The roles of poly(ADP-ribose)-metabolizing enzymes in alkylation-induced cell death

Poly(ADP-ribose) (PAR) has been identified as a DNA damage-inducible cell death signal upstream of apoptosis-inducing factor (AIF). PAR causes the translocation of AIF from mitochondria to the nucleus and triggers cell death. In living cells, PAR molecules are subject to dynamic changes pending on internal and external stress factors. Using RNA interference (RNAi), we determined the roles of poly(ADP-ribose) polymerases-1 and -2 (PARP-1, PARP-2) and poly(ADP-ribose) glycohydrolase (PARG), the key enzymes configuring PAR molecules, in cell death induced by an alkylating agent. We found that PARP-1, but not PARP-2 and PARG, contributed to alkylation-induced cell death. Likewise, AIF translocation was only affected by PARP-1. PARP-1 seems to play a major role configuring PAR as a death signal involving AIF translocation regardless of the death pathway involved. Received 7 November 2007; received after revision 19 December 2007; accepted 21 December 2007 O. Cohausz, C. Blenn: These two authors contributed equally to this work.     

Angiotensin-converting enzyme 2 in acute respiratory distress syndrome

Angiotensin-converting enzyme (ACE) and ACE2 are highly homologous metalloproteases that provide essential catalytic functions in the renin-angiotensin system (RAS). Angiotensin II is one key effector peptide of the RAS, inducing vasoconstriction and exerting multiple biological functions. ACE cleaves angiotensin I to generate angiotensin II, whereas ACE2 reduces angiotensin II levels. Accumulating evidence has demonstrated a physiological and pathological role of ACE2 in the cardiovascular systems. Intriguingly, the SARS coronavirus, the cause of severe acute respiratory syndrome (SARS), utilizes ACE2 as an essential receptor for cell fusion and in vivo infections. Moreover, recent studies have demonstrated that ACE2 protects murine lungs from acute lung injury as well as SARS-Spike protein-mediated lung injury, suggesting a dual role of ACE2 in SARS infections and protection from ARDS. Received 18 May 2006; received after revision 12 March 2007; accepted 24 April 2007     

Serglycin – Structure and biology

Serglycin is a proteoglycan found in hematopoietic cells and endothelial cells. It has important functions related to formation of several types of storage granules. In connective tissue mast cells the covalently attached glycosaminoglycan is heparin, whereas mucosal mast cells and activated macrophages contain oversulfated chondroitin sulfate (type E). In mast cells, serglycin interact with histamine, chymase, tryptase and carboxypeptidase, in neutrophils with elastase, in cytotoxic T cells with granzyme B, in endothelial cells with tissue-type plasminogen activator and in macrophages with tumor necrosis factor-α. Serglycin is important for the retention of key inflammatory mediators inside storage granules and secretory vesicles. Serglycin can further modulate the activities of partner molecules in different ways after secretion from activated immune cells, through protection, transport, activation and interactions with substrates or target cells. Serglycin is a proteoglycan with important roles in inflammatory reactions. Received 2 October 2007; received after revision 7 November 2007; accepted 12 November 2007     

The surface glycopeptidolipids of mycobacteria: structures and biological properties

One of the most important opportunistic pathogens associated with acquired immunodeficiency syndrome (AIDS) is the M. avium complex. M. avium infections are found in up to 70% of individuals in advanced stages of AIDS. It is apparent that M. avium can replicate in host macrophages and persist for long periods. This group of mycobacteria are distinguished by the presence of unique, highly antigenic, surface-located lipids known as the glycopeptidolipids (GPLs). The GPLs are the chemical basis of the 31 distinct serovars of the M. avium complex, and have also been identified in some other species. The M. avium lipids are immunosuppressive and can induce a variety of cytokines that affect general host responses. Despite extensive chemical characterization of the structures of these GPLs, much work is needed to elucidate the molecular mechanism involved in this complex glycosylation pathway and its genetic basis. The challenges for the future lie in explaining the roles of these copious products in the intracellular life and infectivity of mycobacteria. The intention of our review is to offer a concise account of the structures of the M. avium lipids, their putative roles in the host responses, bacterial physiology and pathogenesis, particularly in immunocompromised patients such as those infected with human immunodeficiency virus (HIV). Advances in chemical synthesis of the various haptenic oligosaccharides are also given to demonstrate how these have helped to define the immunogenic determinants. We believe that future research should involve the creation of conditional mutants defective in these lipids for both functional and biosynthesis studies which will complement biological assays using chemically defined or modified neoglycoconjugates. Received 7 May 2001; received after revision 28 June 2001; accepted 28 June 2001     

Antimicrobial skin peptides and proteins

Human skin is permanently exposed to microorganisms, but rarely infected. One reason for this natural resistance might be the existence of a ‘chemical barrier’ consisting in constitutively and inducibly produced antimicrobial peptides and proteins (AMPs). Many of these AMPs can be induced in vitro by proinflammatory cytokines or bacteria. Apart from being expressed in vivo in inflammatory lesions, some AMPs are also focally expressed in skin in the absence of inflammation. This suggests that non-inflammatory stimuli of endogenous and/or exogenous origin can also stimulate AMP synthesis without inflammation. Such mediators might be ideal ‘immune stimulants’ to induce only the innate antimicrobial skin effector molecules without causing inflammation. Received 9 August 2005; received after revision 21 October 2005; accepted 16 November 2005     

含异嗯唑环的药物先导化合物的设计、合成与活性研究

本文综述了将取代异嗯唑作为药效活性基团,引入到四类不同母体分子中,所合成的新型化合物分别具有抗菌、消炎等生物活性,成为有价值的药物先导化合物的研究进展。     

Chemical chaperone therapy for GM1-gangliosidosis

We have proposed a chemical chaperone therapy for lysosomal diseases, based on a paradoxical phenomenon that an exogenous competitive inhibitor of low molecular weight stabilizes the target mutant molecule and restores its catalytic activity as a molecular chaperone intracellularly. After Fabry disease experiments, we investigated a new synthetic chaperone compound N-octyl-4-epi-β-valienamine (NOEV) in a G_M1-gangliosidosis model mice. Orally administered NOEV entered the brain through the blood-brain barrier, enhanced β-galactosidase activity, reduced the substrate storage, and clinically improved neurological deterioration. We hope that chemical chaperone therapy will prove useful for some patients with G_M1-gangliosidosis and potentially other lysosomal storage diseases with central nervous system involvement. Received 10 October 2007; received after revision 31 October 2007; accepted 6 November 2007     

Structure, function and metabolism of sialic acids

Sialic acids represent a family of sugar molecules with an unusual and highly variable chemical structure that are found mostly in the terminal position of oligosaccharide chains on the surface of cells and molecules. These special features enable them to fulfil several important and even diametrical biological functions. Because of the great importance of sialic acids, it is also worth having a look at their metabolism in order to get an idea of the intimate connection between structure and function of these fascinating molecules and the often serious consequences that result from disturbances in the balance of metabolic reactions. The latter can be due to genetic disorders that result in the absence of certain enzyme activity, leading to severe illness or even to death. Received 17 July 1998; received after revision 2 September 1998; accepted 2 September 1998     

Cationic host defence peptides: Innate immune regulatory peptides as a novel approach for treating infections

An increase in antibiotic resistance and the emergence of new pathogens has led to an urgent need for alternative approaches to infection management. Immunomodulatory molecules that do not target the pathogen directly, but rather selectively enhance and/or alter host defence mechanisms, are attractive candidates for therapeutic development. Natural cationic host defence peptides represent lead molecules that boost innate immune responses and selectively modulate pathogen-induced inflammatory responses. This review discusses recent evidence exploring the mechanisms of cationic host defence peptides as innate immune regulators, their role in the interface of innate and adaptive immunity, and their potential application as beneficial therapeutics in overcoming infectious diseases. Received 3 November 2006; received after revision 14 December 2006; accepted 22 January 2007     

Structural studies of elongation and release factors

The elongation and termination steps of protein synthesis are controlled by elongation and release factors, respectively. Elongation factors deliver the aminoacyl tRNA to the ribosomal A site, ensuring the elongation of the nascent polypeptide chain by one amino acid at a time, while release factors recognize the stop codons and trigger the release of the polypeptide from the ribosome. Recently, highresolution crystal structures of ribosomes as well as translation factors on and off the ribosome have contributed a great deal to our understanding of the molecular basis of protein synthesis. This review concentrates on recent developments in our understanding of the elongation and termination steps of protein synthesis, particularly the roles of translation factors and their similarities and differences in the eukaryotic cytosol and prokaryotic systems, through a combination of structural and biochemical studies. Received 25 October 2007; received after revision 5 December 2007; accepted 7 December 2007     

Mammalian aldehyde oxidases: genetics, evolution and biochemistry

Mammalian aldehyde oxidases are a small group of proteins belonging to the larger family of molybdo-flavoenzymes along with xanthine oxidoreductase and other bacterial enzymes. The two general types of reactions catalyzed by aldehyde oxidases are the hydroxylation of heterocycles and the oxidation of aldehydes into the corresponding carboxylic acids. Different animal species are characterized by a different complement of aldehyde oxidase genes. Humans contain a single active gene, while marsupials and rodents are characterized by four such genes clustering at a short distance on the same chromosome. At present, little is known about the physiological relevance of aldehyde oxidases in humans and other mammals, although these enzymes are known to play a role in the metabolism of drugs and compounds of toxicological importance in the liver. The present article provides an overview of the current knowledge of genetics, evolution, structure, enzymology, tissue distribution and regulation of mammalian aldehyde oxidases. Received 30 August 2007; received after revision 2 November 2007; accepted 8 November 2007     

Modulation of protein biophysical properties by chemical glycosylation: biochemical insights and biomedical implications

Glycosylation constitutes one of the most important posttranslational modifications employed by biological systems to modulate protein biophysical properties. Due to the direct biochemical and biomedical implications of achieving control over protein stability and function by chemical means, there has been great interest in recent years towards the development of chemical strategies for protein glycosylation. Since current knowledge about glycoprotein biophysics has been mainly derived from the study of naturally glycosylated proteins, chemical glycosylation provides novel insights into its mechanistic understanding by affording control over glycosylation parameters. This review presents a survey of the effects that natural and chemical glycosylation have on the fundamental biophysical properties of proteins (structure, dynamics, stability, and function). This is complemented by a mechanistic discussion of how glycans achieve such effects and discussion of the implications of employing chemical glycosylation as a tool to exert control over protein biophysical properties within biochemical and biomedical applications. Received 15 December 2006; received after revision 28 March 2007; accepted 25 April 2007     

Catalysis in abiotic structured media: an approach to selective synthesis of biopolymers

Micro- and nanoenvironments formed by amphiphile self-assembled structures, water-ice lattices and minerals have well-defined, repeating, chemical and physical properties that can be used for selective synthesis of biopolymers, such as RNAs and proteins. The advances made in the development of polymerization supported by these micro- and nanosystems are reviewed here. In particular, it is shown that these systems promote non-enzymatic biopolymerization, yielding long polymers whose sequence composition is determined by the interactions between monomers and the supporting environment. When used to compartmentalize enzymatic biopolymerization, micro- and nanostructures allow the implementation of molecular selection and evolution schemes, which are difficult in homogeneous medium, yielding very active molecules. Thus, micro- and nanoenvironment approaches to the synthesis and selection of biopolymers could be developed into a new biotechnological tool for the production of biopolymers with novel functions.Received 3 August 2004; received after revision 6 October 2004; accepted 21 October 2004     

Glycogen synthase kinase 3: A key regulator of cellular fate

The serine/threonine kinase glycogen synthase kinase-3 (GSK-3) was initially identified as a key regulator of insulin-dependent glycogen synthesis. GSK-3 was subsequently shown to function in a wide range of cellular processes including differentiation, growth, motility and apoptosis. Aberrant regulation of GSK-3 has been implicated in a range of human pathologies including Alzheimer’s disease, non-insulin-dependent diabetes mellitus (NIDDM) and cancer. As a consequence, the regulation of GSK-3 and the therapeutic potential of GSK-3 inhibitors have become key areas of investigation. This review will focus on the mechanisms of GSK-3 regulation, with emphasis on modulation by upstream signals, control of substrate specificity and GSK-3 localisation. The details of these mechanisms will be discussed in the context of specific signalling pathways. Received 30 January 2007; received after revision 5 March 2007; accepted 16 April 2007     

Instruments and rules: R. B. Woodward and the tools of twentieth-century organic chemistry

The paper illustrates how organic chemists dramatically altered their practices in the middle part of the twentieth century through the adoption of analytical instrumentation — such as ultraviolet and infrared absorption spectroscopy and nuclear magnetic resonance spectroscopy — through which the difficult process of structure determination for small molecules became routine. Changes in practice were manifested in two ways: in the use of these instruments in the development of ‘rule-based’ theories; and in an increased focus on synthesis, at the expense of chemical analysis. These rule-based theories took the form of generalizations relating structure to chemical and physical properties, as measured by instrumentation. This ‘Instrumental Revolution’ in organic chemistry was two-fold: encompassing an embrace of new tools that provided unprecedented access to structures, and a new way of thinking about molecules and their reactivity in terms of shape and structure. These practices suggest the possibility of a change in the ontological status of chemical structures, brought about by the regular use of instruments. The career of Robert Burns Woodward (1917–1979) provides the central historical examples for the paper. Woodward was an organic chemist at Harvard from 1937 until the time of his death. In 1965, he won the Nobel Prize in Chemistry.     

Signaling in the Chemosensory Systems

The small nematode Caenorhabditis elegans lives in the soil, where mechanical, thermal and most of all chemical stimuli strongly influence its behavior. Here we briefly review how chemical sensitivity is organized at the cellular and molecular level in this organism. C. elegans has less than 40 chemosensory neurons. With few exceptions each neuron senses more than one substance and each substance is sensed by more than one neuron. At the molecular level, as in other organisms, also in C. elegans, seven transmembrane G-protein-coupled receptors (GPCRs), heterotrimeric G proteins, cyclic nucleotidegated ion channels, TRP channels and Ca++ play crucial roles in chemical sensitivity. An unusual feature, possibly due to C. elegans's strong dependence on chemical cues, is the very large number of GPCR chemoreceptor genes (1300-1700) coded in its genome. Genetic approaches have also allowed the identification of new molecules involved in chemical sensitivity that would not have been discovered otherwise. In addition to the basic factors involved in primary signalling, the studies in C. elegans have revealed a network of regulatory pathways and molecules suggesting that fine modulation of the responsiveness of neurons is important, possibly to allow worms to negotiate a continuously changing environment. The experimental versatility of C. elegans has made it possible, in many cases, to determine precisely in which neuron a given molecule or pathway is required and for which biological response. This type of information can contribute to the general field of sensory signalling because it provides correlations between the biochemical properties of molecules and their cellular functions and between these and the in vivo behavioral responses of the animal.     

The BAG proteins: a ubiquitous family of chaperone regulators

The BAG (Bcl-2 associated athanogene) family is a multifunctional group of proteins that perform diverse functions ranging from apoptosis to tumorigenesis. An evolutionarily conserved group, these proteins are distinguished by a common conserved region known as the BAG domain. BAG genes have been found in yeasts, plants, and animals, and are believed to function as adapter proteins forming complexes with signaling molecules and molecular chaperones. In humans, a role for BAG proteins has been suggested in carcinogenesis, HIV infection, and Parkinson’s disease. These proteins are therefore potential therapeutic targets, and their expression in cells may serve as a predictive tool for such diseases. In plants, the Arabidopsis thaliana genome contains seven homologs of the BAG family, including four with domain organization similar to animal BAGs. Three members contain a calmodulin-binding domain possibly reflecting differences between plant and animal programmed cell death. This review summarizes current understanding of BAG proteins in both animals and plants. Received 21 November 2007; received after revision 17 December 2007; accepted 2 January 2008     

Key role of glutamic acid for the cytotoxic activity of the cyclotide cycloviolacin O2

Cyclotides are cyclic plant proteins with potent cytotoxic effects. Here we systematically probed the importance of surface-exposed charged amino acid residues of the cyclotide cycloviolacin O2, using a strategy involving chemical modifications. We show that the single glutamic acid plays a key role for the cytotoxicity: methylation of this residue produced a 48-fold decrease in potency. Virtually no change in potency was observed when masking the single arginine residue using 1,2-cyclohexanedione, while acetylation of the two lysine residues reduced the potency 3-fold. The derivative with modifications at both arginine and lysine residues showed a 7-fold loss of potency. In addition, we show that the activity is dependent on an intact disulfide network and that the short sequences between the six cysteine residues, that is, the backbone loops, are devoid of cytotoxic activity. Received 11 October 2005; received after revision 3 November 2005; accepted 15 November 2005     

Cofactor-induced and mutational activity enhancement of coagulation factor VIIa

Coagulation factor VIIa (FVIIa) is an atypical member of the trypsin family of serine proteases. It fails to attain spontaneously its catalytically competent conformation and requires its protein cofactor tissue factor (TF) to accomplish this. Over a number of years, this unique behaviour of FVIIa has prompted investigations of the TF-induced activation mechanism and the zymogenicity determinants in factor VIIa. Factor VIIa has gained additional interest in the past decade because of its development into a clinically useful haemostatic agent. Here, we present an overview of the current knowledge about the TF-induced allosteric activation of FVIIa and the various molecular approaches to enhance the intrinsic activity and efficacy of FVIIa. Received 18 October 2007; received after revision 12 November 2007; accepted 14 November 2007     

Involvement of small Ras GTPases and their effectors in chronic renal disease

The mechanisms involved in the development of renal fibrosis are poorly understood. Small Ras GTPases control cell proliferation, differentiation, cellular growth and apoptosis, with cell-specific expression in the kidney. Cytokines, high glucose medium or advanced glycation end-products activate Ras in different renal cells. Increased Ras activation has been found in experimental tubulointerstitial fibrosis. Transforming growth factor-β1 (TGF-β1) and Ras signalling pathways are close related: TGF-β1 overcomes Ras mitogenic effects, and Ras counteracts TGF-β signalling. However, Ras activation is also an intracellular signal transduction point for several molecules (e.g. TGF-β1) involved in kidney damage. Ras isoforms play different roles in regulating extracellular matrix synthesis in fibroblasts and mesangial cells. These data give evidence for a role for Ras in renal fibrosis, but no reviews are available on the role of p21 Ras in this process. Thus, our goal is to review the role of Ras activation and signalling in renal fibrosis. Received 7 June 2007; received after revision 17 September 2007; accepted 1 October 2007