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Glucose-6-phosphate dehydrogenase regulation in the hepatopancreas of the anoxia-tolerant marine mollusc, Littorina littorea  [PDF]
Judeh L. Lama,Ryan A.V. Bell,Kenneth B. Storey
PeerJ , 2013, DOI: 10.7717/peerj.21
Abstract: Glucose-6-phosphate dehydrogenase (G6PDH) gates flux through the pentose phosphate pathway and is key to cellular antioxidant defense due to its role in producing NADPH. Good antioxidant defenses are crucial for anoxia-tolerant organisms that experience wide variations in oxygen availability. The marine mollusc, Littorina littorea, is an intertidal snail that experiences daily bouts of anoxia/hypoxia with the tide cycle and shows multiple metabolic and enzymatic adaptations that support anaerobiosis. This study investigated the kinetic, physical and regulatory properties of G6PDH from hepatopancreas of L. littorea to determine if the enzyme is differentially regulated in response to anoxia, thereby providing altered pentose phosphate pathway functionality under oxygen stress conditions. Several kinetic properties of G6PDH differed significantly between aerobic and 24 h anoxic conditions; compared with the aerobic state, anoxic G6PDH (assayed at pH 8) showed a 38% decrease in Km G6P and enhanced inhibition by urea, whereas in pH 6 assays Km NADP and maximal activity changed significantly between the two states. The mechanism underlying anoxia-responsive changes in enzyme properties proved to be a change in the phosphorylation state of G6PDH. This was documented with immunoblotting using an anti-phosphoserine antibody, in vitro incubations that stimulated endogenous protein kinases versus protein phosphatases and significantly changed Km G6P, and phosphorylation of the enzyme with 32P-ATP. All these data indicated that the aerobic and anoxic forms of G6PDH were the high and low phosphate forms, respectively, and that phosphorylation state was modulated in response to selected endogenous protein kinases (PKA or PKG) and protein phosphatases (PP1 or PP2C). Anoxia-induced changes in the phosphorylation state of G6PDH may facilitate sustained or increased production of NADPH to enhance antioxidant defense during long term anaerobiosis and/or during the transition back to aerobic conditions when the reintroduction of oxygen causes a rapid increase in oxidative stress.
Immunohistochemical localization of hepatopancreatic phospholipase in gastropods mollusc, Littorina littorea and Buccinum undatum digestive cells
Zied Zarai, Nicholas Boulais, Pascale Marcorelles, Eric Gobin, Sofiane Bezzine, Hafedh Mejdoub, Youssef Gargouri
Lipids in Health and Disease , 2011, DOI: 10.1186/1476-511x-10-219
Abstract: We have previously producted an antiserum reacting specifically with mSDPLA2. It labeled zymogen granules of the hepatopancreatic acinar cells and the secretory materials of certain epithelial cells in the depths of epithelial crypts in the hepatopancreas of snail. To confirm this localization a laser capture microdissection was performed targeting stained cells of hepatopancreas tissue sections. A Western blot analysis revealed a strong signal at the expected size (30 kDa), probably corresponding to the PLA2.The present results support the presence of two hepatopancreatic intracellular and extracellular PLA2 in the prosobranchs gastropods molluscs, Littorina littorea and Buccinum undatum and bring insights on their localizations.Snails require lipids for metabolic energy and for maintaining the structure and integrity of cell membranes in common with other animals to tolerate environemental strains [1]. The analyses of lipid composition of digestive gland and pedal muscle of two northern freshwater pulmonate snails Lymnaea stagnalis and Lymnaea ovata and three marine prosobranch gastropods Littorina obtusata, Littorina littorea and Buccinum undatum from the White Sea, shown that the content of triacylglycerides both in digestive gland and pedal was higher in littoral dwellers Littorina, the activity of which depends on the tide level. The presence of massive shell enhances demands in energy needed for supporting movement and activity. Because the intensity of energy metabolism is related to quantity of total phospholipids, mitochondria and activity of their oxidizing ferments, the presence of thick shell in marine snails together with motor activity costs more in terms of energy than in freshwater snails with thin shell [1].In different molluscs, food is processed to varying degrees as it passes through the alimentary tract. It is generally assumed that digestion of ingested material takes place in two phases, an extracellular process and intracellular digestion, w
Novel control of lactate dehydrogenase from the freeze tolerant wood frog: role of posttranslational modifications  [PDF]
Jean Abboud,Kenneth B. Storey
PeerJ , 2013, DOI: 10.7717/peerj.12
Abstract: Lactate dehydrogenase (LDH), the terminal enzyme of anaerobic glycolysis, plays a crucial role both in sustaining glycolytic ATP production under oxygen-limiting conditions and in facilitating the catabolism of accumulated lactate when stress conditions are relieved. In this study, the effects on LDH of in vivo freezing and dehydration stresses (both of which impose hypoxia/anoxia stress on tissues) were examined in skeletal muscle of the freeze-tolerant wood frog, Rana sylvatica. LDH from muscle of control, frozen and dehydrated wood frogs was purified to homogeneity in a two-step process. The kinetic properties and stability of purified LDH were analyzed, revealing no significant differences in Vmax, Km and I50 values between control and frozen LDH. However, control and dehydrated LDH differed significantly in Km values for pyruvate, lactate, and NAD, I50 urea, and in temperature, glucose, and urea effects on these parameters. The possibility that posttranslational modification of LDH was responsible for the stable differences in enzyme behavior between control and dehydrated states was assessed using ProQ diamond staining to detect phosphorylation and immunoblotting to detect acetylation, methylation, ubiquitination, SUMOylation and nitrosylation of the enzyme. LDH from muscle of dehydrated wood frogs showed significantly lower levels of acetylation, providing one of the first demonstrations of a potential role for protein acetylation in the stress-responsive control of a metabolic enzyme.
Mitochondrial Acetylation and Diseases of Aging
Gregory R. Wagner,R. Mark Payne
Journal of Aging Research , 2011, DOI: 10.4061/2011/234875
Abstract: In recent years, protein lysine acetylation has emerged as a prominent and conserved regulatory posttranslational modification that is abundant on numerous enzymes involved in the processes of intermediary metabolism. Well-characterized mitochondrial processes of carbon utilization are enriched in acetyl-lysine modifications. Although seminal discoveries have been made in the basic biology of mitochondrial acetylation, an understanding of how acetylation states influence enzyme function and metabolic reprogramming during pathological states remains largely unknown. This paper will examine our current understanding of eukaryotic acetate metabolism and present recent findings in the field of mitochondrial acetylation biology. The implications of mitochondrial acetylation for the aging process will be discussed, as well as its potential implications for the unique and localized metabolic states that occur during the aging-associated conditions of heart failure and cancer growth.
Protein Acetylation in Archaea, Bacteria, and Eukaryotes  [PDF]
J?rg Soppa
Archaea , 2010, DOI: 10.1155/2010/820681
Abstract: Proteins can be acetylated at the alpha-amino group of the N-terminal amino acid (methionine or the penultimate amino acid after methionine removal) or at the epsilon-amino group of internal lysines. In eukaryotes the majority of proteins are N-terminally acetylated, while this is extremely rare in bacteria. A variety of studies about N-terminal acetylation in archaea have been reported recently, and it was revealed that a considerable fraction of proteins is N-terminally acetylated in haloarchaea and Sulfolobus, while this does not seem to apply for methanogenic archaea. Many eukaryotic proteins are modified by differential internal acetylation, which is important for a variety of processes. Until very recently, only two bacterial proteins were known to be acetylation targets, but now 125 acetylation sites are known for E. coli. Knowledge about internal acetylation in archaea is extremely limited; only two target proteins are known, only one of which—Alba—was used to study differential acetylation. However, indications accumulate that the degree of internal acetylation of archaeal proteins might be underestimated, and differential acetylation has been shown to be essential for the viability of haloarchaea. Focused proteomic approaches are needed to get an overview of the extent of internal protein acetylation in archaea. 1. Introduction Many different forms of posttranslational modifications of proteins have been characterized. Posttranslational modifications can influence many different features of proteins, for example, their folding, activity, stability, antigenicity, intracellular localization, and interaction with other proteins or with nucleic acids. The fraction of posttranslationally modified proteins and thus the importance of posttranslational modification is generally believed to be very different for eukaryotes—having a high fraction of modified proteins—and prokaryotes, which are thought to harbor only very few modified proteins. For eukaryotes it is thought that acetylation is the most common covalent modification out of 200 types that have been reported [1]. It has also been argued that acetylation is a regulatory modification of the same importance as phosphorylation [2]. The arguments were that acetylation, like phosphorylation, affects many different proteins, can have a variety of consequences, and can regulate key cellular processes in response to extracellular signals [2]. Nevertheless, the wealth of experimental data on protein phosphorylation in eukaryotes is much higher than on acetylation, and in addition, it was typically
Establishment Failure in Biological Invasions: A Case History of Littorina littorea in California, USA  [PDF]
Andrew L. Chang,April M. H. Blakeslee,A. Whitman Miller,Gregory M. Ruiz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016035
Abstract: The early stages of biological invasions are rarely observed, but can provide significant insight into the invasion process as well as the influence vectors have on invasion success or failure.
The Tale of Protein Lysine Acetylation in the Cytoplasm
Karin Sadoul,Jin Wang,Boubou Diagouraga,Saadi Khochbin
Journal of Biomedicine and Biotechnology , 2011, DOI: 10.1155/2011/970382
Abstract: Reversible posttranslational modification of internal lysines in many cellular or viral proteins is now emerging as part of critical signalling processes controlling a variety of cellular functions beyond chromatin and transcription. This paper aims at demonstrating the role of lysine acetylation in the cytoplasm driving and coordinating key events such as cytoskeleton dynamics, intracellular trafficking, vesicle fusion, metabolism, and stress response.
Ecological Speciation and the Intertidal Snail Littorina saxatilis  [PDF]
Juan Galindo,John W. Grahame
Advances in Ecology , 2014, DOI: 10.1155/2014/239251
Abstract: In recent decades biologists studying speciation have come to consider that the process does not necessarily require the presence of a geographical barrier. Rather, it now seems to be possible for reproductive barriers to evolve within what was hitherto a single ‘‘species.’’ The intertidal snail Littorina saxatilis has been the focus of a considerable amount of work in this context, and it is now thought of as a good case study of ‘‘ecological speciation.’’ We review some of this work and briefly consider prospects for future developments. 1. Introduction In recent decades, there has been a considerable shift in our view of speciation—ecology has come in [1]. Or rather, it has come back in because the role of ecological processes in diversification dates back to Darwin, although some biologists of the 20th century gave a prominent role in speciation to geographical isolation (allopatry) [2, 3]. This shift of view has been reviewed by Mallet [4]. It is our intention here to give an account of work on Littorina saxatilis (Olivi) over the last three decades, highlighting its contribution and promise to the study of speciation. This marine snail is a species in a small and young genus and is probably the most derived member of the genus Littorina. It is thought to have originated in the eastern North Atlantic about 0.65?Ma?bp [5], rapidly colonizing both sides of the Atlantic. Phylogeographic patterns make it likely that more northern populations have undergone repeated subdivision and recontact as shorelines have been subject to glacial action and concomitant sea level changes. Populations on the northwestern coasts of the Iberian Peninsula appear to be genetically distinct from those elsewhere, suggestive of relatively long isolation [5–7]. L. saxatilis is strictly intertidal, though within the intertidal it has a fairly wide vertical distribution, and is found on rocky shores and in estuaries and salt marshes [8]. There are few published data on longevity. Hughes [9] gives a maximum of about four years. Littorina saxatilis is also highly polymorphic, and this has given rise to a great deal of taxonomic confusion and synonymy. It is part of a species complex, the group of rough periwinkles, with its sister species Littorina compressa (Jeffreys) and Littorina arcana Hannaford Ellis [8]. These latter produce egg masses which are deposited in sheltered crevices on the shore, while L. saxatilis females carry their embryos in a brood pouch in the dorsal mantle cavity until they are released as “crawl aways,” with similar morphology to the adult snails.
Implication of Posttranslational Histone Modifications in Nucleotide Excision Repair  [PDF]
Shisheng Li
International Journal of Molecular Sciences , 2012, DOI: 10.3390/ijms131012461
Abstract: Histones are highly alkaline proteins that package and order the DNA into chromatin in eukaryotic cells. Nucleotide excision repair (NER) is a conserved multistep reaction that removes a wide range of generally bulky and/or helix-distorting DNA lesions. Although the core biochemical mechanism of NER is relatively well known, how cells detect and repair lesions in diverse chromatin environments is still under intensive research. As with all DNA-related processes, the NER machinery must deal with the presence of organized chromatin and the physical obstacles it presents. A huge catalogue of posttranslational histone modifications has been documented. Although a comprehensive understanding of most of these modifications is still lacking, they are believed to be important regulatory elements for many biological processes, including DNA replication and repair, transcription and cell cycle control. Some of these modifications, including acetylation, methylation, phosphorylation and ubiquitination on the four core histones (H2A, H2B, H3 and H4) or the histone H2A variant H2AX, have been found to be implicated in different stages of the NER process. This review will summarize our recent understanding in this area.
A Method to Determine Lysine Acetylation Stoichiometries  [PDF]
Ernesto S. Nakayasu,Si Wu,Michael A. Sydor,Anil K. Shukla,Karl K. Weitz,Ronald J. Moore,Kim K. Hixson,Jong-Seo Kim,Vladislav A. Petyuk,Matthew E. Monroe,Ljiljiana Pasa-Tolic,Wei-Jun Qian,Richard D. Smith,Joshua N. Adkins,Charles Ansong
International Journal of Proteomics , 2014, DOI: 10.1155/2014/730725
Abstract: Lysine acetylation is a common protein posttranslational modification that regulates a variety of biological processes. A major bottleneck to fully understanding the functional aspects of lysine acetylation is the difficulty in measuring the proportion of lysine residues that are acetylated. Here we describe a mass spectrometry method using a combination of isotope labeling and detection of a diagnostic fragment ion to determine the stoichiometry of protein lysine acetylation. Using this technique, we determined the modification occupancy for ~750 acetylated peptides from mammalian cell lysates. Furthermore, the acetylation on N-terminal tail of histone H4 was cross-validated by treating cells with sodium butyrate, a potent deacetylase inhibitor, and comparing changes in stoichiometry levels measured by our method with immunoblotting measurements. Of note we observe that acetylation stoichiometry is high in nuclear proteins, but very low in mitochondrial and cytosolic proteins. In summary, our method opens new opportunities to study in detail the relationship of lysine acetylation levels of proteins with their biological functions. 1. Introduction Lysine acetylation (KAc) of proteins is a ubiquitous posttranslational modification (PTM) that controls many cellular processes. The dynamic regulation of KAc by lysine acetyltransferases (KATs) and deacetylases (KDACs) modulates many important cellular functions, such as cell metabolism and gene expression [1, 2]. Recent advances in mass spectrometry combined with immunoaffinity purification are enabling the identification and relative quantification of thousands of acetylation sites in a single experiment [3–5]. These new data have boosted the discovery of regulatory functions of KAc for many proteins, including a variety of metabolic enzymes [2]. Although significant progress has been made, a major remaining hurdle in the field is the determination of acetylation stoichiometry on proteins. The knowledge of KAc stoichiometry is considered essential to better understand the mechanism and impact of this modification on the control protein functions, such as enzymatic activity [2, 6]. Indeed, this problem is not exclusive to KAc as there are almost no systematic determinations of the stoichiometry of PTMs. This has remained a challenge because methods to determine stoichiometry of PTMs are not compatible with enrichment procedures, since both modified and unmodified versions of polypeptides need to be present in the sample. Global studies have been successfully performed to determine the stoichiometries
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