Propofol Inhibits Phosphorylation of N -methyl-d-aspartate Receptor NR1 Subunits in Neurons

2006 ◽  
Vol 104 (4) ◽  
pp. 763-769 ◽  
Author(s):  
Seth Kingston ◽  
Limin Mao ◽  
Lu Yang ◽  
Anish Arora ◽  
Eugene E. Fibuch ◽  
...  
Keyword(s):  
Glutamate Receptors ◽  
Okadaic Acid ◽  
Protein Phosphatase ◽  
Cortical Neurons ◽  
Protein Phosphatase 2A ◽  
Ionotropic Glutamate Receptors ◽  
Dependent Manner ◽  
Calyculin A ◽  
General Anesthetic ◽  
Phosphatase 2A

Background Anesthetics may interact with ionotropic glutamate receptors to produce some of their biologic actions. Cellular studies reveal that the ionotropic glutamate receptors, N-methyl-D-aspartate receptors (NMDARs), can be phosphorylated on their NR1 subunits at the C-terminal serine residues, which is a major mechanism for the regulation of NMDAR functions. It is currently unknown whether anesthetics have any modulatory effects on NMDAR NR1 subunit phosphorylation. Methods The possible effect of a general anesthetic propofol on phosphorylation of NR1 subunits at serine 897 (pNR1S897) and 896 (pNR1S896) was detected in cultured rat cortical neurons. Results Propofol consistently reduced basal levels of pNR1S897 and pNR1S896 in a concentration-dependent manner. This reduction was rapid as the reliable reduction of pNR1S896 developed 1 min after propofol administration. Pretreatment of cultures with the protein phosphatase 2A inhibitors okadaic acid or calyculin A blocked the effect of propofol on the NR1 phosphorylation, whereas okadaic acid or calyculin A alone did not alter basal pNR1S897 and pNR1S896 levels. In addition, propofol decreased tyrosine phosphorylation of protein phosphatase 2A at tyrosine 307, resulting in an increase in protein phosphatase 2A activity. In the presence of propofol, the NMDAR agonist-induced intracellular Ca2+ increase was impaired in neurons with dephosphorylated NR1 subunits. Conclusions Together, these data indicate an inhibitory effect of a general anesthetic propofol on NMDAR NR1 subunit phosphorylation in neurons. This inhibition was mediated through a signaling mechanism involving activation of protein phosphatase 2A.

scholarly journals Inhibition of specific binding of okadaic acid to protein phosphatase 2A by microcystin-LR, calyculin-A and tautomycin: method of analysis of interactions of tight-binding ligands with target protein

1995 ◽  
Vol 306 (3) ◽  
pp. 657-665 ◽  
Author(s):  
A Takai ◽  
K Sasaki ◽  
H Nagai ◽  
G Mieskes ◽  
M Isobe ◽  
...  
Keyword(s):  
Dissociation Constant ◽  
Okadaic Acid ◽  
Protein Phosphatase ◽  
Specific Binding ◽  
Protein Phosphatase 2A ◽  
Tight Binding ◽  
Calyculin A ◽  
Phosphatase Inhibitors ◽  
Protein Phosphatase Inhibitors ◽  
Phosphatase 2A

Several groups have reported that okadaic acid (OA) and some other tight-binding protein phosphatase inhibitors including microcystin-LR (MCLR), calyculin-A and tautomycin prevent each other from binding to protein phosphatase 2A (PP2A). In this paper, we have introduced an improved procedure for examining to what extent the affinity of an enzyme for a labelled tight-binding ligand is reduced by binding of an unlabelled tight-binding, ligand to the enzyme. Using this procedure, we have analysed the dose-dependent reduction of PP2A binding of [24-3H]OA by addition of OA, MCLR, calyculin-A and tautomycin. The results indicate that the binding of the unlabelled inhibitors to the PP2A molecule causes a dramatic (10(6)-10(8)-fold) increase in the dissociation constant associated with the interaction of [24-3H]OA and PP2A. This suggests that OA and the other inhibitors bind to PP2A in a mutually exclusive manner. The protein phosphatase inhibitors may share the same binding site on the PP2A molecule. We have also measured values of the dissociation constant (Ki) for the interaction of these toxins with protein phosphatase 1 (PP1). For MCLR and calyculin-A, the ratio of the Ki value obtained for PP1 to that for PP2A was in the range 4-9, whereas it was 0.01-0.02 for tautomycin. The value of tautomycin is considerably smaller than that (0.4) calculated from previously reported Ki values.

scholarly journals Protein phosphatase 2A regulates life and death decisions via Akt in a context-dependent manner

2007 ◽  
Vol 104 (48) ◽  
pp. 19011-19016 ◽  
Author(s):  
S. Andrabi ◽  
O. V. Gjoerup ◽  
J. A. Kean ◽  
T. M. Roberts ◽  
B. Schaffhausen
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Dependent Manner ◽  
Life And Death ◽  
Phosphatase 2A ◽  
Context Dependent

Inhibitory effect of calyculin A, a Ser/Thr protein phosphatase type I inhibitor, on renin secretion

1998 ◽  
Vol 275 (5) ◽  
pp. F664-F670 ◽  
Author(s):  
Chun Sik Park ◽  
Mi Hyun Kim ◽  
Chae Hun Leem ◽  
Yeon Jin Jang ◽  
Hae Won Kim ◽  
...  
Keyword(s):  
Okadaic Acid ◽  
Light Chain ◽  
Protein Phosphatase ◽  
Myosin Light Chain ◽  
Renin Secretion ◽  
Type I ◽  
Dependent Manner ◽  
Calyculin A ◽  
Selective Inhibitors ◽  
Intracellular Ca

We have recently shown that several putative selective inhibitors of Ca2+-calmodulin-dependent myosin light chain kinase (MLCK), such as ML-9 [1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine], reversibly stimulate renin secretion [C. S. Park, S.-H. Chang, H. S. Lee, S.-H. Kim, J. W. Chang, and C. D. Hong. Am. J. Physiol. 271 ( Cell Physiol. 40): C242–C247, 1996]. We hypothesized that Ca2+ inhibits renin secretion, via phosphorylation of 20-kDa myosin light chain (MLC20), by activating MLCK. In the present studies, we have investigated the types of protein phosphatase (PP) involved in the control of renin secretion through inhibition of MLC dephosphorylation using inhibitors of various types of serine/threonine-specific protein phosphatases. Cyclosporin A, a putative inhibitor of PP type 2 (calcineurin), was without effect. Calyculin A and okadaic acid, putative selective inhibitors of both PP type 1 (PP1) and type 2A (PP2A), significantly inhibited renin secretion under control conditions. Calyculin A had inhibitory effects at least 10-fold more potent than okadaic acid, suggesting that PP1, rather than PP2A, is involved in the control of renin secretion. Furthermore, calyculin A blocked the reversal of renin secretion preinhibited by raised intracellular Ca2+ concentrations in a concentration-dependent manner. Calyculin A (10−6 M) significantly inhibited renin secretion stimulated by lowering intracellular Ca2+ concentrations and blocked the stimulatory effect of ML-9 on renin secretion. Taking all of these results into consideration, we hypothesize that dephosphorylation of MLC20 by Ca2+-independent PP1 stimulates renin secretion, whereas phosphorylation of MLC20 by Ca2+-calmodulin-dependent MLCK inhibits it. This hypothesized regulatory model of renin secretion predicts that the rate of renin secretion at a given time is determined by the ratio of phosphorylated to dephosphorylated MLC20, which is, in turn, determined by the dynamic balance between activity of MLCK and MLC phosphatase.

Protein Phosphatase 2A Inactivates Bcl2’s Antiapoptotic Function by Dephosphorylation and Up-Regulation of Bcl2-p53 Binding.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1436-1436
Author(s):  
Xingming Deng ◽  
Fengqin Gao ◽  
Tammy Flagg ◽  
W. Stratford May
Keyword(s):  
Cell Death ◽  
Cell Survival ◽  
Okadaic Acid ◽  
Protein Phosphatase ◽  
Apoptotic Cell ◽  
Protein Phosphatase 2A ◽  
Survival Function ◽  
Phosphorylation Site ◽  
Apoptotic Cell Death ◽  
Phosphatase 2A

Abstract DNA damage-induced p53/Bcl2 interaction at the outer mitochondrial membranes results in a Bcl2 conformational change and loss of its antiapoptotic function. Our data now indicate that either treatment of cells with the protein phosphatase 2A (PP2A) inhibitor, okadaic acid (10 nM), or specific disruption of PP2A activity by the expression of SV40 small tumor antigen enhances Bcl2 phosphorylation and suppresses the cisplatin-stimulated Bcl2-p53 interaction in association with prolonged cell survival. By contrast, C2-ceramide, a potent PP2A activator, reduces Bcl2 phosphorylation and increases Bcl2-p53 binding and promotes apoptotic cell death, suggesting that PP2A may function as a physiological regulator of Bcl2 by, at least in part, affecting its association with p53. Overexpression of the PP2A catalytic subunit (PP2A/C) suppresses Bcl2 phosphorylation in association with increased p53-Bcl2 binding and apoptotic cell death. By contrast, specific depletion of PP2A/C by RNA interference enhances Bcl2 phosphorylation, suppresses p53-Bcl2 interaction and prolongs cell survival. Purified PP2A can directly enhance the formation of the p53-Bcl2 complex in vitro in an okadaic acid-sensitive manner, supporting a direct mechanism. Importantly, PP2A directly interacts with Bcl2 at its BH4 domain which may function as the PP2A ‘docking site’ to potentially ‘bridge’ PP2A to the flexible loop domain which contains the physiological serine 70 phosphorylation site. Thus, PP2A may provide a double whammy to Bcl2’s survival function by both dephosphorylating and enhancing p53-Bcl2 binding. Therapeutically stimulating Bcl2 dephosphorylation and/or increasing Bcl2/p53 binding by activating PP2A may represent an efficient and novel antineoplastic approach.

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