bims-lycede 2024-09-08 papers

Issue of 2024‒09‒08
three papers selected by
Sofía Peralta, Universidad Nacional de Cuyo

Cell Mol Biol Lett. 2024 Sep 05. 29(1): 116

Lysosome quality control in health and neurodegenerative diseases.

Veronica Ferrari, Barbara Tedesco, Marta Cozzi, Marta Chierichetti, Elena Casarotto, Paola Pramaggiore, Laura Cornaggia, Ali Mohamed, Guglielmo Patelli, Margherita Piccolella, Riccardo Cristofani, Valeria Crippa, Mariarita Galbiati, Angelo Poletti, Paola Rusmini.

Lysosomes are acidic organelles involved in crucial intracellular functions, including the degradation of organelles and protein, membrane repair, phagocytosis, endocytosis, and nutrient sensing. Given these key roles of lysosomes, maintaining their homeostasis is essential for cell viability. Thus, to preserve lysosome integrity and functionality, cells have developed a complex intracellular system, called lysosome quality control (LQC). Several stressors may affect the integrity of lysosomes, causing Lysosomal membrane permeabilization (LMP), in which membrane rupture results in the leakage of luminal hydrolase enzymes into the cytosol. After sensing the damage, LQC either activates lysosome repair, or induces the degradation of the ruptured lysosomes through autophagy. In addition, LQC stimulates the de novo biogenesis of functional lysosomes and lysosome exocytosis. Alterations in LQC give rise to deleterious consequences for cellular homeostasis. Specifically, the persistence of impaired lysosomes or the malfunctioning of lysosomal processes leads to cellular toxicity and death, thereby contributing to the pathogenesis of different disorders, including neurodegenerative diseases (NDs). Recently, several pieces of evidence have underlined the importance of the role of lysosomes in NDs. In this review, we describe the elements of the LQC system, how they cooperate to maintain lysosome homeostasis, and their implication in the pathogenesis of different NDs.

Keywords: Galectins; Lysosomal membrane permeabilization; Lysosome; Lysosome quality control; Neurodegeneration

DOI: https://doi.org/10.1186/s11658-024-00633-2

Nat Commun. 2024 Sep 05. 15(1): 7743

The V-ATPase complex component RNAseK is required for lysosomal hydrolase delivery and autophagosome degradation.

Agata N Makar, Alina Boraman, Peter Mosen, Joanne E Simpson, Jair Marques, Tim Michelberger, Stuart Aitken, Ann P Wheeler, Dominic Winter, Alex von Kriegsheim, Noor Gammoh.

Autophagy is a finely orchestrated process required for the lysosomal degradation of cytosolic components. The final degradation step is essential for clearing autophagic cargo and recycling macromolecules. Using a CRISPR/Cas9-based screen, we identify RNAseK, a highly conserved transmembrane protein, as a regulator of autophagosome degradation. Analyses of RNAseK knockout cells reveal that, while autophagosome maturation is intact, cargo degradation is severely disrupted. Importantly, lysosomal protease activity and acidification remain intact in the absence of RNAseK suggesting a specificity to autolysosome degradation. Analyses of lysosome fractions show reduced levels of a subset of hydrolases in the absence of RNAseK. Of these, the knockdown of PLD3 leads to a defect in autophagosome clearance. Furthermore, the lysosomal fraction of RNAseK-depleted cells exhibits an accumulation of the ESCRT-III complex component, VPS4a, which is required for the lysosomal targeting of PLD3. Altogether, here we identify a lysosomal hydrolase delivery pathway required for efficient autolysosome degradation.

DOI: https://doi.org/10.1038/s41467-024-52049-3

J Cell Sci. 2024 Sep 02. pii: jcs.261938. [Epub ahead of print]

ExoJ: an ImageJ2/Fiji plugin for automated spatiotemporal detection and analysis of exocytosis.

Junjun Liu, Frederik Johannes Verweij, Guillaume van Niel, Thierry Galli, Lydia Danglot, Philippe Bun.

Exocytosis is a dynamic physiological process that enables the release of biomolecules to the surrounding environment via the fusion of membrane compartments to the plasma membrane. Understanding its mechanisms is crucial, as defects can compromise essential biological functions. The development of pH-sensitive optical reporters alongside fluorescence microscopy enables the assessment of individual vesicle exocytosis events at the cellular level. Manual annotation represents, however, a time-consuming task, prone to selection biases and human operational errors. Here, we introduce ExoJ, an automated plugin based on ImageJ2/Fiji. ExoJ identifies user-defined genuine populations of exocytosis events, recording quantitative features including intensity, apparent size and duration. We designed ExoJ to be fully user-configurable, making it suitable to study distinct forms of vesicle exocytosis regardless of the imaging quality. Our plugin demonstrates its capabilities by showcasing distinct exocytic dynamics among tetraspanins and vesicular SNAREs protein reporters. Assessment of performance on synthetic data showed ExoJ is a robust tool, capable to correctly identify exocytosis events independently of signal-to-noise ratio conditions. We propose ExoJ as a standard solution for future comparative and quantitative studies of exocytosis.

Keywords: Exocytosis; Fluorescent imaging; ImageJ; Live-cell imaging; PH-sensitive probe

DOI: https://doi.org/10.1242/jcs.261938