Biomedical subjects

M Sauter

Publications and source records attributed to M Sauter.

At least 19 recordsLinked to original sources

PubMed2002

Up-regulation of the human serum and glucocorticoid-dependent kinase 1 in glomerulonephritis.

Glomerulonephritis is paralleled by excessive formation of transforming growth factor-beta (TGF-beta), which participates in the pathophysiology of the disease. Recently, a novel downstream target of TGF-beta has been identified, i.e. the human serum and glucocorticoid-dependent kinase 1 (hSGK1), a serine/threonine kinase participating in the regulation of Na(+) transport. The present study was performed to elucidate transcriptional regulation of hSGK1 in glomerulonephritis. To this end, in situ hybridization was performed in biopsies from patients with clinical diagnosis of glomerulonephritis. hSGK1 transcript levels were moderately enhanced in 5 out of 9 patients and strongly enhanced in 4 out of 9 patients. Distal nephron epithelial cell hSGK1 transcript levels were low or absent in 7 of the 9 patients but markedly enhanced in 2 of the 9 patients. In conclusion, glomerulonephritis leads to glomerular and in some cases to epithelial up-regulation of hSGK1 transcription.

Adult↗

PubMed2001

The Rev/Rex homolog HERV-K cORF multimerizes via a C-terminal domain.

Expression of human endogenous retrovirus K (HERV-K) is associated with germ-cell neoplasia. HERV-K encodes a protein of the Rev/Rex family, cORF, that supports cellular transformation and binds the promyelocytic leukemia zinc finger (PLZF) protein implicated in spermatogenesis. Rev/Rex function invariably depends on multimerization. Here we show that cORF likewise self-associates to form higher-order oligomers. Amino acids (aa) 47-87 in cORF are sufficient, aa 75-87 essential for self-association. Consistently, this domain is predicted to form a hydrophobic alpha-helix that may represent an oligomerization interface. The existence of a dimerization-competent cORF mutant lacking PLZF-binding activity (cORF47-87) suggests a way of dominant negative inhibition of the proposed tumor susceptibility factor cORF.

Dimerization↗

PubMed2001

Genomic organization of the human endogenous retrovirus HERV-K(HML-2.HOM) (ERVK6) on chromosome 7.

Recently, we reported an almost intact human endogenous retrovirus (HERV-K(HML-2.HOM); HGMW-approved symbol ERVK6) located on human chromosome 7, with open reading frames for all retroviral genes and a mutation only within the reverse transcriptase. We further characterized the genomic organization of this endogenous retrovirus by subcloning and sequencing of the proviral insert contained within a chromosome 7-specific cosmid clone and found HERV-K(HML-2.HOM) to be organized as a tandem repeat. Examination of various human DNA samples for this specific proviral repeat suggests a relatively ubiquitous distribution of the HERV-K(HML-2.HOM) tandem structure. However, we identified two human samples having only a single provirus at this locus. In addition, we investigated the presence of HERV-K(HML-2.HOM) alleles having an intact YXDD motif within the reverse transcriptase domain by sequencing the corresponding polymerase gene from various human DNA samples. We identified a HERV-K(HML-2.HOM) polymerase with an intact YXDD motif in two samples, thus potentially coding for an active reverse transcriptase. Our results show for the first time an endogenous retrovirus tandem repeat in human populations and suggest the existence of alleles harboring an intact human endogenous retrovirus including an intact polymerase gene.

Alleles↗

PubMed2001

HERV-K(OLD): ancestor sequences of the human endogenous retrovirus family HERV-K(HML-2).

Sequences homologous to the human endogenous retrovirus (HERV) family HERV-K(HML-2) are present in all Old World primate species. A previous study showed that a central region of the HERV-K(HML-2) gag genes in Hominoidea species displays a 96-bp deletion compared to the gag genes in lower Old World primates. The more ancient HERV-K(HML-2) sequences present in lower Old World primates were apparently not conserved during hominoid evolution, as opposed to the deletion variants. To further clarify the evolutionary origin of the HERV-K(HML-2) family, we screened GenBank with the 96-bp gag-sequence characteristic of lower Old World primates and identified, to date, 10 human sequence entries harboring either full-length or partially deleted proviral structures, probably representing remnants of a more ancient HERV-K(HML-2) variant. The high degree of mutations demonstrates the long-time presence of these HERV-K(OLD) proviruses in the genome. Nevertheless, they still belong to the HML-2 family as deduced from dot matrix and phylogenetic analyses. We estimate, based on the family ages of integrated Alu elements and on long terminal repeat (LTR) divergence data, that the average age of HERV-K(OLD) proviruses is ca. 28 million years, supporting an integration time before the evolutionary split of Hominoidea from lower Old World primates. Analysis of HERV-K(OLD) LTR sequences led to the distinction of two subgroups, both of which cluster with LTRs belonging to an evolutionarily older cluster. Taken together, our data give further insight into the evolutionary history of the HERV-K(HML-2) family during primate evolution.

Amino Acid Sequence↗

PubMed2000

Human endogenous retrovirus protein cORF supports cell transformation and associates with the promyelocytic leukemia zinc finger protein.

Human endogenous retrovirus sequences (HERVs) reside in the genomes of primates and humans for several million years. The majority of HERVs is non-coding but a limited set is intact and can express proteins. We have recently identified an almost intact HERV-K(HML-2) provirus on chromosome 7 and have documented that most patients with germ cell tumors (GCTs) display antibodies directed against proteins of HERV-K(HML-2). To address whether these proteins merely represent tumor markers or contribute to neoplastic transformation, we examined the transforming potential of various HERV sequences and studied physical interactions between HERV and cellular proteins by yeast two-hybrid and biochemical assays. cORF, a protein encoded by the C-terminal open reading frame within the env gene, supports tumor growth in nude mice and associates with the promyelocytic leukemia zinc finger protein (PLZF). The interaction domains map between amino acid residues 21 and 87 of cORF, and between residues 245 and 543 of PLZF. PLZF is critical for spermatogenesis in mice. Abnormal spermatogenesis or maturation of gonocytes is thought to predispose humans to the development of germ cell tumors. Thus, cORF of human endogenous retroviruses may contribute to tumor development by interfering with processes during spermatogenesis that involve PLZF.

Animals↗

PubMed2000

Deranged transcriptional regulation of cell-volume-sensitive kinase hSGK in diabetic nephropathy.

Transforming growth factor beta (TGF-beta) has been shown to participate in the pathophysiology of diabetic complications. As shown most recently, TGF-beta stimulates the expression of a distinct serine/threonine kinase (hSGK) which had previously been cloned as an early gene transcriptionally regulated by cell volume alterations. The present study was performed to elucidate transcription and function of hSGK in diabetic nephropathy. As shown by Northern blotting, an increase of extracellular glucose concentration increased hSGK mRNA levels in cultured cells, an effect qualitatively mimicked by osmotic cell shrinkage or treatment with TGF-beta (2 microgram/liter), phorbol 12,13-didecanoate (1 microM), or the Ca(2+) ionophore ionomycin (1 microM) and blunted by high concentrations of nifedipine (10 and 100 microM). In situ hybridization revealed that hSGK transcription was markedly enhanced in diabetic nephropathy, with particularly high expression in mesangial cells, interstitial cells, and cells in thick ascending limbs of Henle's loop and distal tubules. According to voltage clamp and tracer flux studies in Xenopus oocytes expressing the renal epithelial Na(+) channel ENaC or the mouse thick ascending limb Na(+),K(+),2Cl(-) cotransporter BSC-1, coexpression with hSGK stimulated ENaC and BSC-1 11-fold and 6-fold, respectively, effects reversed by kinase inhibitors staurosporine (1 microM) and chelerythrine (1 microM) and not elicited by inactive hSGK. In conclusion, excessive extracellular glucose concentrations enhance hSGK transcription, which in turn stimulates renal tubular Na(+) transport. These observations disclose an additional element in the pathophysiology of diabetic nephropathy.

3T3 Cells↗

PubMed2000

A rev-like NES mediates cytoplasmic localization of HERV-K cORF.

The human endogenous retrovirus K (HERV-K)-encoded protein cORF has recently been shown to be a functional homolog of the HIV Rev protein. Rev-mediated RNA export requires interaction between a leucine-rich nuclear export signal (NES) in Rev and the nuclear export receptor Crm1/exportin1. Like Rev, cORF binds to Crm1 and cORF-mediated RNA export depends on Crm1 activity. Here we document that mutation of the putative NES in cORF results in trapping of the protein in the nucleus, suggesting that the cORF NES functions in analogy to the Rev NES.

Amino Acid Motifs↗

PubMed2000

Molecular pathology and structural features of enteroviral replication. Toward understanding the pathogenesis of viral heart disease.

Enteroviruses of the Picornaviridae and primarily coxsackieviruses of group B (CVB) can be detected in humans and various experimental murine models of acute myocarditis and chronic heart muscle diseases indicating enterovirus persistence in the myocardium. Persistent myocardial infection is characterized by restricted viral replication and gene expression in myocytes capable of sustaining chronic inflammation. Viral cytotoxicity was found to be crucial for organ pathology both during acute and persistent infection. In-situ hybridization experiments at the cellular and subcellular level have demonstrated that virus replication is associated with severe structural changes of the cardiomyocyte cytoarchitecture at any stage of the disease. In tissue culture experiments and transgenic mice, it was shown that restricted replication and gene expression of the virus are capable of inducing myocytopathic effects. Investigations at the molecular level revealed that interference of coxsackievirus replication with the cellular metabolism is mediated by cleavage of host cell proteins by virus-encoded proteinases. Notably, there is also evidence that enteroviruses are able to activate specific cellular signal transduction pathways in the course of infection, thus promoting enteroviral replication. In summary, these data indicate that mutual influences of virus replication and subsequent modifications of the host cell metabolism are crucial for cardiac injury and dysfunction during acute and chronic disease.

Animals↗

PubMed2000

Rice in deep water: "how to take heed against a sea of troubles".

Plants are aerobic organisms for which oxygen shortage poses a severe problem. Waterlogging and flooding are the main causes of anaerobiosis and can lead to damage or even death of the plant. Rice is well adapted to semi-aquatic conditions. It is the only cereal that can be grown in flooded areas such as the great river deltas of Asia. In rice, two major strategies have evolved to cope with conditions of flooding. One is to escape submergence and thereby avoid anaerobiosis as much as possible. This is achieved through elongation growth and through extensive aeration of submerged plant parts by way of internal and external air spaces. The second adaptation is a metabolic one which includes the efficient use of carbohydrate resources and maintenance of energy charge when the cells do become anaerobic. The mainly ethanolic fermentation pathway found in anaerobic rice avoids acidification of the cytoplasm and thereby contributes to the maintenance of cell integrity. Genetic analysis indicates that the submergence tolerance trait, which is based on metabolic changes, is encoded by only one or a few as yet unidentified gene(s). Identifying these genes is a major goal in anaerobic stress research.

Acclimatization↗

PubMed2000

The cell cycle genes cycA1;1 and cdc2Os-3 are coordinately regulated by gibberellin in planta.

Internodal growth of deepwater rice (Oryza sativa L.) can achieve rates of up to 10 mm h(-1). In submergence-induced plants, gibberellic acid activates the cell division cycle first at the G1 --> S phase transition with a subsequent increase in mitotic activity. The proteins cycA1;1 and cdc2Os-3 are the regulatory and catalytic subunits, respectively, of cyclin-dependent protein kinases (CDKs) which are central to cell cycle regulation. Both genes are regulated by gibberellic acid in a coordinate manner with transcripts accumulating in the G2 phase prior to the B2-type mitotic cyclins described previously (M. Sauter et al. 1995, Plant J 7: 623-632), suggesting a distinct role in regulating G2/M phase progression. Since cdc2Os-3 belongs to a group of CDKs that have no counterparts in animals, it may function in a plant-specific gibberellin-regulated cell division process.

Cell Cycle↗

PubMed2000

Activation of CDK-activating kinase is dependent on interaction with H-type cyclins in plants.

cDNAs encoding cyclin H homologs were isolated from poplar (Populus tremula X tremuloides) and rice (Oryza sativa) plants, and were designated Pt;cycH;1 and Os;cycH;1, respectively. The deduced amino-acid sequences showed 40-60% similarity to human cyclin H and Schizosaccharomyces pombe Mcs2, with higher similarity in the cyclin box region. While Pt;cycH;1 and Os;cycH;1 were expressed in all tissues examined, the transcripts accumulated abundantly in dividing cells. Expression of Os;cycH;1 was abundant in the S-phase in partially synchronized suspension cells, and was induced by submergence in internodes of deepwater rice. A yeast two-hybrid assay demonstrated that both Pt;CycH;1 and Os;CycH;1 were able to interact with rice R2 kinase, which is structurally and functionally similar to cyclin-dependent kinase (CDK)-activating kinase (CAK) of vertebrates. Moreover, an in vitro pull-down assay showed that Os;CycH;1 specifically bound to R2 but not to other rice CDKs. When R2 was expressed in budding yeast CAK mutant, the suppression activity in terms of temperature-sensitivity was enhanced by co-expression with Os;cycH;1. Furthermore, in vitro kinase assay indicated that the kinase activities of R2 on CDKs and the carboxy-terminal domain (CTD) of the largest subunit of RNA polymerase II were markedly elevated by binding to Os;CycH;1. Our results suggest that cyclin H is a regulatory subunit of CAK, which positively controls CDK- and CTD-kinase activities in plant cells.

Amino Acid Sequence↗

PubMed2000

Adolescent girls' knowledge of and attitudes toward breast self-examination: evaluating an outreach education program.

BACKGROUND: The purpose of the study was to analyze the effectiveness of a one-hour educational intervention to increase knowledge about and improve attitudes towards breast self-examination (BSE) and early cancer detection among adolescent girls. METHODS: The sample used in this quasi-experimental study was selected from schools participating in an education program provided by a regional health education center. The instrument and scales used in the study were developed and pilot-tested for reliability and validity in the area schools prior to the start of the study. The sample consisted of 137 adolescent girls who provided consent forms and participated in the intervention. The comparison group, which consisted of students attending the same schools, was scheduled to receive the intervention at a later date. RESULTS AND CONCLUSIONS: Findings suggest that a one-hour lesson can improve knowledge and attitudes of adolescent girls with respect to BSE and early cancer detection. Suggestions for further research are discussed.

Adolescent↗

PubMed2000

Ethylene induces epidermal cell death at the site of adventitious root emergence in rice.

In deepwater rice (Oryza sativa), adventitious root primordia initiate at the nodes as part of normal development. Emergence of the roots is dependent on flooding of the plant and is mediated by ethylene action. Root growth was preceded by the induced death of epidermal cells of the node external to the tip of the root primordium. Cell death proceeded until the epidermis split open. Through this crack the root eventually emerged. Induced death was confined to nodal epidermal cells covering the tip of the primordia. Our results suggest that this process facilitates adventitious root emergence and prevents injury to the growing root. Cell death was inducible not only by submergence but also by application of 1-aminocyclopropane-1-carboxylic acid, the natural precursor of ethylene and it was suppressed in the presence of 2,5-norbornadiene (bicyclo[2.2.1]hepta-2,5-diene), an inhibitor of ethylene action. Adventitious root growth and epidermal cell death are therefore linked to the ethylene signaling pathway, which is activated in response to low oxygen stress.

Amino Acids, Cyclic↗

PubMed2000

Expression of cell volume-regulated kinase h-sgk in pancreatic tissue.

Transcript levels of the human serine/threonine kinase h-sgk have been found to be highest in pancreas. In the present study, localization and regulation of h-sgk transcription in pancreatic tissue were elucidated. As was apparent from radioactive in situ hybridization, most pancreatic acinar cells expressed high levels of h-sgk mRNA. h-sgk mRNA-positive cells were also found in ductal epithelia but not in pancreatic islets. In biopsy specimens from patients with pancreatitis, h-sgk mRNA levels were decreased in acinar cells but abundant in numerous mononuclear interstitial cells within areas of pancreatic necrosis and fibrosis. As shown by Northern blotting, h-sgk transcription in DAN-G pancreatic tumor cells is upregulated by osmotic cell shrinkage, serum, phorbol esters (phorbol 12,13-didecanoate), and Ca(2+) ionophore A-23187 and decreased by staurosporine and cAMP. In conclusion, h-sgk transcription is regulated not only by cell volume but also by serum, protein kinase C stimulation, cAMP, and increase of intracellular Ca(2+) activity. The kinase may participate not only in normal function of exocrine pancreas but also in fibrosing pancreatitis.

Acute Disease↗

PubMed1999

Human endogenous retrovirus (HERV)-K transcripts in gonadoblastomas and gonadoblastoma-derived germ cell tumours.

Gonadoblastomas are rare tumours of abnormal or dysgenetic gonads, often transforming to invasive seminomatous and nonseminomatous germ cell tumours (GCT). Because of the intimate association of noninvasive and invasive lesions, gonadoblastoma may provide clues as to the molecular pathogenesis of GCT. We studied the expression of the human endogenous retrovirus (HERV)-K gag gene in eight gonadoblastomas arising in phenotypically female patients, including two newborn girls. We also studied testicular biopsies with immature Sertoli cell nodules harbouring neoplastic germ cells, a lesion with morphological resemblance to gonadoblastoma. In five gonadoblastomas, invasive seminoma/dysgerminoma was noted, in two cases with formation of additional GCT components. HERV-K gag transcripts were found with moderate levels in gonocytes of all gonadoblastomas and in neoplastic germ cells in testicular Sertoli cell nodules. All invasive GCT except for teratomas displayed HERV-K transcripts. Thus, expression of HERV-K is induced during fetal or embryonal development and precedes invasive GCT formation. Although the specific role of HERV-K expression remains unknown, the findings place HERV-K expression in an appropriate time frame for it to have a role in the molecular pathogenesis of GCT and suggest a precursor-invasive tumour relationship for ovarian GCT equivalent to the more common carcinoma in situ of the testis and testicular GCT.

Adolescent↗

PubMed1999

Novel ribosomal genes from maize are differentially expressed in the zygotic and somatic cell cycles.

We have isolated cDNAs representing more than 50 different genes from libraries of unfertilised egg cells and zygotes of maize, expression of which is up- or downregulated after in vitro fertilisation (IVF). Among the cDNAs isolated are seven which encode proteins that are probably involved in translation and two encoding proteins probably involved in DNA replication. The latter genes are strongly induced on fertilisation. This indicates that zygotic gene activation (ZGA) - the switch from maternal to embryonic control of development - occurs in the zygote shortly after fertilisation in higher plants - earlier than in animal systems so far investigated. Four novel transcripts for ribosomal proteins (S21A, S21B, L39, P0) involved in ribosome biosynthesis and translation were analysed in more detail. The expression of all four genes correlates with cell division activity and is strongly induced during the G1 phase of the somatic cell cycle. A different mode of regulation operates in the first embryonic cell cycle: relatively large amounts of transcript are stored in the unfertilised egg cells, and by 18 h after IVF, two ribosomal genes are induced while a third is downregulated. These results indicate that using the combination of single-cell culture techniques with novel molecular methods, it is possible to isolate and study numerous genes expressed in female gametes and zygotes of higher plants. The detailed analysis of the four ribosomal protein genes demonstrates that the zygotic and somatic cell cycles are differentially regulated.

Amino Acid Sequence↗

PubMed1999

h-sgk serine-threonine protein kinase gene as transcriptional target of transforming growth factor beta in human intestine.

BACKGROUND & AIMS: Recently, the immediate early gene h-sgk was cloned as a hypertonicity-induced gene from human hepatoma cells. The aim of this study was to localize h-sgk messenger RNA (mRNA) expression in normal and inflamed intestinal mucosa and to identify potential transcriptional regulators. METHODS: h-sgk mRNA in small intestinal mucosa from healthy persons and patients with Crohn's disease was determined by in situ hybridization. Transcriptional regulation was studied by Northern blot analysis of total RNA isolated from cultured human Intestine 407, U937, and HepG2 cells. RESULTS: In normal ileum, h-sgk mRNA was selectively localized to the apical villus enterocytes, whereas no staining was detected in crypt cells. In Crohn's disease, enterocytes of the crypts expressed h-sgk and abundant h-sgk positive inflammatory cells appeared in the lamina propria. Combined h-sgk in situ hybridization and immunohistochemical analysis of CD68 antigen expression identified a part of these cells as macrophages. In addition to spatial correlation of transforming growth factor (TGF)-beta1 protein and h-sgk mRNA expression, h-sgk transcription in human Intestine 407 and HepG2 cells as well as in U937 monocytes/macrophages was strongly induced by TGF-beta1 in vitro. CONCLUSIONS: h-sgk expression in normal and inflamed intestinal mucosa may be regulated by TGF-beta1 and may contribute to the pleiotropic actions of TGF-beta1 in mucosal cell populations.

Antigens, CD↗

PubMed1999

Mechanisms and consequences of enterovirus persistence in cardiac myocytes and cells of the immune system.

In humans and experimental murine models enteroviruses, and in particular coxsackieviruses of group B (CVB), may induce chronic myocarditis associated with a persistent type of heart muscle infection. Persistent myocardial infection has been characterized by restricted viral replication and gene expression, which is capable of sustaining chronic inflammation. Altered replication and transcription of the virus, in addition to an immune response insufficient to recognize and clear infected cells entirely, are essential mechanisms for initiation and maintenance of persistent heart muscle infection. Viral cytotoxicity was found to be crucial for organ pathology both during acute and persistent infection, indicating that enterovirus myocarditis is a virus-induced rather than an immune-mediated disease. Notably, resistance to the development of persistent heart muscle infection is not linked to the H-2 haplotype of the host. In addition to persistently infected myocytes, detection of the replicative minus-strand RNA intermediate provided evidence for virus replication in lymphoid cells of the spleen, predominantly in splenic B lymphocytes, during the course of the disease. Whereas viral RNA was also detected in certain CD4+ helper T cells and Mac1+ macrophages, no enteroviral genomes were identified in CD8+ T cells. Detection of infected activated B lymphocytes both in heart tissue of CVB3-infected immunocompetent mice and syngenic SCID mice receiving splenocytes from CVB3-infected donors support the concept that B cell traffic may contribute to maintenance of chronic disease. Dissection of the diversity of viral and host-specific determinants in susceptible and resistant hosts will allow us to define the protective mechanisms that mediate resistance to the development of life-threatening acute and chronic enterovirus myocarditis.

Animals↗