Aminoacyl-tRNA synthetase complex interacting multifunctional protein 2 (AIMP2) is a component of the eukaryote-specific multisynthetase complex (MSC), a macromolecular assembly of eight aminoacyl-tRNA synthetases (ARS) and three scaffolding components known as aminoacyl-tRNA synthetase interacting multifunctional proteins (AIMP1-3). Recent studies show that bi-allelic mutations in AIMP2 cause a neurodevelopmental syndrome that overlaps phenotypically with disorders caused by recessive ARS mutations. In this work, we further characterize AIMP2 mutations in two patients with severe neurodevelopmental disorders, including one previously unreported compound heterozygous patient. We show patient-derived fibroblast AIMP2 mutations cause decreased protein expression, attenuation of protein synthesis, and dysregulation of the MSC component, methionyl-tRNA synthetase (MARS1). CRISPR-mediated disruption of aimp2 in zebrafish led to increased cell death and atrophy in the developing brain, further supporting a link between AIMP2 dysfunction and neurodevelopmental defects. We tested anticodon engineered suppressor tRNAs on expression of disease-associated nonsense mutations and found that they dramatically increase protein expression of AIMP2 variants. Together, these data demonstrate that AIMP2 depletion leads to neurodevelopmental dysfunction in both human and zebrafish, and suggest that therapies such as anticodon engineered suppressor tRNAs could improve patient outcomes.
Efficient repair of DNA double-strand breaks (DSBs) is essential for maintaining genome stability and conferring tumor radioresistance. Histone H2B monoubiquitination at lysine 120 (H2BK120ub), catalyzed by the RNF20/RNF40 E3 ligase complex, promotes DSB repair by coordinating chromatin remodeling and repair factor recruitment. Here we identify transketolase (TKT) as a non-enzymatic regulator of DNA damage repair in colorectal cancer cells. TKT enhances DNA repair efficiency and radioresistance independently of its catalytic activity by facilitating RNF20-dependent H2BK120ub. Mechanistically, TKT interacts with both the RNF20/RNF40 complex and the FACT chromatin remodeling complex, functioning as a non-enzymatic adaptor that facilitates FACT-RNF20 association and RNF20 foci formation following DNA damage. Disruption of this TKT-FACT-RNF20 axis impairs RNF20 foci formation and H2BK120ub induction, increases DNA damage, and enhances radiosensitivity. These findings reveal a previously unrecognized non-enzymatic adaptor function of TKT in DNA damage repair and highlight a potential vulnerability in radioresistant tumors.
ARID1B, a key subunit of the SWI/SNF (also known as BAF) chromatin remodeling complex, is characterized as a canonical tumor suppressor across various cancer types. Although the downregulation of ARID1B transcript levels has been observed in many cancers, its regulation at the protein level is comparatively less studied. Here, we identify WWP2, an E3 ubiquitin ligase, as a previously undescribed interaction partner of ARID1B. Our results show that WWP2 interacts with the PPxY motif located at the N terminus of ARID1B through its WW domains. We further demonstrate that wild-type WWP2, but not a catalytically inactive mutant counterpart, regulates ARID1B protein stability through ubiquitination-mediated proteasomal degradation. Interestingly, WWP2 appears to facilitate noncanonical K27- and K29-linked polyubiquitination of ARID1B. Additionally, silencing WWP2 expression results in a decrease in ubiquitination and a subsequent increase in ARID1B protein levels, indicating that WWP2 plays a crucial role in regulating ARID1B stability. Finally, based on several tumorigenic assays performed in cell lines and mouse xenograft models, we show that WWP2 may modulate ARID1B-mediated tumor suppression. Our results therefore highlight a new mechanism of post-translational regulation of ARID1B, which may have implications in ARID1B-mediated tumor suppression.
RNF213 was originally identified as a susceptibility gene for Moyamoya disease (MMD), and its variants are also associated with other vascular occlusive disorders, including pulmonary arterial hypertension and large-artery atherosclerosis. RNF213 encodes a large protein with AAA+ ATPase and E3 ubiquitin ligase activities and has been implicated in vasculopathy as well as cellular responses to microbial infection and lipid stress. However, the precise biological functions of RNF213 and the pathogenic mechanisms underlying disease-associated mutations remain poorly understood. Recent studies have suggested lipid-induced stress may play a key role in MMD pathogenesis. Therefore, we performed temporal transcriptomic analyses to identify RNF213-regulated signaling pathways in response to palmitate, the most common saturated fatty acid. Our results demonstrate that RNF213 is required for activation of apoptosis, the unfolded protein response, and NFκB signaling, as well as for the regulation of autophagy and oxidative stress responses following palmitate exposure. These functions were dependent on both the AAA+ ATPase and RZ-finger domains of RNF213 while MMD-associated RNF213 mutations enhanced palmitate-induced signaling responses. Together, these findings suggest that gain-of-function RNF213 mutations, combined with dysregulated lipid metabolism, contribute to the pathogenesis of RNF213-associated vasculopathies.
Host-microbe interactions within the gut have been extensively reviewed in the context of host immune response. Emerging evidence, however, highlights that these inflammatory and immune outcomes are often deeply intertwined with the microbiome-derived secondary metabolites. The gut microbiota functions in concert with the host by providing an extensive repertoire of metabolic enzymes that enhance digestion and capacity to assimilate a broad spectrum of ingested food sources. This symbiotic metabolism generates a diverse array of bioactive metabolites that shape local and systemic physiology, adaptive immune responses, and neuroimmune responses. Here, we focus on microbial metabolism as a central organizing principle of host-microbiota symbiosis. Microbiota-derived metabolites, including short-chain fatty acids, secondary bile acids, tryptophan-derived indoles, sphingolipids, and gaseous byproducts, signal through downstream molecular partners like nuclear receptors, transcriptional regulators, and redox-sensitive homeostatic pathways to regulate host energy homeostasis, but also alter immune functions like gut epithelial integrity, immune tolerance, and neuroimmune crosstalk. Finally, we discuss emerging therapeutic strategies that target microbial metabolic functions-including dietary interventions, engineered probiotics, postbiotics, and receptor-directed approaches-that position microbial metabolism as a tractable axis for modulating immunometabolism homeostasis and potentially mitigating metabolic and inflammatory diseases.
