Myosin I: From yeast to human

Myosin I is a non-filamentous, single-headed, actin-binding motor protein and is present in a wide range of species from yeast to man. The role of these class I myosins have been studied extensively in simple eukaryotes, showing their role in diverse processes such as actin cytoskeleton organization, cell motility, and endocytosis. Recently, studies in metazoans have begun to reveal more specialized functions of myosin I. It will be a major challenge in the future to examine the physiological functions of each class I myosin in different cell types of metazoans.     

From endoderm to pancreas: a multistep journey

The formation of the vertebrate pancreas is a complex process that typifies the basic steps of embryonic development. It involves the establishment of competence, specification, signaling from neighboring tissues, morphogenesis, and the elaboration of tissue-specific genetic networks. A full analysis of this multistep process will help us to understand classic principles of embryonic development. Furthermore, this will provide the blueprint for experimental programming of pancreas formation from embryonic stem cells in the context of diabetes cell-therapy. Although in the past decade many studies have contributed to a solid foundation for understanding pancreatogenesis, important gaps persist in our knowledge of early pancreas formation. This review will summarize the current understanding of the early mechanisms coming into play to pattern the "pre-pancreatic" region within the endoderm and, gradually, specify the pancreatic tissue.     

Curcumin: From ancient medicine to current clinical trials

Curcumin is the active ingredient in the traditional herbal remedy and dietary spice turmeric (Curcuma longa). Curcumin has a surprisingly wide range of beneficial properties, including anti-inflammatory, antioxidant, chemopreventive and chemotherapeutic activity. The pleiotropic activities of curcumin derive from its complex chemistry as well as its ability to influence multiple signaling pathways, including survival pathways such as those regulated by NF-kappaB, Akt, and growth factors; cytoprotective pathways dependent on Nrf2; and metastatic and angiogenic pathways. Curcumin is a free radical scavenger and hydrogen donor, and exhibits both pro- and antioxidant activity. It also binds metals, particularly iron and copper, and can function as an iron chelator. Curcumin is remarkably non-toxic and exhibits limited bioavailability. Curcumin exhibits great promise as a therapeutic agent, and is currently in human clinical trials for a variety of conditions, including multiple myeloma, pancreatic cancer, myelodysplastic syndromes, colon cancer, psoriasis and Alzheimer's disease.     

Vaults and the major vault protein: Novel roles in signal pathway regulation and immunity

The unique and evolutionary highly conserved major vault protein (MVP) is the main component of ubiquitous, large cellular ribonucleoparticles termed vaults. The 100 kDa MVP represents more than 70% of the vault mass which contains two additional proteins, the vault poly (ADP-ribose) polymerase (vPARP) and the telomerase-associated protein 1 (TEP1), as well as several short untranslated RNAs (vRNA). Vaults are almost ubiquitously expressed and, besides chemotherapy resistance, have been implicated in the regulation of several cellular processes including transport mechanisms, signal transmissions and immune responses. Despite a growing amount of data from diverse species and systems, the definition of precise vault functions is still highly complex and challenging. Here we review the current knowledge on MVP and vaults with focus on regulatory functions in intracellular signal transduction and immune defence. Received 27 June 2008; received after revision 25 July 2008; accepted 30 July 2008     

From immune response to cancer: a spot on the low molecular weight protein tyrosine phosphatase

Reversible tyrosine phosphorylation is a key posttranslational regulatory modification of proteins in all eukaryotic cells in normal and pathological processes. Recently a pivotal janus-faced biological role of the low molecular weight protein tyrosine phosphatase (LMWPTP) has become clear. On the one hand this enzyme is important in facilitating appropriate immune responses towards infectious agents, on the other hand it mediates exaggerated inflammatory responses toward innocuous stimuli. The evidence that LMWPTP plays a role in oncological processes has added a promising novel angle. In this review we shall focus on the regulation of LMWPTP enzymatic activity of signaling pathways of different immunological cells, the relation between genetic polymorphism of LMWPTP and predisposition to some type of inflammatory disorders and the contribution of this enzyme to cancer cell onset, growth and migration. Therefore, the LMWPTP is an interesting target for pharmacological intervention, thus modifying both inappropriate cellular immune responses and cancer cell aggressiveness. Received 15 August 2008; received after revision 06 October 2008; accepted 14 October 2008     

Chitotriosidase and gene therapy for fungal infections

Chitotriosidase secreted by activated human macrophages has been implicated in the defence against chitin-bearing pathogens. The antifungal properties of human chitotriosidase were investigated here following retroviral vector-mediated gene transfer of the open reading frame of the chitotriosidase gene into Chinese hamster ovary cells. A chitinase assay confirmed that the engineered cells secreted recombinant chitotriosidase constitutively. Two dimensional gel electrophoresis and western blotting indicated that the recombinant protein is the major, chitin-binding, fifty kilodalton isoform. Culture medium conditioned by the transduced cells inhibited growth of isolates of Aspergillus niger, Candida albicans and Cryptococcus neoformans. Furthermore, longevity was significantly increased in a mouse model of cryptococcosis when cells transduced with the chitotriosidase gene and encapsulated in alginate microspheres were implanted subcutaneously in the animals. Engraftment of microcapsules containing cells transduced with the chitotriosidase gene has the potential to combat infections caused by chitinous pathogens through the prolonged delivery of recombinant chitotriosidase. Received 29 November 2008; received after revision 11 January 2009; accepted 13 January 2009     

Post-transcriptional gene silencing of ribosomal protein S6 kinase 1 restores insulin action in leucine-treated skeletal muscle

Excessive nutrients, especially amino acids, impair insulin action on glucose metabolism in skeletal muscle. We tested the hypothesis that the branched-chain amino acid leucine reduces acute insulin action in primary myotubes via a negative feedback mechanism involving ribosomal protein S6 kinase 1 (S6K1). The effect of S6K1 on glucose metabolism was determined by applying RNA interference (siRNA). Leucine (5 mM) reduced glucose uptake and incorporation to glycogen by 13% and 22%, respectively, compared to the scramble siRNA-transfected control at the basal level. Leucine also reduced insulin-stimulated Akt phosphorylation, glucose uptake and glucose incorporation to glycogen (39%, 39% and 37%, respectively), and this reduction was restored after S6K1 silencing. Depletion of S6K1 enhanced basal glucose utilization and protected against the development of impaired insulin action, in response to excessive leucine. In conclusion, S6K1 plays an important role in the regulation of insulin action on glucose metabolism in skeletal muscle. Received 22 December 2008; received after revision 19 February 2009; accepted 23 February 2009     

Calmodulin-associated post-translational regulation of rat organic cation transporter 2 in the kidney is gender dependent

In this work, regulation of organic cation transporter type 2 from rat (rOCT2) stably transfected in HEK293 cells was investigated by microfluorimetry with 4-(4-(dimethylamino)styryl)-N-methylpyridinium as substrate. The transport mediated by rOCT2 was specifically stimulated by PKA, phosphatidylinositol-3-kinase, p56^lck tyrosine kinase, mitogen-extracellular-signal-regulated-kinase-1/2, calmodulin (CaM), and CaM-kinase-II. The regulatory pattern of rOCT2 differs markedly quantitatively and qualitatively from that of other OCT isoforms. Only CaM-dependent upregulation is conserved throughout the OCT family. For this reason, CaM regulation of rOCT2 was also investigated in isolated S3-segments (known to express only rOCT2) of male and female rat proximal tubules. Inhibition of CaM by calmidazolium significantly decreased rOCT2 activity (−49.0 ± 13.6%, n = 4) in male but not female (9.0 ± 13.0%, n = 4) rats. Real-time PCR and Western blot investigations of CaM expression in rat kidneys showed that male animals have significantly higher CaM expression. This is the first study describing post-translational gender-dependent rOCT2 regulation. Received 26 February 2009; accepted 16 March 2009     

Purinergic regulation of neutrophil chemotaxis

Chemotaxis allows polymorphonuclear neutrophils (PMN) to rapidly reach infected and inflamed sites. However, excessive influx of PMN damages host tissues. Better knowledge of the mechanisms that control PMN chemotaxis may lead to improved treatments of inflammatory diseases. Recent findings suggest that ATP and adenosine are involved in PMN chemotaxis. Therefore, these purinergic signaling processes may be suitable targets for novel therapeutic approaches to ameliorate host tissue damage.     

Bile Acids: Chemistry, Pathochemistry, Biology, Pathobiology, and Therapeutics

Bile acids and bile alcohols in the form of their conjugates are amphipathic end products of cholesterol metabolism with multiple physiological functions. The great variety of bile acids and bile alcohols that are present in vertebrates are tabulated. Bile salts have an enterohepatic circulation resulting from efficient vectorial transport of bile salts through the hepatocyte and the ileal enterocyte; such transport leads to the accumulation of a pool of bile salts that cycles between the liver and intestine. Bile salt anions promote lipid absorption, enhance tryptic cleavage of dietary proteins, and have antimicrobial effects. Bile salts are signaling molecules, activating nuclear receptors in the hepatocyte and ileal enterocyte, as well as an increasing number of G-protein coupled receptors. Bile acids are used therapeutically to correct deficiency states, to decrease the cholesterol saturation of bile, or to decrease the cytotoxicity of retained bile acids in cholestatic liver disease.     

Gene expression in spermiogenesis

Germ cells convey parental genes to the next generation, and only germ cells perform meiosis, which is a mechanism that preserves the parental genes. The fusion of the products of germ cell meiosis, the haploid sperm and egg, creates the next generation. Sperm are the haploid germ cells that contribute genes to the egg. In preparation for this, the haploid round spermatids produced by meiosis undergo drastic morphological changes to become sperm. During this process of spermiogenesis, the nuclear form of the haploid germ cell takes shape, the mitochondria are rearranged in a specific manner, the flagellum develops and the acrosome forms. Spermatogenesis is supported by precise and orderly regulation of gene expression during the changes in chromatin structure, when protamine replaces histone. In this report, we summarize the molecular mechanisms involved in spermiogenesis.Received 2 September 2004; received after revision 7 October 2004; accepted 7 October 2004     

Histone methylation and ubiquitination with their cross-talk and roles in gene expression and stability

Methylation of lysine residues of histones is associated with functionally distinct regions of chromatin, and, therefore, is an important epigenetic mark. Over the past few years, several enzymes that catalyze this covalent modification on different lysine residues of histones have been discovered. Intriguingly, histone lysine methylation has also been shown to be cross-regulated by histone ubiquitination or the enzymes that catalyze this modification. These covalent modifications and their cross-talks play important roles in regulation of gene expression, heterochromatin formation, genome stability, and cancer. Thus, there has been a very rapid progress within past several years towards elucidating the molecular basis of histone lysine methylation and ubiquitination, and their aberrations in human diseases. Here, we discuss these covalent modifications with their cross-regulation and roles in controlling gene expression and stability. Received 24 September 2008; received after revision 21 November 2008; accepted 28 November 2008     

Effects of ulapualide A and synthetic macrolide analogues on actin dynamics and gene regulation

Several marine macrolide toxins act as potent and specific actin-severing molecules. Recent elucidation of their stereochemistries and modes of interaction with actin has allowed the syntheses of bioactive analogues. Here we used synthetic analogues in a structure-function analysis of ulapualide A, a trisoxazole-based macrolide. Ulapualide A harboured potent actin-depolymerising activity both in cells and in vitro. Its synthetic diastereoisomer was three orders of magnitude less active than the natural toxin and synthetic macrolide fragments lacked actin-capping/ severing activity altogether. Modulation of serum response factor (SRF)-dependent gene expression, as described for other actin-binding toxins, was also examined. Specific changes in response to ulapualide A were not observed, primarily due to its profound effects on cytoskeletal integrity and cell adhesion. Several synthetic fragments of ulapualide A also had no effect on SRF-dependent gene expression. However, inhibition was observed with a molecule corresponding to the extended aliphatic side chain of halichondramide, a structurally related macrolide. These findings indicate that side-chain derivatives of trisoxazole-based macrolides may serve to uncouple gene-regulatory events from actin dynamics. E. Vincent and J. Saxton: These two authors contributed equally Received 27 September 2006; received after revision 30 November 2006; accepted 8 January 2007