Cellular Adaptation Relies on Regulatory Proteins Having Episodic Memory: Proteins Modulate Cell Metabolism and Reproduction by Remembering, Transmitting, and Using Data on the Environment.

The ability to memorize changes in the environment is present at all biological levels, from social groups and individuals, down to single cells. Trans-generational memory is embedded subcellularly through genetic and epigenetic mechanisms. Evidence that cells process and remember features of the immediate environment using protein sensors is reviewed. It is argued that this mnemonic ability is encapsulated within the protein conformational space and lasts throughout its lifetime, which can overlap with the lifespan of the organism. Means to determine diachronic changes in protein activity are presented.

Febrile temperatures increase in vitro antibody affinity for malarial and dengue antigens.

Fever is a regulated increase of the body temperature resulting from both infectious and non-infectious causes. Fever is known to play a role in modulating immune responses to infection, but the potential of febrile temperatures in regulating antigen binding affinity to antibodies has not been explored. Here we investigated this process under in vitro conditions using Isothermal titration calorimetry and ELISA. We used selected malarial and dengue antigens against specific monoclonal antibodies, and observed a marked increase in the affinity of these antibody-antigen complexes at 40°C, compared to physiological (37°C) or pathophysiological temperatures (42°C). Induced thermal equilibration of the protein partners at these temperatures in vitro, prior to measurements, further increased their binding affinity. These results suggest another positive and adaptive role for fever in vivo, and highlight the favourable role of thermal priming in enhancing protein-protein affinity for samples with limited availability.

A mathematical model relates intracellular TLR4 oscillations to sepsis progression.

OBJECTIVE: Oscillations of physiological parameters describe many biological processes and their modulation is determinant for various pathologies. In sepsis, toll-like receptor 4 (TLR4) is a key sensor for signaling the presence of Gram-negative bacteria. Its intracellular trafficking rates shift the equilibrium between the pro- and anti-inflammatory downstream signaling cascades, leading to either the physiological resolution of the bacterial stimulation or to sepsis. This study aimed to evaluate the effects of TLR4 increased expression and intracellular trafficking on the course and outcome of sepsis. RESULTS: Using a set of three differential equations, we defined the TLR4 fluxes between relevant cell organelles. We obtained three different regions in the phase space: (1) a limit-cycle describing unstimulated physiological oscillations, (2) a fixed-point attractor resulting from moderate LPS stimulation that is resolved and (3) a double-attractor resulting from sustained LPS stimulation that leads to sepsis. We used this model to describe available hospital data of sepsis patients and we correctly characterize the clinical outcome of these patients.

Human GRP78 affinity towards its signaling partners Ire1α and PERK is differently modulated by an unfolded protein client.

Protein-folding stress is characteristic of specialized secretory cells and plays a dominant role in a multitude of diseases. The unfolded protein response (UPR) thus triggered is a proteostatic signaling network that adapts the protein-folding capacity of the endoplasmic reticulum to the cellular demands. We have measured the binding affinities between human GRP78, an essential chaperone located in ER, and two transmembrane UPR sensors (human PERK and Ire1α), with or without the addition of an unfolded protein client. We reveal distinct binding affinities between the binary and ternary complexes thus formed, that suggest a preference for the PERK signaling branch under stress, and a predilection for the GRP78-UPR sensor complex formation upon stressor removal. These results imply a gated UPR mechanism that tunes the overall cellular behavior to the accumulation of unfolded proteins.

Longitudinal assessment of T-lymphocyte subpopulations during generalized demodicosis in dogs and their relationship with remission.

BACKGROUND: The pathogenesis of canine generalized demodicosis is poorly understood but is thought to involve dysfunction of the immune system. Previous studies showed diminished CD4+ T lymphocyte counts in affected dogs, but none has evaluated this subpopulation through resolution of the disease. HYPOTHESIS/OBJECTIVES: In this longitudinal study, we tested whether quantification of CD4+ cells, CD8+ cells and the ratio of CD4+ to CD8+ cells are good indicators of immunological status and could be used as biomarkers of treatment efficacy and prognosis. ANIMALS: Sixteen dogs of several breeds with diagnoses of generalized demodicosis, plus 30 age/breedmatched healthy dogs. METHODS: Total lymphocytes, CD4+, CD8+ and CD4+:CD8+ ratio were quantified at four time points: at diagnosis, 30 days after diagnosis (during treatment), at first negative parasitological examination and at clinical cure. RESULTS: Absolute numbers of CD4+ cells were significantly lower in affected dogs at the time of diagnosis. Absolute numbers of CD4+ and CD8+ cells were significantly augmented in affected animals compared with control dogs after treatment was established, and this persisted until the first negative parasitological examination, at which time the CD4+ counts equalled those of the control group. CONCLUSIONS AND CLINICAL IMPORTANCE: Our findings suggest that longitudinal quantification of CD4+ and CD8+ T lymphocytes is a useful indicator of the efficacy of demodicosis treatment.

Lipopolysaccharide-induced inhibition of transcription of tlr4 in vitro is reversed by dexamethasone and correlates with presence of conserved NFκB binding sites.

Engagement of Toll-like receptor 4 (TLR4) by lipopolysaccharide (LPS) is a master trigger of the deleterious effects of septic shock. Horses and humans are considered the most sensitive species to septic shock, but the mechanisms explaining these phenomena remain elusive. Analysis of tlr4 promoters revealed high similarity among LPS-sensitive species (human, chimpanzee, and horse) and low similarity with LPS-resistant species (mouse and rat). Four conserved nuclear factor kappa B (NFκB) binding sites were found in the tlr4 promoter and two in the md2 promoter sequences that are likely to be targets for dexamethasone regulation. In vitro treatment of equine peripheral blood mononuclear cells (eqPBMC) with LPS decreased transcripts of tlr4 and increased transcription of md2 (myeloid differentiation factor 2) and cd14 (cluster of differentiation 14). Treatment with dexamethasone rescued transcription of tlr4 after LPS inhibition. LPS-induced transcription of md2 was inhibited in the presence of dexamethasone. Dexamethasone alone did not affect transcription of tlr4 and md2.

Changes in histone acetylation and methylation that are important for persistent but not transient expression of CCR4 in human CD4+ T cells.

Although regulation of CXCR3 and CCR4 is related to Th1 and Th2 differentiation, respectively, many CXCR3(+) and CCR4(+) cells do not express IFN-γ and/or IL-4, suggesting that the chemokine receptor genes might be inducible by mechanisms that are lineage-independent. We investigated the regulation of CXCR3 versus IFNG, and CCR4 versus IL4 in human CD4(+) T cells by analyzing modifications of histone H3. In naïve cord-blood cells, under nonpolarizing conditions not inducing IL4, CCR4 was induced to high levels without many of the activation-associated changes in promoter histone H3 found for both IL4 and CCR4 in Th2 cells. Importantly, CCR4 expression was stable in Th2 cells, but fell in nonpolarized cells after the cells were rested; this decline could be reversed by increasing histone acetylation using sodium butyrate. Patterns of histone H3 modifications in CXCR3(+) CCR4(-) and CXCR3(-) CCR4(+) CD4(+) T-cell subsets from adult blood matched those in cells cultured under polarizing conditions in vitro. Our data show that high-level lineage-independent induction of CCR4 can occur following T-cell activation without accessibility-associated changes in histone H3, but that without such changes expression is transient rather than persistent.

Normal distribution of immunoglobulin isotypes in adult horses.

Studies focusing on the equine humoral response are scarce, with a bias towards the pre- and post-parturition mare and its foal. The present study attempted to expand current knowledge by establishing normal ranges for adult horse serum isotypes. Immunoglobulin (Ig) concentrations were obtained by screening 47 horses of various breeds and in different training regimes. Radial immunodiffusion values (mg/dL) were 196+/-73 for IgA, 2704+/-1424 for IgG, 419+/-220 for IgG(T) and 70+/-30 for IgM. All values passed the Kolmogorov-Smirnov normality test. The results will be of use to the field veterinarian as well for the basic researcher working on horses.

Antimicrobial activity of ethylenediaminedisuccinate metal complexes.

It is shown that metal complexes of the biodegradable ligand ethylenediaminedisuccinic acid (edds) present antimicrobial activity towards fungi and bacteria. [Cd(edds)], in particular, is more toxic than free Cd2+ to Aspergillus niger, behaving as a 'Trojan Horse' in the facilitated delivery of the toxic metal into the fungus.

Slower rescue of ER homeostasis by the unfolded protein response pathway associated with common variable immunodeficiency.

Common variable immunodeficiency (CVID) is a primary immunodeficiency characterized by hypogammaglobulinemia and recurrent infections. Herein we addressed the role of unfolded protein response (UPR) in the pathogenesis of the disease. Augmented unspliced X-box binding protein 1 (XBP-1) mRNA concurrent with co-localization of IgM and BiP/GRP78 were found in one CVID patient. At confocal microscopy analysis this patient's cells were enlarged and failed to present the typical surface distribution of IgM, which accumulated within an abnormally expanded endoplasmic reticulum. Sequencing did not reveal any mutation on XBP-1, neither on IRE-1alpha that could potentially prevent the splicing to occur. Analysis of spliced XBP-1, IRE-1alpha and BiP messages after LPS or Brefeldin A treatment showed that, unlike healthy controls that respond to these endoplasmic reticulum (ER) stressors by presenting waves of transcription of these three genes, this patient's cells presented lower rates of transcription, not reaching the same level of response of healthy subjects even after 48 h of ER stress. Treatment with DMSO rescued IgM and IgG secretion as well as the expression of spliced XBP-1. Our findings associate diminished splicing of XBP-1 mRNA with accumulation of IgM within the ER and lower rates of chaperone transcription, therefore providing a mechanism to explain the observed hypogammaglobulinemia.