Biology subjects

Sauvageau, E.

Publications and source records attributed to Sauvageau, E..

3 recordsLinked to original sources

bioRxiv2024

Phosphorylation on serine 72 modulates Rab7A palmitoylation and retromer recruitment

AbstractThe small GTPase Rab7A has a key role in regulating membrane trafficking at late endosomes. By interacting with several different effectors, this small GTPase controls late endosome mobility, orchestrates fusion events between late endosomes and lysosomes, and participates in the formation of and regulates the fusion between autophagosomes and lysosomes. Rab7A is also responsible for the spatiotemporal recruitment of retromer, which is required for the endosome-to-TGN retrieval of cargo-receptors such as sortilin and CI-MPR. Recently several post-translational modifications have been shown to modulate Rab7A functions, including palmitoylation, ubiquitination and phosphorylation. Here we show that phosphorylation of Rab7A at serine 72 is important to modulate its interaction with retromer, as the non-phosphorylatable Rab7AS72A mutant is not able to interact with and recruit retromer to late endosomes. We have previously shown that Rab7A palmitoylation is also required for efficient retromer recruitment. We found that palmitoylation of Rab7AS72A is reduced compared to the wild-type protein, suggesting an interplay between S72 phosphorylation and palmitoylation in regulating the Rab7A/retromer interaction. Finally, we identify NEK7 as the kinase required to phosphorylate Rab7A to promote retromer binding and recruitment.

cell biology↗

bioRxiv2020

CLN5 and CLN3 function as a complex to regulate endolysosome function

CLN5 is a soluble endolysosomal protein whose function is poorly understood. Mutations in this protein cause a rare neurodegenerative disease, Neuronal Ceroid Lipofuscinosis. We previously found that depletion of CLN5 leads to dysfunctional retromer, resulting in the degradation of the lysosomal sorting receptor, sortilin. However, how a soluble lysosomal protein can modulate the function of a cytosolic protein, retromer, is not known. In this work, we show that deletion of CLN5 not only results in retromer dysfunction, but also in impaired endolysosome fusion events. This results in delayed degradation of endocytic proteins and in defective autophagy. CLN5 modulates these various pathways by regulating downstream interactions between CLN3, an endolysosomal integral membrane protein whose mutations also result in Neuronal Ceroid Lipofuscinosis, Rab7A, and a subset of Rab7A effectors. Our data supports a model where CLN3 and CLN5 function as an endolysosome complex regulating various functions. Summary StatementWe have previously demonstrated that CLN3 is required for efficient endosome-to-trans Golgi Network (TGN) trafficking of sortilin by regulating retromer function. In this work, we show that CLN5, which interacts with CLN3, regulates retromer function by modulating key interactions between CLN3, Rab7A, retromer, and sortilin. Therefore, CLN3 and CLN5 serve as endosomal switch regulating the itinerary of the lysosomal sorting receptors.

cell biology↗

bioRxiv2019

CLN3 regulates endosomal function by modulating Rab7A activity

Mutations in CLN3 are a cause of juvenile NCL (JNCL), also known as Batten Disease. Clinical manifestations includes cognitive regression, progressive loss of vision and motor function, epileptic seizures, and a significantly reduced lifespan. CLN3 localizes to endosomes and lysosomes, and has been implicated in intracellular trafficking and autophagy. However, the precise molecular function of CLN3 remains to be elucidated. We show that CLN3 interacts with Rab7A, a small GTPase that regulates several functions at late endosomes. We found that CLN3 is required for the efficient endosome-to-TGN trafficking of the lysosomal sorting receptors by regulating the Rab7A/retromer interaction. In cells lacking CLN3 or expressing CLN3 harbouring a disease-causing mutation, the lysosomal sorting receptors were degraded. We also demonstrated that CLN3 is required for the Rab7A/PLEKHM1 interaction, which is required for autophagosome/lysosome fusion. Overall, our data provides a molecular explanation behind phenotypes observed in JNCL.

cell biology↗