Rossmann fold ͉ signal transduction N AD and its phosphorylated form, NADP, is a universal cofactor in a large number of redox reactions carried out by a variety of enzymes, especially dehydrogenases. It is widely recognized that NAD(P) is an essential molecule in energy metabolism in all organisms. More recently, mounting evidence suggests that, in addition to its central role in energy metabolism, NAD(P) is also involved in signaling pathways that regulate fundamental processes of cellular functions, including gene transcription and apoptosis (1,2). This realization generated a link between the energy metabolism and the regulated networks of biological processes.One of the NAD signaling mechanisms is through gene silencer proteins known as sirtuins, such as Sir2 in yeast, a NAD-dependent histone deacetylase. Increased activities of Sir2 induced by an increase in NAD production extended lifespan (3). It was shown that a product of NAD-dependent deacetylation by Sir2, nicotinamide, strongly inhibits the activity of Sir2 (4, 5). Similar mechanisms are present in other eukaryotes, including humans (6). NAD is also directly related to transcription regulation. PolyADP-ribose polymerases (PARPs) can modify the acceptor proteins by synthesizing a polyADP-ribose molecule using NAD ϩ as the substrate. The transcription factors that can be modified by PARPs include p53, YY1, NF-B, and TATA-binding protein (1). In other cases, transcription regulation is not carried out by any enzymatic reaction. For instance, the C-terminal-binding protein CtBP is a corepressor that has an increased affinity to its partners, such as adenovirus E1A or cellular repressor ZEB, when NADH binds to CtBP (7). Crystal structures showed that NADH binding to CtBP induced a conformational switch that stabilizes the dimerization of CtBP, which in turn promotes its binding to the repressors (8). In the case of the negative transcriptional regulator NmrA, NAD ϩ binding to NmrA controls the rate of nuclear entry of the GATA transcription-activating protein AreA (9, 10). NmrA has a similar structure to short-chain dehydrogenase/reductase (SDR) family proteins but no enzyme activities, because of the lack of conserved active-site residues (9). NAD(P) exerts its functions by association with proteins. The protein fold that binds NAD(P) was discovered by Rossmann when the crystal structure of lactate dehydrogenase was determined (11). The Rossmann fold is the most common fold, based on its predicted occurrence from the genes known today (12). This motif consists of six ␤-strands connected by ␣-helices with the NAD(P) molecule bound at the top [supporting information (SI) Fig. 5]. The Rossmann fold has always been present as a rigid-body domain in all other known crystal structures until the structure of HSCARG was determined. We found that the common ␣E that connects ␤5 to ␤6 in the Rossmann fold is deformed as an extended loop when NADP is not bound with HSCARG. This allows the formation of an asymmetric dimer between a subunit with NADP bound and an emp...

The use of oseltamivir, widely stockpiled as one of the drugs for use in a possible avian influenza pandemic, has been reported to be associated with neuropsychiatric disorders and severe skin reactions, primarily in Japan. Here we identified a nonsynonymous SNP (single nucleotide polymorphism) in dbSNP database, R41Q, near the enzymatic active site of human cytosolic sialidase, a homologue of virus neuraminidase that is the target of oseltamivir. This SNP occurred in 9.29% of Asian population and none of European and African American population. Our structural analyses and Ki measurements using in vitro sialidase assays indicated that this SNP could increase the unintended binding affinity of human sialidase to oseltamivir carboxylate, the active form of oseltamivir, thus reducing sialidase activity. In addition, this SNP itself results in an enzyme with an intrinsically lower sialidase activity, as shown by its increased Km and decreased Vmax values. Theoretically administration of oseltamivir to people with this SNP might further reduce their sialidase activity. We note the similarity between the reported neuropsychiatric side effects of oseltamivir and the known symptoms of human sialidase-related disorders. We propose that this Asian-enriched sialidase variation caused by the SNP, likely in homozygous form, may be associated with certain severe adverse reactions to oseltamivir.

Angiogenesis is a critical aspect of wound healing. We investigated the role of keratinocytes in promoting angiogenesis in mice with lineage-specific deletion of the transcription factor FOXO1. The results indicate that keratinocyte-specific deletion of Foxo1 reduces VEGFA expression in mucosal and skin wounds and leads to reduced endothelial cell proliferation, reduced angiogenesis, and impaired re-epithelialization and granulation tissue formation. In vitro FOXO1 was needed for VEGFA transcription and expression. In a porcine dermal wound-healing model that closely resembles healing in humans, local application of a FOXO1 inhibitor reduced angiogenesis. This is the first report that FOXO1 directly regulates VEGFA expression and that FOXO1 is needed for normal angiogenesis during wound healing. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.