Biology subjects

Agrotis, A.

Publications and source records attributed to Agrotis, A..

5 recordsLinked to original sources

bioRxiv2024

ATG5 is dispensable for ATG8ylation of cellular proteins

Protein ATG8ylation refers to a post-translational modification involving covalent attachment of ubiquitin-like autophagy-related protein ATG8 (LC3/GABARAP) to other cellular proteins, with reversal mediated by ATG4 proteases. While lipid ATG8ylation is important for autophagosome formation and mechanistically well-characterized, little is known about the mechanism of protein ATG8ylation. Here, we investigated the conjugation machinery of protein ATG8ylation in CRISPR/Cas9-engineered knockout human cell lines, utilizing a deconjugation-resistant (Q116P G120) form of MAP1LC3B. We report that protein ATG8ylation requires the E1-like activating enzyme ATG7 and E2-like conjugating enzyme ATG3, in common with ATG8 lipidation. However, in contrast, the E3-like ATG12-ATG5-ATG16L1 complex involved in lipidation is dispensable for protein ATG8ylation, since ATG5 knockout cells can form ATG8ylated protein conjugates. Further, we uncover that ATG7 itself is a target of ATG8ylation. Overall, our work provides crucial insight into the mechanism of protein ATG8ylation, distinguishing it from ATG8 lipidation, which will aid investigating its functional role.

cell biology↗

bioRxiv2023

Cardiac glycosides restore autophagy flux in an iPSC-derived neuronal model of WDR45 deficiency

Beta-Propeller Protein-Associated Neurodegeneration (BPAN) is one of the commonest forms of Neurodegeneration with Brain Iron Accumulation, caused by mutations in the gene encoding the autophagy-related protein, WDR45. The mechanisms linking autophagy, iron overload and neurodegeneration in BPAN are poorly understood and, as a result, there are currently no disease-modifying treatments for this progressive disorder. We have developed a patient-derived, induced pluripotent stem cell (iPSC)-based midbrain dopaminergic neuronal cell model of BPAN (3 patient, 2 age-matched controls and 2 isogenic control lines) which shows defective autophagy and aberrant gene expression in key neurodegenerative, neurodevelopmental and collagen pathways. A high content imaging-based medium-throughput blinded drug screen using the FDA-approved Prestwick library identified 5 cardiac glycosides that both corrected disease-related defective autophagosome formation and restored BPAN-specific gene expression profiles. Our findings have clear translational potential and emphasise the utility of iPSC-based modelling in elucidating disease pathophysiology and identifying targeted therapeutics for early-onset monogenic disorders.

cell biology↗

bioRxiv2022

Actin remodelling controls proteasome homeostasis upon stress

When cells are stressed, bulk translation is often downregulated to reduce energy demands whilst stress-response proteins are simultaneously upregulated. 19S Regulatory Particle Assembly-Chaperones (RPACs) are selectively translated upon TORC1 inhibition to promote proteasome assembly and activity, maintaining cell viability. However, the molecular mechanism for such selective translational upregulation is unclear. Using yeast, we discover that remodelling of the actin cytoskeleton is important for RPAC translation following TORC1 inhibition. mRNA of the RPAC ADC17 travels along actin cables and is enriched at cortical actin patches under stress, dependent upon the early endocytic protein Ede1. ede1{Delta} cells failed to induce RPACs and proteasome assembly upon TORC1 inhibition. Conversely, artificially tethering ADC17 mRNA to cortical actin patches enhanced its translation upon stress. These findings suggest that actin dense structures such as cortical actin patches may serve as a translation platform for a subset of stress-induced mRNAs including regulators of proteasome homeostasis.

cell biology↗

bioRxiv2021

Proximity interactome of LC3B in normal growth conditions

LC3 (Light Chain 3) is a key player of autophagy, a major stress-responsive proteolysis pathway promoting cellular homeostasis. It coordinates the formation and maturation of autophagosomes and recruits cargo to be further degraded upon autophagosome-lysosome fusion. To orchestrate its functions, LC3 binds to multiple proteins from the autophagosomes inner and outer membranes, but the full extent of these interactions is not known. Moreover, LC3 has been increasingly reported in other cellular locations than the autophagosome, with cellular outcome not fully understood and not all related to autophagy. Furthermore, novel functions of LC3 as well as autophagy can occur in cells growing in a normal medium thus in non-stressed conditions. A better knowledge of the molecule in proximity to LC3 in normal growth conditions will improve the understanding of LC3 function in autophagy and in other cell biology function. Using an APEX2 based proteomic approach, we have detected 407 proteins in proximity to the well-characterised LC3B isoform in non-stress conditions. These include known and novel LC3B proximity proteins, associated with various cell localisation and biological functions. Sixty-nine of these proteins contain a putative LIR (LC3 Interacting Region) including 41 not reported associated to autophagy. Several APEX2 hits were validated by co-immunoprecipitation and co-immunofluorescence. This study uncovers the LC3B global interactome and reveals novel LC3B interactors, irrespective of LC3B localisation and function. This knowledge could be exploited to better understand the role of LC3B in autophagy and non-autophagy cellular processes.

cell biology↗

bioRxiv2020

High-content screening for rare respiratory diseases: readthrough therapy in primary ciliary dyskinesia

Development of therapeutic approaches for rare respiratory diseases is hampered by the lack of systems that allow medium-to-high-throughput screening of fully differentiated respiratory epithelium from affected patients. This is a particular problem for primary ciliary dyskinesia (PCD), a rare genetic disease caused by mutations in genes that adversely affect ciliary movement and consequently mucociliary transport. Primary cell culture of basal epithelial cells from nasal brush biopsies, followed by ciliated differentiation at air-liquid interface (ALI) has proven to be a useful tool in PCD diagnostics but the techniques broader utility, including in pre-clinical PCD research, has been limited by the number of basal cells that it is possible to expand from such biopsies. Here, we describe a high-content, imaging-based screening method, enabled by extensive expansion of PCD patient basal cells and their culture into differentiated human respiratory epithelium in miniaturised 96-well transwell format ALI cultures. Analyses of ciliary beat pattern, beat frequency and ultrastructure indicate that a range of different PCD defects are retained in these cultures. We perform a proof-of-principle personalized investigation in reduced generation of motile cilia (RGMC), a rare and very severe form of PCD, in this case caused by a homozygous nonsense mutation (c.441C>A; p.Cys147*) in the MCIDAS gene. The screening system allowed multiple drugs inducing translational readthrough to be evaluated alone or in combination with inhibitors of nonsense-mediated decay. Restoration of basal body formation in the patients nasal epithelial cells was seen in vitro, suggesting a novel avenue for drug evaluation and development in PCD. SummaryWe describe primary cell culture of nasal epithelial cells from patients with primary ciliary dyskinesia including differentiatiation of these to a ciliary phenotype and high-content screening in miniaturised air-liquid interface cultures.

cell biology↗