Endothelin-1-like immunoreactivity and endothelin receptors in the human placenta from normotensive and hypertensive pregnancies

The levels of endothelin-1-like immunoreactivity (ET-1-LI) and characteristics of endothelin receptors in the chorionic villous tissue of human placenta were determined. The ET-1-LI level in chorionic villous tissue obtained from normal term placenta was 2,450 +/- 940 pg/g wet weight (mean +/- SD, n = 4). Further analysis using gel permeation chromatography and reverse-phase high performance liquid chromatography showed that the main ET-1-LI constituent of ET-1-LI in this tissue was ET-1. Scatchard analysis of [125I]ET-1 binding to the membrane fraction of chorionic villous tissue obtained from term placenta showed high affinity receptor sites with an apparent dissociation constant (Kd) of 23.6 +/- 11.1 pM and a Bmax value of 388 +/- 238 fmol/mg protein (n = 5). The same binding study with [125I]ET 3 showed a Kd of 13.9 +/- 3.8 pM and a Bmax value of 176 +/- 78 fmol/mg protein (n = 5). These results suggest that both ET-A and ET-B receptors (ET-AR and ET-BR) are expressed in chorionic villous tissue. This finding was further confirmed by Northern blot analysis showing the expression of both ET-AR and ET-BR mRNAs in this tissue. ET-1-LI in the umbilical venous plasma of the newborns from women with pregnancy-induced hypertension (PIH) (38.3 +/- 10.4 pg/mL, n = 5) was significantly (P < 0.05) higher than that in the normal newborns from normotensive pregnant women (26.3 +/- 5.2 pg/mL, n = 12). However, in placental chorionic villous tissue obtained from PIH women, both ET-1-LI level and ET binding profile were not different from those in chorionic villous tissue from normotensive pregnant women. These results suggest that the abundant ET-ET receptor system is present in the placental chorionic villous tissue and that this system is not the major factor of the pathogenesis of placental dysfunction occurring in PIH because these systems are similar in normotensive and hypertensive pregnancies.

Amyloid beta protein deposition in normal aging has the same characteristics as that in Alzheimer's disease. Predominance of A beta 42(43) and association of A beta 40 with cored plaques

Two distinct species of amyloid beta protein (A beta) with different C-termini, A beta 42(43) and A beta 40, are deposited in senile plaques (SP) of Alzheimer's disease (AD), with the former being far predominant. To investigate whether A beta 42(43) also predominates over A beta 40 in normal aging, we examined by immunocytochemistry the C-termini of A beta in SP in the brains of non-demented aged individuals and compared the results with those in AD. Virtually all SP were A beta 42(43)-positive; of these 12% in non-demented aged individuals and 25% in AD patients (mean of three areas examined) were also A beta 40-positive. In both the AD and non-demented groups, 2/3 of the A beta 40-positive SP were typical cored SP. These results indicate that A beta 42(43) is the predominant species deposited in SP in normal aging, and there is no qualitative difference in terms of the C-terminus of A beta in the parenchymal amyloid deposition between normal aging and AD.

Effects of dibutyryl cAMP and bromodeoxyuridine on expression of N-acetylglucosaminyltransferases III and V in GOTO neuroblastoma cells

The sugar chain structures of the cell surface change dramatically during cellular differentiation. A human neuroblastoma cell line, GOTO, is known to differentiate into neuronal cells and Schwannian cell-like cells on treatments with dibutyryl cAMP and bromodeoxyuridine, respectively. We have examined the expression of UDP-N-acetylglucosamine: beta-D-mannoside beta-1,4N-acetylglucosaminyltransferase III (GnT-III: EC 2.4.1.144) and UDP-N-acetylglucosamine: alpha-6-D-mannoside beta-1,6N-acetylglucosaminyltransferase V (GnT-V: EC 2.4.1.155), two major branch forming enzymes in N-glycan synthesis, in GOTO cells on two distinct directions of differentiation. In neuronal cell differentiation, GnT-III activity showed a slight increase during initial treatment with Bt2cAMP for 4 days and decreased drastically after the fourth day, but the mRNA level of GnT-III did not show a decrease but in fact a slight increase. GnT-V activity increased to approximately two- to three-fold the initial level with increasing mRNA level after 8 days, and lectin blot analysis showed an increase in reactivity to Datsura stramonium (DSA) of the immunoprecipitated neural cell adhesion molecule (NCAM). In Schwannian cell differentiation, the activity and mRNA level of GnT-III showed no significant change on treatment with BrdU. GnT-V activity also showed no change in spite of the gradual increase in the mRNA level. These results suggest that the activation of GnT-V during neuronal cell differentiation of GOTO cells might be a specific change for branch formation in N-glycans, and this affects the sugar chain structures of some glycoproteins such as NCAM.

Superoxide dismutase and free radicals in sporadic amyotrophic lateral sclerosis: relationship to clinical data

We studied the relationships between the superoxide dismutase (SOD) activity, free radical (FR) levels and clinical data in patients with sporadic amyotrophic lateral sclerosis (SALS). The SOD activities and blood FR levels of 16 patients with SALS (mean age 58.6 +/- 10.2 years), 11 with other neurological disease, including myotonic dystrophy (ND, mean age 53.5 +/- 9.1 years), and 15 normal control subjects (mean age 56.2 +/- 7.3 years) were measured. The mean levels of FR in blood from the patients with SALS and ND and the SOD activities in red blood cells (RBC) from those with ND were significantly higher than the corresponding control values. There was a positive correlation between the SOD activities in RBC and blood hydroxyl radical levels in the patients with ND, but neither the patients with SALS nor the controls showed such a correlation. The SALS patients without pyramidal signs showed slow disease progression and their mean RBC SOD activity was significantly higher than the corresponding control value. We compared the FR levels and SOD activities of 8 patients who needed a respirator within 40 months after the onset of SALS (SALS40, mean age 58.7 +/- 9.4 years), 3 who needed a respirator over 100 months after the onset of SALS (SALS100, mean age 58.3 +/- 15.9 years) and the controls. The mean blood FR levels of the SALS40 and SALS100 patients were significantly higher than the corresponding control values. The mean SOD activity in RBC from the SALS100 group was significantly higher than the SALS40 and control group values. Therefore, we concluded that elevated blood FR levels do not induce RBC SOD in SALS patients and that the disease progressed more rapidly in SALS patients with low than high RBS SOD activities.

Gene expression of N-acetylglucosaminyltransferases III and V: a possible implication for liver regeneration

N-acetylglucosaminyltransferases III and V (GnT-III and -V) are key enzymes in the synthesis of the branches of asparagine-linked oligosaccharides. Although their messenger RNAs (mRNAs) are expressed in various rat tissues, they are not detected in normal rat liver. Expression of the GnT-III and -V mRNAs, however, increased in regenerating liver after two-thirds partial hepatectomy compared with sham-operated rats. The enzymatic activities of GnT-III and -V increased in proportion to mRNA expression. To determine which type of cells in the liver have high activities of these glycosyltransferases, hepatocytes and nonparenchymal cells were separated by means of a two-step collagenase perfusion technique. GnT-III activity was only detected in nonparenchymal cells of normal rat liver. However, during liver regeneration, GnT-III activity increased and thus was also detectable in hepatocytes. GnT-V activity was detected in both types of cells. These data were supported by reverse transcription-polymerase chain reaction results. Although the mechanism underlying the induction of these glycosyltransferases is unknown, lectin blot analysis showed that oligosaccharides in many glycoproteins, including hepatocyte growth factor, a major growth factor associated with liver regeneration, were newly synthesized during liver regeneration. This is the first report on the expression of glycosyltransferases during liver regeneration and suggests that there are different mechanisms involved in regulation of the genes of GnT-III and -V during liver regeneration.

Dephosphorylation of fetal-tau and paired helical filaments-tau by protein phosphatases 1 and 2A and calcineurin

We have reported that many sites of tau in fetal brain (fetal-tau) as well as in paired helical filaments (PHF-tau) are phosphorylated. In the present study, we used site-specific antibodies and peptide mapping to examine protein phosphatases involved in dephosphorylation of fetal-tau and PHF-tau. Immunoblot analysis and electrophoretic mobility showed that protein phosphatases 1 and 2A and calcineurin could dephosphorylate fetal-tau and PHF-tau. Phosphoserines 199, 202, 396, and 413 and phosphothreonine 231, numbered according to the longest human tau isoform, were dephosphorylated, as shown by the immunoblot analysis. Phosphoserine 422 was dephosphorylated by protein phosphatase 2A and calcineurin, but not by protein phosphatase 1. Peptide mapping with Achromobacter lyticus protease 1 showed that phosphoserines 199, 202, 235, and 396 and phosphothreonine 231 were dephosphorylated by protein phosphatases. Fetal-tau was more rapidly dephosphorylated by protein phosphatase 2A and calcineurin than PHF-tau. Interestingly, PHF-tau which had not been solubilized with guanidine HCl was little dephosphorylated by protein phosphatases. Thus, PHF-tau in neurofibrillary tangles of Alzheimer's disease brain is likely to be resistant to dephosphorylation by protein phosphatases.

Recent progress in the molecular biology of the cloned N-acetylglucosaminyltransferases

Several genes which code for the N-acetylglucosaminyltransferases have been cloned and characterized. Physiological and pathophysiological roles of the genes still remain to be elucidated but accumulated evidence suggests that the N-acetylglucosaminyltransferase genes are implicated in differentiation, morphogenesis and cancer metastasis.

Transfection of N-acetylglucosaminyltransferase III gene suppresses expression of hepatitis B virus in a human hepatoma cell line, HB611

beta-D-mannoside beta-1,4-N-acetylglucosaminyltransferase III (GnT-III) catalyzes the addition of N-acetylglucosamine in beta 1-4 linkage to the beta-linked mannose of the trimannosyl core of N-linked oligosaccharides and forms a bisecting GlcNAc structure. Although the biological meaning of the bisecting GlcNAc structure remains unclear, it is known that the attachment of a bisecting GlcNAc inhibits further processing of oligosaccharides by other glycosyltransferases. To investigate whether or not structural changes of oligosaccharides affect secretion and gene expression of hepatitis B virus (HBV), we introduced the GnT-III gene into a human hepatoma cell line, HB611, which secreted HBV-related proteins into the medium. Positive transfectants were cloned by hygromycin resistant selection. Three clones have high activities of GnT-III and secreted lower levels of HBV-related proteins into the medium in comparison with other clones. These clones showed marked suppression of HBV-related mRNAs and an increased binding with E-PHA as judged by lectin blot. Expression of beta actin, alpha fetoprotein, albumin, and prealubmin was not correlated with GnT-III activity in all the seven clones. Treatment of these cells with tunicamycin or swainsonine resulted in enhanced expression of HBV-related mRNA. These results indicate that some glycoproteins whose oligosaccharide structures are changed by over-expression of GnT-III suppress HBV gene expression.

Cerebrospinal fluid corticotropin-releasing hormone in neurodegenerative diseases: reduction in spinocerebellar degeneration

Levels of corticotropin-releasing hormone (CRH) in cerebrospinal fluid (CSF) were examined in patients with spinocerebellar degeneration (SCD) including olivopontocerebellar atrophy (OPCA), dentatorubropallidoluysian atrophy (DRPLA) and Friedreich's ataxia, Parkinson's disease (PD) and senile dementia of the Alzheimer type (SDAT), and normal aged subjects. CRH concentrations in CSF were significantly reduced in SCD compared to SDAT, PD and CSF and normal aged subjects. It is likely that degeneration not only of the cerebral cortex and the limbic system but also of the subcortical structures such as the brainstem and the cerebellum alters levels of CRH in CSF. Together with the recent anatomical and physiological evidence, the results suggest pathophysiological relevance of CRH for the cerebellar symptoms in SCD.

Tau protein immunoreactivity in muscle fibers with rimmed vacuoles differs from that in regenerating muscle fibers

To determine whether tau protein found in muscle fibers with rimmed vacuoles and in regenerating fibers was phosphorylated, we examined eight muscle biopsy samples containing rimmed vacuoles (from five patients with distal myopathy with rimmed vacuole formation and three patients with inclusion body myositis) and three muscle biopsy samples from patients with Duchenne muscular dystrophy containing numerous regenerating fibers. Although both rimmed vacuolated and regenerating fibers had increased immunoreactivity against tubulin and tau protein, tau protein in the former was more highly phosphorylated than that in the latter. While very few microtubules in muscle fibers with rimmed vacuoles were recognizable by electron microscopy, regenerating fibers, especially immature ones, contained numerous microtubules. Since tau protein found in vacuolated fibers is hyperphosphorylated, it can be considered to have reduced ability to bind tubulin molecules. Thus, the tau protein cannot stabilize microtubules, resulting in their depolymerization even in the presence of tubulin molecules.

Microglial cells and amyloid beta protein (A beta) deposition; association with A beta 40-containing plaques

Two distinct species of amyloid beta protein (A beta) with different carboxyl termini, A beta 40 and A beta 42(43), are deposited in plaques in the brains of patients with Alzheimer's disease and Down's syndrome. The relationship between these two forms of A beta and microglial cells was investigated in 16 subjects with Down's syndrome ranging in age from 31 to 64 years. The amount of A beta 40 in plaques was low in persons under 50 years of age, even though high amounts of A beta 42(43) were present. Microglia were observed most commonly in plaques containing both A beta 40 and A beta 42(43) but less commonly in those with A beta 42(43) alone. The presence of microglial cells in plaques may be associated with the accumulation of A beta 40 and these cells may have a role in the production or processing of this particular molecular species.

Organization of the human N-acetylglucosaminyltransferase V gene

UDP-N-acetylglucosamine: alpha-6-D-mannoside beta-1,6-N-acetylglucosaminyltransferase V (GlcNAc transferase V), which catalyzes the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to alpha-6-D-mannoside, is an important enzyme regulating the branch formation in complex-type, N-linked oligosaccharides. It has been reported that the enzymic activity of GlcNAc transferase V increases after viral transformation and the enzymic product is closely related to the metastasis of tumors. We previously reported the purification, cDNA cloning and chromosomal mapping of human GlcNAc transferase V. In this study, we describe the isolation of genomic clones encoding human GlcNAc transferase V and the structure of the gene. The human GlcNAc transferase V gene is divided into 17 exons, and the open reading frame is encoded by exons 2-17, spanning 155 kb. Analysis of the 5'-untranslated regions of mRNAs from various cells showed multiple sequences depending on the cell types. The promoter region of the GlcNAc transferase V gene was characterized by searching for any consensus sequences matching those for transcription-factor binding. The consensus sequences for a TATA box, AP-1, AP-2, and some other transcription factors were found in the 5'-upstream region of exon 1, and consensus sequences for LF-A1, HNF1-HP1, liver-restricted transcription factors and other factors were also found in intron 1. Chloramphenicol acetyltransferase fusion plasmids with either the 5'-upstream region of exon 1 or intron 1 were constructed and transfected into COS-1 cells. Promoter activities of both DNA fragments were detected, indicating that transcription starts within this region. These data suggest that the human GlcNAc transferase V gene employs a multiple promoter system for its transcription, and gene expression may therefore be regulated in tissue-specific and cell-type-specific manners.

GM1 ganglioside-bound amyloid beta-protein (A beta): a possible form of preamyloid in Alzheimer's disease

The earliest event so far known that occurs in the brain affected with Alzheimer's disease (AD) is the deposition and fibril formation of amyloid beta-protein (A beta). A beta is cleaved from a glycosylated membrane protein, called beta-amyloid protein precursor, and normally secreted into the extracellular space. Here we report on the presence of membrane-bound A beta that tightly binds GM1 ganglioside. This suggests that this novel A beta species, rather than secreted A beta, may act as a 'seed' for amyloid and further that intracellular abnormalities in the membrane recycling already exist at the stage of amyloidogenesis.

Suppression of lung metastasis of B16 mouse melanoma by N-acetylglucosaminyltransferase III gene transfection

The beta 1-6 structure of N-linked oligosaccharides, formed by beta-1,6-N-acetylglucosaminyltransferase (GnT-V), is associated with metastatic potential. We established a highly metastatic subclone, B16-hm, from low metastatic B16-F1 murine melanoma cells. The gene encoding beta-1,4-N-acetylglucosaminyltransferase (GnT-III) was introduced into the B16-hm cells, and three clones that stably expressed high GnT-III activity were obtained. In these transfectants, the affinity to leukoagglutinating phytohemagglutinin was reduced, whereas the binding to erythroagglutinating phytohemagglutinin was increased, indicating that the level of beta 1-6 structure was decreased due to competition for substrate between intrinsic GnT-V and ectopically expressed GnT-III. Lung metastasis after intravenous injection of the transfectants into syngeneic and nude mice was significantly suppressed, suggesting that the decrease in beta 1-6 structure suppressed metastasis via a mechanism independent of the murine system. These transfectants also displayed decreased invasiveness into Matrigel and inhibited cell attachment to collagen and laminin. Cell growth was not affected. Our results demonstrate a causative role for beta 1-6 branches in invasion and cell attachment in the extravasation stage of metastasis.

Amyloid beta-proteins 1-40 and 1-42(43) in the soluble fraction of extra- and intracranial blood vessels

To investigate the process of amyloid beta-protein (A beta) accumulation in cerebral amyloid angiopathy (CAA), the levels of A beta were determined in the soluble fraction of extra- and intracranial blood vessels and leptomeninges obtained at autopsy. Two enzyme immunoassays were employed that are known to sensitively and specifically quantify two A beta species, A beta 1-40 and 1-42(43). A beta was detectable in the intracranial blood vessels and leptomeninges with the latter containing the highest levels, while it was undetectable in the extracranial blood vessels. Thus the levels of soluble A beta correlated well with the predilection sites for CAA. Among individuals aged 20 to 90, the A beta levels in the leptomeninges increased sharply in those aged 50 to 70 and thereafter tended to decline. However, only slight degrees of CAA were detected by immunocytochemistry, even when those leptomeninges contained high levels of A beta comparable with those in Alzheimer's disease. The level of A beta 1-42 was almost always severalfold that of A beta 1-40 in the soluble fraction of leptomeninges. This is in good agreement with the immunocytochemical result showing the presence of A beta 40-negative, A beta 42(43)-positive meningeal vessels. These results indicate that A beta 1-42 is the initially deposited species in CAA and that the disruption of A beta homeostasis precedes A beta deposition in the meningeal vessels.

The extent of amyloid deposition in brain in patients with Down's syndrome does not depend upon the apolipoprotein E genotype

The extent of deposition of amyloid beta protein (A beta) was investigated in 20 elderly patients with Down's syndrome, using the end-specific monoclonal antibodies BC05 and BA27 to detect the presence of A beta 42(43) and A beta 40 (respectively), and related to apolipoprotein E (ApoE) genotype. No significant differences in the amount of A beta deposited in the brain, either as A beta 42(43) or A beta 40, were noted in patients possessing an ApoE E4 allele, compared to those without. Patients with an ApoE E4 allele in general died at an earlier age than those with only ApoE E3 alleles, the latter in turn being outlived by those with an ApoE E2 allele. In Down's syndrome therefore, ApoE may influence the timing of onset, or the rate of progression, of disease but without affecting the type or total amount of pathology accumulated.

[Axonal Guillain-Barré syndrome associated with anti-GalNAc-GD1a antibody subsequent to Campylobacter jejuni (PEN 43) enteritis]

We reported a 16-year-old boy who had Guillain-Barré syndrome (GBS) after suffering diarrhea. Campylobacter jejuni was isolated from his stool, and the serotype belonged to PEN 43. Neurologic examination revealed distal-dominant muscle weakness atrophy, and mild sensory disturbance. Motor and sensory nerve conduction velocities were normal, but compound muscle action potentials were markedly reduced. Serum from the patient had high titers of anti-FalNAc-GD1a antibodies. He had HLA-A24, B51, DRB1*04 and DRB1*09. His elder sister showed diarrhea and serum anti-C. jejuni antibody, but did not showed GBS and serum anti-ganglioside antibody. Her HLA types were A24, B51, DRB1*09 and DRB1*14.

Changes of beta-1,4-N-acetylglucosaminyltransferase III (GnT-III) in patients with leukaemia

Changes in the activity and transcription of UDP-N-acetylglucosamine: beta-D-mannoside beta-1,4-N-acetylglucosaminyl-transferase III (GnT-III: EC 2.4.1.144) were investigated in haematological malignancies. GnT-III activity was elevated in patients with chronic myelogeneous leukaemia in blast crisis (CML-BC) and patients with multiple myeloma (MM); whereas most of the normal healthy subjects and patients with other haematological malignancies, including CML in its chronic phase, showed negligible activity. The GnT-III transcript of leukaemic cells from various haematological diseases showed a single band with a similar size. The ratio of GnT-III activity per normalized transcript in CML-BC was considerably higher than in the other conditions, which provided the possibility that in CML-BC the transcript or the enzyme protein might be more stable, or that a post-translational modification of the enzyme might enhance its activity. Furthermore, a lectin blot analysis of patient specimens and a lectin fluorescence study of CML cell lines revealed that E4-PHA binding to surface glycoproteins correlated with GnT-III activity, indicating that more bisecting GlcNAc was added to these glycoproteins, catalysed by elevated GnT-III in CML-BC.

The structures of the human calcium channel alpha 1 subunit (CACNL1A2) and beta subunit (CACNLB3) genes

Calcium influx in pancreatic beta-cells is regulated mainly by L-type voltage-dependent calcium channels (VDCCs) and triggers insulin secretion. The alpha 1 subunit (CACN4) and the beta subunit (beta 3) of VDCCs, both of which are expressed in pancreatic islets, are major components for the VDCC activity, and so they may play a critical role in the regulation of insulin secretion. We have determined the structures of the human CACN4 (CACNL1A2) and the human beta 3 (CACNLB3) genes. The CACNL1A2 gene spans more than 155 kb and has 49 exons. Most of the positions interrupted by introns are well conserved between the CACNL1A2 gene and the previously reported L-type VDCC alpha 1 subunit, CACNL1A1, gene. On the other hand, the CACNLB3 gene distributes in approximately 8 kb and comprises 13 exons, most of which are located together within approximately 5 kb. Comparisons of the genomic sequences of CACNL1A2 with the previously reported cDNA sequences indicate that there are a number of polymorphisms in the human CACNL1A2 gene. In addition, the PCR-SSCP procedure of exon 1 of CACNL1A2 revealed a change from 7 to 8 ATG trinucleotide repeats in a patient with non-insulin-dependent diabetes mellitus (NIDDM), resulting in an addition of methionine at the amino-terminus of CACN4. The determination of the structures of the human CACNL1A2 and CACNLB3 genes should facilitate study of the role of these genes in the development of NIDDM and also other genetic diseases such as long QT syndrome.

Hyperphosphorylation of tau in PHF

Tau in PHF is known to be highly phosphorylated and immunochemical study has indicated the similarity of the phosphorylation between PHF-tau and fetal tau. We have determined the exact phosphorylation sites in both PHF-tau and fetal rat tau by ion-spray mass spectrometry and sequencing of ethanethiol-modified peptides. In PHF-tau, 19 sites have been identified; all the phosphorylation sites except for Ser-262 are localized to the amino- and carboxyl-terminal flanking regions of the microtubule-binding domain. Half of them are shared by fetal tau. Thus, PHF-tau is much more phosphorylated. Whereas most of the sites in fetal tau are proline-directed, half of them in PHF-tau are nonproline-directed. Overall, the hyperphosphorylation of PHF-tau can be considered to consist of fetal-type phosphorylation and additional proline-directed and nonproline-directed phosphorylation. This extraphosphorylation may provide PHF-tau with the unusual characteristics including assembly incompetence.