Biology subjects

Rodger, C.

Publications and source records attributed to Rodger, C..

3 recordsLinked to original sources

bioRxiv2024

Protrudin acts at ER-endosome contacts to promote KIF5-mediated endosomal fission and endosome-to-Golgi transport

Fission of transport tubules from early endosomes is required for endosomal sorting, but mechanisms of endosomal tubule fission (ETF) are incompletely understood. We show protrudin acts at ER-endosome contacts to promote ETF and endosome-to-Golgi traffic. Protrudin-mediated ETF required its ability to interact with ER-localised VAP proteins, endosomal phosphoinositides and KIF5. These properties also regulated the distance between protrudin and endosomal tubules. The defective ETF phenotype of increased endosomal tubulation in cells lacking protrudin was phenocopied by depletion of KIF5, but not FYCO1, a motor protein adaptor implicated in protrudin-dependent late endosome motility. It also required intact microtubules and dynein, consistent with a model where protrudin facilitates a tug-of-war between KIF5 and dynein to fission tubules. In addition to its direct role, protrudin links many other machineries involved in ETF, thus our findings elucidate how ETF is co-ordinated. These machineries are enriched for proteins implicated in hereditary motor neuron disorders, and protrudin or KIF5 depletion caused defective ETF in human neurons. SummaryProtrudin binds ER-localised VAPs and endosomal phosphoinositides to form ER-endosome contacts that promote endosomal tubule fission and endosome-to-Golgi traffic. Protrudin recruits KIF5 to provide a FYCO1-independent force to fission endosomal tubules in neurons and non-polarised cells.

cell biology↗

bioRxiv2024

Atlastin-1 regulates endosomal tubulation and lysosomal proteolysis in human cortical neurons

Mutation of the ATL1 gene is one of the most common causes of hereditary spastic paraplegia (HSP), a group of genetic neurodegenerative conditions characterised by distal axonal degeneration of the corticospinal tract axons. Atlastin-1, the protein encoded by ATL1, is one of three mammalian atlastins, which are homologous dynamin-like GTPases that control endoplasmic reticulum (ER) morphology by fusing tubules to form the three-way junctions that characterise ER networks. However, it is not clear whether atlastin-1 is required for correct ER morphology in human neurons and if so what the functional consequences of lack of atlastin-1 are. Using CRISPR-inhibition we generated human cortical neurons lacking atlastin-1. We demonstrate that ER morphology was altered in these neurons, with a reduced number of three-way junctions. Neurons lacking atlastin-1 had longer endosomal tubules, suggestive of defective tubule fission. This was accompanied by reduced lysosomal proteolytic capacity. As well as demonstrating that atlastin-1 is required for correct ER morphology in human neurons, our results indicate that lack of a classical ER-shaping protein such as atlastin-1 may cause altered endosomal tubulation and lysosomal proteolytic dysfunction. Furthermore, they strengthen the idea that defective lysosome function contributes to the pathogenesis of a broad group of HSPs, including those where the primary localisation of the protein involved is not at the endolysosomal system.

cell biology↗

bioRxiv2021

AP-4 regulates neuronal lysosome composition, function and transport via regulating export of critical lysosome receptor proteins at the trans-Golgi network

The adaptor protein complex-4 or AP-4 is known to mediate autophagosome maturation through regulating sorting of transmembrane cargo such as ATG9A at the Golgi. There is a need to understand AP-4 function in neurons, as mutations in any of its four subunits cause a complex form of hereditary spastic paraplegia (HSP) with intellectual disability. While AP-4 has been implicated in regulating trafficking and distribution of cargo such as ATG9A and APP, little is known about its effect on neuronal lysosomal protein traffic, lysosome biogenesis and function. In this study, we demonstrate that in human iPSC-derived neurons AP-4 regulates lysosome composition, function and transport via regulating export of critical lysosomal receptors, including Sortilin 1, from the trans-Golgi network to endo-lysosomes. Additionally, loss of AP-4 causes endo-lysosomes to stall and build up in axonal swellings potentially through reduced recruitment of retrograde transport machinery to the organelle. These findings of axonal lysosome build-up are highly reminiscent of those observed in Alzheimers disease as well as in neurons modelling the most common form of HSP, caused by spastin mutations. Our findings implicate AP-4 as a critical regulator of neuronal lysosome biogenesis and altered lysosome function and axonal endo-lysosome transport as an underlying defect in AP-4 deficient HSP.

cell biology↗