bims-nocaut 2024-06-23 papers

Issue of 2024‒06‒23
two papers selected by
Quentin Frenger, University of Strasbourg

Autophagy. 2024 Jun 20.

Secretory autophagy - a new paradigm regulating synaptic plasticity.

When exposed to new experiences or changes in the environment, neurons rapidly remodel their synaptic structure and function in a process called activity-induced synaptic remodeling. This process is necessary for transforming transient experiences into stable, lasting memories. The molecular mechanisms underlying acute, activity-dependent synaptic changes are not well understood, partly because processes regulating synaptic plasticity and neurodevelopment are intricately linked. By using an RNAi screen in Drosophila targeting genes associated with human nervous system function, we found that while macroautophagy (referred to as autophagy) is fundamental for both synapse development and synaptic plasticity, activity-induced synaptic remodeling does not rely on genes associated with lysosomal degradation. These findings suggest a requirement for the unconventional secretory autophagy pathway in regulating synaptic plasticity, wherein autophagosomes, instead of fusing with lysosomes for degradation, fuse with the plasma membrane to release their contents extracellularly. To test this hypothesis, we knocked down Sec22, Snap29, and Rab8, molecular components required for secretory autophagy, all of which disrupted structural and functional plasticity. Additionally, by monitoring autophagy, we demonstrated that neuronal activity suppresses degradative autophagy to shift the pathway toward secretory autophagy release. Our work unveils secretory autophagy as a novel trans-synaptic signaling mechanism crucial for activity-induced synaptic remodeling.

Keywords: Activity-induced synaptic remodeling; Drosophila; secretory autophagy; synaptic plasticity

DOI: https://doi.org/10.1080/15548627.2024.2370179

Int J Mol Sci. 2024 Jun 04. pii: 6175. [Epub ahead of print]25(11):

Autophagy Promotes Enrichment of Raft Components within Extracellular Vesicles Secreted by Human 2FTGH Cells.

Valeria Manganelli, Luciana Dini, Stefano Tacconi, Simone Dinarelli, Antonella Capozzi, Gloria Riitano, Serena Recalchi, Tuba Rana Caglar, Federica Fratini, Roberta Misasi, Maurizio Sorice, Tina Garofalo.

Autophagy plays a key role in removing protein aggregates and damaged organelles. In addition to its conventional degradative functions, autophagy machinery contributes to the release of cytosolic proteins through an unconventional secretion pathway. In this research, we analyzed autophagy-induced extracellular vesicles (EVs) in HT1080-derived human fibrosarcoma 2FTGH cells using transmission electron microscopy and atomic force microscopy (AFM). We preliminary observed that autophagy induces the formation of a subset of large heterogeneous intracellular vesicular structures. Moreover, AFM showed that autophagy triggering led to a more visible smooth cell surface with a reduced amount of plasma membrane protrusions. Next, we characterized EVs secreted by cells following autophagy induction, demonstrating that cells release both plasma membrane-derived microvesicles and exosomes. A self-forming iodixanol gradient was performed for cell subfractionation. Western blot analysis showed that endogenous LC3-II co-fractionated with CD63 and CD81. Then, we analyzed whether raft components are enriched within EV cargoes following autophagy triggering. We observed that the raft marker GD3 and ER marker ERLIN1 co-fractionated with LC3-II; dual staining by immunogold electron microscopy and coimmunoprecipitation revealed GD3-LC3-II association, indicating that autophagy promotes enrichment of raft components within EVs. Introducing a new brick in the crosstalk between autophagy and the endolysosomal system may have important implications for the knowledge of pathogenic mechanisms, suggesting alternative raft target therapies in diseases in which the generation of EV is active.

Keywords: ERLIN1; autophagy; exosomes; extracellular vesicles; lipid rafts

DOI: https://doi.org/10.3390/ijms25116175