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J Seemann

Publications and source records attributed to J Seemann.

At least 19 recordsLinked to original sources
PubMed2000

Matrix proteins can generate the higher order architecture of the Golgi apparatus.

The Golgi apparatus in animal cells comprises a reticulum of linked stacks in the pericentriolar and often in the juxtanuclear regions of the cell. The unique architecture of this organelle is thought to depend on the cytoskeleton and cytoplasmic matrix proteins--the best characterized being the golgin family of fibrous, coiled-coil proteins and the GRASP family of stacking proteins. Here we show that these matrix proteins can be separated from oligosaccharide-modifying enzymes in the Golgi stack without affecting their ability to form a ribbon-like reticulum in the correct location near to the nucleus. Our data suggest that the Golgi is a structural scaffold that can exist independently of, but is normally populated by, the enzyme-containing membranes that modify transiting cargo. This new concept of the Golgi further indicates that the Golgi may be an autonomous organelle rather than one that is in simple dynamic equilibrium with the endoplasmic reticulum.

Animals↗
PubMed2000

A complex of mammalian ufd1 and npl4 links the AAA-ATPase, p97, to ubiquitin and nuclear transport pathways.

The AAA-ATPase, p97/Cdc48p, has been implicated in many different pathways ranging from membrane fusion to ubiquitin-dependent protein degradation. Binding of the p47 complex directs p97 to act in the post-mitotic fusion of Golgi membranes. We now describe another binding complex comprising mammalian Ufd1 and Npl4. Yeast Ufd1p is required for ubiquitin-dependent protein degradation whereas yeast Npl4p has been implicated in nuclear transport. In rat liver cytosol, Ufd1 and Npl4 form a binary complex, which exists either alone or bound to p97. Ufd1/Npl4 competes with p47 for binding to p97 and so inhibits Golgi membrane fusion. This suggests that it is involved in another cellular function catalysed by p97, the most likely being ubiquitin-dependent events during mitosis. The fact that the binding of p47 and Ufd1/Npl4 is mutually exclusive suggests that these protein complexes act as adapters, directing a basic p97 activity into different cellular pathways.

Adenosine Triphosphatases↗
PubMed2000

The amino-terminal domain of the golgi protein giantin interacts directly with the vesicle-tethering protein p115.

Giantin is thought to form a complex with p115 and Golgi matrix protein 130, which is involved in the reassembly of Golgi cisternae and stacks at the end of mitosis. The complex is involved in the tethering of coat protomer I vesicles to Golgi membranes and the initial stacking of reforming cisternae. Here we show that the NH(2)-terminal 15% of Giantin suffices to bind p115 in vitro and in vivo and to block cell-free Golgi reassembly. Because Giantin is a long, rod-like protein anchored to the membrane by its extreme COOH terminus, these results support the idea of a long, flexible tether linking vesicles and cisternae.

Base Sequence↗
PubMed2000

The role of the tethering proteins p115 and GM130 in transport through the Golgi apparatus in vivo.

Biochemical data have shown that COPI-coated vesicles are tethered to Golgi membranes by a complex of at least three proteins: p115, giantin, and GM130. p115 binds to giantin on the vesicles and to GM130 on the membrane. We now examine the function of this tethering complex in vivo. Microinjection of an N-terminal peptide of GM130 or overexpression of GM130 lacking this N-terminal peptide inhibits the binding of p115 to Golgi membranes. Electron microscopic analysis of single microinjected cells shows that the number of COP-sized transport vesicles in the Golgi region increases substantially, suggesting that transport vesicles continue to bud but are less able to fuse. This was corroborated by quantitative immunofluorescence analysis, which showed that the intracellular transport of the VSV-G protein was significantly inhibited. Together, these data suggest that this tethering complex increases the efficiency with which transport vesicles fuse with their target membrane. They also provide support for a model of mitotic Golgi fragmentation in which the tethering complex is disrupted by mitotic phosphorylation of GM130.

Animals↗
PubMed1997

Annexin I targets S100C to early endosomes.

Immunofluorescence and subcellular fractionation localize annexin I and the EF hand protein S100C to the same membranous structures which in part correspond to transferrin receptor-positive endosomes. The association of S100C with endosomal membranes is strictly dependent on annexin I binding since a D91stop-S100C mutant protein, in which the residues essential for annexin I binding have been removed, fails to colocalize with membraneous structures. This indicates that annexin I and S100C form a complex in vivo and that the endosomal localization of this complex is mediated through an interaction of annexin I with the endosomal membrane.

Animals↗
PubMed1997

Chiral discrimination using piezoelectric and optical gas sensors.

Odour perception in humans can sometimes discriminate different enantiomers of a chiral compound, such as limonene. Chiral discrimination represents one of the greatest challenges in attempts to devise selective and sensitive gas sensors. The importance of such discrimination for pharmacology is dear, as the physiological effect of enantiomers of drugs and other biologically active molecules may differ significantly. Here we describe two different sensor systems that are capable of recognizing different enantiomers and of qualitatively monitoring the enantiomeric composition of amino-acid derivatives and lactates in the gas phase. One sensor detects changes in mass, owing to binding of the compound being analysed (the 'analyte'), by thickness shear-mode resonance; the other detects changes in the thickness of a surface layer by reflectometric interference spectroscopys. Both devices use the two enantiomers of a chiral polymeric receptor, and offer rapid on-line detection of chiral species with high selectivity.

Alanine↗
PubMed1997

Identification and characterization of a novel type of annexin-membrane interaction: Ca2+ is not required for the association of annexin II with early endosomes.

Annexin II, a member of a family of Ca2+ and membrane binding proteins, has been implicated in regulating membrane organization and membrane transport during endocytosis and Ca2+ regulated secretion. To characterize the mechanistic aspects of the annexin. II action we studied parameters which determine the endosomal association of annexin II. Immunoblot analysis of subcellular membrane fractions prepared from BHK cells in the presence of a Ca2+ chelating agent reveals that annexin II remains associated with endosomal membranes under such conditions. This annexin II behaviour is atypical for the Ca2+ regulated annexins and is corroborated by the finding that ectopically expressed annexin II mutants with inactivated Ca2+ binding sites continue to co-fractionate with endosomal membranes. The Ca(2+)-independent membrane association of annexin II is also not affected by introducing mutations interfering with the complex formation of annexin II with its intracellular protein ligand p11. However, a deletion of the unique N-terminal domain of annexin II, in particular the sequence spanning residues 15 to 24, abolishes the Ca(2+)-independent association of the protein with endosomes. These results describe a novel, Ca(2+)-independent type of annexin-membrane interaction and provide a first explanation for the observed preference of different annexins for different cellular membranes. In the case of annexin II this specificity could be mediated through specific membrane receptors interacting with a unique sequence in the annexin II molecule.

Amino Acid Sequence↗
PubMed1996

Structural requirements for annexin I-S100C complex-formation.

S100C is a member of the S100 family of EF-hand-type Ca(2+)-binding proteins which are thought to bind to and thereby regulate the activity of cellular target proteins in a Ca(2+)-dependent manner. An intracellular ligand for S100C is the Ca2+/phospholipid-binding protein annexin I and we show here that complex-formation is mediated through unique domains within S100C and annexin I. Using a proteolytically truncated annexin I derivative as well as a number of N-terminal annexin I peptides in liposome co-pelleting and ligand-blotting assays we map the S100C-binding site to the N-terminal 13 residues of annexin I. Similar analyses employing recombinantly expressed S100C mutants reveal that residues D91 to 194 in the unique C-terminal extension of this S100 protein are indispensable for annexin I binding. Interaction between S100C and an N-terminal annexin I peptide containing a tryptoplan at position 11 can also be monitored by fluorescence emission spectroscopy after tryptophan excitation. This analysis indicates that the local environment of the tryptophan in annexin I becomes less aqueous on S100C binding, suggesting a hydrophobic nature of the protein-protein interaction. Thus the structural basis of the annexin 1-S100C complex-formation probably resembles to a large extent that of the well-characterized annexin II-p11 interaction.

Animals↗
PubMed1996

The association of annexin I with early endosomes is regulated by Ca2+ and requires an intact N-terminal domain.

Annexin I is a member of a multigene family of Ca2+/phospholipid-binding proteins and a major substrate for the epidermal growth factor (EGF) receptor kinase, which has been implicated in membrane-related events along the endocytotic pathway, in particular in the sorting of internalized EGF receptors occurring in the multivesicular body. We analyzed in detail the intracellular distribution of this annexin by cell fractionation and immunoelectron microscopy. These studies used polyclonal as well as a set of species-specific monoclonal antibodies, whose epitopes were mapped to the lateral surface of the molecule next to a region thought to be involved in vesicle aggregation. Unexpectedly, the majority of annexin I was identified on early and not on multivesicular endosomes in a form that required micromolar levels of Ca2+ for the association. The specific cofractionation with early endosomes was also observed in transfected baby hamster kidney cells when the intracellular fate of ectopically expressed porcine annexin I was analyzed by using the species-specific monoclonal antibodies in Western blots of subcellular fractions. Interestingly, a truncation of the N-terminal 26, but not the N-terminal 13 residues of annexin I altered its intracellular distribution, shifting it from fractions containing early to those containing late and multivesicular endosomes. These findings underscore the regulatory importance of the N-terminal domain and provide evidence for an involvement of annexin I in early endocytotic processes.

Amino Acid Sequence↗
PubMed1994

Remission of secondary Raynaud phenomenon using intra-arterial prostaglandin E1 infusion. A case report.

A man, aged 52 years, who had a secondary Raynaud phenomenon affecting the left hand and index finger had been treated unsuccessfully with intravenous prostaglandin E1 and amputation of the finger was proposed. He was given intra-arterial prostaglandin E1 for 10 days and amputation was not necessary. He recovered almost normal function of his hand and the improvement was maintained after 2 months.

Alprostadil↗
PubMed1992

Zinc concentrations in human tissues. Liver zinc in carcinoma and severe liver disease.

In 58 unselected necropsies, zinc (Zn) in specimens of liver (mean +/- s = 280 +/- 178 micrograms/g d.w./4.28 +/- 2.72 mumol/g d.w.), kidney (170 +/- 57 micrograms/g d.w./2.60 +/- 0.87 mumol/g d.w.), spleen (69 +/- 13 micrograms/g d.w./1.05 +/- 0.20 mumol/g d.w.), and lung (64 +/- 16 micrograms/g d.w./0.98 +/- 0.24 mumol/g d.w.) were analysed by means of flameless atomic absorption spectrometry. In the examined range from 25 to 92 years of age, the Zn concentrations in all tissues measured did not show age or sex-dependency. There was a high correlation between the tissue concentration of Zn and Mg in lung, liver, and spleen, between Zn, Mg, and Pb in liver as well as between Zn and Pb and Zn and Cd in kidney. All hepatic cirrhosis cases had very low Zn conc. in liver tissue, the tumor cases generally increasing Zn conc. in liver tissue with progressive stage of regional invasion and distant metastasis.

Adult↗
PubMed1990

Cadmium in human lung tissue.

In 101 unselected autopsies, cadmium (Cd) in lung tissue was analyzed by means of flameless atomic absorption spectrometry (AAS). The subjects originated from Bochum (BO), Dortmund (DO), and neighbouring cities in the Ruhr District (BO/DO) as well as from Muenster (MS) and vicinity. The sample included eight persons who had died from bronchial carcinoma. The Cd concentration in lung tissue (CdL) did not show a significant age-dependency. There was only a slight increase of CdL in the age around 50. For males, the median CdL value was found to be 1.32 micrograms/g dry wt in the age group from 20-45, 1.48 micrograms/g dry wt from 45-65, and 0.64 micrograms/g dry wt greater than 65 (the corresponding means and standard deviations were 1.48 +/- 1.22, 1.73 +/- 1.42, and 1.18 +/- 1.27 micrograms/g dry wt). CdL in men was twice that in women. There were no differences between the two regions (BO/DO:MS) examined. CdL of the bronchial carcinoma cases were mostly clearly above the expected level, often similar to the Cr and Ni concentration of the same specimens. Besides the amount of inhaled metal aerosols, insufficient lung clearance may play a leading role for their retention in lung parenchyma. However, with regard to the determination of causality between uptake and disease the data are difficult to interpret, in our study due to a lack of enough consistent and reliable data on occupation, environment, and smoking habits, and in general due to a lot of variables which, until now, cannot be sufficiently quantified.

Adolescent↗
PubMed1990

Trace metal analysis of chromium and nickel in lung tissue fixed and stored in formalin.

In an attempt to answer the question whether the determination of chromium and nickel concentration in lung tissue, fixed and stored in formalin is still tolerable despite the related sources of error, the entire system (tissue, tissue abrasion, formalin, plastic container) was analysed by means of flameless atomic absorption spectrometry. It appears that such a procedure can be justified for practical purposes. In order to reduce possible errors, well defined rules are to be observed during specimen collection and processing and specialities have to be taken into account.

Chromium↗
PubMed1990

Risk factors of system clotting in heparin-free haemodialysis.

Heparin-free haemodialysis must be considered for all dialysis patients with a risk of haemorrhage. This technique is associated with increased danger of system coagulation with a blood loss of up to 250 ml. In 84 patients with a risk of haemorrhage, 296 heparin-free haemodialyses were recorded prospectively. First signs of coagulation were found very much more frequently in the venous airtrap than in the dialyser (146 vs 42). System coagulation occurred in 13 of the 296 dialyses (4%) and was prevented by prophylactic switching of the system and dialyser in 140 dialyses (47%). The time of system coagulation was on average 1.8 hours (+/- 0.2) after the beginning of dialysis. The 13 patients with system coagulation had a reduced blood flow on dialysis (217 +/- 52 vs 240 +/- 36 ml/min). Their initially normal clotting time (12 +/- 5 vs 14 +/- 4 min) was more significantly shortened after 2 h (4 +/- 3 vs 8 +/- 3 min). The activities of antithrombin III (87 +/- 34% vs 88 +/- 39%) and protein C (66 +/- 45% vs 59 +/- 37%) do not differ from those of 47 other patients, even at the time of system coagulation, as measured in five patients (92 +/- 34% for antithrombin III, 51 +/- 29% for protein C). System coagulation and shortening of clotting time thus cannot be regarded as a consequence of absorption of these inhibitory factors of plasmatic coagulation. The danger of system coagulation in heparin-free haemodialysis could probably be further reduced by an improvement of the biocompatibility of systems (airtrap) and dialysers (less activation of thrombocytes).

Bleeding Time↗
PubMed1988

Heparin-free hemodialysis with prophylactic change of dialyser and blood lines.

Heparinization during hemodialysis may cause severe bleeding complications in patients with high bleeding risk. Heparin-free hemodialyses (n = 208) were performed in 46 unselected patients with high bleeding risk after kidney transplantation (n = 25), after major surgery (n = 10), and with bleeding disorders (n = 11). Dialyser and blood lines were primed without heparin. In addition to the established measures (high blood flow, intermittent rinsing), system clotting was prevented by prophylactically changing the dialyser and blood lines in 107 of 208 dialyses (52 percent). Total system clotting with blood loss ranging from 100 to 250 ml occurred in six cases (3 percent). Mean hemodialysis time (+/- SD) was 4.1 hours (+/- 0.4), rising volume of the extracorporeal system 1.4 liters/hour (+/- 0.6), blood flow 244 ml/min (+/- 38), clotting time 12 min (+/- 4), and weight loss 2.5 kg (+/- 1.5). Mean hemodialysis creatinine clearance was 110 ml/min (+/- 34) and BUN clearance 138 ml/min (+/- 48). Heparin-free hemodialysis with prophylactic change of system is thus a safe and practical method of treatment for patients at high bleeding risk, but it is less effective, more expensive and the patient requires closer care.

Blood Coagulation↗
PubMed1985

Increased chromium and nickel content in lung tissue.

In random autopsies chromium (n = 23) and nickel (n = 16) together with various other metals, were determined in lung tissue by means of flameless atomic absorption spectrometry. With increasing age a significant increase in concentration of both chromium and nickel was found. This is evaluated as an indicator for a corresponding exposure, which is marked by a local (workplace) and regional (environment) share of a clear increase in the total chromium/nickel load and by a life-long duration. The question arises, whether the selective concentration (long half-life) of the inhaled chromium and nickel particles/compounds in the lung are to be regarded as a stochastic lung cancer risk.

Adult↗