Nogo-A and Nogo-66 receptor in amyotrophic lateral sclerosis

Nogo/reticulon (RTN)-4 has been strongly implicated as a disease marker for the motor neuron disease amyotrophic lateral sclerosis (ALS). Nogo isoforms, including Nogo-A, are ectopically expressed in the skeletal muscle of ALS mouse models and patients and their levels correlate with the disease severity. The notion of a direct involvement of Nogo-A in ALS aetiology is supported by the findings that Nogo-A deletion in mice reduces muscle denervation and prolongs survival, whereas overexpression of Nogo-A destabilizes motor nerve terminals and promotes denervation. Another intriguing, and somewhat paradoxical, recent finding revealed that binding of the Nogo-66 receptor (NgR) by either agonistic or antagonistic Nogo-66-derived peptides protects against p75 neurotrophin receptor (p75(NTR))-dependent motor neuron death. Ligand binding by NgR could result in subsequent engagement of p75(NTR), and this association could preclude pro-apoptotic signalling by the latter. Understanding the intricate interplay among Nogo isoforms, NgR and p75(NTR) in ALS disease progression may provide important, therapeutically exploitable information.     

Increased uptake of folate conjugates by activated macrophages in experimental hyperlipemia

In the pathogenesis of atherosclerosis, macrophages become activated and play a crucial role in plaque formation. Activated synovial macrophages have recently been shown to express receptors for folic acid. We have determined whether activated macrophages also over-express folate receptor (FR) in atherosclerosis. Most normal cells express little or no FR, and, if FR is present on activated macrophages, folate-linked compounds and drugs could be selectively targeted to those cells that do express FR. To evaluate the FR on macrophages of atherosclerotic animals, golden Syrian hamsters were maintained on a hyperlipidemic diet until extensive vascular lesions had developed. Uptake of folic acid conjugated to fluorescent tags was then examined in tissue fragments from lesion-prone areas, and peritoneal activated macrophages were harvested from the same animals. Spectrofluorimetric and fluorescence microscopic analyses showed a significantly greater uptake of folate-conjugates by peritoneal macrophages of hyperlipidemic hamsters compared with those of hamsters fed a normal or folate-deficient diet. Systemically administered folate-fluorescent conjugates were found to accumulate as bright spots in protrusions of atherosclerotic plaques populated by macrophages, whereas a low level of fluorescence was detected uniformly dispersed across the lesion. The uptake of the folate conjugate by U937 macrophage cells grown in a high-lipid culture medium was significantly higher than in controls. Our data thus indicate that hyperlipidemic conditions induce an increased uptake of folate attributable to the over-expression of FRs on activated macrophages. This increase in FR expression can be exploited to deliver folate-linked compounds selectively to atherosclerotic lesions. This work was supported by a grant from the Romanian Academy and Ministry of Education, Research and Technology, Bucharest, Romania, and partially by a grant from Endocyte and the Indiana 21st Century Fund.     

Identification of a New Locus for Autosomal Recessive Charcot–Marie–Tooth Disease with Focally Folded Myelin on Chromosome 11p15

Autosomal recessive Charcot–Marie–Tooth disease type 4B (CMT4B) is a demyelinating hereditary motor and sensory neuropathy characterized by abnormal folding of myelin sheaths. A locus for CMT4B has previously been mapped to chromosome 11q23 in a southern Italian pedigree. We initially excluded linkage in two Tunisian families with CMT4B to chromosome 11q23, demonstrating genetic heterogeneity within the CMT4B phenotype. Subsequently, using homozygosity mapping and linkage analysis in the largest Tunisian pedigree, we mapped a new locus to chromosome 11p15. A maximum two-point lod score of 6.05 was obtained with the marker D11S1329. Recombination events refined the CMT4B locus region to a 5.6-cM interval between markers D11S1331 and D11S4194. The second Tunisian CMT4B family was excluded from linkage to the new locus, demonstrating the existence of at least a third locus for the CMT4B phenotype.     

Molecular dynamics simulation studies of induced fit and conformational capture in U1A–RNA binding: Do molecular substates code for specificity?

Molecular dynamics (MD) simulations on stem loop 2 of U1 small nuclear RNA and a construct of the U1A protein were carried out to obtain predictions of the structures for the unbound forms in solution and to elucidate dynamical aspects of induced fit upon binding. A crystal structure of the complex between the U1A protein and stem loop 2 RNA and an NMR structure for the uncomplexed form of the U1A protein are available from Oubridge et al. (Nature, 1994, Vol. 372, pp. 432-438) and Avis et al. (Journal of Molecular Biology, 1996, Vol. 257, pp. 398-411), respectively. As a consequence, U1A-RNA binding is a particularly attractive case for investigations of induced fit in protein-nucleic acid complexation. When combined with the available structural data, the results from simulations indicate that structural adaptation of U1A protein and RNA define distinct mechanisms for induced fit. For the protein, the calculations indicate that induced fit upon binding involves a non-native thermodynamic substate in which the structure is preorganized for binding. In contrast, induced fit of the RNA involves a distortion of the native structure in solution to an unstable form. However, the RNA solution structures predicted from simulation show evidence that structures in which groups of bases are favorably oriented for binding the U1A protein are thermally accessible. These results, which quantify with computational modeling recent proposals on induced fit and conformational capture by Leuillot and Varani (Biochemistry, 2001, Vol. 40, pp. 7947-7956) and by Williamson (Nature Structural Biology, 2000, Vol. 7, pp. 834-837) suggest an important role for intrinsic molecular architecture and substates other than the native form in the specificity of protein-RNA interactions.     

Inter- and intracellular interactions of Nogo: new findings and hypothesis

The molecule Nogo has captured the imagination of many as a possible key player, and therefore therapeutic target, in the pathological settings of central nervous system (CNS) injury and degenerative pathology. Found in both glial cells and neurons, the endogenous, physiological role of Nogo is as yet unknown. Recently reported targeted disruption of the Nogo gene did not result in any obvious neuro‐anatomical or neurological phenotype. Compared with wild‐type mice, Nogo‐deficient mice also did not exhibit a truly convincing enhancement in their ability to regenerate CNS neurons upon injury. Does the molecule have any important physiological function at all? Other recent discoveries of new interacting partners of Nogo at the mitochondria and the CNS paranode suggest intriguing links to the modulation of apoptosis and developmental organization or signalling at the axoglial junction.     

The effects of fishing, climate change, and other anthropogenic disturbances on red grouper and other reef fishes in the Gulf of Mexico

In this article, we consider the potential effects of anthropogenic disturbances on marine fish species known or suspected to be habitat engineers. The three species of interest inhabit different marine habitats at different life stages, and therefore can have significant influences across the sea floor at broad spatial scales. The primary species include the shallow-water Atlantic goliath grouper (Epinephelus itajara), which inhabits mangrove root systems as juveniles, and caves, shipwrecks, and rocky reefs as adults; red grouper (E. morio), which excavates habitat throughout its benthic life in Karst regions of the Gulf of Mexico and western Atlantic, from the coast to the shelf-edge; and tilefish (Lopholatilus chamaeleonticeps), a species that lives on the continental slope and constructs elaborate, pueblo-esque burrows. The anthropogenic disturbances of greatest interest in the Gulf of Mexico include fishing, hypoxia, red tide, oil and gas exploration, and climatic change. We suggest that to understand the broader effects of both natural and anthropogenic disturbances on biomass and productivity in these species requires that we first understand the strength of interactions between them and the other species residing within their communities (e.g., predators, prey, commensals, and mutualists).