scholarly journals Rapid accumulation and sustained turnover of inositol phosphates in cerebral-cortex slices after muscarinic-receptor stimulation

1989 ◽  
Vol 260 (1) ◽  
pp. 237-241 ◽  
Author(s):  
I H Batty ◽  
S R Nahorski
Keyword(s):  
Cerebral Cortex ◽  
Muscarinic Receptor ◽  
Metabolic Flux ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Receptor Activation ◽  
Inositol Polyphosphate ◽  
Receptor Stimulation ◽  
Cortex Slices ◽  
Rapid Kinetics

The rapid kinetics of [3H]inositol phosphate accumulation and turnover were examined in rat cerebral-cortex slices after muscarinic-receptor stimulation. Markedly increased [3H]inositol polyphosphate concentrations were observed to precede significant stimulated accumulation of [3H]inositol monophosphate. New steady-state accumulations of several 3H-labelled products were achieved after 5-10 min of continued agonist stimulation, but were rapidly and effectively reversed by subsequent receptor blockade. The results show that muscarinic-receptor activation involves phosphoinositidase C-catalysed hydrolysis initially of polyphosphoinositides rather than of phosphatidylinositol. Furthermore, prolonged carbachol stimulation is shown not to cause receptor desensitization, but to allow persistent hydrolysis of [3H]phosphatidylinositol bisphosphate and permit sustained metabolic flux through the inositol tris-/tetrakis-phosphate pathway.

scholarly journals Differences between muscarinic-receptor- and Ca2+-induced inositol polyphosphate isomer accumulation in rat cerebral-cortex slices

1990 ◽  
Vol 267 (3) ◽  
pp. 835-838 ◽  
Author(s):  
J G Baird ◽  
S R Nahorski
Keyword(s):  
Cerebral Cortex ◽  
Muscarinic Receptor ◽  
Degradation Products ◽  
The Other ◽  
Rat Cerebral Cortex ◽  
Inositol Polyphosphate ◽  
Receptor Stimulation ◽  
Other Hand ◽  
Cortex Slices ◽  
Polyphosphate Metabolism

Muscarinic-receptor stimulation or depolarization by elevated K+ leads to increased accumulation of [3H]Ins(1,4,5)P3, [3H]Ins(1,3,4,5)P4 and several degradation products of these polyphosphates separated by h.p.l.c. On the other hand, agents such as ionomycin and maitotoxin, which increase intracellular Ca2+ directly, produce a small accumulation of [3H]Ins(1,4,5)P3 and markedly increase [3H]Ins(1,4)P2, but [3H]Ins(1,3,4,5)P4, [3H]Ins(1,3,4)P3 and [3H]Ins(1,3)P2 are virtually unaffected. Ca2(+)-dependent [3H]inositol polyphosphate metabolism may involve different pools of lipids and/or phosphoinositidases.

scholarly journals Accumulation of inositol polyphosphate isomers in agonist-stimulated cerebral-cortex slices. Comparison with metabolic profiles in cell-free preparations

1989 ◽  
Vol 258 (1) ◽  
pp. 23-32 ◽  
Author(s):  
I H Batty ◽  
A J Letcher ◽  
S R Nahorski
Keyword(s):  
Cerebral Cortex ◽  
Inositol Phosphates ◽  
Periodate Oxidation ◽  
Chemical Degradation ◽  
Inositol Polyphosphate ◽  
Tissue Slices ◽  
Inositol 1 ◽  
Agonist Stimulation ◽  
Cortex Slices ◽  
Hydrolysis Of

1. Basal and carbachol-stimulated accumulations of isomeric [3H]inositol mono-, bis-, tris- and tetrakis-phosphates were examined in rat cerebral-cortex slices labelled with myo-[2-3H]inositol. 2. In control samples the major [3H]inositol phosphates detected were co-eluted on h.p.l.c. with Ins(1)P, Ins(4)P (inositol 1- and 4-monophosphate respectively), Ins(1,4)P2 (inositol 1,4-bisphosphate), Ins(1,4,5)P3 (inositol 1,4,5-tris-phosphate) and Ins(1,3,4,5)P4 (inositol 1,3,4,5-tetrakisphosphate). 3. After stimulation to steady state with carbachol, accumulation of each of these products was markedly increased. 4. Agonist stimulation, however, also evoked much more dramatic increased accumulations of a second [3H]inositol trisphosphate, which was co-eluted on h.p.l.c. with authentic Ins(1,3,4)P3 (inositol 1,3,4-trisphosphate) and of three further [3H]inositol bisphosphates ([3H]InsP2(s]. 5. Examination of the latter by chemical degradation by periodate oxidation and/or h.p.l.c. allowed identification of these as [3H]Ins(1,3)P2, [3H]Ins(3,4)P2 and [3H]Ins(4,5)P2 (inositol 1,3-, 3,4- and 4,5-bisphosphates respectively), which respectively accounted for about 22%, 8% and 3% of total [3H]InsP2 in extracts from stimulated tissue slices. 6. By using a h.p.l.c. method which clearly resolves Ins(1,3,4,5)P4 and Ins(1,3,4,6)P4 (inositol 1,3,4,6-tetrakisphosphate), only the former isomer could be detected in extracts from either control or stimulated tissue slices. Similarly, [3H]inositol pentakis- and hexakis-phosphates were not detectable either in the presence or absence of carbachol under the radiolabelling conditions described. 7. The catabolism of [3H]Ins(1,4,5)P3 and [3H]Ins(1,3,4)P3 by cell-free preparations from cerebral cortex was also studied. 8. In the presence of Mg2+, [3H]Ins(1,4,5)P3 was specifically dephosphorylated via [3H]Ins(1,4)P2 and [3H]Ins(4)P to free [3H]inositol, whereas [3H]Ins(1,3,4)P3 was degraded via [3H]Ins(3,4)P2 and, to a lesser extent, via [3H]Ins(1,3)P2 to D- and/or L-[3H]Ins(1)P and [3H]inositol. 9. In the presence of EDTA, hydrolysis of [3H]Ins(1,4,5)P3 was greater than or equal to 95% inhibited, whereas [3H]Ins(1,3,4)P3 was still degraded, but yielded only a single [3H]InsP2 identified as [3H]Ins(1,3)P2. 10. The significance of these observations with cell-free preparations is discussed in relation to the proportions of the separate isomeric [3H]inositol phosphates measured in stimulated tissue slices.

scholarly journals Muscarinic-receptor stimulation enhances polyphosphoinositide breakdown in guinea-pig ileum smooth muscle

1984 ◽  
Vol 223 (2) ◽  
pp. 527-531 ◽  
Author(s):  
M C Sekar ◽  
B D Roufogalis
Keyword(s):  
Guinea Pig ◽  
Muscarinic Receptor ◽  
Longitudinal Muscle ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Exchange Chromatography ◽  
Guinea Pig Ileum ◽  
Receptor Stimulation ◽  
Inositol 1 ◽  
Stimulation Of

Muscarinic-receptor stimulation by 0.1 mM-carbachol in longitudinal muscle of the guinea-pig ileum increases the incorporation of [3H]inositol into inositol-containing phospholipid. This effect was blocked by 16 microM-atropine. After 60 min incubation, carbachol increased the accumulation of total inositol phosphates 20-fold in the presence of 10 mM-Li+. Less than 20% of the total inositol phosphate corresponded to inositol 1-phosphate by ion-exchange chromatography, whereas of the remainder about two-thirds corresponded to inositol bisphosphate and one third to inositol trisphosphate. It is concluded that stimulation of muscarinic receptors in guinea-pig ileum enhances breakdown of polyphosphoinositides, suggesting that this may be a primary event associated with Ca2+ mobilization in the guinea-pig ileum.

Stimulation of acid secretion and phosphoinositol production by rat parietal cell muscarinic M2 receptors

1988 ◽  
Vol 254 (4) ◽  
pp. G622-G629
Author(s):  
A. Pfeiffer ◽  
H. Rochlitz ◽  
A. Herz ◽  
G. Paumgartner
Keyword(s):  
Acid Secretion ◽  
Muscarinic Receptor ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Receptor Activation ◽  
Receptor Subtype ◽  
Muscarinic Agonists ◽  
Receptor System ◽  
Drug Concentrations ◽  
Stimulation Of

The muscarinic receptor system involved in hydrogen ion production by enriched rat gastric parietal cells was investigated. Muscarinic receptor density determined by [N-methyl-3H]scopolamine binding was 8,100/cell. The receptor appeared to be of the M2 muscarinic receptor subtype, since it had a low affinity (Kd, 189 nM) for the M1 receptor antagonist pirenzepine compared with atropine (Kd, 0.74 nM). Receptor activation by carbachol rapidly augmented levels of polyphosphoinositides, indicating an activation of a phospholipase C. The dose-response relations for the increase in inositol phosphates closely paralleled the binding of carbachol to muscarinic receptors with a Km of 17 microM. The inositol phosphate response was antagonized by pirenzepine with a Ki of 177 nM. The stimulation of inositol phosphate levels by carbachol correlated well with the stimulation of [14C]aminopyrine uptake, determined as an index of acid secretion. The muscarinic agonists oxotremorine, pilocarpine, and bethanechol elicited partial increases in inositol phosphates at maximal drug concentrations, and these partial increases correlated with their ability to stimulate [14C]aminopyrine uptake. These data indicate that inositol polyphosphates may be a second messenger of M2 receptors stimulating acid secretion.

Adrenergic stimulation of inositol phosphate accumulation in tracheal epithelium

1989 ◽  
Vol 66 (1) ◽  
pp. 504-508 ◽  
Author(s):  
T. Bainbridge ◽  
R. D. Feldman ◽  
M. J. Welsh
Keyword(s):  
Adrenergic Receptor ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Second Messengers ◽  
Receptor Activation ◽  
Adrenergic Stimulation ◽  
Cl Secretion ◽  
Phosphate Accumulation ◽  
Inositol Phosphate Accumulation ◽  
Stimulation Of

To determine whether inositol phosphates are important second messengers in the regulation of Cl- secretion by airway epithelia, we examined the relationship between inositol phosphate accumulation and Cl- secretion in response to adrenergic agonists. We found that epinephrine stimulated Cl- secretion and inositol phosphate accumulation with similar concentration dependence. Although isoproterenol stimulated Cl- secretion, there was no effect of beta-adrenergic receptor activation on inositol phosphate accumulation. In contrast, alpha 1-adrenergic receptor activation stimulated inositol phosphate accumulation but failed to induce Cl- secretion. Another Cl- secretagogue, prostaglandin E1, also failed to stimulate inositol phosphate accumulation. These data suggest that inositol phosphate accumulation is neither sufficient nor required for stimulation of Cl- secretion in cultured canine tracheal epithelial cells.

scholarly journals Inositol polyphosphate multikinase regulation ofTrypanosoma bruceilife stage development

2018 ◽  
Vol 29 (9) ◽  
pp. 1137-1152 ◽  
Author(s):  
Igor Cestari ◽  
Atashi Anupama ◽  
Kenneth Stuart
Keyword(s):  
Rna Binding ◽  
Rna Binding Proteins ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Tsetse Fly ◽  
Developmental Changes ◽  
Mammalian Host ◽  
Surface Coat ◽  
Inositol Polyphosphate ◽  
Inositol Polyphosphate Multikinase

Many cellular processes change during the Trypanosoma brucei life cycle as this parasite alternates between the mammalian host and tsetse fly vector. We show that the inositol phosphate pathway helps regulate these developmental changes. Knockdown of inositol polyphosphate multikinase (IPMK), which phosphorylates Ins(1,4,5)P3 and Ins(1,3,4,5)P4, resulted in changes in bloodstream forms that are characteristic of insect stage procyclic forms. These changes include expression of the procyclic surface coat, up-regulation of RNA-binding proteins that we show to regulate stage-specific transcripts, and activation of oxidative phosphorylation with increased ATP production in bloodstream forms. These changes were accompanied by development of procyclic morphology, which also occurred by the expression of a catalytically inactive IPMK, implying that regulation of these processes entails IPMK activity. Proteins involved in signaling, protein synthesis and turnover, and metabolism were affinity-enriched with the IPMK substrate or product. Developmental changes associated with IPMK knockdown or catalytic inactivation reflected processes that are enriched with inositol phosphates, and chemical and genetic perturbation of these processes affected T. brucei development. Hence, IPMK helps regulate T. brucei development, perhaps by affecting inositol phosphate interactions with proteins of the regulatory network that controls energy metabolism and development.

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