title: Phosphoinositide-dependent protein kinase 1 (PDK1) mediates potent inhibitory effects on eosinophils.
abstract: Prostaglandin E2 (PGE2 ) protects against allergic responses via binding to prostanoid receptor EP4, which inhibits eosinophil migration in a PI3K/PKC-dependent fashion. The phosphoinositide-dependent protein kinase 1 (PDK1) is known to act as a downstream effector in PI3K signaling and has been implicated in the regulation of neutrophil migration. Thus, here we elucidate whether PDK1 mediates inhibitory effects of E-type prostanoid receptor 4 (EP4) receptors on eosinophil function. Therefore, eosinophils were isolated from human peripheral blood or differentiated from mouse BM. PDK1 signaling was investigated in shape change, chemotaxis, CD11b, respiratory burst, and Ca(2+) mobilization assays. The specific PDK1 inhibitors BX-912 and GSK2334470 prevented the inhibition by prostaglandin E2 and the EP4 agonist ONO-AE1-329. Depending on the cellular function, PDK1 seemed to act through PI3K-dependent or PI3K-independent mechanisms. Stimulation of EP4 receptors caused PDK1 phosphorylation at Ser396 and induced PI3K-dependent nuclear translocation of PDK1. EP4-induced inhibition of shape change and chemotaxis was effectively reversed by the Akt inhibitor triciribine. In support of this finding, ONO-AE1-329 induced a PI3K/PDK1-dependent increase in Akt phosphorylation. In conclusion, our data illustrate a critical role for PDK1 in transducing inhibitory signals on eosinophil effector function. Thus, our results suggest that PDK1 might serve as a novel therapeutic target in diseases involving eosinophilic inflammation.
authors: Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.
authors: Eva M
authors: EM
authors: Sturm
authors: Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.
authors: Gerald P
authors: GP
authors: Parzmair
authors: Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.
authors: Balázs
authors: B
authors: Radnai
authors: Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.
authors: Robert B
authors: RB
authors: Frei
authors: Department of Dermatology and Venereology, Division of Environmental Dermatology and Venereology, Medical University of Graz, Graz, Austria.
authors: Gunter J
authors: GJ
authors: Sturm
authors: Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Graz, Austria.
authors: Astrid
authors: A
authors: Hammer
authors: Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.
authors: Rufina
authors: R
authors: Schuligoi
authors: Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.
authors: Irmgard Th
authors: IT
authors: Lippe
authors: Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.
authors: Akos
authors: A
authors: Heinemann
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D021581:Active Transport, Cell Nucleus; D000818:Animals; D039481:CD11b Antigen / Q000378:metabolism; D020013:Calcium Signaling; D048430:Cell Shape; D015232:Dinoprostone / Q000378:metabolism; D004804:Eosinophils / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007191:Indazoles / Q000494:pharmacology; D008738:Methyl Ethers / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000819:agonists / Q000378:metabolism; D016897:Respiratory Burst; D012263:Ribonucleosides / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D039481:CD11b Antigen; C555257:GSK 2334470; D007191:Indazoles; D008738:Methyl Ethers; C461399:ONO-AE1-329; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D058309:Receptors, Prostaglandin E, EP4 Subtype; D012263:Ribonucleosides; C023764:triciribine; D019869:Phosphatidylinositol 3-Kinases; D064413:3-Phosphoinositide-Dependent Protein Kinases; C578562:PDPK1 protein, human; C578564:Pdpk1 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D015232:Dinoprostone
keywords: EP4 receptor; Eosinophils; Inflammation; PDK1 Prostaglandins; Signal transduction