Nuclear Magnetic Resonance Solution Structure and Functional Behavior of the Human Proton Channel

The human voltage-gated proton channel [Hv1(1) or VSDO(2)] plays an important role in the human innate immune system. Its structure differs considerably from those of other cation channels. It is built solely of a voltage-sensing domain and thus lacks the central pore domain, which is essential for other cation channels. Here, we determined the solution structure of an N- and C-terminally truncated human Hv1 (Δ-Hv1) in the resting state by nuclear magnetic resonance (NMR) spectroscopy. Δ-Hv1 comprises the typical voltage-sensing antiparallel four-helix bundle (S1–S4) preceded by an amphipathic helix (S0). The solution structure corresponds to an intermediate state between resting and activated forms of voltage-sensing domains. Furthermore, Zn2+-induced closing of proton channel Δ-Hv1 was studied with two-dimensional NMR spectroscopy, which showed that characteristic large scale dynamics of open Δ-Hv1 are absent in the closed state of the channel. Additionally, pH titration studies demonstrated that a higher H+ concentration is required for the protonation of side chains in the Zn2+-induced closed state than in the open state. These observations demonstrate both structural and dynamical changes involved in the process of voltage gating of the Hv1 channel and, in the future, may help to explain the unique properties of unidirectional conductance and the exceptional ion selectivity of the channel

Die Nutzung der Schulbibliothek im Zusammenhang mit der Leseselbstkompetenz der Schüler*innen

Die vorliegende Seminararbeit untersucht einen möglichen Zusammenhang zwischen der Bibliotheksnutzung und Leseselbstkompetenz von Schülerinnen und Schülern der Universitätsschule Dresden. Die Universitätsschule erprobt als staatliche Grund- und Oberschule projektorientierte Formen des Lehrens und Lernens. Als wichtiger Lernort ist demnach auch die Schulbibliothek zu betrachten. An der Studie nahmen ca. 76 Schüler*innen der Klassenstufen drei, vier, fünf und sechs teil. Bestandteil des Fragebogens, welchen die Lernenden ausfüllten, waren Aussagen zur Nutzung der Schulbibliothek, zum persönlichen Leseverhalten und zur präferierten Lektüre, welche die Lernenden individuell anhand einer Likert-Skala bewerten sollten. Die Ergebnisse zeigen, dass ungefähr die Hälfte der Schüler*innen mit den Nutzungsbedingungen, welche durch die Corona-Pandemie stark eingeschränkt sind, zufrieden sind. Es konnte sowohl eine Korrelation zwischen der Leseselbstkompetenz und der Lesemotivation (R=0,45) als auch zwischen der Leseselbstkompetenz und der Mediennutzung (R=0,41) herausgestellt werden

Lysosomal Acid Lipase Hydrolyzes Retinyl Ester and Affects Retinoid Turnover

Lysosomal acid lipase (LAL) is essential for the clearance of endocytosed cholesteryl ester and triglyceride-rich chylomicron remnants. Humans and mice with defective or absent LAL activity accumulate large amounts of cholesteryl esters and triglycerides in multiple tissues. Although chylomicrons also contain retinyl esters (REs), a role of LAL in the clearance of endocytosed REs has not been reported. In this study, we found that murine LAL exhibits RE hydrolase activity. Pharmacological inhibition of LAL in the human hepatocyte cell line HepG2, incubated with chylomicrons, led to increased accumulation of REs in endosomal/lysosomal fractions. Furthermore, pharmacological inhibition or genetic ablation of LAL in murine liver largely reduced in vitro acid RE hydrolase activity. Interestingly, LAL-deficient mice exhibited increased RE content in the duodenum and jejunum but decreased RE content in the liver. Furthermore, LAL-deficient mice challenged with RE gavage exhibited largely reduced post-prandial circulating RE content, indicating that LAL is required for efficient nutritional vitamin A availability. In summary, our results indicate that LAL is the major acid RE hydrolase and required for functional retinoid homeostasis

Mass Photometry of Membrane Proteins

Integral membrane proteins (IMPs) are biologically highly significant but challenging to study because they require maintaining a cellular lipid-like environment. Here, we explore the application of mass photometry (MP) to IMPs and membrane-mimetic systems at the single-particle level. We apply MP to amphipathic vehicles, such as detergents and amphipols, as well as to lipid and native nanodiscs, characterizing the particle size, sample purity, and heterogeneity. Using methods established for cryogenic electron microscopy, we eliminate detergent background, enabling high-resolution studies of membrane-protein structure and interactions. We find evidence that, when extracted from native membranes using native styrene-maleic acid nanodiscs, the potassium channel KcsA is present as a dimer of tetramers—in contrast to results obtained using detergent purification. Finally, using lipid nanodiscs, we show that MP can help distinguish between functional and non-functional nanodisc assemblies, as well as determine the critical factors for lipid nanodisc formation

Die Nutzung der Schulbibliothek im Zusammenhang mit der Leseselbstkompetenz der Schüler*innen

Die vorliegende Seminararbeit untersucht einen möglichen Zusammenhang zwischen der Bibliotheksnutzung und Leseselbstkompetenz von Schülerinnen und Schülern der Universitätsschule Dresden. Die Universitätsschule erprobt als staatliche Grund- und Oberschule projektorientierte Formen des Lehrens und Lernens. Als wichtiger Lernort ist demnach auch die Schulbibliothek zu betrachten. An der Studie nahmen ca. 76 Schüler*innen der Klassenstufen drei, vier, fünf und sechs teil. Bestandteil des Fragebogens, welchen die Lernenden ausfüllten, waren Aussagen zur Nutzung der Schulbibliothek, zum persönlichen Leseverhalten und zur präferierten Lektüre, welche die Lernenden individuell anhand einer Likert-Skala bewerten sollten. Die Ergebnisse zeigen, dass ungefähr die Hälfte der Schüler*innen mit den Nutzungsbedingungen, welche durch die Corona-Pandemie stark eingeschränkt sind, zufrieden sind. Es konnte sowohl eine Korrelation zwischen der Leseselbstkompetenz und der Lesemotivation (R=0,45) als auch zwischen der Leseselbstkompetenz und der Mediennutzung (R=0,41) herausgestellt werden

Fluorescent sperm in a transparent worm: validation of a GFP marker to study sexual selection

Background Sexual selection has initially been thought to occur exclusively at the precopulatory stage in terms of contests among males and female mate choice, but research over the last four decades revealed that it often continues after copulation through sperm competition and cryptic female choice. However, studying these postcopulatory processes remains challenging because they occur internally and therefore are often difficult to observe. In the transparent free-living flatworm Macrostomum lignano, a recently established transgenic line that expresses green fluorescent protein (GFP) in all cell types, including sperm, offers a unique opportunity to non-invasively visualise and quantify the sperm of a GFP-expressing donor inside the reproductive tract of wild-type recipients in vivo. We here test several aspects of the reproductive performance of the transgenic individuals and the accuracy of the techniques involved in assessing the GFP-expressing worms and their sperm. We then show the usefulness of these methods in a study on sperm displacement. Results GFP-expressing worms do not differ from wild-type worms in terms of morphology, mating rate and reproductive success. In addition, we show that the GFP signal is reliably and unequivocally expressed by all GFP-expressing individuals observed under epifluorescence illumination. However, the intensity of the GFP signal emitted by sperm of GFP expressing donors can vary (which we show to be at least in part due to sperm ageing) and the GFP marker is inherited according to Mendel's laws in most, but not all, of the individuals. Nevertheless, we argue these two issues can be addressed with an appropriate experimental design. Finally, we demonstrate the value of the GFP-techniques by comparing the number of GFP-expressing sperm in a wild-type recipient before and after mating with a competing sperm donor, providing clear experimental evidence for sperm displacement in M. lignano. This result suggests that sperm donors can displace previously stored sperm and replace it with their own. Conclusion The availability of the GFP-techniques in a transparent organism provide unique opportunities to visualise and quantify internal processes in the female reproductive tract after mating, which opens new avenues in the study of sexual selection