Biology subjects

Melentijevic, I.

Publications and source records attributed to Melentijevic, I..

3 recordsLinked to original sources

bioRxiv2023

Mechanical force of uterine occupation enables large vesicle extrusion from proteostressed maternal neurons

Large vesicle extrusion from neurons may contribute to spreading pathogenic protein aggregates and promoting inflammatory responses, two mechanisms leading to neurodegenerative disease. Factors that regulate extrusion of large vesicles, such as exophers produced by proteostressed C. elegans touch neurons, are poorly understood. Here we document that mechanical force can significantly potentiate exopher extrusion from proteostressed neurons. Exopher production from the C. elegans ALMR neuron peaks at adult day 2 or 3, coinciding with the C. elegans reproductive peak. Genetic disruption of C. elegans germline, sperm, oocytes, or egg/early embryo production can strongly suppress exopher extrusion from the ALMR neurons during the peak period. Conversely, restoring egg production at the late reproductive phase through mating with males or inducing egg retention via genetic interventions that block egg-laying can strongly increase ALMR exopher production. Overall, genetic interventions that promote ALMR exopher production are associated with expanded uterus lengths and genetic interventions that suppress ALMR exopher production are associated with shorter uterus lengths. In addition to the impact of fertilized eggs, ALMR exopher production can be enhanced by filling the uterus with oocytes, dead eggs, or even fluid, supporting that distention consequences, rather than the presence of fertilized eggs, constitute the exopher-inducing stimulus. We conclude that the mechanical force of uterine occupation potentiates exopher extrusion from proximal proteostressed maternal neurons. Our observations draw attention to the potential importance of mechanical signaling in extracellular vesicle production and in aggregate spreading mechanisms, making a case for enhanced attention to mechanobiology in neurodegenerative disease.

neuroscience↗

bioRxiv2022

Intermediate Filaments Associate with Aggresome-like Structures and Influence Rate of Cellular Expulsion of Neuronal Disease Aggregates

Under conditions of proteostasis disequilibrium, neurons can enhance intracellular and extracellular protective mechanisms to guard against neurotoxicity. In mammals, an intracellular response to severe proteostasis imbalance that results from proteosome inhibition is the formation of juxtanuclear intermediate filament-surrounded, aggregate-filled aggresomes, which sequester threatening aggregates for later disposal via lysosomal degradation. Highly proteo-stressed neurons can also engage the assistance of neighboring cells in aggregate removal by loading threatening materials into large exopher vesicles that are transferred to neighboring cells for remote degradation of contents, a process that has been suggested to be analogous to the process that enables aggregate spreading in the human brain in neurodegenerative disease. In C. elegans these large extruded vesicles are called exophers. Here we document that players involved in aggresome biology are required for the elimination of potentially deleterious materials in neuronal exophers. We show that in proteostressed C. elegans touch receptor neurons, intermediate filament proteins IFD-1 and IFD-2 can assemble into juxtanuclear structures with multiple molecular and cellular characteristics of mammalian aggresomes. IFD-concentrating structures depend upon orthologs of mammalian adapter proteins, dynein motors, and microtubule integrity for aggregate collection into juxtanuclear compartments where they associate with ubiquitinated and neurotoxic polyglutamine expansion proteins. Strikingly, disruption of aggresome-decoration genes encoding IFDs or disruption of the BAG/14-3-3/Hsc70 adapter that promote aggregate loading of aggresome-like organelles, lowers exopher production via a cell autonomous mechanism. Although aggresome-like structures are not mandatory exopher cargo, IFD compartments can be extruded from neurons in exophers, revealing a previously unreported strategy to eliminate neuronal aggresome-like organelles via transfer to neighboring cells. Human IF neurofilament light chain hNFL can partially substitute for C. elegans IFD-2 proteins in promoting exopher production, indicating conservation of the capacity of intermediate filaments to influence neuronal aggregate extrusions across phyla. In sum, we identify a requirement for specific intermediate filaments, counterparts of human biomarkers of neuronal injury and disease and major components of Parkinsons disease Lewy bodies, in C. elegans neuronal aggresome-like organelle formation and large vesicle exopher extrusion from stressed neurons.

cell biology↗

bioRxiv2019

Automated Lifespan Determination Across Caenorhabditis Strains and Species Reveals Assay-Specific Effects of Chemical Interventions

The goal of the Caenorhabditis Intervention Testing Program is to identify robust and reproducible pro-longevity interventions that are efficacious across genetically diverse cohorts in the Caenorhabditis genus. The project design features multiple experimental replicates collected by three different laboratories. Our initial effort employed fully manual survival assays. With an interest in increasing throughput, we explored automation with flatbed scanner-based Automated Lifespan Machines (ALMs). We used ALMs to measure survivorship of 22 Caenorhabditis strains spanning three species. Additionally, we tested five chemicals that we previously found extended lifespan in manual assays. Overall, we found similar sources of variation among trials for the ALM and our previous manual assays, verifying reproducibility of outcome. Survival assessment was generally consistent between the manual and the ALM assays, although we did observe radically contrasting results for certain compound interventions. We found that particular lifespan outcome differences could be attributed to protocol elements such as enhanced light exposure of specific compounds in the ALM, underscoring that differences in technical details can influence outcomes and therefore interpretation. Overall, we demonstrate that the ALMs effectively reproduce a large, conventionally scored dataset from a diverse test set, independently validating ALMs as a robust and reproducible approach towards aging-intervention screening.

physiology↗