scholarly journals Essential role of PI3-kinase and phospholipase A2 in Dictyostelium discoideum chemotaxis

2007 ◽  
Vol 177 (5) ◽  
pp. 809-816 ◽  
Author(s):  
Peter J.M. van Haastert ◽  
Ineke Keizer-Gunnink ◽  
Arjan Kortholt
Keyword(s):  
Phospholipase A2 ◽  
Dictyostelium Discoideum ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Pi3 Kinase ◽  
Ip3 Receptor ◽  
Second Messenger Systems ◽  
Phosphatase And Tensin Homologue ◽  
Mutant Cells

Chemotaxis toward different cyclic adenosine monophosphate (cAMP) concentrations was tested in Dictyostelium discoideum cell lines with deletion of specific genes together with drugs to inhibit one or all combinations of the second-messenger systems PI3-kinase, phospholipase C (PLC), phospholipase A2 (PLA2), and cytosolic Ca2+. The results show that inhibition of either PI3-kinase or PLA2 inhibits chemotaxis in shallow cAMP gradients, whereas both enzymes must be inhibited to prevent chemotaxis in steep cAMP gradients, suggesting that PI3-kinase and PLA2 are two redundant mediators of chemotaxis. Mutant cells lacking PLC activity have normal chemotaxis; however, additional inhibition of PLA2 completely blocks chemotaxis, whereas inhibition of PI3-kinase has no effect, suggesting that all chemotaxis in plc-null cells is mediated by PLA2. Cells with deletion of the IP3 receptor have the opposite phenotype: chemotaxis is completely dependent on PI3-kinase and insensitive to PLA2 inhibitors. This suggest that PI3-kinase–mediated chemotaxis is regulated by PLC, probably through controlling PIP2 levels and phosphatase and tensin homologue (PTEN) activity, whereas chemotaxis mediated by PLA2 appears to be controlled by intracellular Ca2+.

Mechanisms of ATP to cAMP Conversion Catalyzed by the Mammalian Adenylyl Cyclase: A Role of Magnesium Coordination Shells and Proton Wires

2019 ◽  
Author(s):  
Bella Grigorenko ◽  
Igor Polyakov ◽  
Alexander Nemukhin
Keyword(s):  
Adenylyl Cyclase ◽  
Bond Cleavage ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Md Simulations ◽  
Coordination Shell ◽  
Energy Profile ◽  
One Step ◽  
Type V

<p>We report a mechanism of adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP) conversion by the mammalian type V adenylyl cyclase revealed in molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) simulations. We characterize a set of computationally derived enzyme-substrate (ES) structures showing an important role of coordination shells of magnesium ions in the solvent accessible active site. Several stable six-fold coordination shells of Mg<sub>A</sub><sup>2+ </sup>are observed in MD simulations of ES complexes. In the lowest energy ES conformation, the coordination shell of Mg<sub>A</sub><sup>2+ </sup>does not include the O<sub>δ1</sub> atom of the conserved Asp440 residue. Starting from this conformation, a one-step reaction mechanism is characterized which includes proton transfer from the ribose O<sup>3'</sup>H<sup>3' </sup>group in ATP to Asp440 via a shuttling water molecule and P<sup>A</sup>-O<sup>3A</sup> bond cleavage and O<sup>3'</sup>-P<sup>A</sup> bond formation. The energy profile of this route is consistent with the observed reaction kinetics. In a higher energy ES conformation, Mg<sub>A</sub><sup>2+</sup> is bound to the O<sub>δ1</sub>(Asp440) atom as suggested in the relevant crystal structure of the protein with a substrate analog. The computed energy profile initiated by this ES is characterized by higher energy expenses to complete the reaction. Consistently with experimental data, we show that the Asp440Ala mutant of the enzyme should exhibit a reduced but retained activity. All considered reaction pathways include proton wires from the O<sup>3'</sup>H<sup>3' </sup>group via shuttling water molecules. </p>

scholarly journals Role of Long Non-Coding RNAs and the Molecular Mechanisms Involved in Insulin Resistance

2021 ◽  
Vol 22 (14) ◽  
pp. 7256
Author(s):  
Vianet Argelia Tello-Flores ◽  
Fredy Omar Beltrán-Anaya ◽  
Marco Antonio Ramírez-Vargas ◽  
Brenda Ely Esteban-Casales ◽  
Napoleón Navarro-Tito ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Protein Kinase ◽  
Molecular Mechanisms ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Biological Species ◽  
Necrosis Factor Alpha ◽  
Polypyrimidine Tract Binding Protein ◽  
Non Coding Rnas

Long non-coding RNAs (lncRNAs) are single-stranded RNA biomolecules with a length of >200 nt, and they are currently considered to be master regulators of many pathological processes. Recent publications have shown that lncRNAs play important roles in the pathogenesis and progression of insulin resistance (IR) and glucose homeostasis by regulating inflammatory and lipogenic processes. lncRNAs regulate gene expression by binding to other non-coding RNAs, mRNAs, proteins, and DNA. In recent years, several mechanisms have been reported to explain the key roles of lncRNAs in the development of IR, including metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), imprinted maternal-ly expressed transcript (H19), maternally expressed gene 3 (MEG3), myocardial infarction-associated transcript (MIAT), and steroid receptor RNA activator (SRA), HOX transcript antisense RNA (HOTAIR), and downregulated Expression-Related Hexose/Glucose Transport Enhancer (DREH). LncRNAs participate in the regulation of lipid and carbohydrate metabolism, the inflammatory process, and oxidative stress through different pathways, such as cyclic adenosine monophosphate/protein kinase A (cAMP/PKA), phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT), polypyrimidine tract-binding protein 1/element-binding transcription factor 1c (PTBP1/SREBP-1c), AKT/nitric oxide synthase (eNOS), AKT/forkhead box O1 (FoxO1), and tumor necrosis factor-alpha (TNF-α)/c-Jun-N-terminal kinases (JNK). On the other hand, the mechanisms linked to the molecular, cellular, and biochemical actions of lncRNAs vary according to the tissue, biological species, and the severity of IR. Therefore, it is essential to elucidate the role of lncRNAs in the insulin signaling pathway and glucose and lipid metabolism. This review analyzes the function and molecular mechanisms of lncRNAs involved in the development of IR.

scholarly journals The protective effect of the PDE-4 inhibitor rolipram on intracerebral haemorrhage is associated with the cAMP/AMPK/SIRT1 pathway

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xiao-Liu Dong ◽  
Yan-Hui Wang ◽  
Jing Xu ◽  
Nan Zhang
Keyword(s):  
Mouse Model ◽  
Protective Effect ◽  
Intracerebral Haemorrhage ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Pathological Process ◽  
Silent Information Regulator 1 ◽  
Sirt1 Inhibitor ◽  
Amp Activated Protein Kinase

AbstractRolipram specifically inhibits phosphodiesterase (PDE) 4, thereby preventing inactivation of the intracellular second messenger cyclic adenosine monophosphate (cAMP). Rolipram has been shown to play a neuroprotective role in some central nervous system (CNS) diseases. However, the role of PDE4 and the potential protective effect of rolipram on the pathophysiological process of intracerebral haemorrhage (ICH) are still not entirely clear. In this study, a mouse model of ICH was established by the collagenase method. Rolipram reduced brain oedema, blood–brain barrier (BBB) leakage, neuronal apoptosis and inflammatory cytokine release and improved neurological function in our mouse model of ICH. Moreover, rolipram increased the levels of cAMP and silent information regulator 1 (SIRT1) and upregulated the phosphorylation of AMP-activated protein kinase (AMPK). Furthermore, these effects of rolipram could be reversed by the SIRT1 inhibitor sirtinol. In conclusion, rolipram can play a neuroprotective role in the pathological process of ICH by activating the cAMP/AMPK/SIRT1 pathway.

scholarly journals Cytochemical methods for the localization of adenylate cyclase. A review and evaluation of the efficacy of the procedures.

1983 ◽  
Vol 31 (1) ◽  
pp. 85-93 ◽  
Author(s):  
L S Cutler
Keyword(s):  
Adenylate Cyclase ◽  
Cyclic Nucleotides ◽  
Cell Biology ◽  
Enzyme System ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Cellular Functions ◽  
Cytochemical Localization ◽  
Biochemical Evaluation

The cytochemical procedures for localizing adenylate cyclase have been a source of controversy since their introduction. The importance of cyclic adenosine monophosphate (AMP), the product of adenylate cyclase's action on adenosine triphosphate (ATP), in cell biology is clear. Thus, the ability to localize this enzyme system reliably is an important tool in the study of various cellular functions. This report reviews the literature and presents a biochemical evaluation of the methods for localizing adenylate cyclase. The review and data presented serve to clarify many of the controversies surrounding this important cytochemical procedure. It is evident that although there are problems associated with localizing the enzyme, several valid procedures are currently available for the cytochemical localization of adenylate cyclase. In using these procedures, the effects of fixation and the capture agent on adenylate cyclase activity in the particular tissue being studied should be considered. Only repurified adenylyl imidodiphosphate [App(NH)p] should be used in the incubation medium. If care is taken, the use of these techniques can be of great value in the continued study of the role of cyclic nucleotides in cell biology.

The role of phosphodiesterase in aggregation of Dictyostelium discoideum

1978 ◽  
Vol 31 (1) ◽  
pp. 233-243
Author(s):  
M. Darmon ◽  
J. Barra ◽  
P. Brachet
Keyword(s):  
Dictyostelium Discoideum ◽  
Direct Contact ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Extracellular Medium ◽  
Camp Phosphodiesterase ◽  
Cellular Slime Mould ◽  
Cellular Slime ◽  
Mutant Cells

The role of cAMP phosphodiesterase in the cAMP-mediated aggregation of the cellular slime mould Dictyostelium discoideum was investigated with a morphogenetic mutant defective in phosphodiesterase production. Mutant cells become capable of aggregating normally when incubated in the presence of exogenous phosphodiesterase isolated from Idictyostelium or rat brain. Direct contact between enzyme and the cell membrane is not required for this phenotypic suppression. The aggregateless character of this strain presumably results from an over-accumulation of cAMP in the extracellular medium since aggregation can be induced in the absence of added phosphodiesterase under conditions facilitating diffusion of the nucleotide. This suggests that phosphodiesterase is not involved in the generation or recognition of cAMP signals, but that the enzyme is essential in the control of the cAMP signal-to-noise ratio.

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