Adenosine A2 Receptor Occupancy Regulates Stimulated Neutrophil Function via Activation of a Serine/Threonine Protein Phosphatase
| Autor: | Shana Landau, Bruce N. Cronstein, Dwight Naime, M. Carmen Montesinos, Sharon Revan |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
Adenosine
Indoles Neutrophils Phosphatase Carbazoles Adenosine A2A receptor Adenosine-5'-(N-ethylcarboxamide) In Vitro Techniques Biology Biochemistry chemistry.chemical_compound Ethers Cyclic Superoxides Okadaic Acid Phosphoprotein Phosphatases Purinergic P1 Receptor Agonists medicine Humans Pyrroles Enzyme Inhibitors Oxazoles Molecular Biology Analysis of Variance Cell Membrane Cell Biology Okadaic acid Protein phosphatase 2 Cyclic AMP-Dependent Protein Kinases Adenosine receptor Molecular biology Enzyme Activation Intracellular signal transduction Kinetics chemistry Marine Toxins Signal transduction medicine.drug |
| Zdroj: | Journal of Biological Chemistry. 271:17114-17118 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.271.29.17114 |
| Popis: | Adenosine modulates generation of superoxide anion by neutrophils via occupancy of specific adenosine A2A receptors. However, the intracellular signal transduction pathways by which occupancy of neutrophil adenosine A2A receptors inhibits superoxide anion generation (O2.-) are not well understood. We, therefore, tested the hypothesis that signaling at polymorphonuclear leukocyte (PMN) adenosine receptors proceeds via activation of a serine/threonine protein phosphatase (pp). Both the specific pp1 inhibitor calyculin A (10 nM) and the pp2A inhibitor okadaic acid (10 microM) enhanced O2.- generation (185 +/- 24 and 189 +/- 35% of control, respectively, p < 0.0001 for both, n = 8), as reported previously. Calyculin A, but not okadaic acid, completely reversed inhibition of stimulated O2.- generation by the adenosine A2 receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA; IC50 = 30 nM; p < 0.0001, analysis of variance). Calyculin A also reversed the adenosine receptor-mediated desensitization of bound chemoattractant receptors in neutrophils. Treatment of PMNs with NECA increased the pp1 activity of crude membrane preparations in a time- and dose-dependent fashion (EC50 = 40 nM; p < 0.001, analysis of variance, n = 5). NECA inhibited cytosolic protein phosphatase activity by 78 +/- 12% (p < 0.003, n = 6) but did not shift pp1 catalytic subunit from cytosol to plasma membrane. Similar changes were observed in neutrophil cytoplasts depleted of organelles and nucleus. Moreover, the selective protein kinase A inhibitor KT5720 (10 microM) reversed the capacity of dibutyryl cAMP but not NECA to increase pp1 activity (p < 0.01, n = 5) in keeping with its effects on O2.- generation. Western blot analysis of PMN subcellular fractions demonstrated the presence of pp1alpha and pp1gamma1 but not pp1gamma2 isotypes in both cytosol and plasma membrane but not in azurophil or specific granules. We conclude from these studies that signal transduction by adenosine in PMN proceeds via a novel pathway: cAMP-independent activation of a serine/threonine protein phosphatase in the plasma membrane. |
| Databáze: | OpenAIRE |
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