Toxoplasma and Plasmodium protein kinases: roles in invasion and host cell remodelling

Some apicomplexan parasites have evolved distinct protein kinase families to modulate host cell structure and function. Toxoplasma gondii rhoptry protein kinases and pseudokinases are involved in virulence and modulation of host cell signalling. The proteome of Plasmodium falciparum contains a family of putative kinases called FIKKs, some of which are exported to the host red blood cell and might play a role in erythrocyte remodelling. In this review we will discuss kinases known to be critical for host cell invasion, intracellular growth and egress, focusing on (i) calcium-dependent protein kinases and (ii) the secreted kinases that are unique to Toxoplasma (rhoptry protein kinases and pseudokinases) and Plasmodium (FIKKs)

Investigation of LKB1 Ser⁴³¹ phosphorylation and Cys⁴³³ farnesylation using mouse knockin analysis reveals an unexpected role of prenylation in regulating AMPK activity

The LKB1 tumour suppressor protein kinase functions to activate two isoforms of AMPK (AMP-activated protein kinase) and 12 members of the AMPK-related family of protein kinases. The highly conserved C-terminal residues of LKB1 are phosphorylated (Ser(431)) by PKA (cAMP-dependent protein kinase) and RSK (ribosomal S6 kinase) and farnesylated (Cys(433)) within a CAAX motif. To better define the role that these post-translational modifications play, we created homozygous LKB1(S431A/S431A) and LKB1(C433S/C433S) knockin mice. These animals were viable, fertile and displayed no overt phenotypes. Employing a farnesylation-specific monoclonal antibody that we generated, we established by immunoprecipitation that the vast majority, if not all, of the endogenous LKB1 is prenylated. Levels of LKB1 localized at the membrane of the liver of LKB1(C433S/C433S) mice and their fibroblasts were reduced substantially compared with the wild-type mice, confirming that farnesylation plays a role in mediating membrane association. Although AMPK was activated normally in the LKB1(S431A/S431A) animals, we unexpectedly observed in all of the examined tissues and cells taken from LKB1(C433S/C433S) mice that the basal, as well as that induced by the AMP-mimetic AICAR (5-amino-4-imidazolecarboxamide riboside), AMPK activation, phenformin and muscle contraction were significantly blunted. This resulted in a reduced ability of AICAR to inhibit lipid synthesis in primary hepatocytes isolated from LKB1(C433S/C433S) mice. The activity of several of the AMPK-related kinases analysed [BRSK1 (BR serine/threonine kinase 1), BRSK2, NUAK1 (NUAK family, SNF1-like kinase 1), SIK3 (salt-inducible kinase 3) and MARK4 (MAP/microtubule affinity-regulating kinase 4)] was not affected in tissues derived from LKB1(S431A/S431A) or LKB1(C433S/C433S) mice. Our observations reveal for the first time that farnesylation of LKB1 is required for the activation of AMPK. Previous reports have indicated that a pool of AMPK is localized at the plasma membrane as a result of myristoylation of its regulatory AMPKβ subunit. This raises the possibility that LKB1 farnesylation and myristoylation of AMPKβ might promote the interaction and co-localization of these enzymes on a two-dimensional membrane surface and thereby promote efficient activation of AMPK

Allosteric activation of trypanosomatid deoxyhypusine synthase by a catalytically dead paralog

Polyamine biosynthesis is a key drug target in African trypanosomes. The “resurrection drug” eflornithine (difluoromethylornithine), which is used clinically to treat human African trypanosomiasis, inhibits the first step in polyamine (spermidine) biosynthesis, a highly regulated pathway in most eukaryotic cells. Previously, we showed that activity of a key trypanosomatid spermidine biosynthetic enzyme, S-adenosylmethionine decarboxylase, is regulated by heterodimer formation with a catalytically dead paralog (a prozyme). Here, we describe an expansion of this prozyme paradigm to the enzyme deoxyhypusine synthase, which is required for spermidine-dependent hypusine modification of a lysine residue in the essential translation factor eIF5A. Trypanosoma brucei encodes two deoxyhypusine synthase paralogs, one that is catalytically functional but grossly impaired, and the other is inactive. Co-expression in Escherichia coli results in heterotetramer formation with a 3000-fold increase in enzyme activity. This functional complex is also present in T. brucei, and conditional knock-out studies indicate that both DHS genes are essential for in vitro growth and infectivity in mice. The recurrent evolution of paralogous, catalytically dead enzyme-based activating mechanisms may be a consequence of the unusual gene expression in the parasites, which lack transcriptional regulation. Our results suggest that this mechanism may be more widely used by trypanosomatids to control enzyme activity and ultimately influence pathogenesis than currently appreciated

Taxes and their Effects on Business Environment

The paper is focused on the category of public finances , taxation , the description of the meaning , definition of their development and their role in business , goals , reasons for their collection , the basis on which it is made taxes , tax rates , classification , tax principles and effects and their impact on the analysis of taxes in general. Theory of tax analysis is defined by simplicity of economic development of a country, meeting the needs and demands of the citizens of that country in analogous manner, and determining the amounts of budget entry into that state. Taxes aimed at accumulating the necessary tools for the implementation of public expenditure. They vary from time to time and from place to place, they are numerous and varied where strategically are involved all classes of society. The importance of taxes has increased more and more in their historical development, the results have been expressed in the permanent extension of tax taxpayers, the number of tax types and growth of tax load. Free tax is mandatory and non-refundable in the state budget or in the budget of the local government, is set by law and is paid by any person exercising public rights or benefits of public service. Characteristic of tax liability means that tributary tax are obliged to pay tax, otherwise if they do not pay tax compulsory, cashing is done in violent manner. Tax liability arises when a person realizes income, when become a property owner or makes payments, which is subject of tax legislation. Taxes have a fundamental role in the construction of business reform and strategy, and as such is essential to the overall climate for doing business. The Government of Kosovo has undertaken a series of measures related to the business environment by eliminating a series of bureaucratic barriers, but has not substantially affected the tax base and has not properly oriented business climate, in an environment such as we are, in the process of creating and building the state and its institutions. DOI: 10.5901/mjss.2015.v4n1p9

NF45 dimerizes with NF90, Zfr and SPNR via a conserved domain that has a nucleotidyltransferase fold

Nuclear factors NF90 and NF45 form a complex involved in a variety of cellular processes and are thought to affect gene expression both at the transcriptional and translational level. In addition, this complex affects the replication of several viruses through direct interactions with viral RNA. NF90 and NF45 dimerize through their common ‘DZF’ domain (domain associated with zinc fingers). NF90 has additional double-stranded RNA-binding domains that likely mediate its association with target RNAs. We present the crystal structure of the NF90/NF45 dimerization complex at 1.9-Å resolution. The DZF domain shows structural similarity to the template-free nucleotidyltransferase family of RNA modifying enzymes. However, both NF90 and NF45 have lost critical catalytic residues during evolution and are therefore not functional enzymes. Residues on NF90 that make up its interface with NF45 are conserved in two related proteins, spermatid perinuclear RNA-binding protein (SPNR) and zinc-finger RNA-binding protein (Zfr). Using a co-immunoprecipitation assay and site-specific mutants, we demonstrate that NF45 is also able to recognize SPNR and Zfr through the same binding interface, revealing that NF45 is able to form a variety of cellular complexes with other DZF-domain proteins

The Surface Distribution of Oil Spills, the Environmental Status of the Visoka Oilfield, Its Rehabilitation Ways: Case Study

Visoka oilfield was explored in 1963 through the well G-622. In this oilfield had been drilled more than 170 production wells. Through all this years of its exploitation, mainly because of the outdated technology, the environmental pollution reached really dramatic values. The pollution extends on the Visoka village, affecting so the life for the entire community. The oil spills, the gas emissions and the formation water affected and polluted and ―k illed‖ the Gjanica River, its delta and the Adriatic coast in the Semani beach. Due to the technology and the completely wrong policies, used in the past, the wells had been equipped with a pit, whose actually are filled with oil, water and solid wastes. Now these mixtures are more similar with TAR‘s. This is the main evidence which proves that, the area had never been cleaned up properly. Actually the reservoir had been given in use to a foreigner company, based in a petroleum agreement. The concessionary has already preparing the rehabilitation plan. Based on the best international experience the cleaning up ways will be based on the oil spill treatment, mainly through dispersants, the water treatment through dispersants, filtrations processes and reinjection and the emissions cleaning up mainly through reinjection. The polluted soil will be treated through thermal methods, or will be deposited in a closed landfill. Evaluations, calculations and spatial distribution of the oil spills of the Gjanica River and Adriatic Sea are presented in this paper