Neurofibrillary tangles (NFTs) are a pathological hallmark of Alzheimer's disease (AD); however, the relationship between NFTs and disease progression remains controversial. Analyses of tau animal models suggest that phenotypes coincide with accumulation of soluble aggregated tau species but not the accumulation of NFTs. The pathological role of prefilamentous tau aggregates, e.g., tau oligomeric intermediates, is poorly understood, in part because of methodological challenges. Here, we engineered a novel tau oligomer-specific antibody, T22, and used it to elucidate the temporal course and biochemical features of oligomers during NFT development in AD brain. We found that tau oligomers in human AD brain samples were 4-fold higher than those in the controls. We also revealed the role of oligomeric tau conformers in pretangles, neuritic plaques, and neuropil threads in the frontal cortex tissue from AD brains; this analysis uncovers a consistent code that governs tau oligomerization with regard to degree of neuronal cytopathology. These data are the first to characterize the role of tau oligomers in the natural history of NFTs, and they highlight the suitability of tau oligomers as therapeutic targets in AD and related tauopathies.

Chronic exposure to light at night, as in shift work, alters biological clocks (chronodisruption), negatively impacting pregnancy outcome in humans. Actually the interaction of maternal and fetal circadian systems could be a key factor determining a fitting health in adults. We propose that chronic photoperiod shift (CPS) during pregnancy alter maternal circadian rhythms and impair circadian physiology in the adult offspring, increasing health risks. Pregnant rats were exposed to normal photoperiod (12 h light, 12 h dark) or to CPS until 85% of gestation. The effects of gestational CPS were evaluated on the mother and adult offspring. In the mother we measured rhythms of heart rate, body temperature, and activity through gestation and daily rhythms of plasma variables (melatonin, corticosterone, aldosterone, and markers of renal function) at 18 days of gestation. In adult offspring, we measured rhythms of the clock gene expression in the suprachiasmatic nucleus (SCN), locomotor activity, body temperature, heart rate, blood pressure, plasma variables, glucose tolerance, and corticosterone response to ACTH. CPS altered all maternal circadian rhythms, lengthened gestation, and increased newborn weight. The adult CPS offspring presented normal rhythms of clock gene expression in the SCN, locomotor activity, and body temperature. However, the daily rhythm of plasma melatonin was absent, and corticosterone, aldosterone, renal markers, blood pressure, and heart rate rhythms were altered. Moreover, CPS offspring presented decreased glucose tolerance and an abnormal corticosterone response to ACTH. Altogether these data show that gestational CPS induced long-term effects on the offspring circadian system, wherein a normal SCN coexists with altered endocrine, cardiovascular, and metabolic function.

Background: Chemokines exist reversibly as monomers and dimers, but dimer activity remains poorly defined. Results: A disulfide-linked CXCL1 dimer is highly active, and NMR studies show that dimer binds CXCR2 like the monomer. Conclusion:The potent activity of CXCL1 dimer is novel. Significance: Chemokine dimers can be highly active to completely inactive, indicating that dimerization fine-tunes chemokine-specific in vivo functions.

All chemokines share a common structural scaffold that mediate a remarkable variety of functions from immune surveillance to organogenesis. Chemokines are classified as CXC or CC on the basis of conserved cysteines, and the two subclasses bind distinct sets of GPCR class of receptors and also have markedly different quaternary structures, suggesting that the CXC/CC motif plays a prominent role in both structure and function. For both classes, receptor activation involves interactions between chemokine N-loop and receptor N-domain residues (Site-I), and between chemokine N-terminal and receptor extracellular/ transmembrane residues (Site-II). We engineered a CC variant (labeled as CC-CXCL8) of the chemokine CXCL8 by deleting residue X (CXC 3 CC), and found its structure is essentially similar to WT. In stark contrast, CC-CXCL8 bound poorly to its cognate receptors CXCR1 and CXCR2 (K i > 1 M). Further, CC-CXCL8 failed to mobilize Ca 2؉ in CXCR2-expressing HL-60 cells or recruit neutrophils in a mouse lung model. However, most interestingly, CC-CXCL8 mobilizes Ca 2؉ in neutrophils and in CXCR1-expressing HL-60 cells. Compared with the WT, CC-CXCL8 binds CXCR1 N-domain with only ϳ5-fold lower affinity indicating that the weak binding to intact CXCR1 must be due to its weak binding at Site-II. Nevertheless, this level of binding is sufficient for receptor activation indicating that affinity and activity are separable functions. We propose that the CXC motif functions as a conformational switch that couples Site-I and Site-II interactions for both receptors, and that this coupling is critical for high affinity binding but differentially regulates activation.Chemokines mediate a wide variety of biological functions from recruiting leukocytes to the site of injury and infection to organ development, wound healing, and angiogenesis (1-4). Chemokines are characterized by four conserved cysteines that form disulfide bonds, and are classified into CXC and CC families based on cysteine pattern near the N terminus. CXC ligands bind and activate only CXC receptors and CC ligands bind and activate only CC receptors, indicating functional divergence could be as old as the molecules themselves. Structure-function studies consistently show that binding and receptor activation for both classes involves two interactions: between the ligand N-loop and receptor N-domain residues (Site-I) and between the ligand N-terminal and receptor extracellular/transmembrane residues (Site-II) (5-9).Structures of several CXC and CC chemokines have been solved by NMR and x-ray crystallography, and reveal a common structural fold (known as chemokine fold) at the monomer level (10 -15). The CXC/CC motif connects the functionally important N-loop and N-terminal residues, and also plays a structural role by forming disulfide bonds that tether the N-terminal and N-loop residues to the protein core (Fig. 1). In the CXC chemokine CXCL8 (also known as interleukin-8, IL-8), the residue corresponding to X (Gln) in the CXC motif has been mutated with no effec...

The adherens junction complex, composed mainly of vascular endothelial (VE)-cadherin, β-catenin, p120, and γ-catenin, is the main element of the endothelial barrier in postcapillary venules.S-nitrosylation of β-catenin and p120 is an important step in proinflammatory agents-induced hyperpermeability. We investigated in vitro and in vivo whether or not VE-cadherin isS-nitrosylated using platelet-activating factor (PAF) as agonist. We report that PAF-stimulates S-nitrosylation of VE-cadherin, which disrupts its association with β-catenin. In addition, based on inhibition of nitric oxide production, our results strongly suggest that S-nitrosylation is required for VE-cadherin phosphorylation on tyrosine and for its internalization. Our results unveil an important mechanism to regulate phosphorylation of junctional proteins in association with S-nitrosylation.