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M Goethals

Publications and source records attributed to M Goethals.

At least 37 records · Page 2Linked to original sources
PubMed2000

Targeting of aminopeptidase I to the yeast vacuole is mediated by Ssa1p, a cytosolic member of the 70-kDa stress protein family.

The two cytosolic members of the highly conserved 70-kDa stress protein family, Ssa1p and Ssa2p, were specifically retained by the prepro-NH(2) extension of the vacuolar aminopeptidase I precursor (pAPI) conjugated to agarose (Sulfolink). A temperature-sensitive mutant strain a1(ts)a234 (ssa1(ts) ssa2 ssa3 ssa4), when incubated at the restrictive temperature, was able to assemble the API precursor into dodecamers, but failed to pack pAPI into vesicles and to convert it into mature API (mAPI), a process that occurs in the vacuole. Altogether these results indicate that Ssa1p mediates the targeting of pAPI to the vacuole.

Adenosine Triphosphatases↗
PubMed2000

The competitive interaction of actin and PIP2 with actophorin is based on overlapping target sites: design of a gain-of-function mutant.

We studied the effect of mutations in an alpha-helical region of actophorin (residues 91-108) on F-actin and PIP(2) binding. As in cofilin, residues in the NH(2)-terminal half of this region are involved in F-actin binding. We show here also that basic residues in the COOH-terminal half of the region participate in this interaction whereby we extend the previously defined actin binding interface [Lappalainen, P., et al. (1997) EMBO J. 16, 5520-5530]. In addition, we demonstrate that some of the lysines in this alpha-helical region in actophorin are implicated in PIP(2) binding. This indicates that the binding sites of F-actin and PIP(2) on actophorin overlap, explaining the mutually exclusive binding of these ligands. The Ca(2+)-dependent F-actin binding of a number of actophorin mutants (carrying a lysine to glutamic acid substitution at the COOH-terminal positions of the actin binding helical region) may mimic the behavior of members of the gelsolin family. In addition, we show that PIP(2) binding, but not actin binding, of actophorin is strongly enhanced by a point mutation that leads to a reinforcement of the positive electrostatic potential of the studied alpha-helical region.

Actin Depolymerizing Factors↗
PubMed2000

Are better eye movements an advantage in ball games? A study of prosaccadic and antisaccadic eye movements.

The aim of this study was to compare prosaccadic and antisaccadic eye movements of experts in ball sports and controls. In the prosaccadic and antisaccadic task, subjects made saccades respectively towards and away from a suddenly appearing stimulus. By means of infrared-oculography, we compared horizontal eye movements of experts (n=18) and controls (n=20). Experts had shorter overall saccadic latencies, but significantly shorter latencies occurred only on the antisaccade task, not on the prosaccade task. Our findings seem to support the concept that prosaccades and antisaccades have different underlying mechanisms and that expertise in ball games mainly improves antisaccadic performance in terms of latency and variability.

Adult↗
PubMed1999

Experimental study of the flammability limits of toluene-air mixtures at elevated pressure and temperature.

The flammability limits of toluene-air mixtures are experimentally determined at pressures up to 500 kPa and temperatures up to 250 degrees C in a closed spherical vessel. The results at atmospheric pressure are compared with the results obtained in a glass tube. The flammability limits depend linearly upon temperature. A twilight zone characterized by weak pressure rises is observed for toluene at all pressures, while soot is formed at elevated pressures only. The explosion characteristics of toluene are compared with those of methane. Despite their chemical differences, the explosion characteristics of toluene and methane are similar.

Atmospheric Pressure↗
PubMed1999

Beta-amyloid peptide interacts specifically with the carboxy-terminal domain of human apolipoprotein E: relevance to Alzheimer's disease.

Growing evidence indicates the involvement of apolipoprotein E (apoE) in the development of late-onset and sporadic forms of Alzheimer's disease, although its exact role remains unclear. We previously demonstrated that beta-amyloid peptide (Abeta) displays membrane-destabilizing properties and that only apoE2 and E3 isoforms inhibit these properties. In this study, we clearly demonstrate that the carboxy-terminal lipid-binding domain of apoE (e.g., residues 200-299) is responsible for the Abeta-binding activity of apoE and that this interaction involves pairs of apoE amphipathic alpha-helices. We further demonstrate that Abeta is able to inhibit the association of the C-terminal domain of apoE with lipids due to the formation of Abeta/apoE complexes resistant to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. On the contrary, the amino-terminal receptor-binding domain of apoE (e.g., residues 129-169) is not able to form stable complexes with Abeta. These data extend our understanding of human apoE-dependent binding of Abeta by involving the C-terminal domain of apoE in the efficient formation of apoE/Abeta complex.

Alzheimer Disease↗
PubMed1999

Identification of Tyr438 as the major in vitro c-Src phosphorylation site in human gelsolin: a mass spectrometric approach.

Gelsolin is an actin-binding protein (82 kDa) consisting of six repeated segments (S1-S6), each approximately 120 residues long. It interacts with phospholipids and we previously showed that phosphatidylinositol 4,5-bisphosphate promotes phosphorylation of gelsolin by the tyrosine kinase c-Src. We used a combination of different methods, such as thin-layer chromatography and anti-phosphotyrosine-agarose immunoprecipitation of phosphopeptides combined with matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) and post source decay (PSD) analysis, to identify the phosphorylation sites in gelsolin. The major phosphorylation site (Tyr438) was located in subdomain 4 (S4). Phosphorylation of gelsolin in the gelsolin-actin2 complex was inhibited by 90%. Gelsolin phosphorylation by c-Src in the presence of lysophosphatidic acid also revealed Tyr438 as the most prominent site. Additional minor sites were found using the anti-phosphotyrosine bead immunoprecipitation method followed by MALDI-MS and PSD analysis. These sites, representing approximately 5% of the total phosphate incorporation, were identified as Tyr59, Tyr382, Tyr576, and Tyr624. Based on these results we generated antibodies which specifically recognize Tyr438 phosphorylated gelsolin.

Actins↗
PubMed1999

ECG diagnosis of native heart ventricular tachycardia in a heterotopic heart transplant recipient.

A case is reported of haemodynamic collapse in a 51 year old male heterotopic heart transplant recipient caused by native heart ventricular tachycardia. An accurate diagnosis was made by selective right and left sided electrocardiography. Synchronised electrical cardioversion of the native heart (200 J) resulted in restoration of sinus rhythm with prompt relief of symptoms and amelioration of the clinical situation.

Electric Countershock↗
PubMed1998

Contribution of the hydrophobicity gradient of an amphipathic peptide to its mode of association with lipids.

A class of peptides that associate with lipids, known as oblique-orientated peptides, was recently described [Brasseur R., Pillot, T., Lins, L., Vandekerckhove, J. & Rosseneu, M. (1997) Trends Biochem. Sci. 22, 167-171]. Due to an asymmetric distribution of hydrophobic residues along the axis of the alpha-helix, such peptides adopt an oblique orientation which can destabilise membranes or lipid cores. Variants of these oblique peptides, designed to have an homogeneous distribution of hydrophobic and hydrophilic residues along the helical axis, are classified as regular amphipathic peptides. These peptides are expected to lie parallel to the polar/apolar interface with their hydrophobic residues directed towards the apolar and their hydrophilic residues towards the polar phase. An hydrophobic, oblique-orientated peptide was identified at residues 56-68 in the sequence of the lecithin-cholesterol acyltransferase (LCAT), enzyme. This peptide is predicted to penetrate a lipid bilayer at an angle of 40 degrees through its more hydrophobic C-terminal end and thereby induce the destabilisation of a membrane or a lipid core. The LCAT-(56-68) wild-type peptide was synthesised together with the LCAT-(56-68, 0 degrees) variant, in which the hydrophobicity gradient was abolished through residue permutations. In two other variants, designed to keep their oblique orientation, the W61 residue was shifted either towards the more hydrophilic N-terminal at residue 57, or to position 68 at the hydrophobic C-terminal end of the peptide. Peptide-induced vesicle fusion was demonstrated by fluorescence measurements using pyrene-labeled vesicles and by monitoring of vesicle size by gel filtration. The interaction between peptides and lipids was monitored by measurement of the intrinsic tryptophan fluorescence emission of the peptides. Fluorescence polarisation measurements, using diphenyl hexatriene, were carried out to follow changes in the lipid fluidity. The LCAT-(56-68) wild-type peptide and the two oblique variants, induced fusion of unilamellar dimyristoylglycerophosphocholine vesicles. Tryptophan fluorescence emission measurements showed a 12-14 nm blue shift upon addition of the wild-type peptide and of the W61-->68 variant to lipids, whereas the fluorescence of the W61-->57 variant did not change significantly. This observation supports the insertion of the more hydrophobic C-terminal residues into the lipid phase, as predicted by the theoretical calculations. In contrast, the 0 degrees variant peptide had no fusogenic activity, and it associated with lipids to form small discoidal lipid/peptide complexes. The phospholipid transition temperature was decreased after addition of the wild-type, the W61-->68 and W61-->57 fusogenic peptides, whereas the opposite effect was observed with the 0 degrees variant. The behaviour of the wild-type and variant LCAT-(56-68) peptides stresses the contribution of the hydrophobicity gradient along the axis of an amphipathic peptide to the mode of association of this peptide with lipids. This parameter consequently influences the structural modifications occurring to lipids upon association with amphipathic peptides.

Catalytic Domain↗
PubMed1998

Enhanced efficiency of a targeted fusogenic peptide.

Membrane targeting was investigated as a potential strategy to increase the fusogenic activity of an isolated fusion peptide. This was achieved by coupling the fusogenic carboxy-terminal part of the beta-amyloid peptide (Abeta, amino acids 29-40), involved in Alzheimer's disease, to a positively charged peptide (PIP2-binding peptide, PBP) interacting specifically with a naturally occurring negatively charged phospholipid, phosphatidylinositol 4, 5-bisphosphate (PIP2). Peptide-induced vesicle fusion was spectroscopically evidenced by: (i) mixing of membrane lipids, (ii) mixing of aqueous vesicular contents, and (iii) an irreversible increase in vesicle size, at concentrations five to six times lower than the Abeta(29-40) peptide. In contrast, at these concentrations the PBP-Abeta(29-40) peptide did not display any significant activity on neutral vesicles, indicating that negatively charged phospholipids included as targets in the membranes, are required to compensate for the lower hydrophobicity of this peptide. When the alpha-helical structure of the chimeric peptide was induced by dissolving it in trifluoroethanol, an increase of the fusogenic potential of the peptide was observed, supporting the hypothesis that the alpha-helical conformation of the peptide is crucial to trigger the lipid-peptide interaction. The specificity of the interaction between PIP2 and the PBP moiety, was shown by the less efficient targeting of the chimeric peptide to membranes charged with phosphatidylserine. These data thus demonstrate that the specific properties of both the Abeta(29-40) and the PBP peptide are conserved in the chimeric peptide, and that a synergetic effect is reached through chemical linkage of these two fragments.

Dose-Response Relationship, Drug↗
PubMed1998

Different humoral responses during head-up tilt testing among patients with neurocardiogenic syncope.

Neurocardiogenic dysfunction is believed to result from activation of ventricular mechanoreceptors. To asses other humoral and circulatory mechanisms activated during vasovagal syncope, epinephrine, norepinephrine, renin, and aldosterone levels were measured during head-up tilt testing. Twenty-three patients referred because of vasovagal syncope underwent passive head-up tilt testing (80 degrees). Blood samples were taken at baseline, after 30 minutes of supine rest and at syncope. Five patients (four men, one woman; mean age 46 +/- 27 years) had cardioinhibitory syncope. Seven patients (five men, two women; mean age 40 +/- 12 years) had vasodepressor syncope. Eleven patients (eight men, three women; mean age 55 +/- 21 years) had negative results of head-up tilt tests. Among patients with cardioinhibitory syncope, norepinephrine concentration rose significantly from baseline to syncope (0.44 +/- 0.12 ng/ml versus 1.14 +/- 0.72 ng/ml; p < 0.05), whereas no significant change was observed in epinephrine (0.08 +/- 0.03 ng/ml versus 2.74 +/- 2.85 ng/ml; p = not significant [NS]), renin (5.68 +/- 3.03 pg/ml versus 19.58 +/- 11.47 pg/ml; p = NS), or aldosterone concentration (66.60 +/- 16.10 ng/ml versus 109.00 +/- 44.70 ng/ml; p = NS). Patients with vasodepressor syncope had a significant rise in renin (9.03 +/- 4.56 pg/ml versus 52.53 +/- 41.63 pg/ml; p < 0.05) and aldosterone concentration (95.43 +/- 103.03 ng/ml versus 249.57 +/- 191.54 ng/ml; p < 0.05), whereas no change in level of epinephrine (0.12 +/- 0.12 ng/ml versus 0.28 +/- 0.33 ng/ml; p = NS) or norepinephrine (0.60 +/- 0.26 ng/ml versus 0.86 +/- 0.53 ng/ml; p = NS) was detected. Among patients with negative results of tilt tests, levels of renin (7.94 +/- 7.19 pg/ml versus 27.71 +/- 18.50 pg/ml; p < 0.01) and aldosterone (64.64 +/- 28.33 ng/ml versus 160.91 +/- 79.58 ng/ml; p < 0.01) rose significantly, whereas no change was seen in epinephrine (0.12 +/- 0.14 ng/ml versus 0.23 +/- 0.31; p = NS) or norepinephrine concentration (0.54 +/- 0.21 ng/ml versus 0.82 +/- 0.52; p = NS). Patients with cardioinhibitory syncope were characterized by a rise in norepinephrine level and blunted activation of the renin-angiotensin-aldosterone axis at syncope. Unlike patients with cardioinhibitory syncope, the renin-angiotensin-aldosterone axis is activated in patients with vasodepressor syncope and patients with a negative result of head-up tilt test without a statistically significant increase in catecholamine levels. Patients with cardioinhibitory syncope have higher epinephrine levels at syncope compared with patients with a negative result of head-up tilt test and patients with vasodepressor syncope.

Adult↗
PubMed1998

Primary structure of scombrine alpha: two different species with an identical protamine.

We have studied the protamine scombrine alpha from the mackerel Scomber scombrus. Scombrine alpha is found phosphorylated in spermatid nuclei, but not in nuclei of ripe sperm. It is a typical fish protamine, made up of two distinct molecular species, each of 34 amino acid residues. The primary structure of the main component of scombrine alpha is 100% identical to scombrine gamma, the nonmicroheterogeneous protamine from Scomber australasicus (11). The second component of scombrine alpha is a very minor molecular species that has an isoleucine instead of a valine in position 11. Nuclear sperm-specific basic proteins display an enormous interspecific variability and it is very surprising that two different species show identical protamines. In this work we suggest that evolutionary changes in primary structure of protamines are restricted by several constitutive factors, especially when protamines either lack or have a low degree of microheterogeneity.

Amino Acid Sequence↗
PubMed1998

Use-dependent block of Ih in mouse dorsal root ganglion neurons by sinus node inhibitors.

1. The sinus node inhibitors UL FS 49 and DK-AH 269 reduce heart rate by slowing diastolic depolarization rate in the sino-atrial (SA) node, which might originate from the use-dependent blockade of a hyperpolarization-activated current If. A hyperpolarization-activated current Ih, which is present in many types of neurons, is similar to If. We studied the effects of these drugs on Ih in cultured mouse dorsal root ganglion (DRG) neurons. 2. With the whole-cell patch-clamp technique use-dependent block of Ih was observed. The steady-state block following a voltage-clamp pulse train (1-s steps from -38 to -108 mV applied at 0.5 Hz) was dependent on drug concentration and showed an apparent Kd of 0.1 and 0.79 microM with DK AH 269 and UL-FS 49 respectively. 3. The rate of block increased linearly with drug concentration. The rate of recovery from block was, however, much slower compared to cardiac tissue. 4. There was no significant effect of UL-FS 49 on the activation curve. 5. At high concentrations of UL-FS 49 a clear association of the drug with the open channel was observed. 6. When the cell was stimulated at a frequency of 3 Hz, a distinct hyperpolarization was observed in the presence of extracellular Cs+ or when Ih was blocked with UL-FS 49, but not in the absence of Cs+ and UL-FS 49. 7. These results indicate that Ih protects the cell against hyperpolarizations and subsequent inexcitability. The action of the drugs on the hyperpolarization-activated current in cardiac and neuronal tissue show some similarities; however, some pronounced differences indicate that different subtypes of the channel might exist.

Animals↗
PubMed1998

Early benefit of implantable cardioverter defibrillator therapy in patients waiting for cardiac transplantation.

The ICD can effectively recognize and treat ventricular arrhythmias that can lead to sudden death. Sudden death is a major problem in patients awaiting heart transplantation. We reviewed our experience with the ICD in patients with malignant ventricular arrhythmias waiting for cardiac transplantation. Nineteen patients were included. Seventeen were men, mean age was 54 +/- 11 years (range 17-66) and the left ventricular ejection fraction was 22% +/- 10% (range 9%-46%). After a mean follow-up of 6 +/- 5 months (range 1-20 months), 17 patients reached heart transplantation. One patient died and the other is waiting for a transplant. Before transplantation 71% of patients received an appropriate discharge. The mean time to the first appropriate discharge was 2 +/- 2 months (range < 1-6 months), which was significantly shorter than the mean time to first discharge in the other patients (n = 182) receiving a defibrillator in our center (11 +/- 10 months; range 1-58 months) (P < 0.0004). In conclusion, cardiac transplantation candidates with life-threatening ventricular arrhythmias can effectively be protected against sudden arrhythmic death by ICD. These patients have a high incidence of appropriate shocks occurring very early after implantation.

Adolescent↗
PubMed1997

Analogous F-actin binding by cofilin and gelsolin segment 2 substantiates their structural relationship.

Cofilin is representative for a family of low molecular weight actin filament binding and depolymerizing proteins. Recently the three-dimensional structure of yeast cofilin and of the cofilin homologs destrin and actophorin were resolved, and a striking similarity to segments of gelsolin and related proteins was observed (Hatanaka, H., Ogura, K., Moriyama, K., Ichikawa, S., Yahara, I., and Inagaka, F. (1996) Cell 85, 1047-1055; Fedorov, A. A., Lappalainen, P., Fedorov, E. V., Drubin, D. G., and Almo, S. C. (1997) Nat. Struct. Biol. 4, 366-369; Leonard, S. A., Gittis, A. G., Petrella, E. C., Pollard, T. D., and Lattman, E. E. (1997) Nat. Struct. Biol. 4, 369-373). Using peptide mimetics, we show that the actin binding site stretches over the entire cofilin alpha-helix 112-128. In addition, we demonstrate that cofilin and its actin binding peptide compete with gelsolin segments 2-3 for binding to actin filaments. Based on these competition data, we propose that cofilin and segment 2 of gelsolin use a common structural topology to bind to actin and probably share a similar target site on the filament. This adds a functional dimension to their reported structural homology, and this F-actin binding mode provides a basis to further enlighten the effect of members of the cofilin family on actin filament dynamics.

Actin Depolymerizing Factors↗
PubMed1997

A prospective hemodynamic evaluation of patients with chronic atrial fibrillation undergoing radiofrequency catheter ablation of the atrioventricular junction.

A prospective invasive hemodynamic evaluation in 11 unselected patients with medically refractory chronic atrial fibrillation undergoing radiofrequency catheter ablation of the atrioventricular junction was performed. The resultant rate regulation and control caused a hemodynamic and symptomatic improvement despite persistent fibrillation at the atrial level.

Aged↗
PubMed1997

The 118-135 peptide of the human prion protein forms amyloid fibrils and induces liposome fusion.

The prion protein (PrPC) is a glycoprotein of unknown function normally found at the surface of neurons and of glial cells. It is involved in diseases such as bovine spongiform encephalopathy, and Creutzfeldt-Jakob disease in the human, where PrPC is converted into an altered form (termed PrPSc). PrPSc is highly resistant towards proteolytic degradation and accumulates in the central nervous system of affected individuals. By analogy with the pathological events occuring during the development of Alzheimer's disease, controverses still exist regarding the relationship between amyloidogenesis, prion aggregation and neuronal loss. To unravel the mechanism of PrP neurotoxicity and understand the interaction of PrP with cellular membranes, a series of natural and variant peptides spanning residues 118 to 135 of PrP was synthesized. The potential of these peptides to induce fusion of unilamellar lipid vesicles was investigated. According to computer modeling calculations, the 120 to 133 domain of PrP is predicted to be a tilted lipid-associating peptide, and to insert in a oblique way into a lipid bilayer through its N-terminal end. In addition to amyloidogenic properties exhibited in vitro by these peptides, peptide-induced vesicle fusion was demonstrated by several techniques, including lipid- and core-mixing assays. Elongation of the 120 to 133 peptide towards the N- and C-terminal ends of the PrP sequence showed that the 118 to 135 PrP peptide has maximal fusogenic properties, while the variant peptides had no effect. Due to their high hydrophobicity, all peptides tested were able to interact with liposomes to induce leakage of encapsulated calcein. We demonstrate also that the propensity of the peptides to fold as an alpha-helix increases their fusogenic activity, thus accounting for the maximal fusogenic activity of the most stable helix at residues 118 to 135. These data suggest that, by analogy with the C-terminal domain of the beta-amyloid peptide, the fusogenic properties exhibited by the prion peptides might contribute to the neurotoxicity of these peptides by destabilizing cellular membranes.

Amino Acid Sequence↗
PubMed1997

Structural and functional properties of the 154-171 wild-type and variant peptides of human lecithin-cholesterol acyltransferase.

The 154-171 segment of the human lecithin-cholesterol acyltransferase (LCAT) enzyme was identified as the most stable amphipathic helix in the LCAT sequence. Its mean hydrophobicity, hydrophobic moment and its orientation at a lipid/water interface are similar to those of some of the helical repeats of apolipoprotein A-IV and E. This domain was therefore proposed as a candidate peptide accounting for the association between LCAT and its lipid substrate. To investigate this hypothesis we synthesized the LCAT-(154-171)-peptide, two variants containing the natural Y156N and R158C mutations and a variant with increased hydrophobicity through Y156I, L160I, L163I and Y171W substitutions. The structural and lipid-binding properties of these synthetic peptides were investigated by turbidity, fluorescence, electron microscopy and circular dichroism. The wild-type peptide, the R158C variant in its dimeric form, as well as the more hydrophobic peptide, associated with phospholipids, whereas the Y156N and the R158C variant in its monomeric form did not. However, only the complexes generated with the hydrophobic variant were stable enough to resist dissociation during gel filtration. The wild-type peptide and hydrophobic variant formed discoidal complexes with dimyristoylglycerophosphocholine (Myr2GroPCho) as shown by negative staining electron microscopy. Comparison of the properties of the wild-type and hydrophobic variant LCAT-(154-171)-peptide stresses the contribution of the hydrophobic face of the amphipathic helix to the formation and stabilization of the peptide/lipid complexes. This is further confirmed by the decreased affinity of the Y156N variant peptide for lipids, as this mutation decreased the mean hydrophobicity of the hydrophobic face of the amphipathic helix. These results support the hypothesis that the 154-171 segment of LCAT might be involved in the interaction of the enzyme with its lipid substrate and suggest that the decreased activity of the Y156N natural LCAT mutant might result from a decreased affinity of this mutant for lipids.

Amino Acid Sequence↗