scholarly journals Adhesion to fibronectin stimulates inositol lipid synthesis and enhances PDGF-induced inositol lipid breakdown.

1993 ◽  
Vol 121 (3) ◽  
pp. 673-678 ◽  
Author(s):  
H P McNamee ◽  
D E Ingber ◽  
M A Schwartz
Keyword(s):  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Second Messengers ◽  
Lipid Synthesis ◽  
Water Soluble ◽  
Phosphatidylinositol Bisphosphate ◽  
Hydrolysis Products ◽  
Cytoskeletal Regulation ◽  
Inositol Lipids ◽  
Suspended Cells

The aim of these experiments was to investigate whether inositol lipids might mediate some of the effects of extracellular matrix (ECM) on cellular form and functions. The lipid phosphatidylinositol bisphosphate (PIP2) plays a role in cytoskeletal regulation while its hydrolysis products, diacylglycerol and inositol triphosphate, serve as second messengers. We therefore measured the effect of adhesion to fibronectin (FN) on PIP2 and its hydrolysis products, in the presence and absence of the soluble mitogen PDGF. PDGF induced a threefold increase in release of water-soluble inositol phosphates in C3H 10T1/2 fibroblasts when cells were attached to FN, but had little effect in suspended cells. Suppression of inositol phosphate release in unattached cells was not due to dysfunction of the PDGF receptor or failure to activate phospholipase C-gamma; PDGF induced similar tyrosine phosphorylation of PLC-gamma under both conditions. By contrast, the total mass of phosphatidylinositol bisphosphate (PIP2), the substrate for PLC-gamma, was found to decrease by approximately 80% when cells were detached from their ECM attachments and placed in suspension in the absence of PDGF. PIP2 levels were restored when suspended cells were replated on FN, demonstrating that the effect was reversible. Furthermore, a dramatic increase in synthesis of PIP2 could be measured in cells within 2 min after reattachment to FN in the absence of PDGF. These results show that FN acts directly to stimulate PIP2 synthesis, and that it also enhances PIP2 hydrolysis in response to PDGF. The increase in PIP2 induced by adhesion may mediate some of the known effects of FN on cell shape and cytoskeletal organization, while regulation of inositol lipid hydrolysis may provide a means for integrating hormone- and ECM-dependent signaling pathways.

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.

Involvement of second messengers and protein phosphorylation in astrocyte swelling

1992 ◽  
Vol 70 (S1) ◽  
pp. S362-S366 ◽  
Author(s):  
A. S. Bender ◽  
J. T. Neary ◽  
M. D. Norenberg
Keyword(s):  
Cyclic Amp ◽  
Protein Phosphorylation ◽  
Volume Regulation ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Second Messengers ◽  
Astrocyte Swelling ◽  
Regulatory Processes ◽  
Intracellular Signals ◽  
Dependent Protein

In a hypoosmotic model of astrocyte swelling, we found that Ca2+ and intracellular signals such as diacylglycerol and inositol phosphate, as well as protein phosphorylation systems, are implicated in the generation and (or) modulation of volume regulatory processes. Cyclic AMP, which also has a significant effect on astrocyte volume regulation, in addition influences some of these second messengers.Key words: astrocyte, Ca2+-dependent protein kinases, Ca2+ influx, cell volume, cyclic AMP, inositol phosphates, protein phosphorylation.

Augmented phosphoinositide metabolism in aortas from genetically hypertensive rats

1990 ◽  
Vol 258 (1) ◽  
pp. H173-H178 ◽  
Author(s):  
M. B. Turla ◽  
R. C. Webb
Keyword(s):  
Phospholipase C ◽  
Vascular Reactivity ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Second Messengers ◽  
Receptor Activation ◽  
Phosphoinositide Hydrolysis ◽  
Phosphoinositide Metabolism ◽  
Hypertensive Rats ◽  
Wistar Kyoto

Recent studies suggest that serotonergic receptor activation is coupled to phospholipase C-mediated phosphoinositide hydrolysis, which results in the release of intracellular second messengers. The purpose of this study was to determine whether altered phosphoinositide metabolism is the basis for augmented vascular responsiveness to serotonin in genetic hypertension. Thoracic aortic segments isolated from stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto normotensive rats (WKY) were labeled with myo-[3H]inositol and stimulated with serotonin in the presence of LiCl. Accumulation of [3H]inositol phosphates was then quantitated by column chromatography. Basal inositol phosphate accumulation and basal incorporation of myo-[3H]inositol into aortic cell membranes from SHRSP was not significantly different from WKY values. At 2.6 x 10(-7) to 2.6 x 10(-4) M serotonin, phosphoinositide metabolism was significantly augmented in aortae from SHRSP compared with WKY. Depolarization (100 mM KCl) did not increase phosphoinositide hydrolysis above basal levels in SHRSP or WKY. 2-Nitro-4-carboxyphenyl-N,N-diphenyl carbamate (NCDC), an inhibitor of phospholipase C, prevented the serotonin-induced phosphoinositide metabolism. NCDC also partially inhibited phasic contractions (responses in calcium-free solution) to serotonin in aortas from SHRSP and WKY. In conclusion, abnormal phosphoinositide metabolism may be one mechanism responsible for the characteristic increase in vascular reactivity to serotonin in hypertension.

scholarly journals The labelling of polyphosphoinositides with [32P]Pi and the accumulation of inositol phosphates in vasopressin-stimulated hepatocytes

1986 ◽  
Vol 238 (2) ◽  
pp. 491-499 ◽  
Author(s):  
S Palmer ◽  
P T Hawkins ◽  
R H Michell ◽  
C J Kirk
Keyword(s):  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Anion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Water Soluble ◽  
Ionophore A23187 ◽  
Inositol Tetrakisphosphate ◽  
Inositol Phosphate Accumulation ◽  
Phosphatidylinositol 4 ◽  
Phosphate Groups

When hepatocytes were incubated with [32P]Pi, the kinetics for the labelling of the monoester phosphate groups of phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate were similar to each other and slightly slower than that for the labelling of the gamma-phosphate of ATP. Analysis of the water-soluble 3H-labelled materials derived from [3H]inositol-labelled hepatocytes revealed that, in addition to inositol and its mono-, bis- and tris-phosphates (Ins, InsP, InsP2 and InsP3), these cells contained two unidentified radioactive compounds which co-eluted with InsP on anion-exchange chromatography. When [3H]inositol-labelled hepatocytes were stimulated with 0.23 microM-vasopressin in the presence of 10 mM-Li+, there was an accumulation of radioactivity in InsP, InsP2 and InsP3 but not in Ins or the two unidentified compounds. Further analysis of these inositol phosphates by h.p.l.c. revealed that vasopressin also stimulates the accumulation of inositol tetrakisphosphate (InsP4) in these cells. Vasopressin-stimulated InsP and InsP2 accumulations were maximal in the presence of 1-10 mM-Li+ but InsP3 accumulation continued to increase up to 50 mM-Li+. Accumulated inositol phosphates were retained within the cell. Li+ from 1 to 50 mM did not influence the extent of vasopressin-stimulated inositol lipid degradation in hepatocytes. In the absence of Li+, radioactivity in vasopressin-stimulated hepatocytes accumulated almost entirely in free inositol. The vasopressin-stimulated accumulation of inositol phosphates in the presence of 10 mM-Li+ was abolished by a V1-vasopressin antagonist. Inositol phosphate accumulation was not influenced by ionophore A23187, dimethyl sulphoxide or indomethacin.

scholarly journals Inositol lipid synthesis is widespread in host-associated Bacteroidetes

2021 ◽  
Author(s):  
S. L. Heaver ◽  
H. H. Le ◽  
P. Tang ◽  
A. Baslé ◽  
J. Marles-Wright ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Biosynthetic Pathway ◽  
Inositol Phosphate ◽  
Lipid Production ◽  
Lipid Synthesis ◽  
Kinetic Studies ◽  
Human Gut ◽  
Host Interactions ◽  
Phosphatidylinositol Phosphate ◽  
Inositol Lipids

AbstractUbiquitous in eukaryotes, inositol lipids have finely tuned roles in cellular signaling and membrane homeostasis. In Bacteria, however, inositol lipid production is rare. Recently, the prominent human gut bacterium Bacteroides thetaiotaomicron (BT) was reported to produce inositol lipids, including inositol sphingolipids, but the pathways remain ambiguous and their prevalence unclear. Here, we investigated the gene cluster responsible for inositol lipid synthesis in BT using a novel strain with inducible control of sphingolipid synthesis. We characterized the biosynthetic pathway from myo-inositol-phosphate (MIP) synthesis to phosphoinositol-dihydroceramide, including structural and kinetic studies of the enzyme MIP synthase (MIPS). We determined the crystal structure of recombinant BT MIPS with bound NAD cofactor at 2.0 Å resolution, and identified the first reported phosphatase for the conversion of bacterially-derived phosphatidylinositol phosphate (PIP) to phosphatidylinositol (PI). Transcriptomic analysis indicated inositol production is nonessential but its loss alters BT capsule expression. Bioinformatic and lipidomic comparisons of Bacteroidetes species revealed a novel second putative pathway for bacterial PI synthesis without a PIP intermediate. Our results indicate that inositol sphingolipid production, via one of the two pathways, is widespread in host-associated Bacteroidetes, and may be implicated in host interactions both indirectly via the capsule and directly through inositol lipid provisioning.

scholarly journals Inositol 1,2-cyclic 4,5-trisphosphate is not a product of μscarinic receptor-stimulated phosphatidylinositol 4,5-bisphosphate hydrolysis in rat parotid glands

1987 ◽  
Vol 243 (1) ◽  
pp. 211-218 ◽  
Author(s):  
P T Hawkins ◽  
C P Berrie ◽  
A J Morris ◽  
C P Downes
Keyword(s):  
Parotid Gland ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Water Soluble ◽  
Parotid Glands ◽  
Inositol 1 ◽  
Inositol 1,4,5 Trisphosphate ◽  
Cyclic Phosphate ◽  
Rat Parotid ◽  
Cyclic Compounds

We have employed a neutral-pH extraction technique to look for inositol 1,2-cyclic phosphate derivatives in [3H]inositol-labelled parotid gland slices stimulated with carbachol. The incubations were terminated by adding cold chloroform/methanol (1:2, v/v), the samples were dried under vacuum and inositol phosphates were extracted from the dried residues by phenol/chloroform/water partitioning. Water-soluble inositol metabolites were separated by h.p.l.c. at pH 3.7. 32P-labelled inositol phosphate standards (inositol 1-phosphate, inositol 1,2-cyclic phosphate, inositol 1,4,5-trisphosphate and inositol 1,2-cyclic 4,5-trisphosphate) were quantitively recovered through both extraction and chromatography steps. Treatment of inositol cyclic phosphate standards with 5% (w/v) HClO4 for 10 min prior to chromatography resulted in formation of the expected non-cyclic compounds. [3H]Inositol 1-phosphate and [3H]inositol 1,4,5-trisphosphate were both present in parotid gland slices and both increased during stimulation with 1 mM-carbachol. There was no evidence for significant quantities of [3H]inositol 1,2-cyclic phosphate or [3H]inositol 1,2-cyclic 4,5-trisphosphate in control or carbachol-stimulated glands. Parotid gland homogenates rapidly converted inositol 1,4,5-trisphosphate to inositol bisphosphate and inositol tetrakisphosphate, but metabolism of the inositol cyclic trisphosphate was much slower. The results suggest that inositol 1,4,5-trisphosphate, but not inositol 1,2-cyclic 4,5-trisphosphate, is the water-soluble product of muscarinic receptor-stimulated phospholipase C in rat parotid glands.

Inositol lipids and DNA replication

1987 ◽  
Vol 317 (1187) ◽  
pp. 525-536 ◽  
Keyword(s):  
Protein Synthesis ◽  
Growth Factors ◽  
Cell Growth ◽  
Dna Synthesis ◽  
Intracellular Calcium ◽  
Inositol Phosphates ◽  
Water Soluble ◽  
Sequence Of Events ◽  
Inositol Lipids ◽  
Hydrolysis Of

Control of DNA synthesis by growth factors seems to depend upon the generation of intracellular mitogenic signals, which are responsible for initiating the sequence of events leading to the onset of DNA synthesis. Many growth factors have tyrosine kinase activity suggesting the proteins phosphorylated on tyrosine might be likely candidates as intracellular signals. Other candidates are the calcium and hydrogen ions whose concentrations change dramatically during the action of most growth factors, many of which also stimulate the hydrolysis of inositol lipids. In particular, certain growth factors stimulate the hydrolysis of phosphatidylinositol 4,5- bisphosphate to give the two second messengers diacylglycerol and inositol 1,4,5- trisphosphate (Ins1,4,5P 3 ). The former stimulates protein kinase C, which is responsible for increasing intracellular pH by switching on an Na + -H + exchanger. The water-soluble Ins1,4,5P 3 released to the cytosol can be metabolized along two separate pathways: it can either be dephosphorylated to free inositol or it can be converted into additional inositol polyphosphates such as Ins1,3,4,5P 4 and Ins1,3,4P 3 . These inositol phosphates seem to play a key role in regulating intracellular calcium, with Ins1,4,5P 3 functioning to release internal calcium, whereas Ins1,3,4,5P 4 may function to regulate the entry of external calcium. There is evidence to suggest that these internal messengers may converge on certain key processes responsible for initiating the programme of cell growth. It is argued that an increase in intracellular calcium might be an important intracellular signal for activating both the transcription of a family of early genes, typified by fos , as well as the enzyme S6 kinase, which phosphorylates the ribosomal protein S6 which may regulate protein synthesis. The increase in pH seems to play a permissive role and may create the necessary ionic milieu for S6 phosphorylation and protein synthesis to occur. The onset of RNA and protein synthesis, which occur within the first few minutes after the arrival of a growth factor, represent the initial events of the programme of cell growth which culminates in DNA synthesis and cell division.

scholarly journals Inositol phosphate metabolism in bradykinin-stimulated human A431 carcinoma cells. Relationship to calcium signalling

1987 ◽  
Vol 244 (1) ◽  
pp. 129-135 ◽  
Author(s):  
B C Tilly ◽  
P A van Paridon ◽  
I Verlaan ◽  
K W A Wirtz ◽  
S W de Laat ◽  
...  
Keyword(s):  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Second Messengers ◽  
Calcium Signalling ◽  
Carcinoma Cells ◽  
A431 Cells ◽  
Inositol Phosphate Metabolism ◽  
Transient Rise ◽  
Lag Period ◽  
Massive Accumulation

Stimulation of human A431 epidermoid carcinoma cells by bradykinin causes a very rapid release of inositol phosphates and a transient rise in cytoplasmic free Ca2+ concentration ([Ca2+]i). Bradykinin-induced inositol phosphate formation is half-maximal at a concentration of 4 nM and is not affected by pertussis toxin. H.p.l.c. analysis of the various inositol phosphates shows an immediate but transient accumulation of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3], which reaches a peak value of approx. 10 times the basal level within 15 s and slightly precedes the rise in [Ca2+]i, both parameters changing in parallel. After a lag period, bradykinin also induces a massive accumulation of Ins(1,3,4)P3 and inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4]. Our data support the view that part of the newly formed Ins(1,4,5)P3 is converted into Ins(1,3,4)P3 phosphorylation/dephosphorylation with Ins(1,3,4,5)P4 as intermediate. Furthermore, A431 cells were found to contain strikingly high basal levels of two other inositol phosphates, presumably inositol pentakisphosphate (InsP5) and inositol hexakisphosphate (InsP6), representing more than 50% of the total 3H radioactivity incorporated into inositol phosphates. The presumptive InsP5 and InsP6 are only slightly affected by bradykinin. Although Ins(1,3,4)P3 and InsP4 could function as second messengers, our results suggest that, unlike Ins(1,4,5)P3, neither Ins(1,3,4)P3 nor InsP4 are involved in Ca2+ mobilization.

scholarly journals Luteinizing hormone stimulates the formation of inositol trisphosphate and cyclic AMP in rat granulosa cells. Evidence for phospholipase C generated second messengers in the action of luteinizing hormone

1986 ◽  
Vol 238 (2) ◽  
pp. 597-604 ◽  
Author(s):  
J S Davis ◽  
L L Weakland ◽  
L A West ◽  
R V Farese
Keyword(s):  
Lipid Metabolism ◽  
Luteinizing Hormone ◽  
Cyclic Amp ◽  
Granulosa Cells ◽  
Cyclic Gmp ◽  
Time Course ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Second Messengers ◽  
Inositol Trisphosphate

The following studies were conducted to determine whether luteinizing hormone (LH), a hormone which increases cellular levels of cyclic AMP, also provokes increases in ‘second messengers’ derived from inositol lipid metabolism (i.e. inositol phosphates and diacylglycerol). Rat granulosa cells isolated from mature Graafian follicles were prelabelled for 3 h with myo-[2-3H]inositol. LH provoked rapid (5 min) and sustained (up to 60 min) increases in the levels of inositol mono-, bis, and trisphosphates (IP, IP2 and IP3, respectively). Time course studies revealed that IP3 was formed more rapidly than IP2 and IP following LH treatment. The response to LH was concentration-dependent with maximal increases at LH concentrations of 1 microgram/ml. LiCl (2-40 mM) enhanced the LH-provoked accumulation of all [3H]inositol phosphates, presumably by inhibiting the action of inositol phosphate phosphatases. The effectiveness of LH, however, was dependent on the concentration of lithium employed; maximal increases in IP were observed at 10 mM-LiCl, whereas maximal increases in IP2 and IP3 were observed at 20 mM- and 40 mM-LiCl, respectively. The stimulatory effects of LH on inositol phosphate and progesterone accumulation were also compared with changes in cyclic nucleotide levels. LH rapidly increased levels of inositol phosphates, progesterone and cyclic AMP, but transiently reduced levels of cyclic GMP. These results demonstrate that LH increases both cyclic AMP and inositol trisphosphate (and presumably diacylglycerol) in rat granulosa cells. Our findings suggest that two messenger systems exist to mediate the action of LH in granulosa cells.

scholarly journals Requirement for calcium ions in acetylcholine-stimulated phosphodiesteratic cleavage of phosphatidyl-myo-inositol 4,5-bisphosphate in rabbit iris smooth muscle

1980 ◽  
Vol 192 (3) ◽  
pp. 783-791 ◽  
Author(s):  
Rashid A. Akhtar ◽  
Ata A. Abdel-Latif
Keyword(s):  
Smooth Muscle ◽  
Specific Activity ◽  
Inositol Phosphates ◽  
Inositol Trisphosphate ◽  
Water Soluble ◽  
Ionophore A23187 ◽  
Experimental Conditions ◽  
Phosphatidylinositol Bisphosphate ◽  
Low Concentrations ◽  
Rabbit Iris

1. The mechanism of acetylcholine-stimulated breakdown of phosphatidyl-myo-inositol 4,5-bisphosphate and its dependence on extracellular Ca2+ was investigated in the rabbit iris smooth muscle. 2. Acetylcholine (50μm) increased the breakdown of phosphatidylinositol bisphosphate in [3H]inositol-labelled muscle by 28% and the labelling of phosphatidylinositol by 24% of that of the control. Under the same experimental conditions there was a 33 and 48% increase in the production of 3H-labelled inositol trisphosphate and inositol monophosphate respectively. Similarly carbamoylcholine and ionophore A23187 increased the production of these water-soluble inositol phosphates. Little change was observed in the 3H radioactivity of inositol bisphosphate. 3. Both inositol trisphosphatase and inositol monophosphatase were demonstrated in subcellular fractions of this tissue and the specific activity of the former was severalfold higher than that of the latter. 4. The acetylcholine-stimulated production of inositol trisphosphate and inositol monophosphate was inhibited by atropine (20μm), but not tubocurarine (100μm); and it was abolished by depletion of extracellular Ca2+ with EGTA, but restored on addition of low concentrations of Ca2+ (20μm). 5. Calcium-antagonistic agents, such as verapamil (20μm), dibenamine (20μm) or La3+ (2mm), also abolished the production of the water-soluble inositol phosphates in response to acetylcholine. 6. Release of inositol trisphosphate from exogenous phosphatidylinositol bisphosphate by iris muscle microsomal fraction (‘microsomes’) was stimulated by 43% in the presence of 50μm-Ca2+. 7. The results indicate that increased Ca2+ influx into the iris smooth muscle by acetylcholine and ionophore A23187 markedly activates phosphatidylinositol bisphosphate phosphodiesterase and subsequently increases the production of inositol trisphosphate and its hydrolytic product inositol monophosphate. The marked increase observed in the production of inositol monophosphate could also result from Ca2+ activation of phosphatidylinositol phosphodiesterase. However, there was no concomitant decrease in the 3H radioactivity of this phospholipid.

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