Biology subjects

Alzheimer, C.

Publications and source records attributed to Alzheimer, C..

6 recordsLinked to original sources

bioRxiv2026

Molecular assembly of the KCNQ1-KCNE1-BACE1 complex

We previously showed that the {beta}-secretase BACE1 directly modulates KCNQ1 channels through a non-proteolytic mechanism. Here, we dissect the molecular interplay among KCNQ1, its canonical auxiliary subunit KCNE1, and BACE1 using bimolecular fluorescence complementation (BiFC), electrophysiology, single-molecule pull-down (SiMPull), and a Forster resonance energy transfer (FRET)-based interaction assay. BiFC validated KCNQ1 homotetramerization and confirmed specific interactions of KCNQ1 with KCNE1 and with BACE1 at the plasma membrane. To map interaction determinants, we generated six KCNE1/BACE1 chimeras. BiFC and electrophysiological recordings revealed domain-specific contributions: BACE1s large extracellular domain primarily mediates its modulatory effects on KCNQ1 gating, while--consistent with previous reports--the KCNE1 transmembrane segment is necessary and sufficient to confer an IKs-like phenotype, and the KCNE1 intracellular domain tunes the voltage dependence of activation. Notably, a chimera combining the BACE1 extracellular region with KCNE1 transmembrane and intracellular regions produced an IKs-like current with additional BACE1-like slowing of activation, indicating functional additivity. Stoichiometry measurements by SiMPull and bleaching-step analysis demonstrated that KCNQ1 channel complexes predominantly recruit two BACE1 molecules. Although BACE1 oligomerizes at the plasma membrane, BiFC and FRET showed that KCNQ1 co-expression reduces BACE1 homomeric assembly, and this effect is unchanged by KCNE1 co-expression. Together, our data support a model in which BACE1 binds directly to KCNQ1, occupies a site distinct from KCNE1, and modulates KCNQ1 gating via its extracellular domain while remaining compatible with KCNE1 co-assembly.

biophysics↗

bioRxiv2025

BACE1 regulates sleep-wake cycle through both enzymatic and non-enzymatic actions.

The {beta}-secretase BACE1 has become a prime target in Alzheimers disease (AD) therapy, because it drives the production of pathogenic amyloid {beta} peptides. However, clinical trials with BACE1-targeting drugs were halted due to adverse effects on cognitive performance. We propose here that cognitive impairment by BACE1 inhibitors may be a corollary of a higher function of BACE1 related to proper sleep regulation. To address non-enzymatic effects of BACE1 on ion channels likely involved in the sleep-wake cycle, we analyzed sleep patterns in both BACE1-KO mice and a newly generated transgenic line expressing a proteolysis-deficient BACE1 variant (BACE1-KI). We found that BACE1-KI and BACE1-KO mice displayed common and distinct sleep-wake disturbances. Compared to their respective wild-type littermates, both mutant lines slept less during the light phase (when they preferentially rest). Furthermore, transition rates between wake and sleep states were altered, as were sleep spindles and EEG power spectra mainly in the gamma range. Thus, a better understanding of how BACE1 interferes with sleep-modulated behaviors is needed if clinical trials with BACE1-targeted inhibitors are to resume.

animal behavior and cognition↗

bioRxiv2025

Functional recovery of adult brain tissue arrested in time during cryopreservation by vitrification

Cryopreserving the adult brain is challenging due to damage from ice formation, and traditional freezing methods fail to maintain neural architecture and function. Vitrification offers a promising alternative but has not been surveyed in the brain. Here, we demonstrate near-physiological recovery of the adult murine hippocampus after vitrification of brain slices and of the whole brain in situ. Key features of the hippocampus are preserved, including structural integrity, metabolic responsiveness, neuronal excitability, and synaptic transmission and plasticity. Notably, hippocampal long-term potentiation was well preserved, indicating that the cellular machinery of learning and memory remains operational. These findings extend known biophysical limits for cerebral hypothermic shutdown by demonstrating recovery after complete cessation of molecular mobility in the vitreous state. This suggests that the brain can be arrested in time and then reactivated, opening avenues for potential clinical applications. Significance StatementWhile the brain is considered exceptionally sensitive, we show that the hippocampus can resume normal electrophysiological activity after being rendered completely immobile in a cryogenic glass. The work extends known biophysical tolerance limits for the brain from the hypothermic to the cryogenic range and establishes a protocol for its long-term storage in a viable state.

neuroscience↗

bioRxiv2022

Two-Dimensional-Dwell-Time Analysis of Ion Channel Gating using High Performance Computing Clusters

The power of single-channel patch-clamp recordings is widely acknowledged among ion channel enthusiasts. The method allows observing the action of a single protein complex in real time and hence the deduction of the underlying conformational changes in the ion channel protein. Commonly, recordings are modeled using hidden Markov chains, connecting open and closed states in the experimental data with protein conformations. The rates between states denote transition probabilities that, for instance, could be modified by membrane voltage or ligand binding. Preferably, the time resolution of recordings should be in the range of microseconds or below, potentially bridging Molecular Dynamic simulations and experimental patch-clamp data. Modeling algorithms have to deal with limited recording bandwidth and a very noisy background. It was previously shown that the fit of 2-Dimensional-Dwell-Time histograms (2D-fit) with simulations is very robust in that regard. Errors introduced by the low-pass filter or noise cancel out to a certain degree when comparing experimental and simulated data. In addition, the topology of models, that is, the chain of open and closed states could be inferred from 2D-histograms. However, the 2D-fit was never applied to its full potential. The reason was the extremely time-consuming and unreliable fitting process, due to the stochastic variability in the simulations. We have now solved both issues by introducing a Message Passing Interface (MPI) allowing massive parallel computing on a High Performance Computing (HPC) cluster and obtaining ensemble solutions. With the ensembles, we have optimized the fit algorithm and demonstrated how important the ranked solutions are for difficult tasks related to a noisy background, fast gating events beyond the corner frequency of the low-pass filter and topology estimation of the underlying Markov model. The fit can reliably extract events down to a signal-to-noise ratio of one and rates up to ten times higher than the filter frequency. It is even possible to identify equivalent Markov topologies. Finally, we have shown that, by combining the objective function of the 2D-fit with the deviation of the current amplitude distributions automatic determination of the current level of the conducting state is possible. It is even possible to infer the level with an apparent current reduction due to the application of the low-pass filter. Making use of an HPC cluster, the power of 2D-Dwell-Time analysis can be used to its fullest, allowing extraction of the matching Markov model from a time series with minor input of the experimenter. Additionally, we add the benefit of estimating the reliability of the results by generating ensemble solutions.

physiology↗

bioRxiv2020

Pyridoxal Kinase Inhibition by Artemisinins Downregulates Inhibitory Neurotransmission

The anti-malarial artemisinins have also been implicated in the regulation of various other cellular pathways. Despite their widespread application, the cellular specificities and molecular mechanisms of target recognition by artemisinins remain poorly characterized. We recently demonstrated how these drugs modulate inhibitory postsynaptic signaling by direct binding to the scaffolding protein gephyrin. Here, we report the crystal structure of the central metabolic enzyme pyridoxal kinase (PDXK), which catalyzes the production of the active form of vitamin-B6 (also known as pyridoxal 5-phosphate, PLP), in complex with artesunate at 2.4-[A] resolution. Partially overlapping binding of artemisinins with the substrate pyridoxal inhibits PLP biosynthesis as demonstrated by kinetic measurements. Electrophysiological recordings from hippocampal slices and activity measurements of glutamic acid decarboxylase (GAD), a PLP-dependent enzyme synthesizing the neurotransmitter {gamma}-aminobutyric acid (GABA), define how artemisinins interfere presynaptically with GABAergic signaling. Our data provide a comprehensive picture of artemisinin-induced effects on inhibitory signaling in the brain.

neuroscience↗

bioRxiv2018

Doxorubicin induces caspase-mediated proteolysis of KV7.1

The voltage-gated potassium channel Kv7.1 (KCNQ1) co-assembles with KCNE1 to generate the cardiac potassium current IKs. Gain- and loss-of-function mutations in KCNQ1 are associated with atrial fibrillation and long-QT (LQT) syndrome, respectively, highlighting the importance of modulating IKS activity for proper cardiac function. On a post-translational level, IKS can be regulated by phosphorylation, ubiquitination and sumoylation. Here, we report proteolysis of Kv7.1 as a novel, irreversible posttranslational modification. The identification of two C-terminal fragments (CTF1 and CTF2) of Kv7.1 led us to identify an aspartate critical for the generation of CTF2 and caspases as responsible for mediating Kv7.1 proteolysis. Activating caspases by apoptotic stimuli significantly reduced Kv7.1/KCNE1 currents, which was abrogated in cells expressing caspase-resistant Kv7.1 D459A/KCNE1 channels. An increase in cleavage of Kv7.1 could be detected in the case of LQT mutation G460S, which is located adjacent to the cleavage site. Application of apoptotic stimuli or doxorubicin-induced cardiotoxicity provoked caspase-mediated cleavage of endogenous Kv7.1 in human cardiomyocytes. In summary, our findings establish caspases as novel regulatory components for modulating Kv7.1 activity which may have important implications for the molecular mechanism of doxorubicin-induced cardiotoxicity.\n\nNon-standard Abbreviations and Acronyms

biochemistry↗