Ndel1 promotes axon regeneration via intermediate filaments

Failure of axons to regenerate following acute or chronic neuronal injury is attributed to both the inhibitory glial environment and deficient intrinsic ability to re-grow. However, the underlying mechanisms of the latter remain unclear. In this study, we have investigated the role of the mammalian homologue of aspergillus nidulans NudE, Ndel1, emergently viewed as an integrator of the cytoskeleton, in axon regeneration. Ndel1 was synthesized de novo and upregulated in crushed and transected sciatic nerve axons, and, upon injury, was strongly associated with neuronal form of the intermediate filament (IF) Vimentin while dissociating from the mature neuronal IF (Neurofilament) light chain NF-L. Consistent with a role for Ndel1 in the conditioning lesion-induced neurite outgrowth of Dorsal Root Ganglion (DRG) neurons, the long lasting in vivo formation of the neuronal Ndel1/Vimentin complex was associated with robust axon regeneration. Furthermore, local silencing of Ndel1 in transected axons by siRNA severely reduced the extent of regeneration in vivo. Thus, Ndel1 promotes axonal regeneration; activating this endogenous repair mechanism may enhance neuroregeneration during acute and chronic axonal degeneration.     

Ecto-Phosphorylation of CD98 Regulates Cell-Cell Interactions

Ecto-phosphorylation plays an important role in many cellular functions. The transmembrane glycoprotein CD98 contains potential phosphorylation sites in its extracellular C-terminal tail. We hypothesized that extracellular signaling through ecto-protein kinases (ePKs) might lead to ecto-phosphorylation of CD98 and influence its multiple functions, including its role in cell-cell interactions. Our results show that recombinant CD98 was phosphorylated in vitro by ePKs from Jurkat cells and by the commercial casein kinase 2 (CK2). Alanine substitutions at serines-305/307/309 or serines-426/430 attenuated CK2-mediated CD98 phosphorylation, suggesting that these residues are the dominant phosphorylation sites for CK2. Furthermore, CD98 expressed in the basolateral membranes of intestinal epithelial Caco2-BBE cells was ecto-phosphorylated by Jurkat cell-derived ePKs and ecto-CK2 was involved in this process. Importantly, cell attachment studies showed that the ecto-phosphorylation of CD98 enhanced heterotypic cell-cell interactions and that the extracellular domain of CD98, which possesses the serine phosphorylation sites, was crucial for this effect. In addition, phosphorylation of recombinant CD98 increased its interactions with Jurkat and Caco2-BBE cells, and promoted cell attachment and spreading. In conclusion, here we demonstrated the ecto-phosphorylation of CD98 by ePKs and its functional importance in cell-cell interactions. Our findings reveal a novel mechanism involved in regulating the multiple functions of CD98 and raise CD98 as a promising target for therapeutic modulations of cell-cell interactions.     

Influenza A H5N1 clade 2.3.4 virus with a different antiviral susceptibility profile replaced clade 1 virus in humans in northern Vietnam

Background

Prior to 2007, highly pathogenic avian influenza (HPAI) H5N1 viruses isolated from poultry and humans in Vietnam were consistently reported to be clade 1 viruses, susceptible to oseltamivir but resistant to amantadine. Here we describe the re-emergence of human HPAI H5N1 virus infections in Vietnam in 2007 and the characteristics of the isolated viruses.

Methods and Findings

Respiratory specimens from patients suspected to be infected with avian influenza in 2007 were screened by influenza and H5 subtype specific polymerase chain reaction. Isolated H5N1 strains were further characterized by genome sequencing and drug susceptibility testing. Eleven poultry outbreak isolates from 2007 were included in the sequence analysis. Eight patients, all of them from northern Vietnam, were diagnosed with H5N1 in 2007 and five of them died. Phylogenetic analysis of H5N1 viruses isolated from humans and poultry in 2007 showed that clade 2.3.4 H5N1 viruses replaced clade 1 viruses in northern Vietnam. Four human H5N1 strains had eight-fold reduced in-vitro susceptibility to oseltamivir as compared to clade 1 viruses. In two poultry isolates the I117V mutation was found in the neuraminidase gene, which is associated with reduced susceptibility to oseltamivir. No mutations in the M2 gene conferring amantadine resistance were found.

Conclusion

In 2007, H5N1 clade 2.3.4 viruses replaced clade 1 viruses in northern Vietnam and were susceptible to amantadine but showed reduced susceptibility to oseltamivir. Combination antiviral therapy with oseltamivir and amantadine for human cases in Vietnam is recommended.     

Galactomannan detection in bronchoalveolar lavage fluid

Prompt diagnosis of invasive pulmonary aspergillosis (IPA) remains a challenge. Galactomannan (GM) assay in serum has been incorporated into diagnostic criteria for IPA, but its performance varies depending on the population in which the test is used. GM assay on bronchoalveolar lavage (BAL) fluid aims to improve upon the test by applying it directly on samples from the target organ. The studies that have examined the utility of BAL-GM are a heterogeneous group, but the results are intriguing, especially in patients who are at risk for IPA from causes other than hematologic malignancy and neutropenia. BAL-GM had sensitivities ranging from 60% to 100% in this group, often far exceeding the performance of serum GM assay. The test shows promise as a useful adjunctive diagnostic modality in the diagnosis of IPA.     

The diversity of O-linked glycans expressed during Drosophila melanogaster development reflects stage- and tissue-specific requirements for cell signaling

Appropriate glycoprotein O-glycosylation is essential for normal development and tissue function in multicellular organisms. To comprehensively assess the developmental and functional impact of altered O-glycosylation, we have extensively analyzed the non-glycosaminoglycan, O-linked glycans expressed in Drosophila embryos. Through multidimensional mass spectrometric analysis of glycans released from glycoproteins by beta-elimination, we detected novel as well as previously reported O-glycans that exhibit developmentally modulated expression. The core 1 mucin-type disaccharide (Galbeta1-3GalNAc) is the predominant glycan in the total profile. HexNAcitol, hexitol, xylosylated hexitol, and branching extension of core 1 with HexNAc (to generate core 2 glycans) were also evident following release and reduction. After Galbeta1-3GalNAc, the next most prevalent glycans were a mixture of novel, isobaric, linear, and branched forms of a glucuronyl core 1 disaccharide. Other less prevalent structures were also extended with HexA, including an O-fucose glycan. Although the expected disaccharide product of the Fringe glycosyltransferase, (GlcNAcbeta1-3)fucitol, was not detectable in whole embryos, mass spectrometry fragmentation and exoglycosidase sensitivity defined a novel glucuronyl trisaccharide as GlcNAcbeta1-3(GlcAbeta1-4)fucitol. Consistent with the spatial distribution of the Fringe function, the GlcA-extended form of the Fringe product was enriched in the dorsal portion of the wing imaginal disc. Furthermore, loss of Fringe activity reduced the prevalence of the O-Fuc trisaccharide. Therefore, O-Fuc glycans necessary for the modulation of important signaling events in Drosophila are, as in vertebrates, substrates for extension beyond the addition of a single HexNAc.     

Disruption of the ugt1 locus in mice resembles human Crigler-Najjar type I disease

The 9 UDP-glucuronosyltranferases (UGTs) encoded by the UGT1 locus in humans are key enzymes in the metabolism of most drugs as well as endogenous substances such as bile acids, fatty acids, steroids, hormones, neurotransmitters, and bilirubin. Severe unconjugated hyperbilirubinemia in humans that suffer from Crigler-Najjar type I disease results from lesions in the UGT1A1 gene and is often fatal. To examine the physiological importance of the Ugt1 locus in mice, this locus was rendered non-functional by interrupting exon 4 to create Ugt1(-/-) mice. Because UGT1A1 in humans is responsible for 100% of the conjugated bilirubin, it followed that newborn Ugt1(-/-) mice developed serum levels of unconjugated bilirubin that were 40-60 times higher than Ugt1(+/-) or wild-type mice. The result of extreme unconjugated bilirubin in Ugt1(-/-) mice, comparable to the induced levels noted in patients with Crigler-Najjar type 1 disease, is fatal in neonatal Ugt1(-/-) mice within 2 weeks following birth. The extreme jaundice is present as a phenotype in skin color after 8 h. Neonatal Ugt1(-/-) mice exhibit no detectable UGT1A-specific RNA, which corresponds to a complete absence of UGT1A proteins in liver microsomes. Conserved glucuronidation activity attributed to the Ugt1 locus can be defined in Ugt1(-/-) mice, because UGT2-dependent glucuronidation activity is unaffected. Remarkably, the loss of UGT1A functionality in liver results in significant alterations in cellular metabolism as investigated through changes in gene expression. Thus, the loss of UGT1A function in Ugt1(-/-) mice leads to a metabolic syndrome that can serve as a model to further investigate the toxicities associated with unconjugated bilirubin and the impact of this disease in humans.     

Vascular smooth muscle cell polyploidy: An adaptive or maladaptive response?

Polyploidy is a state in which a cell contains multiple copies of its entire genome, while a normal diploid cell contains only two sets of homologous chromosomes. Although widely studied and pervasive in nature, the signals and mechanisms of polyploidization and its accompanying operational consequences are still unclear. This review focuses on relevant questions in deciphering the regulation of polyploidization of vascular smooth muscle cells (VSMC) in mammals and the role of polyploidy in various vascular pathologies, such as hypertension and aging. Additionally, we will explore new investigations in polyploidization of VSMCs involving the rapidly expanding fields of oxidative stress and senescence. J. Cell. Physiol. 215: 588-592, 2008. (c) 2008 Wiley-Liss, Inc.