Étienne Geoffroy St.‐Hilaire: father of “evo‐devo”?

SUMMARY In the early decades of the nineteenth century, the most important disagreement among comparative anatomists was not evolution versus "special creation" but between advocates of "transcendental morphology" and those of teleological anatomy—form versus function. In France this dichotomy was represented by the 1830–1832 public debate between Geoffroy St.-Hilaire (form) and Cuvier (function). Geoffroy's aim was to establish links of homology (known to him as "analogies") between the four "embranchements" into which Cuvier had divided the animal kingdom. Despite the fanciful nature of some of his homologies, Geoffroy, who was guided by his " principe de connections ," set in motion a school of morphology, some of whose conclusions, notably the homology of the dorsal surface of segmented invertebrates with the ventral surface of vertebrates, has been corroborated by recent studies in developmental genetics.     

Can the combination of electrochemical regeneration of NAD+, selectivity of L‐α‐amino‐acid dehydrogenase,and reductive amination of α‐keto‐acid be applied to the inversion of configuration of a L‐α‐amino‐acid?

The inversion of configuration of L‐alanine can be carried out by combining its selective oxidation in the presence of NAD⁺ and L‐alanine dehydrogenase, electrochemical regeneration of the NAD⁺ at a carbon felt anode, and reductive amination of pyruvate, i.e., reduction of its imino derivative at a mercury cathode, the reaction mixture being buffered with concentrated ammonium/ammonia (1.28M / 1.28M). The dehydrogenase exhibits astonishing activity and stability under such extreme conditions of pH and ionic strength. The main drawback of the process is its slowness. At best, the complete inversion of a 10 mM solution of L‐alanine requires 140 h. A careful and detailed quantitative analysis of each of the key steps involved shows that the enzyme catalyzed oxidation is so thermodynamically uphill that it can be driven efficiently to completion only when both the coenzyme regeneration and the pyruvate reduction are very effective. The first condition is easily fulfilled. Under the best conditions, it is the rate of the chemical reaction producing the imine which controls the whole process kinetically. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 101–107, 1999.     

Phylogeny of γ‐proteobacteria: resolution of one branch of the universal tree?

The reconstruction of bacterial evolutionary relationships has proven to be a daunting task because variable mutation rates and horizontal gene transfer (HGT) among species can cause grave incongruities between phylogenetic trees based on single genes. Recently, a highly robust phylogenetic tree was constructed for 13 gamma-proteobacteria using the combined alignments of 205 conserved orthologous proteins.1 Only two proteins had incongruent tree topologies, which were attributed to HGT between Pseudomonas species and Vibrio cholerae or enterics. While the evolutionary relationships among these species appears to be resolved, further analysis suggests that HGT events with other bacterial partners likely occurred; this alters the implicit assumption of gamma-proteobacteria monophyly. Thus, any thorough reconstruction of bacterial evolution must not only choose a suitable set of molecular markers but also strive to reduce potential bias in the selection of species.     

Who Is the King? The α‐Hydroxy‐β‐oxo‐α,β‐enone Moiety or the Catechol B Ring: Relationship between the Structure of Quercetin Derivatives and Their Pro‐Oxidative Abilities

Quercetin and other flavonoids have been reported to exhibit both antioxidant and pro‐oxidant properties. Most studies about the pro‐oxidative ability were conducted in the presence of metal ions, and the essential functional moiety of quercetin responsible for the pro‐oxidative effect is still unclear. In this study, we evaluated the pro‐oxidative abilities in the absence of metal ions of two quercetin derivatives, i.e., quercetin‐3′‐O‐β‐D ‐glucoside ( 1 ) and quercetin‐3‐O‐β‐D ‐glucoside ( 2 ), by assessing DNA cleavage and HO^.‐radical production. The binding mode between these compounds and DNA was studied by fluorescence and viscometric titrations. The results showed that 1 can efficiently induce oxidative damage to plasmid DNA, while 2 shows poor activity. Both 1 and 2 bind to DNA via groove‐binding. These results proved that the α‐hydroxy‐β‐oxo‐α,β‐enone moiety contributes to the pro‐oxidative activity of quercetin.     

Role of α2‐macroglobulin in regulating amyloid β‐protein neurotoxicity: protective or detrimental factor?

alpha2-Macroglobulin (alpha2M) has been identified as a carrier protein for beta-amyloid (Abeta) decreasing fibril formation and affecting the neurotoxicity of this peptide. The alpha2-macroglobulin receptor/low density lipoprotein receptor related protein (LRP) is involved in the internalization and degradation of the alpha2M/Abeta complexes and its impairment has been reported to occur in Alzheimer's disease. Previous studies have shown alpha2M to determine an enhancement or a reduction of Abeta toxicity in different culture systems. In order to clarify the role of alpha2M in Abeta neurotoxicity, we challenged human neuroblastoma cell lines with activated alpha2M in combination with Abeta. Our results show that in neuroblastoma cells expressing high levels of LRP, the administration of activated alpha2M protects the cells from Abeta neurotoxicity. Conversely, when this receptor is not present alpha2M determines an increase in Abeta toxicity as evaluated by MTT and TUNEL assays. In LRP-negative cells transfected with the full-length human LRP, the addition of activated alpha2M resulted to be protective against Abeta-induced neurotoxicity. By means of recombinant proteins we ascribed the neurotoxic activity of alpha2M to its FP3 fragment which has been previously shown to bind and neutralize transforming growth factor-beta. These studies provide evidence for both a neuroprotective and neurotoxic role of alpha2M regulated by the expression of its receptor LRP.     

The α‐sheet: A missing‐in‐action secondary structure?

The α-sheet has been speculated to play a role as a toxic conformer in amyloid diseases. However, except for relatively short fragments, its detection has remained elusive. Here, we present molecular dynamics simulations that support the existence of the α-sheet as a stable, metastable, or long-lived secondary structure in polyglutamine and, to a lesser extent, in polyasparagine aggregates.     

SIRT1 longevity factor suppresses NF‐κB ‐driven immune responses: regulation of aging via NF‐κB acetylation?

The aging process involves changes in immune regulation, i.e. adaptive immunity declines whereas innate immunity becomes activated. NF-kappaB signaling is the master regulator of the both immune systems. Two recent articles highlight the role of the NF-kappaB system in aging and immune responses. Adler et al showed that the NF-kappaB binding domain is the genetic regulatory motif which is most strongly associated with the aging process. Kwon et al studying HIV-1 infection and subsequent immune deficiency process demonstrated that HIV-1 Tat protein binds to SIRT1 protein, a well-known longevity factor, and inhibits the SIRT1-mediated deacetylation of the p65 component of the NF-kappaB complex. As a consequence, the transactivation efficiency of the NF-kappaB factor was greatly potentiated, leading to the activation of immune system and later to the decline of adaptive immunity. These observations support the scenario where immune responses and aging process can be enforced by the potentiation of NF-kappaB transactivation efficiency. Longevity factors, such as SIRT1 and its activators, might regulate the efficiency of the NF-kappaB signaling, the major outcome of which is inflamm-aging via proinflammatory responses.     

Proteasomal dysfunction induced by 4‐hydroxy‐2,3‐trans‐nonenal,an end‐product of lipid peroxidation: a mechanism contributing to neurodegeneration?

4-Hydroxy-2,3-trans-nonenal (HNE) is a neurotoxic unsaturated aldehyde end-product of lipid peroxidation. The addition of HNE to NT-2 and SK-N-MC cell lines induces apoptosis and we now investigated the time-course of events occurring prior to apoptosis. Treatment of both NT-2 and SK-N-MC cell lines with HNE led to HNE association with the proteasome, increased levels of protein carbonyls and ubiquitinated proteins, and decreased proteasomal function. There was also decreased metabolic activity, cytochrome c release and activation of caspase 3, followed by apoptotic changes including chromatin condensation, cell shrinkage and DNA fragmentation and laddering. Overexpression of mutant superoxide dismutase 1 proteins associated with amyotrophic lateral sclerosis decreased proteasomal activities in the absence of HNE and accelerated the apoptosis induced by HNE. By contrast, overexpression of wild-type superoxide dismutase 1 did not affect basal levels of proteasomal activity. The data suggest that accumulation of ubiquitinated proteins and impairment of proteasomal function are important events in HNE toxicity. We propose that the proteasomal system is a significant target of HNE neurotoxicity in a wide range of neurodegenerative diseases, especially if abnormal proteins are being expressed.     

How do reaction conditions affect the enantiopure synthesis of 2‐substituted‐1,4‐benzodioxane derivatives?

Several biologically active compounds structurally include the enantiopure 2‐substituted‐1,4‐benzodioxane scaffold. The straightforward racemization that affects reactions involving most of the common chemical reactives is thus a crucial issue. The developing of a completely stereo‐controlled synthetic route that does not affect the enantiomeric excess is consequently mandatory. It is also important to set up a reliable chiral HPLC method, able to follow the reaction, and to improve the synthetic performances. Here, we report the chiral investigation of two different synthons, we specifically evaluated the synthetic pathways that could be run in order to afford them, avoiding the racemization processes, which could normally occur in basic conditions. In addition, we developed peculiar chiral HPLC methods in order to resolve the enantiomers, define the enantiomeric excess, and fully characterize these compounds.     

“New”‐clear functions of PDK1: Beyond a master kinase?

Activation of cytosolic phosphoinositide-3 kinase (PI-3K) signaling pathway has been well established to regulate gene expression, cell cycle, and survival by feeding signals to the nucleus. In addition, strong evidences accumulated over the past few years indicate the presence of an autonomous inositol lipid metabolism and PI-3K signaling within the nucleus. Much less, however, is known about the role and regulation of this nuclear PI-3K pathway. Components of the PI-3K signaling pathway, including PI 3-kinase and its downstream kinase Akt, have been identified at the nuclear level. Consistent with the presence of a complete PI-3K signaling pathway in the nucleus, we have recently found that phosphoinositide-dependent kinase 1 (PDK1), a kinase functioning downstream of PI-3K and upstream of Akt, is a nucleo-cytoplasmic shuttling protein. In the present review, we update our current knowledge on the regulatory mechanisms and the functional roles of PDK1 nuclear translocation. We also summarize some of the kinase-independent activities of PDK1 in cell signaling.     

The Wnt/β‐catenin pathway: master regulator of liver zonation?

The liver contains two systems for the removal of ammonia - the urea cycle and the enzyme glutamine synthetase. These systems are expressed in a complementary fashion in two distinct populations of hepatocytes, referred to as periportal and perivenous cells. One of the unresolved problems in hepatology has been to elucidate the molecular mechanisms responsible for induction and maintenance of the cellular heterogeneity for ammonia detoxification. There is now a potential molecular explanation for the zonation of the urea cycle and glutamine synthetase based on the Wnt/beta-catenin pathway.     

Do ‘we’ ‘do’ God? Linda Woodhead & Rebecca Catto (eds), Religion and change in modern Britain. London: Routledge.

What does it mean to talk of the religion ‘of’ a given country? I reflect on an edited volume dealing with religion in Britain and consider two related themes: the secular considered as ‘absence’ or ‘presence’, and the siting of religion not in conventional denominations or ritual practices but in spaces of encounter between religions, and between the so‐called ‘religious’ and ‘secular’.     

A gene for speed? The evolution and function of α‐actinin‐3

The alpha-actinins are an ancient family of actin-binding proteins that play structural and regulatory roles in cytoskeletal organisation and muscle contraction. alpha-actinin-3 is the most-highly specialised of the four mammalian alpha-actinins, with its expression restricted largely to fast glycolytic fibres in skeletal muscle. Intriguingly, a significant proportion ( approximately 18%) of the human population is totally deficient in alpha-actinin-3 due to homozygosity for a premature stop codon polymorphism (R577X) in the ACTN3 gene. Recent work in our laboratory has revealed a strong association between R577X genotype and performance in a variety of athletic endeavours. We are currently exploring the function and evolutionary history of the ACTN3 gene and other alpha-actinin family members. The alpha-actinin family provides a fascinating case study in molecular evolution, illustrating phenomena such as functional redundancy in duplicate genes, the evolution of protein function, and the action of natural selection during recent human evolution.