Munoz-Ruiz, R. | bioRxiv Science

bioRxiv2024

Antibacterial effectors in Dictyostelium discoideum: specific activity against different bacterial species

Dictyostelium discoideum is a phagocytic amoeba continuously eating, killing and digesting bacteria. Previous studies have detected in D. discoideum cell extracts a bacteriolytic activity effective against Klebsiella pneumoniae bacteria. In this study we characterized bacteriolytic activities found in D. discoideum cell extracts against five different bacteria (K. pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis). We first analyzed the bacteriolytic activity against these five bacteria in parallel over a range of pH values. We then measured the remaining bacteriolytic activity in D. discoideum kil1 and modA KO mutants. We also performed partial fractionation of D. discoideum extracts and assessed activity against different bacteria. Together our results indicate that optimal bacteriolytic activity against different bacteria results from the action of different effectors. Proteomic analysis allowed us to propose a list of potential bacteriolytic effectors. IMPORTANCEMany antibacterial effectors have been characterized over the last decades, and their biological importance, mode of action and specificity is often still under study. Here we characterized in vitro bacteriolytic activity in D. discoideum extracts against five species of gram-negative and gram-positive bacteria. Our results reveal that optimal lysis of different bacteria mobilizes different effectors. Proteomic analysis generated a list of potential bacteriolytic effectors. This work opens the way for future analysis of the role of individual effectors in living D. discoideum cells.

cell biology↗

bioRxiv2020

Functional characterization of Neurofilament Light b splicing and misbalance in zebrafish

Neurofilaments (NFs), a major cytoskeletal component of motor neurons, play a key role in their differentiation, establishment and maintenance of their morphology and mechanical strength. The de novo assembly of these neuronal intermediate filaments requires the presence of the neurofilament light subunit, NEFL, which expression is reduced in motor neurons in Amyotrophic Lateral Sclerosis (ALS). This study used zebrafish as a model to characterize the NEFL homologue neflb, which encodes two different isoforms via splicing of the primary transcript (neflbE4 and neflbE3). In vivo imaging showed that neflb is crucial for proper neuronal development, and that disrupting the balance between its two isoforms specifically affects NF assembly and motor axon growth, with resulting motor deficits. This equilibrium is also disrupted upon partial depletion of TDP-43, a RNA binding protein that is mislocalized into cytoplasmic inclusions in ALS. The study supports interaction of NEFL expression and splicing with TDP-43 in a common pathway, both biologically and pathogenetically.

neuroscience↗