The rockefeller university

A critical component of the function of IgG antibodies is their capacity to engage specialized cellular receptors, Fc gamma receptors (Fc gamma Rs), expressed on effector leukocytes. Highlighting the importance of Fc gamma R-mediated signaling in the regulation of the fate, activation, and differentiation status of leukocytes, Fc gamma Rs are ubiquitously expressed by nearly all leukocyte populations. Here, we report that while at steady state, T cells are negative for all classes of Fc gamma Rs, CD8 T cells specifically induce the expression of the activating Fc gamma R, Fc gamma RIIIa, in response to viral infection in cohorts of COVID-19 and dengue patients, as well as in virus infection models using Fc gamma R humanized mouse strains. In in vivo mechanistic studies, we demonstrate that induction of Fc gamma RIIIa expression on effector CD8 T cells follows a well-defined trajectory that closely tracks the course and magnitude of the immune response, while immune resolution is characterized by receptor downregulation. Uniquely to these CD8 T cells, Fc gamma RIIIa crosslinking alone is paradoxically insufficient to elicit T cell activation and cytotoxicity. However, when coupled with T cell receptor (TCR) stimulation, it results in synergistic cellular activation and, compensates for the downregulation of canonical costimulatory molecules on terminal effector CD8 T cells. These results reveal a previously unappreciated role for Fc gamma RIIIa as a unique costimulatory molecule that synergizes with TCR signaling to lower the effective threshold required for CD8 T cell activation, highlighting the role of virally induced antibodies in modulating CD8 effector cell responses.

Clinical and animal studies suggest that multiple brain systems are involved in mediating reward-motivated and related emotional behavior including the consumption of commonly used drugs and palatable food, and there is evidence that the repeated ingestion of or exposure to these rewarding substances may in turn stimulate these brain systems to produce an overconsumption of these substances along with co-occurring emotional disturbances. To understand this positive feedback loop, this review focuses on a specific population of hypothalamic peptide neurons expressing melanin-concentrating hormone (MCH), which are positively related to dopamine reward and project to forebrain areas that mediate this behavior. It also examines neurons expressing the peptide hypocretin/orexin (HCRT) that are anatomically and functionally linked to MCH neurons and the molecular systems within these peptide neurons that stimulate their development and ultimately affect behavior. This report first describes evidence in animals that exposure in adults and during adolescence to rewarding substances, such as the drugs alcohol, nicotine and cocaine and palatable fat-rich food, stimulates the expression of MCH as well as HCRT and their intracellular molecular systems. It also increases reward-seeking and emotional behavior, leading to excess consumption and abuse of these substances and neurological conditions, completing this positive feedback loop. Next, this review focuses on the model involving embryonic exposure to these rewarding substances. In addition to revealing a similar positive feedback circuit, this model greatly advances our understanding of the diverse changes that occur in these neuropeptide/molecular systems in the embryo and how they relate, perhaps causally, to the disturbances in behavior early in life that predict a later increased risk of developing substance use disorders. Studies using this model demonstrate in animals that embryonic exposure to these rewarding substances, in addition to stimulating the expression of peptide neurons, increases the intracellular molecular systems in neuroprogenitor cells that promote their development. It also alters the morphology, migration, location and neurochemical profile of the peptide neurons and causes them to develop aberrant neuronal projections to forebrain structures. Moreover, it produces disturbances in behavior at a young age, which are sex-dependent and occur in females more than in males, that can be directly linked to the neuropeptide/molecular changes in the embryo and predict the development of behavioral disorders later in life. These results supporting the close relationship between the brain and behavior are consistent with clinical studies, showing females to be more vulnerable than males to developing substance use disorders with co-occurring emotional conditions and female offspring to respond more adversely than male offspring to prenatal exposure to rewarding substances. It is concluded that the continued consumption of or exposure to rewarding substances at any stage of life can, through such peptide brain systems, significantly increase an individual's vulnerability to developing neurological disorders such as substance use disorders, anxiety, depression, or cognitive impairments.

While human and mouse memory B cells (MBCs) can express the transcription factor T-bet, its role in regulating MBC function remains unclear. We characterized multiple transcriptionally distinct clusters of mature, somatically mutated nucleoprotein (NP)-specific MBCs in lymph nodes (LNs) and lungs of influenza-infected mice. Although none of the MBCs expressed the plasma cell (PC) lineage commitment factor Blimp1, one cluster was enriched for Tbx21+ cells. Similar to the previously described human T-bet + effector MBC (eMBC) population, Tbx21+ mouse MBCs upregulated gene networks associated with effector metabolism, protein synthesis, and the unfolded protein response. Constitutive and inducible ablation of T-bet in murine B cells showed that T-bet expression by MBCs was required for persistence of LN and lung eMBCs with rapid in vitro and in vivo PC differentiation potential. Thus, T-bet marks NP + eMBCs that are poised to differentiate, and it regulates maintenance of lung-resident MBCs and local PC responses following virus re-exposure.

Replicative helicases are assembled on chromosomes by helicase loaders before the initiation of DNA replication. Here, we investigate the mechanisms employed by the bacterial Vibrio cholerae (Vc) DnaB replicative helicase and the DciA helicase loader. Structural analysis of the ATP gamma S form of the VcDnaB-ssDNA complex reveals a configuration distinct from that observed with GDP center dot AlF4. With ATP gamma S, the amino-terminal domain (NTD) tier, previously found as an open spiral in the GDP center dot AlF4 complex, adopts a closed planar arrangement. Furthermore, the DnaB subunit at the top of the carboxy-terminal domain (CTD) spiral is displaced by approximately 25 & Aring; between the two forms. We suggest that remodeling the NTD layer between closed planar and open spiral configurations, along with the migration of two distinct CTDs to the top of the DnaB spiral, repeated three times, mediates hand-over-hand translocation. Biochemical analysis indicates that VcDciA utilizes its Lasso domain to interact with DnaB near its Docking-Helix Linker-Helix interface. Up to three copies of VcDciA bind to VcDnaB, suppressing its ATPase activity during loading onto physiological DNA substrates. Our data suggest that DciA loads DnaB onto DNA using the ring-opening mechanism.

Polyphenic traits in animals often exhibit nonlinear scaling with body size. Static allometries (i.e., scaling relationships) themselves can exhibit plasticity, such that individuals of the same size and genotype differ in body proportions across different environments. In ants, both larval environment and genotype regulate the expression of caste- associated traits, including body size and ovariole number. However, it remains untested whether caste- associated traits are independently regulated by environmental variables or whether they covary due to coupled developmental mechanisms. If caste traits are regulated independently, developmental plasticity should affect both trait expression and the scaling relationships between traits. Using the clonal raider ant, Ooceraea biroi, we tested this by manipulating the rearing environment of genetically identical larvae. We found that caregiver genotype, temperature, and food quantity influenced caste morphology strictly in tandem with body size, producing similar static allometries across rearing conditions (i.e., no allometric plasticity was detected). In contrast, clonal genotypes differed in average body size and their static allometries. Thus, size- matched individuals of the same genotype from different rearing environments exhibited no differences in mean caste trait expression, while those of different genotypes did. This absence of plasticity in the static allometries of different caste traits suggests that they are developmentally coupled due to systemic regulatory factors. Our findings contrast with reports of allometric plasticity in other insects, suggesting that ant caste traits are exceptionally integrated and therefore constrained in their independent responses to environmental variation. We discuss how these results inform contemporary hypotheses for ant caste development and evolution.

Motivated by recent data pointing to the existence of homo- oligomeric assemblies of membrane proteins called higher- order transient structures, and their apparent role in connecting components of membrane signal pathways, we examine here by cryoelectron microscopy some of the protein-protein interactions that occur in cluster formation. Metabotropic glutamate receptors and HCN ion channels inside clusters contact their neighbors through structured extracellular and intracellular domains, respectively. Other ion channels, including Kv2.1 and Slo1, appear to form clusters through prominent intrinsically disordered sequences in the cytoplasm. These distinct modes of interaction are associated with clusters exhibiting varying degrees of compactness and order. We conclude that nature utilizes a variety of ways to form connections between membrane proteins in self- assembled clusters.

Postmitotic neurons have high levels of methylated cytosine and its oxidized intermediates such as 5-hydroxymethylcytosine1. However, the functional relevance of these epigenetic modifications of DNA are poorly understood. Here we show that some cytidine analogues, such as cytarabine, cause DNA double-strand breaks during TET-mediated active 5-methylcytosine demethylation by interrupting TDG-dependent base excision repair. These double-strand breaks are frequently converted into deletions and translocations by DNA ligase 4. In vivo, Purkinje and Golgi cells in the cerebellum are the only neuronal populations that exhibit high levels of DNA damage due to cytarabine. In Purkinje cells, TET targets highly expressed gene bodies marked by enhancer-associated histone modifications. Many of these genes control movement coordination, which explains the long-recognized cerebellar neurotoxicity of cytarabine2. We show that other cytidine analogues, such as gemcitabine, cause only single-strand breaks in neurons, which are repaired by DNA ligase 3 with minimal toxicity. Our findings uncover a mechanistic link between TET-mediated DNA demethylation, base excision repair and gene expression in neurons. The results also provide a rational explanation for the different neurotoxicity profiles of an important class of antineoplastic agents.

Aim: Although several SERPINA1 genetic variants have been reported for their pathogenicity to induce liver disorders through phenotype-driven approaches, data regarding genotype-driven approaches of the SERPINA1 locus remain unavailable. This study aimed to characterize the clinical and liver biological profiles of patients harboring nonbenign SERPINA1 variants. Methods: We conducted a retrospective, exome-based genotype-first reverse phenotyping study using structured electronic health record data from consecutive patients from January 1, 2015, to January 31, 2022. Statistical associations were assessed using frequentist and Bayesian models, with validation in the UK Biobank cohort. Results: Among 1377 patients analyzed, 15 SERPINA1 variants classified as nonbenign were identified in 217 (15.7%) patients. Data were available for 126 patients (median age, 41.5 years; 52.4% male). Liver disease, hyperferritinemia, and pulmonary emphysema were observed in 32.5% (41/126), 23% (29/126), and 5.6% (7/126) of the patients, respectively. The median follow-up duration was 1.3 years and encompassed 1085 biological observations. We confirmed associations with well-documented variants of SERPINA1 (p.Glu366Lys, p.Pro393Ser, p.Ala308Ser, p.Glu288Val, and p.Phe76del). We identified three novel genetic associations with liver markers: c.*10G > A, c.1065 + 10C > T, and p.Arg63Cys. The UK Biobank data confirmed significant gene- and variant-level associations, notably for the variants identified in our study, which ranked in the top decile of statistical associations. Conclusions: This study supports the utility of a genotype-first approach in characterizing hepatic manifestations of nonbenign SERPINA1 variants. The findings highlight novel genotype-biomarker associations and suggest a role for SERPINA1 genetic testing in patients with unexplained liver abnormalities.

A remarkable feature of CRISPR-Cas systems is their ability to acquire short sequences from invading viruses to create a molecular record of infection. These sequences, called spacers, are inserted into the CRISPR locus and mediate sequence-specific immunity in prokaryotes. In type II-A CRISPR systems, Cas1, Cas2 and Csn2 form a supercomplex with Cas9 to integrate viral sequences. While the structure of the integrase complex has been described, a detailed functional analysis of the spacer acquisition machinery is lacking. We developed a genetic system that combines deep mutational scanning (DMS) of Streptococcus pyogenes cas genes with a method to select bacteria that acquire new spacers. Here, we show that this procedure reveals key interactions at the Cas1-Cas2 interface critical for spacer integration, identifies Cas variants with enhanced spacer acquisition and immunity against phage infection, and provides insights into the molecular determinants of spacer acquisition, offering a platform to improve CRISPR-Cas-based applications.