CCR5 is a CC chemokine receptor expressed on memory lymphocytes, macrophages, and dendritic cells and also constitutes the main coreceptor for macrophagetropic (or R5) strains of human immunodeficiency viruses. In the present study, we investigated whether CCR5 was palmitoylated in its carboxyl-terminal domain by generating alanine substitution mutants for the three cysteine residues present in this region, individually or in combination. We found that wild-type CCR5 was palmitoylated, but a mutant lacking all three Cys residues was not. Through the use of green fluorescent fusion proteins and immunofluorescence studies, we found that the absence of receptor palmitoylation resulted in sequestration of CCR5 in intracellular biosynthetic compartments. By using the fluorescence recovery after photobleaching technique, we showed that the non-palmitoylated mutant had impaired diffusion properties within the endoplasmic reticulum. We next studied the ability of the mutants to bind and signal in response to chemokines. Chemokines binding and activation of G i -mediated signaling pathways, such as calcium mobilization and inhibition of adenylate cyclase, were not affected. However, the duration of the functional response, as measured by a microphysiometer, and the ability to increase [ 35 S]guanosine 5-3-O-(thio)triphosphate binding to membranes were severely affected for the non-palmitoylated mutant. The ability of RANTES (regulated on activation normal T cell expressed and secreted) and aminooxypentane-RANTES to promote CCR5 endocytosis was not altered by cysteine replacements. Finally, we found that the absence of receptor palmitoylation reduced the human immunodeficiency viruses coreceptor function of CCR5, but this effect was secondary to the reduction in surface expression. In conclusion, we found that palmitoylated cysteines play an important role in the intracellular trafficking of CCR5 and are likely necessary for efficient coupling of the receptor to part of its repertoire of signaling cascades.

Blood-Brain Barrier (BBB) and Blood-Spinal Cord Barrier (BSCB) impairment is an additional accident occurring during the amyotrophic lateral sclerosis (ALS) progression. In this work we aimed to decipher if BBB/BSCB leakage appeared before critical detrimental events and could serve as a marker preceding clinical symptoms. Three different BBB leakage markers: Evans Blue, IgG and hemosiderin, were used to look at the SOD1-linked ALS rat model at presymptomatic and symptomatic stages. Although IgG and hemosiderin could be detected at presymptomatic stage, Evans Blue extravasation which fits best with BBB/BSCB impairment could only be seen at symptomatic stages. BBB/BSCB impairment was further substantiate by showing at symptomatic stages decreased mRNA expression of ZO-1 and occludin as well as agrin, a basal membrane constituent. Electron microscopic data substantiate a toxic environment around endothelial cell and perivascular swollen astrocyte end-feet showing oedema-linked BBB opening. Classifications termsSection : Disease-related Neuroscience Keywords : ALS, mutant SOD1, rat, blood-brain barrier, blood-spinal cord barrier, Evans BlueAbbreviations alpha-SMA, alpha-smooth muscle actin; ALS, amyotrophic lateral sclerosis; BBB, blood-brain barrier; BSCB, blood-spinal cord barrier; SOD1, superoxide dismutase 1; ZO-1, zonula occludens-1

Glibenclamide is well known to interact with the sulphonylurea receptor (SUR) and has been shown more recently to inhibit the cystic fibrosis transmembrane conductance regulator protein (CFTR), both proteins that are members of the ABC [adenosine 5'-triphosphate (ATP)-binding cassette] transporters. The effect of glibenclamide and two synthetic sulphonylcyanoguanidine derivatives (dubbed BM-208 and BM-223) was examined on P-glycoprotein, the major ABC transporter responsible for multidrug resistance (MDR) in cancer cells. To this end, we employed different cell lines that do or do not express P-glycoprotein, as confirmed by Western blotting: first, a tumour cell line (VBL600) selected from a human T-cell line (CEM) derived from an acute leukaemia; second, an epithelial cell line derived from a rat colonic adenocarcinoma (CC531(mdr+)) and finally, a non tumour epithelial cell line derived from the proximal tubule of the opossum kidney (OK). Glibenclamide and the two related derivatives inhibited P-glycoprotein because firstly, they acutely increased [3H]colchicine accumulation in P-glycoprotein-expressing cell lines only; secondly BM-223 reversed the MDR phenomenon, quite similarly to verapamil, by enhancing the cytotoxicity of colchicine, taxol and vinblastine and thirdly, BM-208 and BM-223 blocked the photoaffinity-labelling of P-glycoprotein by [3H]azidopine. Furthermore, glibenclamide is itself a substrate for P-glycoprotein, since the cellular accumulation of [3H]glibenclamide was low and substantially increased by addition of P-glycoprotein substrates (e. g., vinblastine and cyclosporine) only in the P-glycoprotein-expressing cell lines. We conclude that glibenclamide and two sulphonylcyanoguanidine derivatives inhibit P-glycoprotein and that sulphonylurea drugs would appear to be general inhibitors of ABC transporters, suggesting an interaction with some conserved motif.

Abrupt osmotic changes during rapid correction of chronic hyponatremia result in demyelinative brain lesions, but the sequence of events linking rapid osmotic changes to myelin loss is not yet understood. Here, in a rat model of osmotic demyelination syndrome, we found that massive astrocyte death occurred after rapid correction of hyponatremia, delineating the regions of future myelin loss. Astrocyte death caused a disruption of the astrocyte-oligodendrocyte network, rapidly upregulated inflammatory cytokines genes, and increased serum S100B, which predicted clinical manifestations and outcome of osmotic demyelination. These results support a model for the pathophysiology of osmotic brain injury in which rapid correction of hyponatremia triggers apoptosis in astrocytes followed by a loss of trophic communication between astrocytes and oligodendrocytes, secondary inflammation, microglial activation, and finally demyelination.

Neuropathological analysis in Alzheimer's disease (AD) and experimental evidence in transgenic models overexpressing frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17) mutant tau suggest that amyloid-β pathology enhances the development of tau pathology. In this work, we analyzed this interaction independently of the overexpression of an FTDP-17 mutant tau, by analyzing tau pathology in wild-type (WT), 5xFAD, APP −/− and tau −/− mice after stereotaxic injection in the somatosensory cortex of short-length native human AD-PHF. Gallyas and phosphotau-positive tau inclusions developed in WT, 5xFAD, and APP −/− but not in tau −/− mice. Ultrastructural analysis demonstrated their intracellular localization and that they were composed of straight filaments. These seeded tau inclusions were composed only of endogenous murine tau exhibiting a tau antigenic profile similar to tau aggregates in AD. Insoluble tau level was higher and ipsilateral anteroposterior and contralateral cortical spreading of tau inclusions was more important in AD-PHF-injected 5xFAD mice than in WT mice. The formation of large plaque-associated dystrophic neurites positive for oligomeric and phosphotau was observed in 5xFAD mice injected with AD-PHF but never in control-injected or in non-injected 5xFAD mice. An increased level of the p25 activator of CDK5 kinase was found in AD-PHF-injected 5xFAD mice. These data demonstrate in vivo that the presence of Aβ pathology enhances experimentally induced tau seeding of endogenous, wild-type tau expressed at physiological level, and demonstrate the fibrillar nature of heterotopically seeded endogenous tau. These observations further support the hypothesis that Aβ enhances tau pathology development in AD through increased pathological tau spreading.

In Alzheimer disease, the development of tau pathology follows neuroanatomically connected pathways, suggesting that abnormal tau species might recruit normal tau by passage from cell to cell. Herein, we analyzed the effect of stereotaxic brain injection of human Alzheimer high-molecular-weight paired helical filaments (PHFs) in the dentate gyrus of wild-type and mutant tau THY-Tau22 mice. After 3 months of incubation, wild-type and THY-Tau22 mice developed an atrophy of the dentate gyrus and a tau pathology characterized by Gallyas and tau-positive grain-like inclusions into granule cells that extended in the hippocampal hilus and eventually away into the alveus, and the fimbria. Gallyas-positive neuropil threads and oligodendroglial coiled bodies were also observed. These tau inclusions were composed only of mouse tau, and were immunoreactive with antibodies to 4R tau, phosphotau, misfolded tau, ubiquitin, and p62. Although local hyperphosphorylation of tau was increased in the dentate gyrus in THY-Tau22 mice, the development of neurofibrillary tangles made of mutant human tau was not accelerated in the hippocampus, indicating that wild-type human PHFs were inefficient in seeding tau aggregates made of G272V/P301S mutant human tau. Our results indicate thus that injection of human wild-type Alzheimer PHF seeded aggregation of wild-type murine tau into an argyrophilic 4R tau pathology, and constitutes an interesting model independent of expression of a mutant tau protein.

In Alzheimer's disease (AD), selective expression of tau isoforms might underlie the susceptibility of different brain areas to develop neurofibrillary tangles and this pattern might change in the disease. In this study, we have analyzed in control subjects and in sporadic AD patients the pattern of expression of tau mRNA and tau proteins in areas unaffected (cerebellar cortex, white matter), moderately affected (occipital striate cortex, thalamus, caudate nucleus, and putamen) or strongly affected by neurofibrillary tangles (temporal and frontal associative cortex). After RT-PCR amplification, five products corresponding to the tau mRNAs containing exons 2 and 3, exon 2, without exons 2 or 3, with exon 10 and without exon 10 were identified. In control subjects, these five PCR products were present in all areas except in white matter, where transcripts with exons 2 or exons 2 and 3 were not identified. In AD patients, the same pattern of transcripts was observed in different areas, regardless of the presence of neurofibrillary lesions. After dephosphorylation of soluble tau proteins, the six tau isoforms were identified in the same areas by immunoblotting, including in the white matter, suggesting that most tau isoforms with exons 2 and 3 are transported along axons. The relative expression of 0N3R isoforms was higher in the temporal cortex than in the cerebellar cortex, both in control and AD subjects. The qualitative pattern of expression was identical in subjects with or without an APOE4 allele. Our results suggest that splicing regulation of the tau gene and the relative expression of tau isoforms are not significantly changed in sporadic cases of the disease, although differential expression of tau isoforms in temporal cortex might underlie this brain area susceptibility to neurofibrillary tangles formation.

The present data support the involvement of AA in the early PT dysfunction found in CHN; furthermore, they suggest a causal relationship between DNA adduct formation, decreased megalin expression, and inhibition of receptor-mediated endocytosis of LMWP.