The rockefeller university

Hepatic mitochondria play critical roles in sustaining systemic nutrient balance, nitrogen detoxification, and cellular bioenergetics. These functions depend on tightly regulated mitochondrial processes, including amino acid catabolism, ammonia clearance via the urea cycle, and transport through specialized solute carriers. Genetic disruptions in these pathways underlie a range of inborn errors of metabolism, often resulting in systemic toxicity and neurological dysfunction. Here, we review the physiological functions of hepatic mitochondrial amino acid metabolism, with a focus on subcellular compartmentalization, disease mechanisms, and therapeutic strategies. We discuss how emerging genetic and metabolic interventions-including dietary modulation, cofactor replacement, and gene therapy-are reshaping treatment of liver-based metabolic disorders. Understanding these pathways offers mechanistic insights into metabolic homeostasis and reveals actionable vulnerabilities in metabolic disease and cancer.

Corynebacterium diphtheriae clade species secrete single-domain endo-beta-N-acetylglucosaminidases (ENGases) that specifically bind to human IgG antibodies and hydrolyze their N297-linked glycans. Here, we define the molecular mechanisms of IgG-specific deglycosylation for the entire family of corynebacterial IgG-specific ENGases, including but not limited to CU43 and CM49. By solving the crystal structure of CU43 in a 1:1 complex with the IgG1 Fc region, combined with targeted and saturation mutagenesis analysis and activity measurements using engineered antibodies, we establish an inter-protomeric mechanism of recognition and deglycosylation of IgG antibodies. Using in silico modeling, small-angle X-ray scattering and saturation mutagenesis we determine that CM49 uses a unique binding site on the Fc region, to process N297-linked glycans. Moreover, we demonstrate that CU43 treatment is highly effective in abrogating Fc effector functions in humanized mouse models, while preserving the neutralizing capacity of anti-influenza IgG antibodies, thereby conferring protection against lethal influenza challenge.

The Rev response element (RRE) forms an oligomeric complex with the viral protein Rev to facilitate the nuclear export of intron-retaining viral RNAs during the late phase of HIV-1 (human immunodeficiency virus type 1) infection. However, the structures and mechanisms underlying this process remain largely unknown. Here, we determined the crystal structure of the HIV-1 RRE stem-loop II (SLII), revealing a unique three-way junction architecture in which the base stem (IIa) bifurcates into the stem-loops (IIb and IIc) to compose Rev binding sites. The crystal structures of various SLII mutants demonstrated that while some mutants retain the same "compact" fold as the wild type, other single-nucleotide mutants induce drastic conformational changes, forming an "extended" SLII structure. Through in vitro Rev binding assays and Rev activity measurements in HIV-1-infected cells using structure-guided SLII mutants designed to favor specific conformers, we showed that while the compact fold represents a functional SLII, the alternative extended conformation inhibits Rev binding and oligomerization and consequently stimulates HIV-1 RNA nuclear export dysfunction. The propensity of SLII to adopt multiple conformations as captured in crystal structures and their influence on Rev oligomerization illuminate emerging perspectives on RRE structural plasticity-based regulation of HIV-1 nuclear export and provide opportunities for developing anti-HIV drugs targeting specific RRE conformations.

Mismatch repair deficient (MMRd) tumors harbor thousands of somatic mutations enriched for insertion-deletion (indels) conferring high sensitivity to immunotherapy. We sought to reproduce this phenotype using mutagenic agents to engineer an MMRd genotype in immunoresistant cells. The combination of temozolomide (TMZ) and cisplatin led to a rapid accumulation of a high mutational load enriched for indels in murine cell lines resulting from the epigenetic loss of Msh2. Pretreated cells showed sensitivity to PD-1 blockade. Systemic treatment with TMZ, cisplatin, and anti-PD-1 bearing immunoresistant tumor cells led to increased survival, intratumoral T cell infiltration, and downregulation of Msh2 expression without affecting healthy tissues. In a clinical trial with 18 patients with refractory mismatch repair proficient colorectal cancer, no responses were seen, but MMRd signatures emerged in cell-free DNA. These findings show that recapitulating an MMRd genotype through chemical mutagenesis can generate an immunogenic phenotype.

BackgroundArthropod-borne viruses (arboviruses) such as dengue virus (DENV) and Zika virus (ZIKV) pose a significant threat to global health. Novel approaches to control the spread of arboviruses focus on harnessing the antiviral immune system of their primary vector, the Aedes aegypti mosquito. In arthropods, genes of the Vago family are often presented as analogs of mammalian cytokines with potential antiviral functions, but the role of Vago genes upon virus infection in Ae. aegypti is largely unknown.ResultsWe conducted a phylogenetic analysis of the Vago gene family in Diptera, which led us to focus on a Vago-like gene that we named VLG-1. Using CRISPR/Cas9-mediated gene editing, we generated a VLG-1 mutant line of Ae. aegypti, which revealed a broad impact of VLG-1 on the mosquito transcriptome, affecting several biological processes potentially related to viral replication, including the oxidative stress response. Surprisingly, experimental viral challenge of the VLG-1 mutant line indicated a modest proviral role for this gene during DENV and ZIKV infections in vivo. In the absence of VLG-1, virus dissemination throughout the mosquito's body was slightly impaired, albeit not altering virus transmission rates.ConclusionsOur results challenge the conventional understanding of Vago-like genes as antiviral factors and underscore the need for further in vivo research to elucidate the molecular mechanisms underlying mosquito-arbovirus interactions.

Mitotic onset is a critical transition for eukaryotic cell proliferation. The commonly held view of mitotic control is that the master regulator, cyclin-dependent kinase (CDK), is first activated in the cytoplasm, at the centrosome, initiating mitosis1, 2-3. Bistability in CDK activation ensures that the transition is irreversible, but how this unfolds in a spatially compartmentalized cell is unknown4, 5, 6, 7-8. Here, using fission yeast, we show that CDK is first activated in the nucleus, and that the bistable responses differ markedly between the nucleus and the cytoplasm, with a stronger response in the nucleus driving mitotic signal propagation from there to the cytoplasm. Abolishing cyclin-CDK localization to the centrosome led to activation occurring only in the nucleus, spatially uncoupling the nucleus and cytoplasm mitotically, suggesting that centrosomal cyclin-CDK acts as a 'signal relayer'. We propose that the key mitotic regulatory system operates in the nucleus in proximity to DNA, which enables incomplete DNA replication and DNA damage to be effectively monitored to preserve genome integrity and to integrate ploidy within the CDK control network. This spatiotemporal regulatory framework establishes core principles for control of the onset of mitosis and highlights that the CDK control system operates within distinct regulatory domains in the nucleus and cytoplasm.

Loss-of-function (LOF) variants in IL6ST, encoding GP130, can cause hyper-IgE syndrome (HIES). Monoallelic LOF variants in IL6ST lead to HIES when located in the intracellular domain downstream of box 1/2 and upstream of the STAT3 phosphorylation sites and the recycling motif, due to their dominant negative (DN) activity. In this region, 2 previously unreported IL6ST variants, p.K702Sfs7* and p.Y759Wfs26*, were identified in 2 families with autosomal dominant (AD) HIES. Both variants were LOF and exhibited DN effects, leading to the accumulation of mutant GP130 on the cell surface. The p.K702Sfs7* mutation was the most upstream N-terminal mutation linked to HIES caused by heterozygous IL6STvariants. Comprehensive screening of IL6ST mutants revealed that most premature terminations downstream of amino acid F641, at the end of the transmembrane domain, resulted in LOF and DN effects via GP130 accumulation on the cell surface. The absence of the recycling motif (positions 782-787) in surface-expressed LOF GP130 led to its accumulation, contributing to the DN effect. The importance of intracellular truncating IL6STvariants can possibly be predicted based on the location of the premature stop codon. GP130 accumulation on the cell surface is a characteristic and potentially diagnostic finding in patients with HIES with heterozygous IL6STvariants.

Over 500 primary immunodeficiency diseases (PID) have been described, but immunological assessment after a severe infection is not routine. We aimed to evaluate the feasibility of a PID screening protocol and calculate PID prevalence in children admitted for severe infection in a pediatric intensive care unit (PICU). This monocentric retrospective study evaluated the feasibility of a PID monitoring protocol after severe infection in children aged 1 month to 16 years-old hospitalized in the Montpellier University Hospital from January 2018 to December 2020. Follow-up consultations at 3 and 12 months included the three main PID screening scores, comprehensive immunological and genetic screenings. Among 1125 children admitted to the PICU, 46 had severe infections and caused by bacterial (48%), viral (39%) or fungal (2%) pathogens. Before infection, none had completed any screening score recommended by dedicated societies (Jeffrey Modell Foundation, German Patients' Organization for Primary Immunodeficiencies, French Reference Center for Hereditary Immunodeficiencies). At 3 months, three patients had a PID diagnosis (6.5% prevalence, 95% CI 1.4-17.9). These were associated with a deletion of chromosomal region 22q11.21 (DiGeorge syndrome), ELANE mutation (Elastase deficiency or Severe Congenital Neutropenia 1), and C5 deficiency Forty children (87%) presented immunological anomalies without a formal PID diagnosis. These persisted in only 4/17 children tested at 12 months. The most frequent abnormalities were low NK lymphocytes (41.18%), and abnormal B lymphocyte population distribution (25%). The observed PID prevalence post-severe infection matches previous reports, even with a high rate of viral infections, often overlooked. Systematic PID investigation after severe infection, regardless of the pathogen, should be implemented to improve early detection and treatment.

To produce a murine monoclonal antibody (mAb) that binds to glycoprotein IIb/IIIa (alpha IIb beta 3) and inhibits clot retraction (CR), we immunized mice with human platelets and tested hybridoma supernatants for their ability to bind to alpha IIb beta 3 and inhibit CR. The immunoglobulin G1 (IgG1) mAb R6H8 completely inhibited CR at 20 mu g/mL. Paradoxically, at 5 mu g/mL, R6H8 initiated platelet aggregation and induced P-selectin expression, fibrinogen binding, and PAC-1 binding. At 20 mu g/mL, however, R6H8 completely inhibited aggregation induced by thrombin PAR-1 receptor activating peptide SFLLRN (T6; 25 mu g/mL) and T6-induced fibrinogen and PAC-1 binding to platelets. Platelet aggregation induced by R6H8 was inhibited by mAb IV.3, which blocks the Fc gamma IIa receptor (Fc gamma RIIa), and the Fab fragment of R6H8 did not induce platelet aggregation, suggesting that R6H8 binds to both alpha IIb beta 3 and Fc gamma RIIa. Cryogenic electron microscopy analysis of the R6H8 Fab-alpha IIb beta 3 complex revealed that R6H8 (1) binds to the alpha IIb beta 3 RGD binding pocket via an Arg-Tyr-Asp (RYD) sequence in its heavy chain complementarity-determining region 3; (2) interacts with beta 3 Asp126, producing a reorientation of Asp126 and loss of the adjacent to metal ion-dependent adhesion site Ca2+; and (3) initiates swing-out of the beta 3 hybrid domain. We conclude that R6H8 is an alpha IIb beta 3 ligand-mimetic mAb that activates platelets via Fc gamma RIIa at low concentrations and potently inhibits platelet aggregation and CR at high concentrations. R6H8 simulates the actions of a number of pathological antibodies, including platelet-activating antibodies developed after therapy with alpha IIb beta 3 inhibitors and platelet-activating antibodies in heparin-induced thrombocytopenia and vaccine-induced immune thrombotic thrombocytopenia. As such, it may be a valuable reagent for better understanding these disorders and identifying potential therapies.

Proper fuelling of the brain is critical to sustain cognitive function, but the role of fatty acid (FA) combustion in this process has been elusive. Here we show that acute block of a neuron-specific triglyceride lipase, DDHD2 (a genetic driver of complex hereditary spastic paraplegia), or of the mitochondrial lipid transporter CPT1 leads to rapid onset of torpor in adult male mice. These data indicate that in vivo neurons are probably constantly fluxing FAs derived from lipid droplets (LDs) through beta-oxidation to support neuronal bioenergetics. We show that in dissociated neurons, electrical silencing or blocking of DDHD2 leads to accumulation of neuronal LDs, including at nerve terminals, and that FAs derived from axonal LDs enter mitochondria in an activity-dependent fashion to drive local mitochondrial ATP production. These data demonstrate that nerve terminals can make use of LDs during electrical activity to provide metabolic support and probably have a critical role in supporting neuron function in vivo.