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.

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 Ca2+-induced insulin secretion from electrically permeabilized islets. Loss of the Ca2+-induced secretory response is accompanied by loss of Ca2+-induced protein phosphorylation

1992 ◽  
Vol 285 (3) ◽  
pp. 973-978 ◽  
Author(s):  
P M Jones ◽  
S J Persaud ◽  
S L Howell
Keyword(s):  
Protein Kinase C ◽  
Insulin Secretion ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Protein Phosphorylation ◽  
Prolonged Exposure ◽  
Kinase C ◽  
Dependent Protein ◽  
32P Incorporation ◽  
Rat Islets Of Langerhans

Increasing the cytosolic Ca2+ concentration of electrically permeabilized rat islets of Langerhans caused rapid increases in insulin secretion and in 32P incorporation into islet proteins. However, the secretory responsiveness of permeabilized islets was relatively transient, with insulin secretion approaching basal levels within 20-30 min despite the continued presence of stimulatory concentrations of Ca2+. The loss of Ca2(+)-induced insulin secretion was accompanied by a marked reduction in Ca2(+)-dependent protein phosphorylation, but not in cyclic AMP-dependent protein phosphorylation. Similarly, permeabilized islets which were no longer responsive to Ca2+ were able to mount appropriate secretory responses to cyclic AMP and to a protein kinase C-activating phorbol ester. These results suggest that prolonged exposure to elevated cytosolic Ca2+ concentrations results in a specific desensitization of the secretory mechanism to Ca2+, perhaps as a result of a decrease in Ca2(+)-dependent kinase activity. Furthermore, these studies suggest that secretory responses of B-cells to cyclic AMP and activators of protein kinase C are not dependent upon the responsiveness of the cells to changes in cytosolic Ca2+.

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 Physiology of Astroglial Excitability

Function ◽  
2020 ◽  
Vol 1 (2) ◽  
Author(s):  
Alexei Verkhratsky ◽  
Alexey Semyanov ◽  
Robert Zorec
Keyword(s):  
Cyclic Amp ◽  
Second Messengers ◽  
Synaptic Connectivity ◽  
Neural Cells ◽  
Intracellular Signals ◽  
Multiple Receptors ◽  
Concentration Of Ions ◽  
The Central Nervous System ◽  
Evidence Review ◽  
Underlying Mechanisms

Abstract Classic physiology divides all neural cells into excitable neurons and nonexcitable neuroglia. Neuroglial cells, chiefly responsible for homeostasis and defense of the nervous tissue, coordinate their complex homeostatic responses with neuronal activity. This coordination reflects a specific form of glial excitability mediated by complex changes in intracellular concentration of ions and second messengers organized in both space and time. Astrocytes are equipped with multiple molecular cascades, which are central for regulating homeostasis of neurotransmitters, ionostasis, synaptic connectivity, and metabolic support of the central nervous system. Astrocytes are further provisioned with multiple receptors for neurotransmitters and neurohormones, which upon activation trigger intracellular signals mediated by Ca2+, Na+, and cyclic AMP. Calcium signals have distinct organization and underlying mechanisms in different astrocytic compartments thus allowing complex spatiotemporal signaling. Signals mediated by fluctuations in cytosolic Na+ are instrumental for coordination of Na+ dependent astrocytic transporters with tissue state and homeostatic demands. Astroglial ionic excitability may also involve K+, H+, and Cl−. The cyclic AMP signalling system is, in comparison to ions, much slower in targeting astroglial effector mechanisms. This evidence review summarizes the concept of astroglial intracellular excitability.

Possible Roles for Protein Phosphorylation in Platelet Responses

1979 ◽  
Author(s):  
R.J. Haslam ◽  
J.E.B. Fox ◽  
S.E. Salama ◽  
J.A. Lynham
Keyword(s):  
Cyclic Amp ◽  
Protein Phosphorylation ◽  
Protein Kinases ◽  
Platelet Function ◽  
Subcellular Fractionation ◽  
Human Platelets ◽  
Type I ◽  
Sds Page ◽  
Dependent Protein ◽  
32P Incorporation

The relationships between the phosphorylation of specific platelet polypeptides and platelet function were studied using washed human platelets labelled by preincubation with [32p] Pi. Platelet polypeptides were separated by SDS-PAGE and 32P incorporation into them determined by autoradiography. Whereas induction of platelet aggregation alone did not affect protein phosphorylation, induction of the release reaction increased 3P incorporation into several polypeptides (P75,P47,P40,P27,P20,P19), including the P-light chain of platelet myosin (P20). These changes were inhibited by drugs that blocked Ca2 movements and may be due to activation of Ca2+-dependent protein kinases. Compounds that inhibited platelet function by increasing cyclic AMP (e.g. PCE1) also suppressed these reactions but, in addition, increased phosphorylation of other polypeptides (P50,P49,P36,P24,P22). Type I and Type II cyclic AMP-dependent protein kinases were present in platelets and may mediate Che latter effects of cyclic AMP. Subcellular fractionation of 32p-labelled platelets that had been exposed to PCE1 showed that P24 was present in membranes that could take up Ca2+ by an ATP-dependent mechanism. Membranes from PCE1-treated platelets took up Ca2+ more rapidly than control membranes. Thus, the cyclic AMP-dependent phosphorylation of P24 may stimulate the removal of Ca2+ from platelet cytosol and suppress Ca2+-dependent phosphorylation reactions necessary for release of granule constituents.

Cyclic AMP-dependent protein phosphorylation in the rat anterior pituitary

Synapse ◽  
1990 ◽  
Vol 5 (3) ◽  
pp. 241-246 ◽  
Author(s):  
Scott T. Cain ◽  
James Cliff Pryor ◽  
Charles B. Nemeroff
Keyword(s):  
Cyclic Amp ◽  
Protein Phosphorylation ◽  
Anterior Pituitary ◽  
Dependent Protein

scholarly journals Use of phosphosynapsin I-specific antibodies for image analysis of signal transduction in single nerve terminals

2000 ◽  
Vol 113 (20) ◽  
pp. 3573-3582 ◽  
Author(s):  
A. Menegon ◽  
D.D. Dunlap ◽  
F. Castano ◽  
F. Benfenati ◽  
A.J. Czernik ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Nerve Terminal ◽  
Polyclonal Antibodies ◽  
Second Messengers ◽  
Nerve Terminals ◽  
Dependent Protein Kinase ◽  
Spatially Resolved ◽  
Dependent Protein

We have developed a semi-quantitative method for indirectly revealing variations in the concentration of second messengers (Ca(2+), cyclic AMP) in single presynaptic boutons by detecting the phosphorylation of the synapsins, excellent nerve terminal substrates for cyclic AMP- and Ca(2+)/calmodulin-dependent protein kinases. For this purpose, we employed polyclonal, antipeptide antibodies recognising exclusively synapsin I phosphorylated by Ca(2+)/calmodulin-dependent protein kinase II (at site 3) or synapsins I/II phosphorylated by either cAMP-dependent protein kinase or Ca(2+)/calmodulin-dependent protein kinase I (at site 1). Cerebellar granular neurones in culture were double-labelled with a monoclonal antibody to synapsins I/II and either of the polyclonal antibodies. Digitised images were analysed to determine the relative phosphorylation stoichiometry at each individual nerve terminal. We have found that: (i) under basal conditions, phosphorylation of site 3 was undetectable, whereas site 1 exhibited some degree of constitutive phosphorylation; (ii) depolarisation in the presence of extracellular Ca(2+) was followed by a selective and widespread increase in site 3 phosphorylation, although the relative phosphorylation stoichiometry varied among individual terminals; and (iii) phosphorylation of site 1 was increased by stimulation of cyclic AMP-dependent protein kinase but not by depolarisation and often occurred in specific nerve terminal sub-populations aligned along axon branches. In addition to shedding light on the regulation of synapsin phosphorylation in living nerve terminals, this approach permits the spatially-resolved analysis of the activation of signal transduction pathways in the presynaptic compartment, which is usually too small to be studied with other currently available techniques.

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