Myosin VIIA is required for aminoglycoside accumulation in cochlear hair cells.

Myosin VIIA is expressed by sensory hair cells and has a primary structure predicting a role in membrane trafficking and turnover, processes that may underlie the susceptibility of hair cells to aminoglycoside antibiotics. [3H]Gentamicin accumulation and the effects of aminoglycosides were therefore examined in cochlear cultures of mice with different missense mutations in the myosin VIIA gene, Myo7a, to see whether myosin VIIA plays a role in aminoglycoside ototoxicity. Hair cells from homozygous mutant Myo7a(sh1) mice, with a mutation in a non-conserved region of the myosin VIIA head, respond rapidly to aminoglycoside treatment and accumulate high levels of gentamicin. Hair cells from homozygous mutant Myo7a(6J) mice, with a mutation at a highly conserved residue close to the ATP binding site of the myosin VIIA head, do not accumulate [3H]gentamicin and are protected from aminoglycoside ototoxicity. Hair cells from heterozygotes of both alleles accumulate [3H]gentamicin and respond to aminoglycosides. Although aminoglycoside uptake is thought to be via apical surface-associated endocytosis, coated pit numbers on the apical membrane of heterozygous and homozygous Myo7a(6J) hair cells are similar. Pulse-chase experiments with cationic ferritin confirm that the apical endocytotic pathway is functional in homozygous Myo7a(6J) hair cells. Transduction currents can be recorded from both heterozygous and homozygous Myo7a(6J) hair cells, suggesting it is unlikely that the drug enters via diffusion through the mechanotransducer channel. The results show that myosin VIIA is required for aminoglycoside accumulation in hair cells. Myosin VIIA may transport a putative aminoglycoside receptor to the hair cell surface, indirectly translocate it to sites of membrane retrieval, or retain it in the endocytotic pathway

Influence of Membrane-Fusogen Distance on the Secondary Structure of Fusogenic Coiled Coil Peptides

Liposomal membrane fusion is an important tool to study complex biological fusion mechanisms. We use lipidated derivatives of the specific heterodimeric coiled coil pair E: (EIAALEK)3 and K: (KIAALKE)3 to study and control the fusion of liposomes. In this model system, peptides are tethered to their liposomes via a poly(ethylene glycol) (PEG) spacer and a lipid anchor. The efficiency of the fusion mechanism and function of the peptides is highly affected by the PEG-spacer length and the lipid anchor type. Here, the influence of membrane–fusogen distance on the peptide–membrane interactions and the peptide secondary structures is studied with Langmuir film balance and infrared reflection absorption spectroscopy. We found that the introduction of a spacer to monolayer-tethered peptide E changes its conformation from solvated random coils to homo-oligomers. In contrast, the described peptide–monolayer interaction of peptide K is not affected by the PEG-spacer length. Furthermore, the coexistence of different conformations when both lipopeptides E and K are present at the membrane surface is demonstrated empirically, which has many implications for the design of effective fusogenic recognition units and the field of artificial membrane fusion.Article / Letter to editorLIC/CB/Supramolecular & Biomat. Chem

Evaluatie van de verzuringsdoelstellingen: kwantificering van de effecten van emissievarianten op half-natuurlijke terrestrische ecosystemen

In het kader van de evaluatie verzuringsdoelstellingen zijn depositiescenario's geëvalueerd met de dynamische modellen SMART2/MOVE. Het blijkt dat door naijleffecten overschrijdingen van normen kunnen optreden, terwijl kritische depositieniveaus niet meer overschreden worden. De vertraging is ongeveer tien jaar. Voor adequate bescherming van bossen en natuurgebieden is het van belang dat naast Nederlandse ook buitenlandse emissies gereduceerd worden

Dynamic nitrogen deposition thresholds during forest stand development in a Douglas fir forest analysed with two nitrogen models SMART2 and MERLIN

In contrast to the classical critical load (CL) concept, based on long-term steady-state conditions, a dynamic deposition threshold (DDT) is introduced. This DDT takes into account all relevant dynamic aspects of vegetation development/forest growth, mineralisation, immobilisation and denitrification, depending on the successional stage of the forest. DDT values for nitrogen were determined for a Douglas fir rotation by two process-based nitrogen models SMART2 and MERLIN using three different criteria for critical nitrogen leaching. During most of the rotation time, the predicted DDT values were higher than the corresponding traditional CL. SMART2 and MERLIN predicted a maximum DDT of 4.9 and 4.6 kmol N per ha per year (69 and 64 kg N per ha per year, respectively), when accepting a critical N leaching level of 1.73 kmol N per ha per year related to impacts on ground water quality. This is due mainly to relatively high tree uptake during the first 50 years of a forest rotation, compared to a long-term estim

Imaging the lipid bilayer of giant unilamellar vesicles using red-to-blue light upconversion

Red-to-blue triplet–triplet annihilation upconversion was obtained in giant unilamellar vesicles. The upconverted light was homogeneously distributed across the membrane and could be utilized for the imaging of individual giant vesicles in three dimensions. These results show the great potential of TTA-UC for imaging applications under anoxic conditions

Zelfsturing kan niet zonder doelen en monitoring

De leden van de Vereniging ‘Noardlike Fryske Wâlden’, grotendeels melkveehouders, willen graag zelf sturen op milieudoelen in de Noordelijke Friese Wouden. Hierbij willen zij collectief op milieudoelstellingen worden afgerekend, in plaats van individueel te moeten voldoen aan generieke middelvoorschriften. Twee zaken zijn noodzakelijk voor deze vorm van zelfsturing. Ten eerste moeten er heldere doelen voor milieuprestaties en milieukwaliteit zijn waarop gestuurd kan worden. Ten tweede moet er een monitoringsysteem zijn om vast te stellen of de doelen worden gehaald. Dit artikel beschrijft de ontwikkeling van milieumonitoring om de gewenste zelfsturing mogelijk te make

3MG: Meervoudige Milieu Monitoring voor Gebiedssturing; Een case study voor de Noordelijke Friese Wouden

Sinds 2005 is TransForum betrokken bij een praktijkproject in de Noordelijke Friese Wouden (het project NFW) waarin samen met boeren, bestuurders, overheden en maatschappelijke groepen wordt gezocht naar mogelijkheden om de beoogde zelfsturing vorm en inhoud te geven. Om voor milieukwaliteitdoelen een onderbouwd antwoord te kunnen geven heeft TransForum naast het praktijkproject NFW een meer analytisch gericht wetenschappelijk project ondersteund waarin een operationeel meetinstrument is ontwikkeld en getoetst. In deze studie is gebruik gemaakt van gegevens van aanwezige meetnetten in combinatie met geïntegreerde modellen. Het betreft: ammoniakemissie, stikstofdepositie, grondwaterkwaliteit, oppervlaktewaterkwalitei

Molecular misreading: The occurrence of frameshift proteins in different diseases

Neuronal homoeostasis requires a constant balance between biosynthetic and catabolic processes. Eukaryotic cells primarily use two distinct mechanisms for degradation: the proteasome and autophagy of aggregates by the lysosomes. We focused on the UPS (ubiquitin-proteasome system). As a result of molecular misreading, misframed UBB (ubiquitin B) (UBB+1) is generated. UBB+1 accumulates in the neuritic plaques and neurofibrillary tangles in all patients with AD (Alzheimer's disease) and in the neuronal and glial hallmarks of other tauopathies and in polyglutamine diseases such as Huntington's disease. UBB+1 is not present in synucleinopathies such as Parkinson's disease. We showed that UBB+1 causes UPS dysfunction, aggregation and apoptotic cell death. UBB+1 is also present in non-neurological cells, hepatocytes of the diseased liver and in muscles during inclusion body myositis. Other frequently occurring (age-related) diseases such as Type 2 (non-insulin-dependent) diabetes mellitus are currently under investigation. These findings point to the importance of the UPS in diseases and open new avenues for target identification of the main players of the UPS. Treatment of these diseases with tools (e.g. viral RNA interference constructs) to intervene with specific targets is the next step