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BioRxiv : the Preprint Server For... May 2024The risk of hypoglycemia and its serious medical sequelae restrict insulin replacement therapy for diabetes mellitus. Such adverse clinical impact has motivated...
UNLABELLED
The risk of hypoglycemia and its serious medical sequelae restrict insulin replacement therapy for diabetes mellitus. Such adverse clinical impact has motivated development of diverse glucose-responsive technologies, including algorithm-controlled insulin pumps linked to continuous glucose monitors ("closed-loop systems") and glucose-sensing ("smart") insulins. These technologies seek to optimize glycemic control while minimizing hypoglycemic risk. Here, we describe an alternative approach that exploits an endogenous glucose-dependent switch in hepatic physiology: preferential insulin signaling (under hyperglycemic conditions) preferential counter-regulatory glucagon signaling (during hypoglycemia). Motivated by prior reports of glucagon-insulin co-infusion, we designed and tested an ultra-stable glucagon-insulin fusion protein whose relative hormonal activities were calibrated by respective modifications; physical stability was concurrently augmented to facilitate formulation, enhance shelf life and expand access. An N-terminal glucagon moiety was stabilized by an α-helix-compatible Lys -Glu lactam bridge; A C-terminal insulin moiety was stabilized as a single chain with foreshortened C domain. Studies demonstrated (a) resistance to fibrillation on prolonged agitation at 37 °C and (b) dual hormonal signaling activities with appropriate balance. Glucodynamic responses were monitored in rats relative to control fusion proteins lacking one or the other hormonal activity, and continuous intravenous infusion emulated basal subcutaneous therapy. Whereas efficacy in mitigating hyperglycemia was unaffected by the glucagon moiety, the fusion protein enhanced endogenous glucose production under hypoglycemic conditions. Together, these findings provide proof of principle toward a basal glucose-responsive insulin biotechnology of striking simplicity. The fusion protein's augmented stability promises to circumvent the costly cold chain presently constraining global insulin access.
SIGNIFICANCE STATEMENT
The therapeutic goal of insulin replacement therapy in diabetes is normalization of blood-glucose concentration, which prevents or delays long-term complications. A critical barrier is posed by recurrent hypoglycemic events that results in short- and long-term morbidities. An innovative approach envisions co-injection of glucagon (a counter-regulatory hormone) to exploit a glycemia-dependent hepatic switch in relative hormone responsiveness. To provide an enabling technology, we describe an ultra-stable fusion protein containing insulin- and glucagon moieties. Proof of principle was obtained in rats. A single-chain insulin moiety provides glycemic control whereas a lactam-stabilized glucagon extension mitigates hypoglycemia. This dual-hormone fusion protein promises to provide a basal formulation with reduced risk of hypoglycemia. Resistance to fibrillation may circumvent the cold chain required for global access.
PubMed: 38826486
DOI: 10.1101/2024.05.20.594997 -
BioRxiv : the Preprint Server For... May 2024In allosteric proteins, identifying the pathways that signals take from allosteric ligand-binding sites to enzyme active sites or binding pockets and interfaces remains...
In allosteric proteins, identifying the pathways that signals take from allosteric ligand-binding sites to enzyme active sites or binding pockets and interfaces remains challenging. This avenue of research is motivated by the goals of understanding particular macromolecular systems of interest and creating general methods for their study. An especially important protein that is the subject of many investigations in allostery is the SARS-CoV-2 main protease (Mpro), which is necessary for coronaviral replication. It is both an attractive drug target and, due to intense interest in it for the development of pharmaceutical compounds, a gauge of the state-of-the-art approaches in studying protein inhibition. Here we develop a computational method for characterizing protein allostery and use it to study Mpro. We propose a role of the protein's C-terminal tail in allosteric modulation and warn of unintuitive traps that can plague studies of the role of protein dihedrals angles in transmitting allosteric signals.
PubMed: 38826232
DOI: 10.1101/2024.05.22.595309 -
The Journal of Toxicological Sciences 2024Nitric oxide (NO) plays a physiological role in signal transduction and excess or chronic NO has toxic effects as an inflammatory mediator. NO reversibly forms protein...
Nitric oxide (NO) plays a physiological role in signal transduction and excess or chronic NO has toxic effects as an inflammatory mediator. NO reversibly forms protein S-nitrosylation and exerts toxicological functions related to disease progression. DNA methyltransferases, epigenome-related enzymes, are inhibited in enzymatic activity by S-nitrosylation. Therefore, excess or chronic NO exposure may cause disease by altering gene expression. However, the effects of chronic NO exposure on transcriptome are poorly understood. Here, we performed transcriptome analysis of A549, AGS, HEK293T, and SW48 cells exposed to NO (100 μM) for 48 hr. We showed that the differentially expressed genes were cell-specific. Gene ontology analysis showed that the functional signature of differentially expressed genes related to cell adhesion or migration was upregulated in several cell lines. Gene set enrichment analysis indicated that NO stimulated inflammation-related gene expression in various cell lines. This finding supports previous studies showing that NO is closely involved in inflammatory diseases. Overall, this study elucidates the pathogenesis of NO-associated inflammatory diseases by focusing on changes in gene expression.
Topics: Humans; Nitric Oxide; Gene Expression Profiling; Transcriptome; Cell Adhesion; HEK293 Cells; Cell Movement; Inflammation; Signal Transduction
PubMed: 38825487
DOI: 10.2131/jts.49.281 -
The Journal of Biological Chemistry May 2024Adaptive immune responses comprise the activation of T cells by peptide antigens that are presented by proteins of the Major Histocompatibility Complex (MHC) on the... (Review)
Review
Adaptive immune responses comprise the activation of T cells by peptide antigens that are presented by proteins of the Major Histocompatibility Complex (MHC) on the surface of an antigen-presenting cell. As a consequence of the T cell receptor interacting productively with a certain peptide-MHC complex, a specialized cell-cell junction known as the immunological synapse forms and is accompanied by changes in the spatiotemporal patterning and function of intracellular signaling molecules. Key modifications occurring at the cytoplasmic leaflet of the plasma and internal membranes in activated T cells comprise lipid switches that affect the binding and distribution of proteins within or near the lipid bilayer. Here, we describe two major classes of lipid switches that act at this critical water/membrane interface. Phosphoinositides are derived from phosphatidylinositol, an amphiphilic molecule that contains two fatty acid chains and a phosphate group that bridges the glycerol backbone to the carbohydrate inositol. The inositol ring can be variably (de-)phosphorylated by dedicated kinases and phosphatases, thereby creating phosphoinositide signatures that define the composition and properties of signaling molecules, molecular complexes, or whole organelles. Palmitoylation refers to the reversible attachment of the fatty acid palmitate to a substrate protein's cysteine residue. DHHC enzymes, named after the four conserved amino acids in their active site, catalyze this post-translational modification and thereby change the distribution of proteins at, between, and within membranes. T cells utilize these two types of molecular switches to adjust their properties to an activation process that requires changes in motility, transport, secretion, and gene expression.
PubMed: 38823638
DOI: 10.1016/j.jbc.2024.107428 -
BMC Neurology May 2024To investigate the risk factors and underlying causes of pregnancy-related cerebral venous thrombosis (PCVT).
OBJECTIVES
To investigate the risk factors and underlying causes of pregnancy-related cerebral venous thrombosis (PCVT).
METHODS
A retrospective cohort of 16 patients diagnosed with CVT during pregnancy and postpartum (within six weeks after delivery) in a comprehensive hospital in China between 2009 and 2022 were carefully reviewed, focusing on demographic, clinical, and etiological characteristics, especially underlying causes. We matched 16 PCVT patients with 64 pregnant and puerperal women without PCVT to explore risk factors and clinical susceptibility to PCVT.
RESULTS
PCVT occurred commonly during the first trimester (43.75%) and the puerperium (37.5%). The frequency of anemia, thrombocytosis and thrombocytopenia during pregnancy, dehydration, and pre-pregnancy anemia was significantly higher in women with PCVT than in those without PCVT (P < 0.05). Among the 16 patients, five were diagnosed with antiphospholipid syndrome and one was diagnosed with systemic lupus erythematosus. Three patients had distinct protein S deficiency and one had protein C deficiency. Whole Exome Sequencing (WES) was performed for five patients and revealed likely pathogenic mutations associated with CVT, including heterozygous PROC c.1218G > A (p. Met406Ile), heterozygous PROS1 c.301C > T (p. Arg101Cys), composite heterozygous mutation in the F8 gene (c.144-1259C > T; c.6724G > A (p. Val2242Met)) and homozygous MTHFR c.677C > T (p. Ala222Val).
CONCLUSIONS
The occurrence of anemia, thrombocytopenia and thrombocytosis during pregnancy, dehydration and pre-pregnancy anemia suggested a greater susceptibility to PCVT. For confirmed PCVT patients, autoimmune diseases, hereditary thrombophilia, and hematological disorders were common causes. Screening for potential etiologies should be paid more attention, as it has implications for treatment and long-term management.
Topics: Humans; Female; Pregnancy; Retrospective Studies; Adult; Intracranial Thrombosis; Risk Factors; Venous Thrombosis; China; Young Adult; Pregnancy Complications, Hematologic; Protein S Deficiency
PubMed: 38822265
DOI: 10.1186/s12883-024-03676-2 -
NPJ Systems Biology and Applications May 2024Yeast metabolism can be engineered to produce xenobiotic compounds, such as cannabinoids, the principal isoprenoids of the plant Cannabis sativa, through heterologous...
Yeast metabolism can be engineered to produce xenobiotic compounds, such as cannabinoids, the principal isoprenoids of the plant Cannabis sativa, through heterologous metabolic pathways. However, yeast cell factories continue to have low cannabinoid production. This study employed an integrated omics approach to investigate the physiological effects of cannabidiol on S. cerevisiae CENPK2-1C yeast cultures. We treated the experimental group with 0.5 mM CBD and monitored CENPK2-1C cultures. We observed a latent-stationary phase post-diauxic shift in the experimental group and harvested samples in the inflection point of this growth phase for transcriptomic and metabolomic analysis. We compared the transcriptomes of the CBD-treated yeast and the positive control, identifying eight significantly overexpressed genes with a log fold change of at least 1.5 and a significant adjusted p-value. Three notable genes were PDR5 (an ABC-steroid and cation transporter), CIS1, and YGR035C. These genes are all regulated by pleiotropic drug resistance linked promoters. Knockout and rescue of PDR5 showed that it is a causal factor in the post-diauxic shift phenotype. Metabolomic analysis revealed 48 significant spectra associated with CBD-fed cell pellets, 20 of which were identifiable as non-CBD compounds, including fatty acids, glycerophospholipids, and phosphate-salvage indicators. Our results suggest that mitochondrial regulation and lipidomic remodeling play a role in yeast's response to CBD, which are employed in tandem with pleiotropic drug resistance (PDR). We conclude that bioengineers should account for off-target product C-flux, energy use from ABC-transport, and post-stationary phase cell growth when developing cannabinoid-biosynthetic yeast strains.
Topics: Saccharomyces cerevisiae; Cannabidiol; Lipidomics; Saccharomyces cerevisiae Proteins; Metabolomics; ATP-Binding Cassette Transporters; Transcriptome; Gene Expression Regulation, Fungal; Drug Resistance, Fungal; Gene Expression Profiling
PubMed: 38821949
DOI: 10.1038/s41540-024-00382-0 -
Proceedings of the National Academy of... Jun 2024SARS-CoV-2 employs its spike protein's receptor binding domain (RBD) to enter host cells. The RBD is constantly subjected to immune responses, while requiring efficient...
SARS-CoV-2 employs its spike protein's receptor binding domain (RBD) to enter host cells. The RBD is constantly subjected to immune responses, while requiring efficient binding to host cell receptors for successful infection. However, our understanding of how RBD's biophysical properties contribute to SARS-CoV-2's epidemiological fitness remains largely incomplete. Through a comprehensive approach, comprising large-scale sequence analysis of SARS-CoV-2 variants and the identification of a fitness function based on binding thermodynamics, we unravel the relationship between the biophysical properties of RBD variants and their contribution to viral fitness. We developed a biophysical model that uses statistical mechanics to map the molecular phenotype space, characterized by dissociation constants of RBD to ACE2, LY-CoV016, LY-CoV555, REGN10987, and S309, onto an epistatic fitness landscape. We validate our findings through experimentally measured and machine learning (ML) estimated binding affinities, coupled with infectivity data derived from population-level sequencing. Our analysis reveals that this model effectively predicts the fitness of novel RBD variants and can account for the epistatic interactions among mutations, including explaining the later reversal of Q493R. Our study sheds light on the impact of specific mutations on viral fitness and delivers a tool for predicting the future epidemiological trajectory of previously unseen or emerging low-frequency variants. These insights offer not only greater understanding of viral evolution but also potentially aid in guiding public health decisions in the battle against COVID-19 and future pandemics.
Topics: SARS-CoV-2; Spike Glycoprotein, Coronavirus; Humans; COVID-19; Angiotensin-Converting Enzyme 2; Protein Binding; Thermodynamics; Mutation; Machine Learning
PubMed: 38820002
DOI: 10.1073/pnas.2314518121 -
Cell Jun 2024In eukaryotes, the Suv39 family of proteins tri-methylate lysine 9 of histone H3 (H3K9me) to form constitutive heterochromatin. However, how Suv39 proteins are nucleated...
In eukaryotes, the Suv39 family of proteins tri-methylate lysine 9 of histone H3 (H3K9me) to form constitutive heterochromatin. However, how Suv39 proteins are nucleated at heterochromatin is not fully described. In the fission yeast, current models posit that Argonaute1-associated small RNAs (sRNAs) nucleate the sole H3K9 methyltransferase, Clr4/SUV39H, to centromeres. Here, we show that in the absence of all sRNAs and H3K9me, the Mtl1 and Red1 core (MTREC)/PAXT complex nucleates Clr4/SUV39H at a heterochromatic long noncoding RNA (lncRNA) at which the two H3K9 deacetylases, Sir2 and Clr3, also accumulate by distinct mechanisms. Iterative cycles of H3K9 deacetylation and methylation spread Clr4/SUV39H from the nucleation center in an sRNA-independent manner, generating a basal H3K9me state. This is acted upon by the RNAi machinery to augment and amplify the Clr4/H3K9me signal at centromeres to establish heterochromatin. Overall, our data reveal that lncRNAs and RNA quality control factors can nucleate heterochromatin and function as epigenetic silencers in eukaryotes.
Topics: Heterochromatin; Schizosaccharomyces pombe Proteins; Schizosaccharomyces; Cell Cycle Proteins; Histone-Lysine N-Methyltransferase; Histones; Centromere; RNA, Long Noncoding; Methyltransferases; Methylation
PubMed: 38815580
DOI: 10.1016/j.cell.2024.04.042 -
The EMBO Journal May 2024The complement is a conserved cascade that plays a central role in the innate immune system. To maintain a delicate equilibrium preventing excessive complement...
The complement is a conserved cascade that plays a central role in the innate immune system. To maintain a delicate equilibrium preventing excessive complement activation, complement inhibitors are essential. One of the major fluid-phase complement inhibitors is C4b-binding protein (C4BP). Human C4BP is a macromolecular glycoprotein composed of two distinct subunits, C4BPα and C4BPβ. These associate with vitamin K-dependent protein S (ProS) forming an ensemble of co-occurring higher-order structures. Here, we characterize these C4BP assemblies. We resolve and quantify isoforms of purified human serum C4BP using distinct single-particle detection techniques: charge detection mass spectrometry, and mass photometry accompanied by high-speed atomic force microscopy. Combining cross-linking mass spectrometry, glycoproteomics, and structural modeling, we report comprehensive glycoproteoform profiles and full-length structural models of the endogenous C4BP assemblies, expanding knowledge of this key complement inhibitor's structure and composition. Finally, we reveal that an increased C4BPα to C4BPβ ratio coincides with elevated C-reactive protein levels in patient plasma samples. This observation highlights C4BP isoform variation and affirms a distinct role of co-occurring C4BP assemblies upon acute phase inflammation.
PubMed: 38811852
DOI: 10.1038/s44318-024-00128-y -
Cell Reports May 2024Protein aggregation, which can sometimes spread in a prion-like manner, is a hallmark of neurodegenerative diseases. However, whether prion-like aggregates form during...
Protein aggregation, which can sometimes spread in a prion-like manner, is a hallmark of neurodegenerative diseases. However, whether prion-like aggregates form during normal brain aging remains unknown. Here, we use quantitative proteomics in the African turquoise killifish to identify protein aggregates that accumulate in old vertebrate brains. These aggregates are enriched for prion-like RNA-binding proteins, notably the ATP-dependent RNA helicase DDX5. We validate that DDX5 forms aggregate-like puncta in the brains of old killifish and mice. Interestingly, DDX5's prion-like domain allows these aggregates to propagate across many generations in yeast. In vitro, DDX5 phase separates into condensates. Mutations that abolish DDX5 prion propagation also impair the protein's ability to phase separate. DDX5 condensates exhibit enhanced enzymatic activity, but they can mature into inactive, solid aggregates. Our findings suggest that protein aggregates with prion-like properties form during normal brain aging, which could have implications for the age-dependency of cognitive decline.
PubMed: 38810650
DOI: 10.1016/j.celrep.2023.112787