scholarly journals Phospholipase D in Phytophthora infestans and Its Role in Zoospore Encystment

2002 ◽  
Vol 15 (9) ◽  
pp. 939-946 ◽  
Author(s):  
Maita Latijnhouwers ◽  
Teun Munnik ◽  
Francine Govers
Keyword(s):  
Phytophthora Infestans ◽  
G Proteins ◽  
Phospholipase D ◽  
Kinase Activity ◽  
Mechanical Agitation ◽  
Protein Activator ◽  
Late Blight Pathogen ◽  
Stimulation Of

We show that differentiation of zoospores of the late blight pathogen Phytophthora infestans into cysts, a process called encystment, was triggered by both phosphatidic acid (PA) and the G-protein activator mastoparan. Mastoparan induced the accumulation of PA, indicating that encystment by mastoparan most likely acts through PA. Likewise, mechanical agitation of zoospores, which often is used to induce synchronized encystment, resulted in increased levels of PA. The levels of diacylglycerolpyrophosphate (DGPP), the phosphorylation product of PA, increased simultaneously. Also in cysts, sporangiospores, and mycelium, mastoparan induced increases in the levels of PA and DGPP. Using an in vivo assay for phospholipase D (PLD) activity, it was shown that the mastoparan-induced increase in PA was due to a stimulation of the activity of this enzyme. Phospholipase C in combination with diacylglycerol (DAG) kinase activity also can generate PA, but activation of these enzymes by mastoparan was not detected under conditions selected to highlight 32P-PA production via DAG kinase. Primary and secondary butanol, which, like mastoparan, have been reported to activate G-proteins, also stimulated PLD activity, whereas the inactive tertiary isomer did not. Similarly, encystment was induced by n- and sec-butanol but not by tert-butanol. Together, these results show that Phytophthora infestans contains a mastoparan- and bu-tanol-inducible PLD pathway and strongly indicate that PLD is involved in zoospore encystment. The role of G-proteins in this process is discussed.

scholarly journals Essential role of IRAK-4 protein and its kinase activity in Toll-like receptor–mediated immune responses but not in TCR signaling

2007 ◽  
Vol 204 (5) ◽  
pp. 1013-1024 ◽  
Author(s):  
Tatsukata Kawagoe ◽  
Shintaro Sato ◽  
Andreas Jung ◽  
Masahiro Yamamoto ◽  
Kosuke Matsui ◽  
...  
Keyword(s):  
Immune Responses ◽  
Kinase Activity ◽  
Interleukin 1 ◽  
Cell Receptor ◽  
Nuclear Factor Κb ◽  
Toll Like Receptor ◽  
Tcr Signaling ◽  
Mitogen Activated Protein

Interleukin-1 receptor–associated kinase 4 (IRAK-4) was reported to be essential for the Toll-like receptor (TLR)– and T cell receptor (TCR)–mediated signaling leading to the activation of nuclear factor κB (NF-κB). However, the importance of kinase activity of IRAK family members is unclear. In this study, we investigated the functional role of IRAK-4 activity in vivo by generating mice carrying a knockin mutation (KK213AA) that abrogates its kinase activity. IRAK-4KN/KN mice were highly resistant to TLR-induced shock response. The cytokine production in response to TLR ligands was severely impaired in IRAK-4KN/KN as well as IRAK-4−/− macrophages. The IRAK-4 activity was essential for the activation of signaling pathways leading to mitogen-activated protein kinases. TLR-induced IRAK-4/IRAK-1–dependent and –independent pathways were involved in early induction of NF-κB–regulated genes in response to TLR ligands such as tumor necrosis factor α and IκBζ. In contrast to a previous paper (Suzuki, N., S. Suzuki, D.G. Millar, M. Unno, H. Hara, T. Calzascia, S. Yamasaki, T. Yokosuka, N.J. Chen, A.R. Elford, et al. 2006. Science. 311:1927–1932), the TCR signaling was not impaired in IRAK-4−/− and IRAK-4KN/KN mice. Thus, the kinase activity of IRAK-4 is essential for the regulation of TLR-mediated innate immune responses.

Possible role of cyclic GMP in stimulus-secretion coupling by salt gland of the duck

1979 ◽  
Vol 237 (5) ◽  
pp. C200-C204 ◽  
Author(s):  
D. J. Stewart ◽  
J. Sax ◽  
R. Funk ◽  
A. K. Sen
Keyword(s):  
Cyclic Amp ◽  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Salt Gland ◽  
Domestic Ducks ◽  
Stimulus Secretion Coupling ◽  
Stimulation Of

Stimulation of salt galnd secretion in domestic ducks in vivo increased the cyclic GMP concentration of the tissue, but had no effect on cyclic AMP levels. Methacholine, which is known to stimulate sodium transport by the glands both in vivo and in vitro, stimulated ouabain-sensitive respiration in salt gland slices. Cyclic GMP stimulated ouabain-sensitive respiration to the same extent as methacholine. Guanylate cyclase stimulators, hydroxylamine and sodium azide, also stimulated ouabain-sensitive respiration. The stimulation of ouabain-sensitive respiration by methacholine was blocked either by atropine or by removal of calcium from the incubation medium. The stimulation of ouabain-sensitive respiration by cyclic GMP still occurred in the absence of calcium. The above observations seem to indicate that cyclic GMP acts as a tertiary link in the process of stimulus-secretion coupling in the tissue.

Modification of cardiac β-adrenoceptor mechanisms by H2O2

1998 ◽  
Vol 274 (2) ◽  
pp. H416-H423 ◽  
Author(s):  
Sujata Persad ◽  
Heinz Rupp ◽  
Rashi Jindal ◽  
Jugpal Arneja ◽  
Naranjan S. Dhalla
Keyword(s):  
Oxidative Stress ◽  
Signal Transduction ◽  
Adenylyl Cyclase ◽  
G Proteins ◽  
Cardiac Dysfunction ◽  
Biochemical Parameters ◽  
Adenylyl Cyclase Activity ◽  
High Concentrations ◽  
Stimulation Of

From the role of oxidative stress in cardiac dysfunction, we investigated the effect of H2O2, an activated species of oxygen, on β-adrenoceptors, G proteins, and adenylyl cyclase activities. Rat heart membranes were incubated with different concentrations of H2O2before the biochemical parameters were measured. Both the affinity and density of β1-adrenoceptors were decreased, whereas the density of the β2-adrenoceptors was decreased and the affinity was increased by 1 mM H2O2. Time- and concentration-dependent biphasic changes in adenylyl cyclase activities in the absence or presence of isoproterenol were observed when membranes were incubated with H2O2; however, activation of the enzyme by isoproterenol was increased or unaltered. The adenylyl cyclase activities in the absence or presence of forskolin, NaF, and Gpp(NH)p were depressed by H2O2. Catalase alone or in combination with mannitol was able to significantly decrease the magnitude of alterations due to H2O2. The cholera toxin-stimulated adenylyl cyclase activity and ADP ribose labeling of Gs proteins were decreased by treatment with 1 mM H2O2, whereas Gi protein activities, as reflected by pertussis toxin-stimulation of adenylyl cyclase and ADP ribosylation, were unaltered. The Gs and Gi protein immunoreactivities, estimated by labeling with respective antibodies, indicate a decrease in binding to the 45-kDa band of Gs protein, whereas no change in the binding of antibodies to the 52-kDa band of Gs protein or the 40-kDa subunit of Gi protein was evident when the membranes were treated with 1 mM H2O2. These results suggest that H2O2in high concentrations may attenuate the β-adrenoceptor-linked signal transduction in the heart by changing the functions of Gs proteins and the catalytic subunit of the adenylyl cyclase enzyme.

scholarly journals Pedunculopontine glutamatergic neurons control spike patterning in substantia nigra dopaminergic neurons

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Daniel J Galtieri ◽  
Chad M Estep ◽  
David L Wokosin ◽  
Stephen Traynelis ◽  
D James Surmeier
Keyword(s):  
Substantia Nigra ◽  
Dopaminergic Neurons ◽  
Substantia Nigra Pars Compacta ◽  
Glutamatergic Synapses ◽  
Glutamatergic Neurons ◽  
Oscillatory Mechanisms ◽  
Goal Directed Behavior ◽  
Stimulation Of

Burst spiking in substantia nigra pars compacta (SNc) dopaminergic neurons is a key signaling event in the circuitry controlling goal-directed behavior. It is widely believed that this spiking mode depends upon an interaction between synaptic activation of N-methyl-D-aspartate receptors (NMDARs) and intrinsic oscillatory mechanisms. However, the role of specific neural networks in burst generation has not been defined. To begin filling this gap, SNc glutamatergic synapses arising from pedunculopotine nucleus (PPN) neurons were characterized using optical and electrophysiological approaches. These synapses were localized exclusively on the soma and proximal dendrites, placing them in a good location to influence spike generation. Indeed, optogenetic stimulation of PPN axons reliably evoked spiking in SNc dopaminergic neurons. Moreover, burst stimulation of PPN axons was faithfully followed, even in the presence of NMDAR antagonists. Thus, PPN-evoked burst spiking of SNc dopaminergic neurons in vivo may not only be extrinsically triggered, but extrinsically patterned as well.

Polar head groups are important for barrier-protective effects of oxidized phospholipids on pulmonary endothelium

2007 ◽  
Vol 292 (4) ◽  
pp. L924-L935 ◽  
Author(s):  
Anna A. Birukova ◽  
Panfeng Fu ◽  
Santipongse Chatchavalvanich ◽  
Dylan Burdette ◽  
Olga Oskolkova ◽  
...  
Keyword(s):  
Protective Effects ◽  
Oxidized Phospholipids ◽  
Barrier Dysfunction ◽  
Polar Head ◽  
Cell Counts ◽  
Head Groups ◽  
Stimulation Of

We have previously described protective effects of oxidized 1-palmitoyl-2-arachidonoyl- sn-glycero-3-phosphocholine (OxPAPC) on pulmonary endothelial cell (EC) barrier function and demonstrated the critical role of cyclopentenone-containing modifications of arachidonoyl moiety in OxPAPC protective effects. In this study we used oxidized phosphocholine (OxPAPC), phosphoserine (OxPAPS), and glycerophosphate (OxPAPA) to investigate the role of polar head groups in EC barrier-protective responses to oxidized phospholipids (OxPLs). OxPAPC and OxPAPS induced sustained barrier enhancement in pulmonary EC, whereas OxPAPA caused a transient protective response as judged by measurements of transendothelial electrical resistance (TER). Non-OxPLs showed no effects on TER levels. All three OxPLs caused enhancement of peripheral EC actin cytoskeleton. OxPAPC and OxPAPS completely abolished LPS-induced EC hyperpermeability in vitro, whereas OxPAPA showed only a partial protective effect. In vivo, intravenous injection of OxPAPS or OxPAPC (1.5 mg/kg) markedly attenuated increases in the protein content, cell counts, and myeloperoxidase activities detected in bronchoalveolar lavage fluid upon intratracheal LPS instillation in mice, although OxPAPC showed less potency. All three OxPLs partially attenuated EC barrier dysfunction induced by IL-6 and thrombin. Their protective effects against thrombin-induced EC barrier dysfunction were linked to the attenuation of the thrombin-induced Rho pathway of EC hyperpermeability and stimulation of Rac-mediated mechanisms of EC barrier recovery. These results demonstrate for the first time the essential role of polar OxPL groups in blunting the LPS-induced EC dysfunction in vitro and in vivo and suggest the mechanism of agonist-induced hyperpermeability attenuation by OxPLs via reduction of Rho and stimulation of Rac signaling.

scholarly journals Cytoplasmic Dynein Nucleates Microtubules to Organize Them into Radial Arrays In Vivo

2004 ◽  
Vol 15 (6) ◽  
pp. 2742-2749 ◽  
Author(s):  
Viacheslav Malikov ◽  
Anna Kashina ◽  
Vladimir Rodionov
Keyword(s):  
Cytoplasmic Dynein ◽  
Exact Function ◽  
Necessary And Sufficient ◽  
Stimulation Of ◽  
In Cells

Numerous evidence demonstrates that dynein is crucial for organization of microtubules (MTs) into radial arrays, but its exact function in this process is unclear. Here, we studied the role of cytoplasmic dynein in MT radial array formation in the absence of the centrosome. We found that dynein is a potent MT nucleator in vitro and that stimulation of dynein activity in cytoplasmic fragments of melanophores induces nucleation-dependent formation of MT radial array in the absence of the centrosome. This new property of dynein, in combination with its known role as an MT motor that is essential for MT array organization in the absence and presence of the centrosome, makes it a unique molecule whose activity is necessary and sufficient for the formation and maintenance of MT radial arrays in cells.

scholarly journals Dual role for phosphoinositides in regulation of yeast and mammalian phospholipase D enzymes

2002 ◽  
Vol 159 (6) ◽  
pp. 1039-1049 ◽  
Author(s):  
Vicki A. Sciorra ◽  
Simon A. Rudge ◽  
Jiyao Wang ◽  
Stuart McLaughlin ◽  
JoAnne Engebrecht ◽  
...  
Keyword(s):  
Phospholipase D ◽  
Membrane Trafficking ◽  
Dual Role ◽  
Biological Functions ◽  
Ph Domain ◽  
Catalytically Active ◽  
Acidic Phospholipids ◽  
Stimulation Of

Phospholipase D (PLD) generates lipid signals that coordinate membrane trafficking with cellular signaling. PLD activity in vitro and in vivo is dependent on phosphoinositides with a vicinal 4,5-phosphate pair. Yeast and mammalian PLDs contain an NH2-terminal pleckstrin homology (PH) domain that has been speculated to specify both subcellular localization and regulation of PLD activity through interaction with phosphatidylinositol 4,5-bisphosphate (PI[4,5]P2). We report that mutation of the PH domains of yeast and mammalian PLD enzymes generates catalytically active PI(4,5)P2-regulated enzymes with impaired biological functions. Disruption of the PH domain of mammalian PLD2 results in relocalization of the protein from the PI(4,5)P2-containing plasma membrane to endosomes. As a result of this mislocalization, mutations within the PH domain render the protein unresponsive to activation in vivo. Furthermore, the integrity of the PH domain is vital for yeast PLD function in both meiosis and secretion. Binding of PLD2 to model membranes is enhanced by acidic phospholipids. Studies with PLD2-derived peptides suggest that this binding involves a previously identified polybasic motif that mediates activation of the enzyme by PI(4,5)P2. By comparison, the PLD2 PH domain binds PI(4,5)P2 with lower affinity but sufficient selectivity to function in concert with the polybasic motif to target the protein to PI(4,5)P2-rich membranes. Phosphoinositides therefore have a dual role in PLD regulation: membrane targeting mediated by the PH domain and stimulation of catalysis mediated by the polybasic motif.

Role of G proteins in stimulation of Na-H exchange by cell shrinkage

1992 ◽  
Vol 262 (2) ◽  
pp. C533-C536 ◽  
Author(s):  
B. A. Davis ◽  
E. M. Hogan ◽  
W. F. Boron
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Transport Processes ◽  
Cell Shrinkage ◽  
Protein Activation ◽  
Kinase C ◽  
G Protein Activation ◽  
Barnacle Muscle Fibers ◽  
Stimulation Of

Many cells respond to shrinkage by stimulating specific ion transport processes (e.g., Na-H exchange). However, it is not known how the cell senses this volume change, nor how this signal is transduced to an ion transporter. We have studied the activation of Na-H exchange in internally dialyzed barnacle muscle fibers, measuring intracellular pH (pHi) with glass microelectrodes. When cells are dialyzed to a pHi of approximately 7.2, Na-H exchange is active only in shrunken cells. We found that the shrinkage-induced stimulation of Na-H exchange, elicited by increasing medium osmolality from 975 to 1,600 mosmol/kgH2O, is inhibited approximately 72% by including in the dialysis fluid 1 mM guanosine 5'-O-(2-thiodiphosphate). The latter is an antagonist of G protein activation. Even in unshrunken cells, Na-H exchange is activated by dialyzing the cell with 1 mM guanosine 5'-O-(3-thiotriphosphate), which causes the prolonged activation of G proteins. Activation of Na-H exchange is also elicited in unshrunken cells by injecting cholera toxin, which activates certain G proteins. Neither exposing cells to 100 nM phorbol 12-myristate 13-acetate nor dialyzing them with a solution containing 20 microM adenosine 3',5'-cyclic monophosphate (cAMP) (or 50 microM dibutyryl cAMP) plus 0.5 mM 3-isobutyl-1-methylxanthine substantially stimulates the exchanger. Thus our data suggest that a G protein plays a key role in the transduction of the shrinkage signal to the Na-H exchanger via a pathway that involves neither protein kinase C nor cAMP.

scholarly journals 0074 Inhibitory Neurons in the Dorsomedial Medulla Promote REM Sleep

SLEEP ◽  
2020 ◽  
Vol 43 (Supplement_1) ◽  
pp. A30-A30
Author(s):  
J Stucynski ◽  
A Schott ◽  
J Baik ◽  
J Hong ◽  
F Weber ◽  
...  
Keyword(s):  
Rem Sleep ◽  
Nrem Sleep ◽  
Inhibitory Neurons ◽  
Brain State ◽  
Sleep Regulation ◽  
Optogenetic Stimulation ◽  
Electrophysiological Recordings ◽  
Stimulation Of

Abstract Introduction The neural circuits controlling rapid eye movement (REM) sleep, and in particular the role of the medulla in regulating this brain state, remains an active area of study. Previous electrophysiological recordings in the dorsomedial medulla (DM) and electrical stimulation experiments suggested an important role of this area in the control of REM sleep. However the identity of the involved neurons and their precise role in REM sleep regulation are still unclear. Methods The properties of DM GAD2 neurons in mice were investigated through stereotaxic injection of CRE-dependent viruses in conjunction with implantation of electrodes for electroencephalogram (EEG) and electromyogram (EMG) recordings and optic fibers. Experiments included in vivo calcium imaging (fiber photometry) across sleep and wake states, optogenetic stimulation of cell bodies, chemogenetic excitation and suppression (DREADDs), and connectivity mapping using viral tracing and optogenetics. Results Imaging the calcium activity of DM GAD2 neurons in vivo indicates that these neurons are most active during REM sleep. Optogenetic stimulation of DM GAD2 neurons reliably triggered transitions into REM sleep from NREM sleep. Consistent with this, chemogenetic activation of DM GAD2 neurons increased the amount of REM sleep while inhibition suppressed its occurrence and enhanced NREM sleep. Anatomical tracing revealed that DM GAD2 neurons project to several areas involved in sleep / wake regulation including the wake-promoting locus coeruleus (LC) and the REM sleep-suppressing ventrolateral periaquaductal gray (vlPAG). Optogenetic activation of axonal projections from DM to LC, and DM to vlPAG was sufficient to induce REM sleep. Conclusion These experiments demonstrate that DM inhibitory neurons expressing GAD2 powerfully promote initiation of REM sleep in mice. These findings further characterize the dorsomedial medulla as a critical structure involved in REM sleep regulation and inform future investigations of the REM sleep circuitry. Support R01 HL149133

Selective autonomic stimulation of canine trachealis with dimethylphenylpiperazinium

1981 ◽  
Vol 51 (2) ◽  
pp. 428-437 ◽  
Author(s):  
A. R. Leff ◽  
N. M. Munoz
Keyword(s):  
Adrenal Gland ◽  
Contractile Response ◽  
Sympathetic Innervation ◽  
Adrenergic Stimulation ◽  
Parasympathetic Ganglia ◽  
Regional Administration ◽  
Adrenal Secretion ◽  
Stimulation Of

The response of canine tracheal muscle to autonomic stimulation with 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP) was studied isometrically in 39 dogs in vivo. Intra-arterial (ia) DMPP (2.5 X 10(-4) to 2.5 X 10(-2) mg/kg) caused selective dose related contraction [maximum 30.1 +/- 6.5 gram-force (gf)/cm] due to regional stimulation of parasympathetic ganglia. This contraction was blocked by regional administration of atropine 10(-3) mg/kg ia and hexamethonium 5 X 10(-2) mg/kg ia. Nonselective intravenous (iv) administration of DMPP 2.5 X 10(-2) mg/kg caused parasympathetic tracheal contraction [+13.4 +/- 1.64 gf/cm] followed by later sympathetic relaxation [-11.8 +/- 2.3 gf/cm]; 0.5 mg/kg iv atropine abolished contraction but did not affect relaxation. The role of the adrenal gland vs. direct sympathetic innervation in producing tracheal relaxation after sympathetic stimulation was also studied. Tracheal relaxation to 2.5 X 10(-2) mg/kg iv DMPP was -18.2 +/- 4.0 gf/cm before adrenalectomy (ADX) and -4.3 +/- 0.9 gf/cm afterward (P less than 0.001). In contrast, tracheal contraction resulting from alpha-adrenergic stimulation after 2.5 X 10(-2) mg/kg iv DMPP in beta-blocked (BB) dogs was not significantly altered by ADX. At 2.5 X 10(-1) mg/kg iv DMPP, the alpha-adrenergic contractile response was still 70% of the response prior to ADX. We conclude that sympathetic tracheal relaxation in dogs is predominantly mediated by circulating catecholamine from the adrenal gland, but that alpha-adrenergic contraction after BB results predominantly from direct sympathetic innervation and is not greatly augmented by adrenal secretion. We also report a new method for selective stimulation of airway cholinergic nerves in vivo without systemic effects.

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