title: Does GRK-β arrestin machinery work as a "switch on" for GPR17-mediated activation of intracellular signaling pathways?
abstract: During oligodendrocyte-precursor cell (OPC) differentiation program, an impairment in the regulatory mechanisms controlling GPR17 spatio-temporal expression and functional activity has been suggested to contribute to defective OPC maturation, a crucial event in the pathogenesis of multiple sclerosis. GRK-β arrestin machinery is the primary actor in the control of G-protein coupled receptor (GPCR) functional responses and changes in these regulatory protein activities have been demonstrated in several immune/inflammatory diseases. Herein, in order to shed light on the molecular mechanisms controlling GPR17 regulatory events during cell differentiation, the role of GRK/β-arrestin machinery in receptor desensitization and signal transduction was investigated, in transfected cells and primary OPC. Following cell treatment with the two classes of purinergic and cysteinyl-leukotriene (cysLT) ligands, different GRK isoforms were recruited to regulate GPR17 functional responses. CysLT-mediated receptor desensitization mainly involved GRK2; this kinase, via a G protein-dependent mechanism, promoted a transient binding of the receptor to β-arrestins, rapid ERK phosphorylation and sustained nuclear CREB activation. Furthermore, GRK2, whose expression parallels that of the receptor during differentiation process, appeared to be crucial to induce cysLT-mediated maturation of OPCs. On the other hand, purinergic ligand exclusively recruited the GRK5 subtype, and induced, via a G protein-independent/β-arrestin-dependent mechanism, a receptor/β-arrestin stable association, slower and sustained ERK stimulation and marginal CREB activation. These results show that purinergic and cysLT ligands, through the recruitment of specific GRK isoforms, address distinct intracellular pathways, most likely reinforcing the same final response. The identification of these mechanisms and players controlling GPR17 responses during OPC differentiation could be useful to identify new targets in demyelination diseases and to develop new therapeutical strategies.
authors.affiliation: Department of Pharmacy, University of Pisa, 56126 Pisa, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Daniele
authors.affiliation: Department of Pharmacy, University of Pisa, 56126 Pisa, Italy. Electronic address: maria.trincavelli@farm.unipi.it.
authors.forename: Maria Letizia
authors.initials: ML
authors.lastname: Trincavelli
authors.affiliation: Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133 Milan, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Fumagalli
authors.affiliation: Department of Pharmacy, University of Pisa, 56126 Pisa, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Zappelli
authors.affiliation: Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133 Milan, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Lecca
authors.affiliation: Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133 Milan, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Bonfanti
authors.affiliation: Department of Pharmacy, University of Salerno, 84084 Salerno, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Campiglia
authors.affiliation: Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133 Milan, Italy.
authors.forename: Maria P
authors.initials: MP
authors.lastname: Abbracchio
authors.affiliation: Department of Pharmacy, University of Pisa, 56126 Pisa, Italy. Electronic address: claudia.martini@unipi.it.
authors.forename: Claudia
authors.initials: C
authors.lastname: Martini
mesh_terms: D000818:Animals; D019390:Arrestins / Q000378:metabolism*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000378:metabolism*; D054774:G-Protein-Coupled Receptor Kinase 5 / Q000378:metabolism*; D006801:Humans; D009836:Oligodendroglia / Q000502:physiology; D010766:Phosphorylation; D061251:Primary Cell Culture; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*; D015398:Signal Transduction; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; C121670:GPR17 protein, human; D043562:Receptors, G-Protein-Coupled; D000071557:beta-Arrestins; C496567:GRK2 protein, human; D054769:G-Protein-Coupled Receptor Kinase 2; D054774:G-Protein-Coupled Receptor Kinase 5; C517898:GRK5 protein, human; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: GPCR desensitization; GRK/β-arrestin machinery; Intracellular signaling; Oligodendrocyte differentiation; Signaling transduction