VITAMIN B12 OR COBALAMIN DEFICIENCY occurs frequently (> 20%) among elderly people, but it is often unrecognized because the clinical manifestations are subtle; they are also potentially serious, particularly from a neuropsychiatric and hematological perspective. Causes of the deficiency include, most frequently, food-cobalamin malabsorption syndrome (> 60% of all cases), pernicious anemia (15%–20% of all cases), insufficent dietary intake and malabsorption. Food-cobalamin malabsorption, which has only recently been identified as a significant cause of cobalamin deficiency among elderly people, is characterized by the inability to release cobalamin from food or a deficiency of intestinal cobalamin transport proteins or both. We review the epidemiology and causes of cobalamin deficiency in elderly people, with an emphasis on food-cobalamin malabsorption syndrome. We also review diagnostic and management strategies for cobalamin deficiency

The heterodimeric ubiquitin conjugating enzyme (E2) UBC13-UEV mediates polyubiquitylation through lysine 63 of ubiquitin (K63), rather than lysine 48 (K48). This modification does not target proteins for proteasome-dependent degradation. Searching for potential regulators of this variant polyubiquitylation we have identified four proteins, namely RNF8, KIA00675, KF1, and ZNRF2, that interact with UBC13 through their RING finger domains. These domains can recruit, in addition to UBC13, other E2s that mediate canonical (K48) polyubiquitylation. None of these RING finger proteins were known previously to recruit UBC13. For one of these proteins, RNF8, we show its activity as a ubiquitin ligase that elongates chains through either K48 or K63 of ubiquitin, and its nuclear co-localization with UBC13. Thus, our screening reveals new potential regulators of non-canonical polyubiquitylation.

UEV proteins are enzymatically inactive variants of the E2 ubiquitin-conjugating enzymes that regulate noncanonical elongation of ubiquitin chains. In Saccharomyces cerevisiae, UEV is part of the RAD6-mediated error-free DNA repair pathway. In mammalian cells, UEV proteins can modulate c-FOS transcription and the G2-M transition of the cell cycle. Here we show that the UEV genes from phylogenetically distant organisms present a remarkable conservation in their exon-intron structure. We also show that the human UEV1 gene is fused with the previously unknown gene Kua. In Caenorhabditis elegans and Drosophila melanogaster, Kua and UEV are in separated loci, and are expressed as independent transcripts and proteins. In humans, Kua and UEV1 are adjacent genes, expressed either as separate transcripts encoding independent Kua and UEV1 proteins, or as a hybrid Kua-UEV transcript, encoding a two-domain protein. Kua proteins represent a novel class of conserved proteins with juxtamembrane histidine-rich motifs. Experiments with epitope-tagged proteins show that UEV1A is a nuclear protein, whereas both Kua and Kua-UEV localize to cytoplasmic structures, indicating that the Kua domain determines the cytoplasmic localization of Kua-UEV. Therefore, the addition of a Kua domain to UEV in the fused Kua-UEV protein confers new biological properties to this regulator of variant polyubiquitination.

Redox-based mechanisms play critical roles in the regulation of multiple cellular functions. NF-B, a master regulator of inflammation, is an inducible transcription factor generally considered to be redox-sensitive, but the modes of interactions between oxidant stress and NF-B are incompletely defined. Here, we show that oxidants can either amplify or suppress NF-B activation in vitro by interfering both with positive and negative signals in the NF-B pathway. NF-B activation was evaluated in lung A549 epithelial cells stimulated with tumor necrosis factor ␣ (TNF␣), either alone or in combination with various oxidant species, including hydrogen peroxide or peroxynitrite. Exposure to oxidants after TNF␣ stimulation produced a robust and long lasting hyperactivation of NF-B by preventing resynthesis of the NF-B inhibitor IB, thereby abrogating the major negative feedback loop of NF-B. This effect was related to continuous activation of inhibitor of B kinase (IKK), due to persistent IKK phosphorylation consecutive to oxidant-mediated inactivation of protein phosphatase 2A. In contrast, exposure to oxidants before TNF␣ stimulation impaired IKK phosphorylation and activation, leading to complete prevention of NF-B activation. Comparable effects were obtained when interleukin-1␤ was used instead of TNF␣ as the NF-B activator. This study demonstrates that the influence of oxidants on NF-B is entirely context-dependent, and that the final outcome (activation versus inhibition) depends on a balanced inhibition of protein phosphatase 2A and IKK by oxidant species. Our findings provide a new conceptual framework to understand the role of oxidant stress during inflammatory processes.Oxidant stress is a critical pathophysiological mechanism that stands at the foreground of a number of inflammatory diseases. In such conditions, highly reactive oxygen and nitrogen species exert their biological activity by inflicting various oxidative damages to biomolecules and by modulating the activity of redox-sensitive signal transduction pathways (1). The transcription factor nuclear factor B (NF-B)2 is a master regulator of inflammation and apoptosis, which is considered a prototypical example of such sensitivity to oxidant stress (2). NF-B is a family of dimeric proteins normally retained in the cytoplasm of nonstimulated cells, bound to inhibitory proteins, the IBs (3). The critical step in NF-B activation relies on its dissociation from the IB protein, resulting from stimulus-induced phosphorylation of IB, followed by its polyubiquitination and proteasomal degradation. IB itself is phosphorylated by IB kinase (IKK), composed of a heterodimer of two catalytic subunits, IKK␣/␤, and a regulatory subunit, IKK␥ (4). A considerable variety of stimuli lead to IKK activation and downstream NF-B signaling, comprising inflammatory cytokines, various microbial components, as well as genotoxic, physical, or chemical stress factors (5).Since the first report by Schreck et al. (6) that NF-B could be activated directly by H 2 O 2 in a subclone of Ju...

These findings indicate that peroxynitrite represents a key mediator of HMGB1 overexpression and release by cardiac cells and provide a novel mechanism linking myocardial oxidative/nitrosative stress with post-infarction myocardial inflammation.