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In the common cellular space, hundreds of binding reactions occur reliably and enable this remarkable compatibility have not yet been adequately elucidated. In order to delineate these principles, we consider the intracellular sensing of transition metals in bacteria-an integral part of cellular metal homeostasis. Protein cytosolic sensors typically interact with metals through three types of lateral chain residues, containing oxygen, nitrogen, or sulfur. The very existence of complete sets of mutually compatible sensors is a nontrivial problem solved by evolution, since each metal sensor has to bind to its cognate metal without being "mismetallated" by noncognate competitors. Here, based solely on theoretical considerations and limited information about binding transition-metal sensor sets are severely limited in their number by compatibility requirements, leaving only a handful of possible sensor compositions for each transition metal. Our theoretical results turn out to be broadly consistent with experimental data crucial role in the organization and functioning of intracellular processes.

The cGAS-STING pathway, well-known to elicit interferon (IFN) responses, is also a key inducer of autophagy upon virus infection or other stimuli. Whereas the mediators for cGAS-induced IFN responses are well characterized, much less is known about how cGAS elicits autophagy. Here, we report that TRIM23, a unique TRIM protein harboring both ubiquitin E3 ligase and GTPase activity, is crucial for cGAS-STING-dependent antiviral autophagy. Genetic ablation of TRIM23 impairs autophagic control of HSV-1 infection. HSV-1 infection or cGAS-STING stimulation induces TBK1-mediated TRIM23 phosphorylation at S39, which triggers TRIM23 autoubiquitination and GTPase activity and ultimately elicits autophagy. Fibroblasts from a patient with herpes simplex encephalitis heterozygous for a dominant-negative, kinase-inactivating TBK1 mutation fail to activate autophagy by TRIM23 and cGAS-STING. Our results thus identify the cGAS-STING-TBK1-TRIM23 axis as a key autophagy defense pathway and may stimulate new therapeutic interventions for viral or inflammatory diseases.

Crimean-Congo hemorrhagic fever virus (CCHFV) is an enveloped, negative-sense RNA virus that is spread by ticks across Europe, Africa, and Asia and causes a lethal disease in humans (similar to 30%-40% case fatality). There are currently no approved vaccines or therapeutics. Antibody-based therapeutics targeting the CCHFV surface glycoproteins Gn and Gc, which are responsible for viral attachment and fusion during entry, are a promising therapeutic approach. We previously isolated three broadly neutralizing Gc-targeting human monoclonal antibodies (mAbs) and showed certain cocktails of these mAbs demonstrated synergistic virus neutralization. Furthermore, physical linkage of two of these mAbs into a dual variable domain (DVD) bispecific antibody (bsAb) DVD-121-801 resulted in improved neutralization and therapeutic protection against a lethal CCHFV challenge in mice. However, the molecular requirements for the activity of DVD-121-801, and why it is augmented over monospecific parental mAbs, remain the topic of investigation. Here, we generated a new panel of bsAb variants of DVD-121-801 to explore the spacing and avidity requirements and further optimize its protective efficacy against divergent CCHFV isolates. We evaluated these variants for neutralization, fusion inhibition, and protection with virus-like particles, authentic viruses, and in vivo challenge studies. We found that neutralization potency was relatively unaffected by spacing or identity of variable domains within the bsAb, but that one next-generation design employing longer and more flexible linkers between variable domains (DVD-121-801GS) had a greater breadth of therapeutic protection. Our efforts highlight the importance of antibody avidity and lead to an improved bsAb variant of DVD-121-801 for further therapeutic development. IMPORTANCE Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus endemic to Europe, Africa, and Asia that causes severe disease in humans (30%-40% case fatality). There are currently no approved vaccines or therapeutics. In prior work, physical linkage of two Gc-specific monoclonal antibodies (mAbs) targeting distinct epitopes into a dual variable domain (DVD) bispecific antibody (bsAb), termed DVD-121-801, resulted in potent neutralization in vitro and therapeutic protection in vivo. Here, a panel of variants of this bsAb was developed and evaluated for neutralization potency, fusion inhibition, and therapeutic efficacy, and our work shows this panel to be effective against multiple isolates of CCHFV. Furthermore, incorporating longer, more flexible linkers between variable domains resulted in a lead candidate with improved activity and therapeutic potential compared to the parental bsAb. Utilizing this panel, we also explored the contribution of antibody avidity in antibody-mediated protection against CCHFV infection.

Gating in voltage-dependent ion channels is regulated by the transmembrane voltage. This form of regulation is enabled by voltage-sensing domains (VSDs) that respond to transmembrane voltage differences by changing their conformation and exerting force on the pore to open or close it. Here, we use cryogenic electron microscopy to study the neuronal K(v)2.1 channel in lipid vesicles with and without a voltage difference across the membrane. Hyperpolarizing voltage differences displace the positively charged S4 helix in the voltage sensor by one helical turn (similar to 5 angstrom). When this displacement occurs, the S4 helix changes its contact with the pore at two different interfaces. When these changes are observed in fewer than four voltage sensors, the pore remains open, but when they are observed in all four voltage sensors, the pore constricts. The constriction occurs because the S4 helix, as it displaces inward, squeezes the right-handed helical bundle of pore-lining S6 helices. A similar conformational change occurs upon hyperpolarization of the EAG1 channel but with two helical turns displaced instead of one. Therefore, while K(v)2.1 and EAG1 are from distinct architectural classes of voltage-dependent ion channels, called domain-swapped and non-domain-swapped, the way the voltage sensors gate their pores is very similar.

Changes in gene expression are a key driver of phenotypic evolution, leading to a persistent interest in the evolution of transcriptomes. Traditionally, gene expression is modeled as a continuous trait, leaving qualitative transitions largely unexplored. In this paper, we detail the development of new Bayesian inference techniques to study the evolutionary turnover of organ-specific transcriptomes, which we define as instances where orthologous genes gain or lose expression in a particular organ. To test these techniques, we analyze the transcriptomes of 2 male reproductive organs, testes and accessory glands, across 11 species of the Drosophila melanogaster species group. We first discretize gene expression states by estimating the probability that each gene is expressed in each organ and species. We then define a phylogenetic model of correlated transcriptome evolution in 2 or more organs and fit it to the expression state data. Inferences under this model imply that many genes have gained and lost expression in each organ, and that the 2 organs experienced accelerated transcriptome turnover on different branches of the Drosophila phylogeny.

Diabetes is a major risk factor for cardiovascular disease, but the molecular mechanisms underlying diabetic vasculopathy have been elusive. Here we report that inositol hexakisphosphate kinase 1 (IP6K1) mediates hyperglycemia-induced endothelial senescence by rewiring liver kinase B1 (LKB1) signaling from the AMPK pathway to the p53 pathway. We found that hyperglycemia upregulated IP6K1, which disrupted Hsp/Hsc70 and carboxyl terminus of Hsc70-interacting protein-mediated LKB1 degradation, leading to increased expression levels of LKB1. High glucose also strengthened the binding of IP6K1 to AMPK, suppressing LKB1-mediated AMPK activation. Thus, elevated LKB1 did not lead to activation of the AMPK pathway. Instead, it bound more to p53, resulting in p53-dependent endothelial senescence. Endothelial cell-specific deletion of IP6K1 alleviated, whereas endothelial cell-specific overexpression of IP6K1 exaggerated, hyperglycemia-induced endothelial senescence. This study reveals a regulatory mechanism of IP6K1 in switching LKB1 activation of the AMPK pathway to activation of the p53 pathway. IP6K1 represents a potential therapeutic target for treating hyperglycemia-induced endothelial dysfunction.Article Highlights Diabetes is a major risk factor for cardiovascular diseases. The mechanisms of hyperglycemia-induced endothelial dysfunction have been elusive. We found that inositol hexakisphosphate kinase 1 (IP6K1) mediates hyperglycemia-induced endothelial senescence by switching liver kinase B1 (LKB1) activation of the AMPK pathway to activation of the p53 pathway. Hyperglycemia upregulates IP6K1, which stabilizes LKB1 by disrupting Hsp/Hsc70 and carboxyl terminus of Hsc70-interacting protein-mediated LKB1 degradation but suppresses LKB1-dependent AMPK activation. Elevated LKB1 binds more to p53, resulting in p53-dependent endothelial senescence. Endothelial cell-specific deletion of IP6K1 attenuates, whereas endothelial cell-specific overexpression of IP6K1 exaggerates, hyperglycemia-induced endothelial senescence.

Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD) are clonal myeloid disorders associated with mitogen-activated protein (MAP)-kinase-activating mutations and an increased risk of neurodegeneration. We found microglial mutant clones in LCH and ECD patients, whether or not they presented with clinical symptoms of neurodegeneration, associated with microgliosis, astrocytosis, and neuronal loss, predominantly in the rhombencephalon gray nuclei. Neurological symptoms were associated with PU.1+ clone size (p = 0.0003) in patients with the longest evolution of the disease, indicating a phase of subclinical incipient neurodegeneration. Genetic barcoding analysis suggests that clones may originate from definitive or yolk sac hematopoiesis, depending on the patients. In a mouse model, disease topography was attributable to a local clonal proliferative advantage, and microglia depletion by a CSF1R-inhibitor limited neuronal loss and improved survival. These studies characterize a neurodegenerative disease associated with clonal proliferation of inflammatory microglia. The long preclinical stage represents a therapeutic window before irreversible neuronal depletion.