclerosis. We measured PWV in 105 subjects (84 males and 21 females; age 59 +/- 0.5) who received coronary angiographic examination (CAG). PWV was measured by simultaneous recording of pulse waves from the left carotid and the left femoral arteries, electrocardiogram and phonocardiogram. The subjects were classified into 4 groups according to the number of major coronary arteries having stenosis, that is, N group with normal CAG, 1 vessel disease (VD) group, 2VD group and 3VD group. The PWV value was significantly greater only in 3VD group (n = 10, age 63 +/- 3.6, PWV 10.0 +/- 0.88 m/sec) than that in N group (n = 18, age 53 +/- 2.0, PWV 8.0 +/- 0.34 m/sec). No significant difference was observed between PWV value in N group and that in all patients with coronary artery stenosis (n = 87, age 60 +/- 2.0, PWV 8.9 +/- 0.2 m/sec). To further investigate the relationship between PWV values and CAG findings, we used a CAG score which means the sum of the points assigned to each coronary artery segment (American Heart Association) according to the severity of stenosis (0, 1, 2, 3, and 4 for normal, less than 49% stenosis, 50 to 74% stenosis, 75 to 99% stenosis, and complete occlusion, respectively). The PWV values significantly correlated with the CAG score and also with age by a simple regression analysis. Multivariate analysis, however, revealed that PWV values did no longer correlate with CAG score. PWV values still significantly correlated with age.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
[A case of hepatic infarction complicating disseminating intravascular coagulation].
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Carcinoma, Hepatocellular↗