Subunit Of Complex Research Articles

Loss of cytoplasmic actin filaments raises nuclear actin levels to drive INO80C-dependent chromosome fragmentation.

Loss of cytosolic actin filaments upon TORC2 inhibition triggers chromosome fragmentation in yeast, which results from altered base excision repair of Zeocin-induced lesions. To find the link between TORC2 kinase and this yeast chromosome shattering (YCS) we performed phosphoproteomics. YCS-relevant phospho-targets included plasma membrane-associated regulators of actin polymerization, such as Las17, the yeast Wiscott-Aldrich Syndrome protein. Induced degradation of Las17 was sufficient to trigger YCS in presence of Zeocin, bypassing TORC2 inhibition. In yeast, Las17 does not act directly at damage, but instead its loss, like TORC2 inhibition, raises nuclear actin levels. Nuclear actin, in complex with Arp4, forms an essential subunit of several nucleosome remodeler complexes, including INO80C, which facilitates DNA polymerase elongation. Here we show that the genetic ablation of INO80C activity leads to partialYCS resistance, suggesting that elevated levels of nuclear G-actin may stimulate INO80C to increase DNA polymerase processivity and convert single-strand lesions into double-strand breaks.

ARID1A is a Coactivator of STAT5 that Contributes to CD8+ T Cell Dysfunction and Anti-PD-1 Resistance in Gastric Cancer.

ARID1A deletion mutation contributes to improved treatment of several malignancies with immune checkpoint inhibitors (ICIs). However, its role in modulating of tumor immune microenvironment (TIME) of gastric cancer (GC) remains unclear. Here, we report an increase of CD8+ T cells infiltration in GC patients with ARID1A-mutation (MUT), which enhances sensitivity to ICIs. Kaplan-Meier survival analysis showed that ARID1A-mutation patients with gastrointestinal malignancies benefit from immunotherapy. Transcriptome analysis implicated that ARID1A regulates STAT5 downstream targets to inhibit T-cell mediated toxicity. Integrated dual luciferase assay and ChIP-qPCR analyses indicated that ARID1A coordinated with STAT5 to facilitate the transcription of the immunosuppressive factors TGF-β1 and NOX4. ARID1A recruited canonical BAF complex (cBAF) subunits, including SMARCB1 and SMARCD1, to sustain DNA accessibility. Downregulation of ARID1A reduced chromatin remodeling into configurations which make GC more sensitive to ICIs. In addition, targeting STAT5 effectively improved anti-PD-1 efficiency in ARID1A-wild type (WT) GC patients. Taken together, ARID1A is a coactivator of STAT5, function as a chromatin organizer in GC ICIs resistance, and targeting STAT5 is an effective strategy to improve the efficiency of ICIs in GC.

Abstract PR015: Decoding RNA metabolism by RNA-linked CRISPR screening in human cells

Abstract RNAs undergo a complex choreography of metabolic processes in human cells that are regulated by thousands of RNA-associated proteins. While the effects of individual RNA-associated proteins on RNA metabolism have been extensively characterized, the full complement of regulators for most RNA metabolic events remain unknown. Here we present a massively parallel RNA-linked CRISPR (ReLiC) screening approach to measure the responses of diverse RNA metabolic events to knockout of 2,092 human genes encoding all known RNA-associated proteins. ReLiC screens highlight modular interactions between gene networks regulating splicing, translation, and decay of mRNAs. When combined with biochemical fractionation of polysomes, ReLiC reveals striking pathway-specific coupling between growth fitness and mRNA translation. Perturbing different components of the translation and proteostasis machineries have distinct effects on ribosome occupancy, while perturbing mRNA transcription leaves ribosome occupancy largely intact. Isoform-selective ReLiC screens capture differential regulation of intron retention and exon skipping by SF3b complex subunits. Chemogenomic screens using ReLiC decipher translational regulators upstream of mRNA decay and uncover a role for the ribosome collision sensor GCN1 during treatment with the anti-leukemic drug homoharringtonine. Our work demonstrates ReLiC as a versatile platform for discovering and dissecting regulatory principles of human RNA metabolism. Citation Format: Patrick J Nugent, Heungwon Park, Arvind Rasi Subramaniam. Decoding RNA metabolism by RNA-linked CRISPR screening in human cells [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RNAs as Drivers, Targets, and Therapeutics in Cancer; 2024 Nov 14-17; Bellevue, Washington. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(11_Suppl):Abstract nr PR015.

Molecular mechanisms of MAZ targeting up-regulation of NDUFS3 expression to promote malignant progression in melanoma.

Myc-associated Zinc-finger Protein (MAZ) has been implicated in the malignant progression of various tumors. However, its expression and functional relationship of MAZ in melanoma have not been previously investigated. This study confirms elevated expression of MAZ in melanoma, correlating with poor patient prognosis. Furthermore, our findings demonstrate that MAZ enhances melanoma progression by promoting proliferation, migration and invasion. It is worth noting that we found that MAZ can target and regulate the transcription of NADH dehydrogenase [ubiquinone] iron-sulfur protein 3 (NDUFS3), a core subunit of mitochondrial complex I, to enhance mitochondrial metabolism and thus promote malignant progression of melanoma. Predictive modeling indicates that the co-expression of MAZ and NDUFS3 could serve as a potential prognostic marker for melanoma patients.

The Mediator complex subunit MoMed15 plays an important role in conferring sensitivity to isoprothiolane by modulating xenobiotic metabolism in M. oryzae.

Rice blast caused by Magnaporthe oryzae is one of the most economically important rice diseases. Fungicides such as isoprothiolane (IPT) have been used extensively for rice blast control, but resistance to IPT in M. oryzae is an emerging threat. In this study, molecular mechanisms of resistance in IPT-resistant mutants were identified. Through whole-genome sequencing and genetic transformation, we identified the gene MoMed15, encoding a transcriptional glutamine-rich co-activator Mediator complex subunit, in which mutations or deletion resulted in moderate IPT resistance. Further research found that MoMed15 physically interacted with the IPT resistance regulatory factor MoIRR to simultaneously regulate both MoIRR expression and the expression of multiple xenobiotic-metabolizing enzymes in response to IPT stress. We hypothesize that some xenobiotic-metabolizing enzymes enhance IPT toxicity by modifying the IPT structure. Variation of MoMed15 affected the recruitment of the transcriptional Mediator complex and decreased the expression of these xenobiotic-metabolizing enzymes, resulting in moderate IPT resistance. We also found that MoPGR1, encoding a protein that activates cytochrome P450 enzymes, was essential to confer IPT sensitivity, and its expression was directly regulated by MoIRR.IMPORTANCEIsoprothiolane (IPT) has been used extensively for the management of rice blast disease and IPT-resistant subpopulations have emerged in Chinese rice fields. The emergence of resistant pathogen populations has led to a steep increase in fungicide use, increasing pesticide risk for the applicator and the environment. The molecular mechanisms of IPT resistance in M. oryzae remain elusive. In this study, we demonstrated that transcriptional co-activator MoMed15 interacts with IPT resistance regulator MoIRR to recruit the Mediator complex, which promotes the expression of xenobiotic-metabolizing enzymes, leading to exacerbated IPT toxicity. The MoMed15 could be used for IPT resistance detection in rice fields.

Loss of Brcc3 in Zebrafish Embryos Increases Their Susceptibility to DNA Damage Stress

DNA double-strand breaks (DSBs) represent one of the most severe forms of genetic damage in organisms, yet vertebrate models capable of monitoring DSBs in real-time remain scarce. BRCA1/BRCA2-containing complex subunit 3 (BRCC3), also known as BRCC36, functions within various multiprotein complexes to mediate diverse biological processes. However, the physiological role of BRCC3 in vertebrates, as well as the underlying mechanisms that govern its activity, are not well understood. To explore these questions, we generated brcc3-knockout zebrafish using CRISPR/Cas9 gene-editing technology. While brcc3 mutant zebrafish appear phenotypically normal and remain fertile, they exhibit significantly increased rates of mortality and deformity following exposure to DNA damage. Furthermore, embryos lacking Brcc3 display heightened p53 signaling, elevated γ-H2AX levels, and increased apoptosis in response to DNA-damaging agents such as ultraviolet (UV) light and Etoposide (ETO). Notably, genetic inactivation of p53 or pharmacological inhibition of Ataxia-telangiectasia mutated (ATM) activity rescues the hypersensitivity to UV and ETO observed in Brcc3-deficient embryos. These findings suggest that Brcc3 plays a critical role in DNA damage response (DDR), promoting cell survival during embryogenesis. Additionally, brcc3-null mutant zebrafish offer a promising vertebrate model for real-time monitoring of DSBs.

METTL14 regulates inflammation in ulcerative colitis via the lncRNA DHRS4-AS1/miR-206/A3AR axis.

As a chronic inflammatory bowel disease, the pathogenesis of ulcerative colitis (UC) has not been fully elucidated. N6-methyladenosine (m6A) modification, observed in various RNAs, is implicated in inflammatory bowel diseases. Methyltransferase-like 14 (METTL14) is the major subunit of the methyltransferase complex catalyzing m6A modifications. Here, we designated to examine the regulatory effects and mechanisms of METTL14 on long non-coding RNA (lncRNA) during UC progression. METTL14 knockdown decreased cell viability, promoted apoptosis, increased cleaved PARP and cleaved Caspase-3 levels, while reducing Bcl-2 levels. METTL14 knockdown also led to a significant increase in NF-κB pathway activation and inflammatory cytokine production in the Caco-2 cells treated with TNF-α. Moreover, the suppression of METTL14 aggravated colonic damage and inflammation in our dextran sulfate sodium (DSS)-induced murine colitis model. METTL14 silencing suppressed DHRS4-AS1 expression by reducing the m6A modification of DHRS4-AS1 transcripts. Furthermore, DHRS4-AS1 mitigated inflammatory injury by targeting the miR-206/adenosine A3 receptor (A3AR) axis. DHRS4-AS1 overexpression counteracted the enhancing impact of METTL14 knockdown on TNF-α-induced inflammatory injury in Caco-2 cells. In conclusion, our findings suggest that METTL14 protects against colonic inflammatory injury in UC via regulating the DHRS4-AS1/miR-206/A3AR axis, thus representing a potential therapeutic target for UC.

Combined effect of basic antiherpetic drugs with a new inhibitor of the terminase complex of herpes simplex virus type 1 in Vero cell culture

More than 90% of the world’s population are carriers of herpes simplex virus type 1 (HSV-1). The infection manifests itself in the formation of blisters and ulcers on the face or genitals, and can cause blindness, encephalitis, and generalized infection. All modern first- and second-line antiherpetic drugs selectively inhibit viral DNA-polymerase. The purine-benzoxazine conjugate LAS-131 [(S)-4-[6-(purin-6-yl)aminohexanoyl]-7,8-difluoro-3,4-dihydro-3-methyl-2H-[1,4]benzoxazine], which we described earlier, uses the large subunit of the HSV-1 terminase complex as a biotarget and selectively inhibits its reproduction in vitro. For the first time, we have obtained fundamentally new results on the combined effect of LAS-131 on human herpesvirus infection with practically significant antiviral compounds – nucleoside analogues (acyclovir [ACV], penciclovir [PCV], ganciclovir [GCV], brivudine [BVDU], iododeoxyuridine [IDU], adenine arabinoside [Ara-A], as well as a nucleoside phosphonate analogue (cidofovir [CDV]) and a pirophosphate analogue (foscarnet [FOS]). Using a inhibition assay of cytopathic effect (CPE) induced by a virus, it was shown that when combined with LAS-131, the concentrations of the compounds in combinations providing inhibition of HSV-1-induced CPE by 50%, decreased by 2 times (additive effect, FOS) or more (synergistic effect, ACV, PCV, GCV, IDU, BVDU, Ara-A, CDV). Reducing the concentrations of agents creates non-permissive conditions for the reproduction of HSV-1 and opens up new real possibilities for controlling human herpesvirus infection.

Anomalies of ATP-dependent chromatin remodeling complexes and human neurodevelopmental genetic disorders

ATP-dependent chromatin remodeling complexes play crucial roles in various biological processes including enhancing local DNA accessibility, regulating gene transcription, and facilitating DNA replication and repair. Based on their functional structural domains, these complexes may be categorized into four families, including SWI/SNF, ISWI, CHD and INO80. Such families are vital factors for regulating gene expression and play pivotal roles in developmental processes. Variants of genes encoding the components of such complexes have been closely associated with human developmental disorders and neurodevelopmental genetic syndromes. This review has summarized the classification, fundamental functions and underlying mechanism of the ATP-dependent chromatin remodeling complexes, as well as common neurological genetic disorders due to variants of genes encoding the subunits of such complexes.

POLG p.A962T Mutation Leads to Neuronal Mitochondrial Dysfunction That is Restored After Mitochondrial Transplantation

Mutations in DNA polymerase gamma (POLG) are known as the predominant cause of inherited mitochondrial disorders. But how these POLG mutations disturb mitochondrial function remains to be determined. Furthermore, no effective therapy, to date, has been reported for POLG diseases. Using differentiated SH-SY5Y cells, a human neuronal model cell line, the current study investigated whether the novel POLG variant p.A962T impairs mitochondrial function. This involved quantifying mitochondrial DNA (mtDNA) content using PCR and assessing the expression levels of the subunits of complex IV (COXI-IV), a complex I subunit NDUFV1 and Cytochrome C (Cyto C) release using Western blotting. Activities of mitochondrial complex I, II, and IV were measured using colorimetric assays. Mitochondrial membrane potential (ΔΨm) and ATP were evaluated using fluorescence assays and luminescent assays, respectively. In addition, we investigated whether mitochondrial transplantation (MT) using Pep-1-conjugated mitochondria could compensate for mitochondrial defects caused by the variant in cells carrying mutant POLG. The results of this study showed that POLG p.A962T mutation resulted in mitochondrial defects, including mitochondrial DNA (mtDNA) depletion, membrane potential (ΔΨm) depolarization and adenosine triphosphate (ATP) reduction. Mechanistically, POLG mutation-caused mtDNA depletion led to the loss of mtDNA-encoded subunits of complex I and IV and thus compromised their activities. POLG p.A962T mutation is a pathogenic mutation leading to mitochondrial malfunction and mtDNA depletion in neurons. Cell-penetrating peptide Pep-1-mediated MT treatment compensated for mitochondrial defects induced by these POLG variants, suggesting the therapeutic application of this method in POLG diseases.

The Cryptococcus neoformans STRIPAK complex controls genome stability, sexual development, and virulence.

This study focused on a highly conserved protein signaling complex known as STRIPAK, which is important for various developmental processes in fungi and humans. By investigating the functions of this complex in Cryptococcus neoformans , it was discovered to play crucial roles in maintaining genome stability, sexual development, and pathogenesis. In particular, mutations in the genes encoding two subunits of the STRIPAK complex were found to lead to significant defects, including abnormal growth and cell morphology, compromised stress response, and impaired virulence. Interestingly, mutation of a third STRIPAK complex subunit resulted in hypervirulence, characterized by increased thermotolerance, enhanced production of melanin pigment and polysaccharide capsule, and reduced survival in infected animals. Our findings reveal that the STRIPAK complex is an important regulator of growth and virulence of C. neoformans , highlighting its potential as a target for therapies aimed at combating fungal infections. This work furthers understanding of how the STRIPAK complex functions in Cryptococcus , and also in other organisms including humans, where related protein phosphatase complexes govern key cellular processes.

TORC1 Regulates Thermotolerance via Modulating Metabolic Rate and Antioxidant Capacity in Scallop Argopecten irradians irradians

Target of rapamycin complex 1 (TORC1) is a key regulator of metabolism in eukaryotes across multiple pathways. Although TORC1 has been extensively studied in vertebrates and some invertebrates, research on this complex in scallops is limited. In this study, we identified the genes encoding TORC1 complex subunits in the scallop Argopecten irradians irradians through genome-wide in silico scanning. Five genes, including TOR, RAPTOR, LST8, DEPTOR, and PRAS40, that encode the subunits of TORC1 complex were identified in the bay scallop. We then conducted structural characterization and phylogenetic analysis of the A. i. irradians TORC1 (AiTORC1) subunits to determine their structural features and evolutionary relationships. Next, we analyzed the spatiotemporal expressions of AiTORC1-coding genes during various embryo/larvae developmental stages and across different tissues in healthy adult scallops. The results revealed stage- and tissue-specific expression patterns, suggesting diverse roles in development and growth. Furthermore, the regulation of AiTORC1-coding genes was examined in temperature-sensitive tissues (the mantle, gill, hemocyte, and heart) of bay scallops exposed to high-temperature (32 °C) stress over different durations (0 h, 6 h, 12 h, 24 h, 3 d, 6 d, and 10 d). The expression of AiTORC1-coding genes was predominantly suppressed in the hemocyte but was generally activated in the mantle, gill, and heart, indicating a tissue-specific response to heat stress. Finally, functional validation was performed using the TOR inhibitor rapamycin to suppress AiTORC1, leading to an enhanced catabolism, a decreased antioxidant capacity, and a significant reduction in thermotolerance in bay scallops. Collectively, this study elucidates the presence, structural features, evolutional relationships, expression profiles, and roles in antioxidant capacity and metabolism regulation of AiTORC1 in the bay scallop, providing a preliminary understanding of its versatile functions in response to high-temperature challenges in marine mollusks.

Neddylation of protein, a new strategy of protein post-translational modification for targeted treatment of central nervous system diseases

Neddylation, a type of protein post-translational modification that links the ubiquitin-like protein NEDD8 to substrate proteins, can be involved in various significant cellular processes and generate multiple biological effects. Currently, the best-characterized substrates of neddylation are the Cullin protein family, which is the core subunit of the Cullin-RING E3 ubiquitin ligase complex and controls many important biological processes by promoting ubiquitination and subsequent degradation of various key regulatory proteins. The normal or abnormal process of protein neddylation in the central nervous system can lead to a series of occurrences of normal functions and the development of diseases, providing an attractive, reasonable, and effective targeted therapeutic strategy. Therefore, this study reviews the phenomenon of neddylation in the central nervous system and summarizes the corresponding substrates. Finally, we provide a detailed description of neddylation involved in CNS diseases and treatment methods that may be used to regulate neddylation for the treatment of related diseases.

An EED/PRC2-H19 Loop Regulates Cerebellar Development.

EED (embryonic ectoderm development) is a core subunit of the polycomb repressive complex 2 (PRC2), which senses the trimethylation of histone H3 lysine 27 (H3K27). However, its biological function in cerebellar development remains unknown. Here, we show that EED deletion from neural stem cells (NSCs) or cerebellar granule cell progenitors (GCPs) leads to reduced GCPs proliferation, cell death, cerebellar hypoplasia, and motor deficits in mice. Joint profiling of transcripts and ChIP-seq analysis in cerebellar granule cells reveals that EED regulates bunches of genes involved in cerebellar development. EED ablation exhibits overactivation of a developmental repressor long non-coding RNA H19. Importantly, an obvious H3K27ac enrichment is found at Ctcf, a trans-activator of H19, and H3K27me3 enrichment at the H19 imprinting control region (ICR), suggesting that EED regulates H19 in an H3K27me3-dependent manner. Intriguingly, H19 deletion reduces EED expression and the reprogramming of EED-mediated H3K27me3 profiles, resulting in increased proliferation, differentiation, and decreased apoptosis of GCPs. Finally, molecular and genetic evidence provides that increased H19 expression is responsible for cerebellar hypoplasia and motor defects in EED mutant mice. Thus, this study demonstrates that EED, H19 forms a negative feedback loop, which plays a crucial role in cerebellar morphogenesis and controls cerebellar development.

A rare genetic association of one silent (ADGRV1) and other unquiet (MED13L) mutation: A case report

Two genes likely to cause epilepsy, one silent and the other manifesting in a patient with drug-resistant epilepsy, can be quite unusual. Herein, we described the case of a 2-year-old girl who presented with predominant language development delay, facial dysmorphism, and refractory epilepsy with normal neuroimaging and metabolic profiles, which prompted us to consider genetic etiology. Her genetic test revealed two novel likely pathogenic mutations, in Mediator complex subunit 13-like (MED13L) and adhesion G protein-coupled receptor V1 (ADGRV1). Sanger sequencing of her parents revealed an ADGRV1 variant in her unaffected mother. The child had a phenotypic match with the MED13L genotype. However, only a few cases of MED13L have reported refractory epilepsy and the corresponding mutation was missense. To the best of our knowledge, this is the first case of frameshift mutation in MED13L presenting with refractory epilepsy. Although the child harbored two likely pathogenic mutations, the one inherited from her mother in ADGRV1 did not manifest, whereas the frameshift mutation in MED13L had expressed as refractory epilepsy, which has not been described hitherto.

Sex Differences in Response to Diet Enriched with Glutathione Precursors in the Aging Heart.

Common features of the aging heart are dysregulated metabolism, inflammation, and fibrosis. Elevated oxidative stress is another hallmark of cardiac aging that can exacerbate each of these conditions. We hypothesize that by increasing natural antioxidant levels (glutathione), we will improve cardiac function. Twenty-one-month-old mice were fed Glycine and N-Acetyl Cysteine (GlyNAC) (glutathione precursors)-supplemented or control diets for 12 weeks. Heart function was monitored longitudinally, and the exercise performance was determined at the end of the study. We found that the GlyNAC diet was beneficial for old male but not old female mice, leading to an increase of Ndufb8 expression (a subunit of the mitochondrial respiratory chain complex), and higher enzymatic activity for CPT1b and CrAT, two carnitine acyltransferases that are critical to cardiomyocyte metabolism. Although no quantifiable change of collagen turnover was detected, hearts from GlyNAC-fed old males exhibited a slight but significant enrichment in Fmod, a protein that can inhibit collagen fibril formation, possibly reducing extracellular matrix (ECM) stiffness and thus improving diastolic function. Cardiac diastolic function was modestly improved in males but not females, and surprisingly GlyNAC-fed female mice showed a decline in exercise performance. In summary, our work supports the concept that aged male and female hearts are phenotypically different. These basic differences may affect the response to pharmacological and diet interventions, including antioxidants.

Clinical, Laboratory, and Molecular Characteristics of Inherited Vitamin K-Dependent Coagulation Factors Deficiency.

Vitamin K-dependent coagulation factors deficiency (VKCFD) is a rare autosomal recessive genetic disease characterized by impaired levels of multiple coagulation factors (II, VII, IX, and X) and natural anticoagulants (proteins C and S). VKCFD is part of familial multiple coagulation factor deficiencies, reporting overall 50 affected families thus far. Disease manifestations are quite heterogeneous, bleeding symptoms may vary, and even, although generally mild, some patients may succumb to fatal outcomes. VKCFD diagnosis may be delayed because the disease phenotype simulates the most frequently acquired deficiencies of vitamin K. First-line coagulation assays, prothrombin time/international normalized ratio (PT/INR) and activated partial thromboplastin time (aPTT), are both prolonged; mixing test typically normalizes the clotting times; and vitamin K-dependent coagulation factors will be variably decreased. Molecularly, VKCFD is associated with mutations in γ-glutamyl-carboxylase (GGCX) or vitamin K epoxide reductase complex subunit 1 (VKORC1) genes. Vitamin K is involved not only in the biosynthesis of coagulation proteins but also in bone metabolism and cell proliferation. Therapeutic options are based on vitamin K supplementation, coagulation factors (prothrombin complex), and fresh frozen plasma, in case of severe bleeding episodes. Two case studies here illustrate the diagnostic challenges of VKCFD: case 1 depicts a woman with a history of bleeding episodes, diagnosed, only in her third decade of life with inherited homozygous GGCX gene mutation. Case 2 shows a man with an acquired vitamin K deficiency caused by Crohn's disease. Better understanding of GGCX and VKORC1 mutations aids in prognosis and treatment planning, with emerging insights suggesting potential limitations in the effectiveness of vitamin K supplementation in certain mutations.

HADHA Regulates Respiratory Complex Assembly and Couples FAO and OXPHOS.

Oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO) are key bioenergetics pathways. The machineries for both processes are localized in mitochondria. Secondary OXPHOS defects have been documented in patients with primary FAO deficiencies, and vice versa. However, the underlying mechanisms remain unclear. Intrigued by the observations that regulation of supercomplexes (SCs) assembly in a mouse OXPHOS deficient cell line and its derivatives is associated with the changes in lipid metabolism, a proteomics analysis is carried out and identified mitochondrial trifunctional protein (MTP) subunit alpha (hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunit alpha, HADHA) as a potential regulatory factor for SCs assembly. HADHA-Knockdown cells and mouse embryonic fibroblasts (MEFs) derived from HADHA-Knockout mice displayed both reduced SCs assembly and defective OXPHOS. Stimulation of OXPHOS induced in cell culture by replacing glucose with galactose and of lipid metabolism in mice with a high-fat diet (HFD) both exhibited increased HADHA expression. HADHA Heterozygous mice fed with HFD showed enhanced steatosis associated with a reduction of SCs assembly and OXPHOS function. The results indicate that HADHA participates in SCs assembly and couples FAO and OXPHOS.

Human DCP1 is crucial for mRNA decapping and possesses paralog-specific gene regulating functions.

The mRNA 5'-cap structure removal by the decapping enzyme DCP2 is a critical step in gene regulation. While DCP2 is the catalytic subunit in the decapping complex, its activity is strongly enhanced by multiple factors, particularly DCP1, which is the major activator in yeast. However, the precise role of DCP1 in metazoans has yet to be fully elucidated. Moreover, in humans, the specific biological functions of the two DCP1 paralogs, DCP1a and DCP1b, remain largely unknown. To investigate the role of human DCP1, we generated cell lines that were deficient in DCP1a, DCP1b, or both to evaluate the importance of DCP1 in the decapping machinery. Our results highlight the importance of human DCP1 in decapping process and show that the EVH1 domain of DCP1 enhances the mRNA-binding affinity of DCP2. Transcriptome and metabolome analyses outline the distinct functions of DCP1a and DCP1b in human cells, regulating specific endogenous mRNA targets and biological processes. Overall, our findings provide insights into the molecular mechanism of human DCP1 in mRNA decapping and shed light on the distinct functions of its paralogs.

TC10 differently controls the dynamics of Exo70 in growth cones of cortical and hippocampal neurons

The exocyst is an octameric protein complex that acts as a tether for GOLGI-derived vesicles at the plasma membrane during exocytosis. It is involved in membrane expansion during axonal outgrowth. Exo70 is a major subunit of the exocyst complex and is controlled by TC10, a Rho family GTPase. How TC10 affects the dynamics of Exo70 at the plasma membrane is not well understood. There is also evidence that TC10 controls Exo70 dynamics differently in nonpolar cells and axons. To address this, we used super-resolution microscopy to study the spatially resolved effects of TC10 on Exo70 dynamics in HeLa cells and the growth cone of cortical and hippocampal neurons. We generated single particle localization and trajectory maps and extracted mean square displacements, diffusion coefficients, and alpha coefficients to characterize Exo70 diffusion. We found that the diffusivity of Exo70 was different in nonpolar cells and in the growth cone of neurons. TC10 stimulated the mobility of Exo70 in HeLa cells, but decreased the diffusion of Exo70 in the growth cone of cortical neurons. In contrast to cortical neurons, TC10 overexpression did not affect the mobility of Exo70 in the axonal growth cone of hippocampal neurons. These data suggest that mainly exocyst tethering in cortical neurons was under the control of TC10.