scholarly journals p38 MAPK Activation Elevates Serotonin Transport Activity via a Trafficking-independent, Protein Phosphatase 2A-dependent Process

2005 ◽  
Vol 280 (16) ◽  
pp. 15649-15658 ◽  
Author(s):  
Chong-Bin Zhu ◽  
Ana M. Carneiro ◽  
Wolfgang R. Dostmann ◽  
William A. Hewlett ◽  
Randy D. Blakely
Keyword(s):  
Protein Kinase ◽  
P38 Mapk ◽  
Protein Phosphatase ◽  
Surface Density ◽  
Protein Phosphatase 2A ◽  
Protein Kinase G ◽  
Mapk Activation ◽  
Phosphatase 2A ◽  
Sert Activity ◽  
Stimulation Of

Presynaptic, plasma membrane serotonin (5-hydroxytryptamine; 5-HT) transporters (SERTs) clear 5-HT following vesicular release and are regulated through trafficking-dependent pathways. Recently, we (Zhu, C.-B., Hewlett, W. A., Feoktistov, I., Biaggioni, I., and Blakely, R. D. (2004)Mol. Pharmacol.65, 1462–1474) provided evidence for a trafficking-independent mode of SERT regulation downstream of adenosine receptor (AR) activation that is sensitive to p38 MAPK inhibitors. Here, we probe this pathway in greater detail, demonstrating elevation of 5-HT transport by multiple p38 MAPK activators (anisomycin, H2O2, and UV radiation), in parallel with p38 MAPK phosphorylation, as well as suppression of anisomycin stimulation by p38 MAPK siRNA treatments. Studies with transporter-transfected Chinese hamster ovary cells reveal that SERT stimulation is shared with the human norepinephrine transporter but not the human dopamine transporter. Saturation kinetic analyses of anisomycin-SERT activity reveal a selective reduction in 5-HTKmsupported by a commensurate increase in 5-HT potency (Ki) for displacing surface antagonist binding. Anisomycin treatments that stimulate SERT activity do not elevate surface SERT surface density whereas stimulation is lost with preexposure of cells to the surface-SERT inactivating reagent, 2-(trimethylammonium)ethyl methane thiosulfonate. Guanylyl cyclase (1H-(1,2,4)-oxadiazolo[4,3-a]-quinoxalin-1-one) and protein kinase G inhibitors (H8, DT-2) block AR stimulation of SERT yet fail to antagonize SERT stimulation by anisomycin. We thus place p38 MAPK activation downstream of protein kinase G in a SERT-catalytic regulatory pathway, distinct from events controlling SERT surface density. In contrast, the activity of protein phosphatase 2A inhibitors (fostriecin and calyculin A) to attenuate anisomycin stimulation of 5-HT transport suggests that protein phosphatase 2A is a critical component of the pathway responsible for p38 MAPK up-regulation of SERT catalytic activity.

scholarly journals Cytokine Activation of p38 Mitogen-Activated Protein Kinase and Apoptosis Is Opposed by alpha-4 Targeting of Protein Phosphatase 2A for Site-Specific Dephosphorylation of MEK3

2007 ◽  
Vol 27 (12) ◽  
pp. 4217-4227 ◽  
Author(s):  
Todd D. Prickett ◽  
David L. Brautigan
Keyword(s):  
Protein Kinase ◽  
P38 Mapk ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Phosphorylation Site ◽  
Mitogen Activated Protein Kinase ◽  
Mapk Activation ◽  
Tnf Α ◽  
Mitogen Activated Protein ◽  
Phosphatase 2A

ABSTRACT alpha-4 is an essential gene and is a dominant antiapoptotic factor in various tissues that is a regulatory subunit for type 2A protein phosphatases. A multiplexed phosphorylation site screen revealed that knockdown of alpha-4 by small interfering RNA (siRNA) increased p38 mitogen-activated protein kinase (MAPK) and c-Jun phosphorylation without changes in JNK or ERK. FLAG-alpha-4 coprecipitated hemagglutinin-MEK3 plus endogenous protein phosphatase 2A (PP2A) and selectively enhanced dephosphorylation of Thr193, but not Ser189, in the activation loop of MEK3. Overexpression of alpha-4 suppressed p38 MAPK activation in response to tumor necrosis factor alpha (TNF-α). The alpha-4 dominant-negative domain (DND) (residues 220 to 340) associated with MEK3, but not PP2A, and its overexpression sensitized cells to activation of p38 MAPK by TNF-α and interleukin-1β, but not by ansiomycin or sorbitol. The response was diminished by nocodazole or by siRNA knockdown of the Opitz syndrome protein Mid1 that binds alpha-4 to microtubules. Interference by alpha-4 DND or alpha-4 siRNA increased caspase 3/7 activation in response to TNF-α. Growth of transformed cells in soft agar was enhanced by alpha-4 and suppressed by alpha-4 DND. The results show that alpha-4 targets PP2A activity to MEK3 to suppress p38 MAPK activation by cytokines, thereby inhibiting apoptosis and anoikis.

scholarly journals Protein kinase A activates protein phosphatase 2A by phosphorylation of the B56  subunit

2007 ◽  
Vol 104 (8) ◽  
pp. 2979-2984 ◽  
Author(s):  
J.-H. Ahn ◽  
T. McAvoy ◽  
S. V. Rakhilin ◽  
A. Nishi ◽  
P. Greengard ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Phosphatase 2A ◽  
Kinase A

scholarly journals The Serine/Threonine Protein Phosphatase 2A (PP2A) Regulates Syk Activity in Human Platelets

2020 ◽  
Vol 21 (23) ◽  
pp. 8939
Author(s):  
Stephanie Makhoul ◽  
Elena Kumm ◽  
Pengyu Zhang ◽  
Ulrich Walter ◽  
Kerstin Jurk
Keyword(s):  
Protein Kinase ◽  
Platelet Activation ◽  
Protein Phosphatase ◽  
Feedback Inhibition ◽  
Protein Phosphatase 2A ◽  
Human Platelets ◽  
Membrane Receptors ◽  
Functional Link ◽  
S Protein ◽  
Phosphatase 2A

Distinct membrane receptors activate platelets by Src-family-kinase (SFK)-, immunoreceptor-tyrosine-based-activation-motif (ITAM)-dependent stimulation of spleen tyrosine kinase (Syk). Recently, we reported that platelet activation via glycoprotein (GP) VI or GPIbα stimulated the well-established Syk tyrosine (Y)-phosphorylation, but also stoichiometric, transient protein kinase C (PKC)-mediated Syk serine(S)297 phosphorylation in the regulatory interdomain-B, suggesting possible feedback inhibition. The transient nature of Syk S297 phosphorylation indicated the presence of an unknown Syk pS297 protein phosphatase. In this study, we hypothesize that the S-protein phosphatase 2A (PP2A) is responsible for Syk pS297 dephosphorylation, thereby affecting Syk Y-phosphorylation and activity in human washed platelets. Using immunoblotting, we show that specific inhibition of PP2A by okadaic acid (OA) alone leads to stoichiometric Syk S297 phosphorylation, as analyzed by Zn2+-Phos-tag gels, without affecting Syk Y-phosphorylation. Pharmacological inhibition of Syk by PRT060318 or PKC by GF109203X only minimally reduced OA-induced Syk S297 phosphorylation. PP2A inhibition by OA preceding GPVI-mediated platelet activation induced by convulxin extended Syk S297 phosphorylation but inhibited Syk Y-phosphorylation. Our data demonstrate a novel biochemical and functional link between the S-protein phosphatase PP2A and the Y-protein kinase Syk in human platelets, and suggest that PP2A represents a potential enhancer of GPVI-mediated Syk activity caused by Syk pS297 dephosphorylation.

scholarly journals Phosphorylation of SET Protein at Ser171 by Protein Kinase D2 Diminishes Its Inhibitory Effect on Protein Phosphatase 2A

PLoS ONE ◽  
2012 ◽  
Vol 7 (12) ◽  
pp. e51242 ◽  
Author(s):  
Atsushi Irie ◽  
Kumiko Harada ◽  
Norie Araki ◽  
Yasuharu Nishimura
Keyword(s):  
Protein Kinase ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Inhibitory Effect ◽  
Phosphatase 2A

scholarly journals Fructose-2,6-bisphosphatase and 6-phosphofructo-2-kinase are separable in yeast

1987 ◽  
Vol 246 (3) ◽  
pp. 755-759 ◽  
Author(s):  
M Kretschmer ◽  
W Schellenberger ◽  
A Otto ◽  
R Kessler ◽  
E Hofmann
Keyword(s):  
Alkaline Phosphatase ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Dependent Protein Kinase ◽  
Km Value ◽  
Phosphatase 2A ◽  
Dependent Protein

Fructose-2,6-bisphosphatase was purified from yeast and separated from 6-phosphofructo-2-kinase and alkaline phosphatase. The enzyme released Pi from the 2-position of fructose 2,6-bisphosphate and formed fructose 6-phosphate in stoichiometric amounts. The enzyme displays hyperbolic kinetics towards fructose 2,6-bisphosphate, with a Km value of 0.3 microM. It is strongly inhibited by fructose 6-phosphate. The inhibition is counteracted by L-glycerol 3-phosphate. Phosphorylation of the enzyme by cyclic-AMP-dependent protein kinase causes inactivation, which is reversible by the action of protein phosphatase 2A.

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