Pathogenic role of mitogen activated protein kinases in protozoan parasites.

Protozoan parasites with complex life cycles have high mortality rates affecting billions of human lives. Available anti-parasitic drugs are inadequate due to variable efficacy, toxicity, poor patient compliance and drug-resistance. Hence, there is an urgent need for the development of safer and better chemotherapeutics. Mitogen Activated Protein Kinases (MAPKs) have drawn much attention as potential drug targets. This review summarizes unique structural and functional features of MAP kinases and their possible role in pathogenesis of obligate intracellular protozoan parasites namely, Leishmania, Trypanosoma, Plasmodium and Toxoplasma. It also provides an overview of available knowledge concerning the target proteins of parasite MAPKs and the need to understand and unravel unknown interaction network(s) of MAPK(s).

Drugging the Phosphoinositide 3-Kinase (PI3K) and Phosphatidylinositol 4-Kinase (PI4K) Family of Enzymes for Treatment of Cancer, Immune Disorders, and Viral/Parasitic Infections.

The lipid kinases that generate the lipid signalling phosphoinositides have been established as fundamental signalling enzymes that control numerous aspects of how cells respond to their extracellular environment. In addition, they play critical roles in regulating membrane trafficking and lipid transport within the cell. The class I phosphoinositide kinases which generate the critical lipid signal PIP3 are hyperactivated in numerous human pathologies including cancer, overgrowth syndromes, and primary immunodeficiencies. The type III phosphatidylinositol 4-kinase beta isoform (PI4KB), which are evolutionarily similar to the class I PI3Ks, have been found to be essential host factors mediating the replication of numerous devastating pathogenic viruses. Finally, targeting the parasite variant of PI4KB has been established as one of the most promising strategies for the development of anti-malarial and anti-cryptosporidium strategies. Therefore, the development of targeted isoform selective inhibitors for these enzymes are of paramount importance. The first generation of PI3K inhibitors have recently been clinically approved for a number of different cancers, highlighting their therapeutic value. This review will examine the history of the class I PI3Ks, and the type III PI4Ks, their relevance to human disease, and the structural basis for their regulation and inhibition by potent and selective inhibitors.

Effects of BTK signalling in pathogenic microorganism infections.

As a cytoplasmic protein tyrosine kinase, Bruton's tyrosine kinase (Btk) is widely considered as a vital kinase in many aspects of different physiologic processes. It is engaged in many important signalling pathways related to the immune response, such as the B cell receptor pathway, pattern-recognition receptor pathway, and triggering receptor expressed on myeloid cell pathway. Recent studies have increasingly focused on the important role of Btk in various inflammatory diseases, which are related to Btk expression in myeloid innate immune cells, such as macrophages, dendritic cells and neutrophils. Although some investigations have explored the role of Btk in microbial infections, many aspects remain elusive, and some of the results are opposite and controversial. Considering the complicated and multiple roles of Btk in the immune system, we summarized the engagement of Btk signalling in various pathogenic microorganism infections, the possible mechanisms involved and its therapeutic potential in the control of infectious diseases.

Progress and challenges in aminoacyl-tRNA synthetase-based therapeutics.

Aminoacyl-tRNA synthetases (ARSs) are universal enzymes that catalyze the attachment of amino acids to the 3' ends of their cognate tRNAs. The resulting aminoacylated tRNAs are escorted to the ribosome where they enter protein synthesis. By specifically matching amino acids to defined anticodon sequences in tRNAs, ARSs are essential to the physical interpretation of the genetic code. In addition to their canonical role in protein synthesis, ARSs are also involved in RNA splicing, transcriptional regulation, translation, and other aspects of cellular homeostasis. Likewise, aminoacylated tRNAs serve as amino acid donors for biosynthetic processes distinct from protein synthesis, including lipid modification and antibiotic biosynthesis. Thanks to the wealth of details on ARS structures and functions and the growing appreciation of their additional roles regulating cellular homeostasis, opportunities for the development of clinically useful ARS inhibitors are emerging to manage microbial and parasite infections. Exploitation of these opportunities has been stimulated by the discovery of new inhibitor frameworks, the use of semi-synthetic approaches combining chemistry and genome engineering, and more powerful techniques for identifying leads from the screening of large chemical libraries. Here, we review the inhibition of ARSs by small molecules, including the various families of natural products, as well as inhibitors developed by either rational design or high-throughput screening as antibiotics and anti-parasitic therapeutics.

Design of Drugs by Filtering Through ADMET, Physicochemical and Ligand-Target Flexibility Properties.

There is a synergistic interaction between medicinal chemistry, chemoinformatics, and bioinformatics. The last one includes analyses of sequences as well as structural analysis which employ computational techniques such as docking studies and molecular dynamics (MD) simulations. Over the last years these techniques have allowed the development of new accurate computational tools for drug design. As a result, there have been an increased number of publications where computational methods such as pharmacophore modeling, de novo drug design, evaluation of physicochemical properties, and analysis of ADMET (absorption, distribution, metabolism, excretion, and toxicity) properties have been quite useful for eliminating the compounds with poor physicochemical or toxicological properties. Furthermore, using MD simulations and docking analysis, it is possible to estimate the binding energy of the protein-ligand complexes by using scoring functions, as well as to structurally depict the binding pose of the compounds on proteins, in order to select the best evaluated compounds for subsequent synthetizing and evaluation through biological assays. In this work, we describe some computational tools that have been used for structure-based drug design of new compounds that target histone deacetylases (HDACs), which are known to be potential targets in cancer and parasitic diseases.

Sensing of invading pathogens by GBPs: At the crossroads between cell-autonomous and innate immunity.

Guanylate-binding proteins (GBPs) are conserved family of IFN-inducible GTPases that play an important role in the host immunity against bacterial, viral, and protozoan pathogens. GBPs protect the host by associating with intracellular microbes, their vacuolar niche or, in the case of viruses, with their replication complex. This association results in a restriction of the respective pathogen, yet the exact molecular mechanisms of the antimicrobial functions of GBPs are still unclear. Recent work has linked the GBPs with the activation of inflammasomes, multi-protein complexes that assemble upon recognition of pathogen- or host-derived signals and that drive the release of cytokines and host cell death. Here, we will focus on the most recent findings that have started to unravel the manifold restriction mechanism controlled by GBPs in mouse and human cells, and that shed light on the molecular cues that control GBP recruitment to bacterial membranes.

The dihydroorotate dehydrogenases: Past and present.

The flavoenzyme dihydroorotate dehydrogenase catalyzes the stereoselective oxidation of (S)-dihydroorotate to orotate in the fourth of the six conserved enzymatic reactions involved in the de novo pyrimidine biosynthetic pathway. Inhibition of pyrimidine metabolism by selectively targeting DHODHs has been exploited in the development of new therapies against cancer, immunological disorders, bacterial and viral infections, and parasitic diseases. Through a chronological narrative, this review summarizes the efforts of the scientific community to achieve our current understanding of structural and biochemical properties of DHODHs. It also attempts to describe the latest advances in medicinal chemistry for therapeutic development based on the selective inhibition of DHODH, including an overview of the experimental techniques used for ligand screening during the process of drug discovery.

[Pyrophosphate in medicine]. / Pyrofosfaatti lääketieteessä.

In all organisms from bacteria to humans, specific hydrolases--pyrophosphatases--hydrolyse inorganic pyrophosphate to phosphate. Without this, DNA, RNA and protein synthesis stops. Pyrophosphatases are thus essential for all life. In humans, disorders in pyrophosphate metabolism cause chondrocalcinosis and hypophosphatasia. Currently, pyrophosphate analogues, e.g. alendronate, are in clinical use in osteoporosis and Paget's disease but also for e.g. complications of prostate cancer. In bacteria and protozoan parasites, membrane-bound pyrophosphatases (mPPases), which do not occur in humans, convert pyrophosphate to a proton or sodium gradient. mPPases, which are crucial for protozoan parasites, are thus promising drug targets e.g. for malaria and leishmaniasis.

Parasite Cathepsin D-Like Peptidases and Their Relevance as Therapeutic Targets.

Inhibition of aspartic cathepsin D-like peptidases (APDs) has been often discussed as an antiparasite intervention strategy. APDs have been considered as virulence factors of Trypanosoma cruzi and Leishmania spp., and have been demonstrated to have important roles in protein trafficking mechanisms of apicomplexan parasites. APDs also initiate blood digestion as components of multienzyme proteolytic complexes in malaria, platyhelminths, nematodes, and ticks. Increasing DNA and RNA sequencing data indicate that parasites express multiple APD isoenzymes of various functions that can now be specifically evaluated using new functional-genomic and biochemical tools, from which we can further assess the potential of APDs as targets for novel effective intervention strategies against parasitic diseases that still pose an alarming threat to mankind.

[Enolase and parasitic infection].

Enolase is one kind of important glycolytic enzymes which widely exists in most organisms. A number of recent studies confirm that this enzyme has the functions of activating the plasminogen, involving in the processes of infection and migration of parasites, reducing the immune function of the host as well as preventing parasites from the immune attack of the host. This paper reviews the current research advances in the parasite enolase, and explores its potential for diagnosis, drug development and vaccine target of parasitic diseases.

The rhomboid-like superfamily: molecular mechanisms and biological roles.

The rhomboid proteases were first discovered as regulators of Drosophila EGF receptor signaling; soon after, it was recognized that they represented the founder members of a widespread family of intramembrane serine proteases conserved in all kingdoms. More recently still, the family was promoted to a superfamily, encompassing a wide variety of distantly related proteins. One of the surprises has been that many members of the rhomboid-like superfamily are not active proteases. Given the size of this clan, and its relatively recent discovery, there is still much to learn. Nevertheless, we already understand much about how rhomboid proteases perform their surprising function of cleaving transmembrane domains. We also already know that members of the rhomboid-like superfamily participate in biological functions as diverse as growth factor signaling, mitochondrial dynamics, inflammation, parasite invasion, and the machinery of protein quality control. Their potential medical significance is now becoming apparent in several areas.

Modulation of paraoxonases during infectious diseases and its potential impact on atherosclerosis.

The paraoxonase (PON) gene family includes three members, PON1, PON2 and PON3, aligned in tandem on chromosome 7 in humans and on chromosome 6 in mice. All PON proteins share considerable structural homology and have the capacity to protect cells from oxidative stress; therefore, they have been implicated in the pathogenesis of several inflammatory diseases, particularly atherosclerosis. The major goal of this review is to highlight the modulation of each of the PONs by infective (bacterial, viral and parasitic) agents, which may shed a light on the interaction between infectious diseases and PONs activities in order to effectively reduce the risk of developing atherosclerosis.

The role of iNOS-mediated DNA damage in infection- and asbestos-induced carcinogenesis.

Chronic inflammation contributes to a substantial part of environmental carcinogenesis. Various infectious diseases and physical, chemical, and immunological factors participate in inflammation-related carcinogenesis. Under inflammatory conditions, reactive oxygen and nitrogen species are generated from inflammatory and epithelial cells, and resulting DNA damage may participate in carcinogenesis. 8-Nitroguanine is a mutagenic DNA lesion formed during chronic inflammation. We performed immunohistochemical analysis, and demonstrated that 8-nitroguanine was formed at the sites of carcinogenesis in animal models and patients with various cancer-prone infectious and inflammatory diseases, caused by parasites, viruses, and asbestos exposure. In asbestos-exposed mice, 8-nitroguanine was formed in bronchial epithelial cells, and it is noteworthy that crocidolite induced significantly more intense 8-nitroguanine formation than chrysotile, inconsistent with their carcinogenic potentials. On the basis of these findings, we have proposed that 8-nitroguanine could be a potential biomarker to evaluate the risk of inflammation-related carcinogenesis.

Apicomplexa, trypanosoma and parasitic nematode protein kinases as antiparasitic therapeutic targets.

Parasitic infections caused by Plasmodium, Trypanosoma, Leishmania, Toxoplasma and parasitic nematodes affect hundreds of millions of individuals worldwide and are the cause of significant mortality and morbidity, particularly in developing countries. These diseases also have an impact on individuals from developed countries; for example, some US troops in Iraq and Afghanistan have been infected with Leishmania. The annual mortality associated with parasitic infections is estimated to be 1.5 million deaths. The socioeconomic impact of the morbidity associated with parasitic infections is significant, and the development of new drugs, aimed at novel targets, is urgently needed to develop effective treatments for these diseases. The small-molecule inhibitors discussed in this review constitute useful tools with which to explore the relevance of kinase inhibition in inducing antiparasitic activity. The aim of recent target-based approaches used in the development of parasite kinase inhibitors is to identify novel antiparasitic agents with therapeutic potential.

Arginase in parasitic infections: macrophage activation, immunosuppression, and intracellular signals.

A type 1 cytokine-dependent proinflammatory response inducing classically activated macrophages (CaMvarphis) is crucial for parasite control during protozoan infections but can also contribute to the development of immunopathological disease symptoms. Type 2 cytokines such as IL-4 and IL-13 antagonize CaMvarphis inducing alternatively activated macrophages (AaMvarphis) that upregulate arginase-1 expression. During several infections, induction of arginase-1-macrophages was showed to have a detrimental role by limiting CaMvarphi-dependent parasite clearance and promoting parasite proliferation. Additionally, the role of arginase-1 in T cell suppression has been explored recently. Arginase-1 can also be induced by IL-10 and transforming growth factor-beta (TGF-beta) or even directly by parasites or parasite components. Therefore, generation of alternative activation states of macrophages could limit collateral tissue damage because of excessive type 1 inflammation. However, they affect disease outcome by promoting parasite survival and proliferation. Thus, modulation of macrophage activation may be instrumental in allowing parasite persistence and long-term host survival.

Proteases in parasitic diseases.

Parasitic diseases represent major global health problems of immense proportion. Schistosomiasis, malaria, leishmaniasis, Chagas disease, and African sleeping sickness affect hundreds of millions of people worldwide, cause millions of deaths annually, and present an immense social and economic burden. Recent advances in genomic analysis of several of the major global parasites have revealed key factors involved in the pathogenesis of parasite diseases. Among the major virulence factors identified are parasite-derived proteases. This review focuses on the direct role of proteases in disease pathogenesis. Well-characterized examples of the roles proteases play in pathogenesis include their involvement in invasion of the host by parasite migration through tissue barriers, degradation of hemoglobin and other blood proteins, immune evasion, and activation of inflammation.

Protein phosphatase 2A: the Trojan Horse of cellular signaling.

Dynamic phosphorylation and dephosphorylation of proteins are fundamental mechanisms utilized by cells to transduce signals. Whereas transduction by protein kinases has been a major focus of studies in the last decade, protein phosphatase 2A (PP2A) enzymes emerge in this millenium as the most fashionable players in cellular signaling. Viral proteins target specific PP2A enzymes in order to deregulate chosen cellular pathways in the host and promote viral progeny. The observation that a variety of viruses utilize PP2A to alienate cellular behavior emphasizes the fundamental importance of PP2A in signal transduction. This review will primarily focus on discussing the uniqueness of PP2A regulation and uncovering the critical role played by protein-protein interactions in the modulation of PP2A signaling. Moreover, the place of PP2A in signaling pathways and its functional significance for human diseases will be discussed.