Biology subjects

Sadoul, R.

Publications and source records attributed to Sadoul, R..

3 recordsLinked to original sources

bioRxiv2025

CARM1-mediated methylation controls interactions of ALIX with key partners important for cytokinesis

CARM1 is an arginine methyltransferase with a well-established role in regulating gene expression, but its cytoplasmic functions remain largely uncharacterized. Here, we identified ALIX, a protein acting with the ESCRT-III machinery in numerous membrane remodeling events, as a main cytoplasmic partner and a relevant substrate of CARM1. We demonstrate that CARM1 methylates arginine residues within the proline-rich motif of ALIX. At the molecular level, ALIX methylation impairs SH3-dependent association with CD2AP, CIN85, and endophilin-A2 that are required for cytokinesis. Using a mutant of ALIX that is unable to bind these proteins, we further show that these interactions are essential for ALIX functions during cytokinesis. Altogether, this work highlights the significance of arginine methylation as a regulatory post-translational modification important for the final step of cell division, by modulating interactions between proline-rich domains and their SH3-containing partners.

cell biology↗

bioRxiv2025

Lack of evidence for cargo release of CD63-EVs into recipient cells

Extracellular vesicles (EVs), including exosomes, are widely believed to mediate intercellular communication by delivering molecular cargo to recipient cells. However, the efficiency and mechanisms of such cargo delivery remain unclear. In this study, we investigated whether EVs bearing the canonical exosomal marker CD63 are capable of fusing with recipient cell membranes to release their contents. Using the highly sensitive NanoBiT split luciferase system, we tracked potential fusion events between HiBiT-tagged CD63-EVs and HEK cells expressing cytosolic or endosome-localized LgBiT. While HiBiT and LgBiT reconstitution was readily detected when EVs carried the viral fusion protein VSV-G, no luminescence was observed with native CD63-EVs, despite their uptake or binding by recipient cells. Similarly, EVs carrying HiBiT-HSP70 failed to show evidence of cargo release. These findings demonstrate that unmodified CD63-EVs do not fuse with the plasma or endosomal membranes of recipient cells, suggesting that EV-mediated cargo delivery via membrane fusion is inefficient or absent under physiological conditions. Our results challenge the prevailing view of exosome function in intercellular communication and underscore the need for re-evaluation of EV cargo transfer mechanisms.

cell biology↗

bioRxiv2020

ALG-2 interacting protein-X (Alix) is required for activity-dependent bulk endocytosis at brain synapses

In chemical synapses undergoing high frequency stimulation, vesicle components can be retrieved from the plasma membrane via a clathrin-independent process called activity dependent bulk endocytosis (ADBE). Alix (ALG-2 interacting protein X)/ PDCD6IP) is an adaptor protein binding to ESCRT and endophilin-A proteins which is required for clathrin-independent endocytosis in fibroblasts. Alix is expressed in neurons and concentrates at synapses during epileptic seizures. Here, we used cultured neurons to show that Alix is recruited to presynapses where it interacts with, and concentrates endophilin-A during conditions triggering ADBE. Using Alix knockout (ko) neurons we showed that this recruitment, which requires interaction with the calcium-binding protein ALG-2, is necessary for ABDE. We also found that presynaptic compartments of Alix ko hippocampi display subtle morphological defects compatible with flawed synaptic activity and plasticity detected electrophysiologically. Furthermore, mice lacking Alix in the forebrain undergo less seizures during kainate-induced status epilepticus and reduced propagation of the epileptiform activity. These results thus show that impairment of ADBE due to the lack of neuronal Alix alters synaptic recovery during physiological or pathological repeated stimulations.

neuroscience↗