Overexpression of UBA5 in Cells Mimics the Phenotype of Cells Lacking UBA5

UBA5 inhibition restricts lung adenocarcinoma via blocking macrophage M2 polarization and cisplatin resistance

UBA5, a ubiquitin-like activated enzyme involved in ufmylation and sumoylation, presents a viable target for pancreatic and breast cancer treatments, yet its role in lung adenocarcinoma (LUAD) remains underexplored. This study reveals UBA5's tumor-promoting effect in LUAD, as evidenced by its upregulation in patients and positive correlation with TNM stages. Elevated UBA5 levels predict poor outcomes for these patients. Pharmacological inhibition of UBA5 using DKM 2-93 significantly curtails the growth of A549, H1299, and cisplatin-resistant A549 (A549/DDP) LUAD cells in vitro. Additionally, UBA5 knockdown via shRNA lentivirus suppresses tumor growth both in vitro and in vivo. High UBA5 expression adversely alters the tumor immune microenvironment, affecting immunostimulators, MHC molecules, chemokines, receptors, and immune cell infiltration. Notably, UBA5 expression correlates positively with M2 macrophage infiltration, the predominant immune cells in LUAD. Co-culture experiments further demonstrate that UBA5 knockdown directly inhibits M2 macrophage polarization and lactate production in LUAD. Moreover, in vivo studies show reduced M2 macrophage infiltration following UBA5 knockdown. UBA5 expression is also associated with increased tumor heterogeneity, including tumor mutational burden, microsatellite instability, neoantigen presence, and homologous recombination deficiency. Experiments indicate that UBA5 overexpression promotes cisplatin resistance in vitro, whereas UBA5 inhibition enhances cisplatin sensitivity in both in vitro and in vivo settings. Overall, these findings suggest that targeting UBA5 inhibits LUAD by impeding cancer cell proliferation, M2 macrophage polarization, and cisplatin resistance.

Patient derived model of UBA5-associated encephalopathy identifies defects in neurodevelopment and highlights potential therapies

UBA5 encodes for the E1 enzyme of the UFMylation cascade, which plays an essential role in ER homeostasis. The clinical phenotypes of UBA5-associated encephalopathy include developmental delays, epilepsy and intellectual disability. To date, there is no humanized neuronal model to study the cellular and molecular consequences of UBA5 pathogenic variants. We developed and characterized patient-derived cortical organoid cultures and identified defects in GABAergic interneuron development. We demonstrated aberrant neuronal firing and microcephaly phenotypes in patient-derived organoids. Mechanistically, we show that ER homeostasis is perturbed along with exacerbated unfolded protein response pathway in cells and organoids expressing UBA5 pathogenic variants. We also assessed two gene expression modalities that augmented UBA5 expression to rescue aberrant molecular and cellular phenotypes. Our study provides a novel humanized model that allows further investigations of UBA5 variants in the brain and highlights novel systemic approaches to alleviate cellular aberrations for this rare, developmental disorder.

UFMylation: a ubiquitin-like modification

Post-translational modifications (PTMs) add a major degree of complexity to the proteome and are essential controllers of protein homeostasis. Amongst the hundreds of PTMs identified, ubiquitin and ubiquitin-like (UBL) modifications are recognized as key regulators of cellular processes through their ability to affect protein-protein interactions, protein stability, and thus the functions of their protein targets. Here, we focus on the most recently identified UBL, ubiquitin-fold modifier 1 (UFM1), and the machinery responsible for its transfer to substrates (UFMylation) or its removal (deUFMylation). We first highlight the biochemical peculiarities of these processes, then we develop on how UFMylation and its machinery control various intertwined cellular processes and we highlight some of the outstanding research questions in this emerging field.

A guide to UFMylation, an emerging posttranslational modification

Ubiquitin Fold Modifier-1 (UFM1) is a ubiquitin-like modifier (UBL) that is posttranslationally attached to lysine residues on substrates via a dedicated system of enzymes conserved in most eukaryotes. Despite the structural similarity between UFM1 and ubiquitin, the UFMylation machinery employs unique mechanisms that ensure fidelity. While physiological triggers and consequences of UFMylation are not entirely clear, its biological importance is epitomized by mutations in the UFMylation pathway in human pathophysiology including musculoskeletal and neurodevelopmental diseases. Some of these diseases can be explained by the increased endoplasmic reticulum (ER) stress and disrupted translational homeostasis observed upon loss of UFMylation. The roles of UFM1 in these processes likely stem from its function at the ER where ribosomes are UFMylated in response to translational stalling. In addition, UFMylation has been implicated in other cellular processes including DNA damage response and telomere maintenance. Hence, the study of UFM1 pathway mechanics and its biological function will reveal insights into fundamental cell biology and is likely to afford new therapeutic opportunities for the benefit of human health. To this end, we herein provide a comprehensive guide to the current state of knowledge of UFM1 biogenesis, conjugation, and function with an emphasis on the underlying mechanisms.