Biology subjects

Nussbaum-Krammer, C.

Publications and source records attributed to Nussbaum-Krammer, C..

8 recordsLinked to original sources

bioRxiv2025

Explosive shock wave exposure leads to age-accelerated motor and sensory decline in C. elegans

BackgroundMilitary and law enforcement personnel are routinely exposed to shock waves from weapon systems and explosive devices during training and operations. Even when such shock wave exposure results in mild traumatic brain injury (mTBI) without abnormalities on routine imaging, persistent neurological symptoms may occur. Yet, the biological processes that link an acute blast wave insult to progressive neuronal dysfunction remain poorly defined. MethodsWe established Caenorhabditis elegans nematodes as a genetically accessible animal model for blast-related mTBI (br-mTBI). Animals were exposed in gelatin to shock waves generated by a custom-built shock wave generator (SWG), which produces explosive shock waves with an abrupt overpressure peak followed by a negative pressure phase. The resulting pressure-time curves are very similar to the profiles of conventional explosives in free-field setups. To enable mechanistic studies under controlled laboratory conditions, we developed a complementary platform using a medical radial extracorporeal shock wave therapy (rESWT) device. Motor behavior, mechanosensory function, neuronal morphology and cytoskeletal integrity were analyzed during aging. ResultsSWG-derived shock waves induced immediate but reversible motor and sensory deficits, followed by an accelerated age-dependent decline in movement and touch sensitivity. The rESWT platform accurately reproduced these phenotypes. Touch receptor neurons showed progressive structural abnormalities, including degeneration, alongside acute PTL-1/Tau mislocalization consistent with cytoskeletal injury. ConclusionsDefined shock wave exposure is sufficient to provoke long-term neuronal functional decline in C. elegans, accompanied by structural deterioration and premature neurodegeneration. This tractable model enables lifelong phenotyping and mechanistic dissection of how an acute shock wave insult progresses to chronic neuronal dysfunction, and provides a scalable platform for identifying molecular and pharmacological modifiers that promote resilience.

neuroscience↗

bioRxiv2024

Structural polymorphism of alpha-synuclein fibrils alters pathway of Hsc70 mediated disaggregation

The pathological aggregation of -synuclein into amyloid fibrils is a hallmark of synucleinopathies including Parkinsons disease. Despite this commonality, synucleinopathies display divergent disease phenotypes that have been attributed to disease specific three-dimensional structures of -synuclein fibrils, each with a unique toxic gain-of-function profile. The Hsc70 chaperone is remarkable in its ability to disassemble pre-existing amyloid fibrils of different proteins in an ATP and co-chaperone dependent manner. We find however, using six well-defined conformational polymorphs of -synuclein fibrils, that the activity of the Hsc70 disaggregase machinery is sensitive to differences in the amyloid conformation, confirming that fibril polymorphism directly affects interactions with the proteostasis network. Amyloid conformation influences not only how efficiently fibrils are cleared by the Hsc70 machinery but also the preferred pathway of disaggregation. We further show that, in vitro, the active processing of fibrils by the Hsc70 machinery inadvertently produces seeding competent species that further promote protein aggregation. Amyloid conformation thus is an important feature that can tilt the balance between beneficial or detrimental protein quality control activities in the context of disease.

biochemistry↗

bioRxiv2024

Evaluation of near-infrared light therapy for the treatment of neurodegenerative diseases: Limited penetration depth into the brain likely hinders efficacy

BackgroundNear-infrared (NIR) light therapy is used to treat various musculoskeletal disorders. It has been proposed that transcranial NIR light treatment may also be beneficial for Alzheimers disease (AD). However, the ability of NIR light to penetrate the scalp and skull efficiently and induce cytoprotective responses in the brain parenchyma has not been sufficiently examined so far. This study aimed to evaluate whether the amount of NIR light that can penetrate through the human skull can cause a biological effect. MethodsThree commercially available devices (a medical laser emitting light at a wavelength of 905 nm and two LED helmets operating at wavelengths of 810 nm and 1070 nm, respectively) were used to measure the NIR light transmittance through human post-mortem skulls with a thermal power sensor. Furthermore, the biological effects of the fraction of light power that passed through the skull were investigated in a human neuronal cell line and in C. elegans. ResultsThe 905 nm laser achieved transmittances of up to 0.31% (173 {micro}W/cm2) of its input power, and the LED helmets 0.71% (41 {micro}W/cm2; 810 nm) and 0.45% (19 {micro}W/cm2; 1070 nm) of their respective input powers. NIR light exposure at a power density of 134 mW/cm2 was sufficient to activate mitochondrial metabolism in cultured human neurons and C. elegans, as demonstrated by increased cytochrome c oxidase activity and induction of mitochondrial chaperones. However, this stimulatory effect was no longer observed when the applied power density was reduced to 2.5 mW/cm2. ConclusionsMore than 99% of the NIR light emitted by the investigated devices was either absorbed or scattered by the human skull. The residual NIR light that would reach underlying brain structures was too weak to elicit biological effects. In conclusion, NIR light treatment is unlikely to be effective to treat brain diseases such as AD due to the low penetrability of the skull.

neuroscience↗

bioRxiv2024

A Novel C. elegans Model for Tau spreading Reveals Genes Critical for Endolysosomal Integrity and Seeded Tau Aggregation

The spreading of Tau pathology is closely associated with the progression of neurodegeneration and cognitive decline in Alzheimers disease and other tauopathies. A key event in this process is the rupture of endolysosomal vesicles following the intercellular transfer of Tau aggregates, releasing the transferred Tau species into the cytosol where they can promote the aggregation of endogenous Tau. However, understanding of the cellular pathways involved in this process remains limited. In this study, we investigated cellular pathways that prevent endolysosomal vesicle rupture. We established a new C. elegans model of Tau spreading by introducing an mCherry-labelled, disease-associated aggregation-prone fragment of human Tau (F3{Delta}K281::mCh) into the six touch receptor neurons. F3{Delta}K281::mCh transgenic animals exhibited significant neurotoxicity and mechanosensory deficits due to the accumulation of this Tau fragment. In addition, its intercellular transmission compromised the endolysosomal system in receiving hypodermal cells. Using this model, we conducted an unbiased genome-wide RNAi screen and identified 59 genes critical for maintaining endolysosomal integrity. GO-term analysis revealed an enrichment of genes related to the ESCRT complex, the ubiquitin-proteasome system, mRNA splicing, and fatty acid metabolism. Silencing of selected conserved genes exacerbated seeded Tau aggregation in a human induced pluripotent stem cell (hiPSC)-derived cortical neuron model and triggered endolysosomal rupture in HEK293T cells, confirming the crucial role of endolysosomal damage in seeded Tau aggregation. Overall, this study discovered novel cellular pathways that safeguard endolysosomal integrity. These findings may guide the development of therapeutics that improve endolysosomal integrity to halt the progression of Tau pathology.

cell biology↗

bioRxiv2024

Sphingolipid imbalance aggravates fibrillar Tau-induced endomembrane rigidification and rupture

Endolysosomal dysfunction is a hallmark of Alzheimers disease (AD) and related tauopathies, yet underlying mechanisms remain poorly understood. This study investigates the role of sphingolipid metabolism in maintaining endolysosomal membrane integrity and its impact on tau aggregation and toxicity in Caenorhabditis elegans and human cell culture models. Fluorescence recovery after photobleaching and C-Laurdan dye imaging revealed that silencing sphingolipid metabolism genes reduced endolysosomal vesicle membrane fluidity, increasing their rupture. The accumulation of aggregated tau in endolysosomal vesicles further aggravated endomembrane rigidification and damage and promoted seeded tau aggregation, potentially by facilitating the escape of tau seeds from the endolysosomal system. Supplementation with unsaturated fatty acids improved membrane fluidity, suppressing endolysosomal rupture and seeded tau aggregation in cell models, and alleviating tau-associated neurotoxicity in C. elegans. Together, this study provides mechanistic insight into how perturbation of sphingolipid metabolism promotes endolysosomal membrane damage and contributes to the escape of aggregated tau from this compartment, suggesting that restoration of membrane fluidity may represent a strategy to limit tau propagation and toxicity.

cell biology↗

bioRxiv2022

Dissecting aggregation and seeding dynamics of α-Syn polymorphs using the phasor approach to FLIM

Synucleinopathies are a heterogenous group of neurodegenerative diseases characterized by the progressive accumulation of pathological -synuclein (-Syn). The importance of structural polymorphism of -Syn assemblies for distinct synucleinopathies and their progression is increasingly recognized. However, the underlying mechanisms are poorly understood. Here we use fluorescence lifetime imaging microscopy (FLIM) to investigate seeded aggregation of -Syn in a biosensor cell line. We show that conformationally distinct -Syn polymorphs exhibit characteristic fluorescence lifetimes. FLIM further revealed that -Syn polymorphs were differentially processed by cellular clearance pathways, yielding fibrillar species with increased seeding capacity. Thus, FLIM is not only a powerful tool to distinguish different amyloid structures, but also to monitor the dynamic process of amyloid remodeling by the cellular environment. Our data suggest that the accumulation of highly seeding competent degradation products for particular polymorphs may account for accelerated disease progression in some patients.

molecular biology↗

bioRxiv2019

Disassembly of Tau fibrils by the human Hsp70 disaggregation machinery generates small seeding-competent species

The accumulation of amyloid Tau aggregates is implicated in Alzheimers disease and other Tauopathies. Molecular chaperones are known for their function in maintaining protein homeostasis by preventing the formation or promoting the disaggregation of amorphous and amyloid protein aggregates. Here we show that an ATP-dependent human chaperone system disassembles Tau fibrils in vitro. This function is mediated by the core chaperone Hsc70, assisted by specific co-chaperones, in particular class B J-domain proteins and an Hsp110-type NEF. Recombinant fibrils assembled from all six Tau isoforms as well as Sarkosyl-resistant Tau aggregates extracted from cell culture were processed by the Hsp70 disaggregation machinery, demonstrating the ability of this machinery to recognize a broad range of Tau aggregates. Chaperone treatment released monomeric, and small oligomeric Tau species, which induced the aggregation of self-propagating Tau species in a Tau cell culture model. We infer from these results that the activity of the Hsp70 disaggregation machinery is a double-sided sword as it attempts to eliminate Tau amyloids but with the price of generating new seeds. The Hsp70 disaggregase therefore has a crucial function in the Tau propagation cycle, rendering it a potential drug target in Tauopathies.

molecular biology↗

bioRxiv2019

HSP110 dependent HSP70 disaggregation machinery mediates prion-like propagation of amyloidogenic proteins in metazoa

The gradual accumulation and prion-like propagation of -synuclein and other amyloidogenic proteins is associated with devastating neurodegenerative diseases. The metazoan disaggregation machinery, a specific combination of HSP70 and its co-chaperones, is able to disassemble -synuclein fibrils in vitro, but the physiological consequence in vivo is unknown. To explore this, we used Caenorhabditis elegans models that exhibit pathological features of -synuclein, such as misfolding, intercellular spreading and toxicity. We inhibited the HSP70 disaggregase by depleting the crucial component HSP-110 and monitored the effect on -synuclein related phenotypes. The knockdown of HSP-110 not only impaired HSP70 disaggregation activity and prevented the resolubilization of amorphous heat shock induced firefly luciferase aggregates, but also compromised the cellular folding capacity. In stark contrast, HSP-110 depletion reduced -synuclein foci formation, cell-to-cell transmission and toxicity. Similar effects were observed for a polyQ model substrate, confirming that inhibition of HSP70 disaggregation function mitigates amyloid toxicity. These data demonstrate that the metazoan HSP70 disaggregation complex plays a critical role in the prion-like propagation of amyloid-type conformers. Therefore, the HSP70 disaggregation activity is a double-edged sword as it is essential for the maintenance of cellular proteostasis while being involved in the generation of toxic amyloid-type protein species.

cell biology↗